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• How do I align my partition table properly?

  - by Jorge Castro

  I am in the process of building my first RAID5 array. I've used mdadm to create the following set up: root@bondigas:~# mdadm --detail /dev/md1 /dev/md1: Version : 00.90 Creation Time : Wed Oct 20 20:00:41 2010 Raid Level : raid5 Array Size : 5860543488 (5589.05 GiB 6001.20 GB) Used Dev Size : 1953514496 (1863.02 GiB 2000.40 GB) Raid Devices : 4 Total Devices : 4 Preferred Minor : 1 Persistence : Superblock is persistent Update Time : Wed Oct 20 20:13:48 2010 State : clean, degraded, recovering Active Devices : 3 Working Devices : 4 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 64K Rebuild Status : 1% complete UUID : f6dc829e:aa29b476:edd1ef19:85032322 (local to host bondigas) Events : 0.12 Number Major Minor RaidDevice State 0 8 16 0 active sync /dev/sdb 1 8 32 1 active sync /dev/sdc 2 8 48 2 active sync /dev/sdd 4 8 64 3 spare rebuilding /dev/sde While that's going I decided to format the beast with the following command: root@bondigas:~# mkfs.ext4 /dev/md1p1 mke2fs 1.41.11 (14-Mar-2010) /dev/md1p1 alignment is offset by 63488 bytes. This may result in very poor performance, (re)-partitioning suggested. Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=16 blocks, Stripe width=48 blocks 97853440 inodes, 391394047 blocks 19569702 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=0 11945 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 102400000, 214990848 Writing inode tables: ^C 27/11945 root@bondigas:~# ^C I am unsure what to do about "/dev/md1p1 alignment is offset by 63488 bytes." and how to properly partition the disks to match so I can format it properly.

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• SQL SERVER – Concurrency Basics – Guest Post by Vinod Kumar

  - by pinaldave

  This guest post is by Vinod Kumar. Vinod Kumar has worked with SQL Server extensively since joining the industry over a decade ago. Working on various versions from SQL Server 7.0, Oracle 7.3 and other database technologies – he now works with the Microsoft Technology Center (MTC) as a Technology Architect. Let us read the blog post in Vinod’s own voice. Learning is always fun when it comes to SQL Server and learning the basics again can be more fun. I did write about Transaction Logs and recovery over my blogs and the concept of simplifying the basics is a challenge. In the real world we always see checks and queues for a process – say railway reservation, banks, customer supports etc there is a process of line and queue to facilitate everyone. Shorter the queue higher is the efficiency of system (a.k.a higher is the concurrency). Every database does implement this using checks like locking, blocking mechanisms and they implement the standards in a way to facilitate higher concurrency. In this post, let us talk about the topic of Concurrency and what are the various aspects that one needs to know about concurrency inside SQL Server. Let us learn the concepts as one-liners: Concurrency can be defined as the ability of multiple processes to access or change shared data at the same time. The greater the number of concurrent user processes that can be active without interfering with each other, the greater the concurrency of the database system. Concurrency is reduced when a process that is changing data prevents other processes from reading that data or when a process that is reading data prevents other processes from changing that data. Concurrency is also affected when multiple processes are attempting to change the same data simultaneously. Two approaches to managing concurrent data access: Optimistic Concurrency Model Pessimistic Concurrency Model Concurrency Models Pessimistic Concurrency Default behavior: acquire locks to block access to data that another process is using. Assumes that enough data modification operations are in the system that any given read operation is likely affected by a data modification made by another user (assumes conflicts will occur). Avoids conflicts by acquiring a lock on data being read so no other processes can modify that data. Also acquires locks on data being modified so no other processes can access the data for either reading or modifying. Readers block writer, writers block readers and writers. Optimistic Concurrency Assumes that there are sufficiently few conflicting data modification operations in the system that any single transaction is unlikely to modify data that another transaction is modifying. Default behavior of optimistic concurrency is to use row versioning to allow data readers to see the state of the data before the modification occurs. Older versions of the data are saved so a process reading data can see the data as it was when the process started reading and not affected by any changes being made to that data. Processes modifying the data is unaffected by processes reading the data because the reader is accessing a saved version of the data rows. Readers do not block writers and writers do not block readers, but, writers can and will block writers. Transaction Processing A transaction is the basic unit of work in SQL Server. Transaction consists of SQL commands that read and update the database but the update is not considered final until a COMMIT command is issued (at least for an explicit transaction: marked with a BEGIN TRAN and the end is marked by a COMMIT TRAN or ROLLBACK TRAN). Transactions must exhibit all the ACID properties of a transaction. ACID Properties Transaction processing must guarantee the consistency and recoverability of SQL Server databases. Ensures all transactions are performed as a single unit of work regardless of hardware or system failure. A – Atomicity C – Consistency I – Isolation D- Durability Atomicity: Each transaction is treated as all or nothing – it either commits or aborts. Consistency: ensures that a transaction won’t allow the system to arrive at an incorrect logical state – the data must always be logically correct.  Consistency is honored even in the event of a system failure. Isolation: separates concurrent transactions from the updates of other incomplete transactions. SQL Server accomplishes isolation among transactions by locking data or creating row versions. Durability: After a transaction commits, the durability property ensures that the effects of the transaction persist even if a system failure occurs. If a system failure occurs while a transaction is in progress, the transaction is completely undone, leaving no partial effects on data. Transaction Dependencies In addition to supporting all four ACID properties, a transaction might exhibit few other behaviors (known as dependency problems or consistency problems). Lost Updates: Occur when two processes read the same data and both manipulate the data, changing its value and then both try to update the original data to the new value. The second process might overwrite the first update completely. Dirty Reads: Occurs when a process reads uncommitted data. If one process has changed data but not yet committed the change, another process reading the data will read it in an inconsistent state. Non-repeatable Reads: A read is non-repeatable if a process might get different values when reading the same data in two reads within the same transaction. This can happen when another process changes the data in between the reads that the first process is doing. Phantoms: Occurs when membership in a set changes. It occurs if two SELECT operations using the same predicate in the same transaction return a different number of rows. Isolation Levels SQL Server supports 5 isolation levels that control the behavior of read operations. Read Uncommitted All behaviors except for lost updates are possible. Implemented by allowing the read operations to not take any locks, and because of this, it won’t be blocked by conflicting locks acquired by other processes. The process can read data that another process has modified but not yet committed. When using the read uncommitted isolation level and scanning an entire table, SQL Server can decide to do an allocation order scan (in page-number order) instead of a logical order scan (following page pointers). If another process doing concurrent operations changes data and move rows to a new location in the table, the allocation order scan can end up reading the same row twice. Also can happen if you have read a row before it is updated and then an update moves the row to a higher page number than your scan encounters later. Performing an allocation order scan under Read Uncommitted can cause you to miss a row completely – can happen when a row on a high page number that hasn’t been read yet is updated and moved to a lower page number that has already been read. Read Committed Two varieties of read committed isolation: optimistic and pessimistic (default). Ensures that a read never reads data that another application hasn’t committed. If another transaction is updating data and has exclusive locks on data, your transaction will have to wait for the locks to be released. Your transaction must put share locks on data that are visited, which means that data might be unavailable for others to use. A share lock doesn’t prevent others from reading but prevents them from updating. Read committed (snapshot) ensures that an operation never reads uncommitted data, but not by forcing other processes to wait. SQL Server generates a version of the changed row with its previous committed values. Data being changed is still locked but other processes can see the previous versions of the data as it was before the update operation began. Repeatable Read This is a Pessimistic isolation level. Ensures that if a transaction revisits data or a query is reissued the data doesn’t change. That is, issuing the same query twice within a transaction cannot pickup any changes to data values made by another user’s transaction because no changes can be made by other transactions. However, this does allow phantom rows to appear. Preventing non-repeatable read is a desirable safeguard but cost is that all shared locks in a transaction must be held until the completion of the transaction. Snapshot Snapshot Isolation (SI) is an optimistic isolation level. Allows for processes to read older versions of committed data if the current version is locked. Difference between snapshot and read committed has to do with how old the older versions have to be. It’s possible to have two transactions executing simultaneously that give us a result that is not possible in any serial execution. Serializable This is the strongest of the pessimistic isolation level. Adds to repeatable read isolation level by ensuring that if a query is reissued rows were not added in the interim, i.e, phantoms do not appear. Preventing phantoms is another desirable safeguard, but cost of this extra safeguard is similar to that of repeatable read – all shared locks in a transaction must be held until the transaction completes. In addition serializable isolation level requires that you lock data that has been read but also data that doesn’t exist. Ex: if a SELECT returned no rows, you want it to return no. rows when the query is reissued. This is implemented in SQL Server by a special kind of lock called the key-range lock. Key-range locks require that there be an index on the column that defines the range of values. If there is no index on the column, serializable isolation requires a table lock. Gets its name from the fact that running multiple serializable transactions at the same time is equivalent of running them one at a time. Now that we understand the basics of what concurrency is, the subsequent blog posts will try to bring out the basics around locking, blocking, deadlocks because they are the fundamental blocks that make concurrency possible. Now if you are with me – let us continue learning for SQL Server Locking Basics. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Concurrency

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• Evil DRY

  - by StefanSteinegger

  DRY (Don't Repeat Yourself) is a basic software design and coding principle. But there is just no silver bullet. While DRY should increase maintainability by avoiding common design mistakes, it could lead to huge maintenance problems when misunderstood. The root of the problem is most probably that many developers believe that DRY means that any piece of code that is written more then once should be made reusable. But the principle is stated as "Every piece of knowledge must have a single, unambiguous, authoritative representation within a system." So the important thing here is "knowledge". Nobody ever said "every piece of code". I try to give some examples of misusing the DRY principle. Code Repetitions by Coincidence There is code that is repeated by pure coincidence. It is not the same code because it is based on the same piece of knowledge, it is just the same by coincidence. It's hard to give an example of such a case. Just think about some lines of code the developer thinks "I already wrote something similar". Then he takes the original code, puts it into a public method, even worse into a base class where none had been there before, puts some weird arguments and some if or switch statements into it to support all special cases and calls this "increasing maintainability based on the DRY principle". The resulting "reusable method" is usually something the developer not even can give a meaningful name, because its contents isn't anything specific, it is just a bunch of code. For the same reason, nobody will really understand this piece of code. Typically this method only makes sense to call after some other method had been called. All the symptoms of really bad design is evident. Fact is, writing this kind of "reusable methods" is worse then copy pasting! Believe me. What will happen when you change this weird piece of code? You can't say what'll happen, because you can't understand what the code is actually doing. So better don't touch it anymore. Maintainability just died. Of course this problem is with any badly designed code. But because the developer tried to make this method as reusable as possible, large parts of the system get dependent on it. Completely independent parts get tightly coupled by this common piece of code. Changing on the single common place will have effects anywhere in the system, a typical symptom of too tight coupling. Without trying to dogmatically (and wrongly) apply the DRY principle, you just had a system with a weak design. Now you get a system which just can't be maintained anymore. So what can you do against it? When making code reusable, always identify the generally reusable parts of it. Find the reason why the code is repeated, find the common "piece of knowledge". If you have to search too far, it's probably not really there. Explain it to a colleague, if you can't explain or the explanation is to complicated, it's probably not worth to reuse. If you identify the piece of knowledge, don't forget to carefully find the place where it should be implemented. Reusing code is never worth giving up a clean design. Methods always need to do something specific. If you can't give it a simple and explanatory name, you did probably something weird. If you can't find the common piece of knowledge, try to make the code simpler. For instance, if you have some complicated string or collection operations within this code, write some general-purpose operations into a helper class. If your code gets simple enough, its not so bad if it can't be reused. If you are not able to find anything simple and reasonable, copy paste it. Put a comment into the code to reference the other copies. You may find a solution later. Requirements Repetitions by Coincidence Let's assume that you need to implement complex tax calculations for many countries. It's possible that some countries have very similar tax rules. These rules are still completely independent from each other, since every country can change it of its own. (Assumed that this similarity is actually by coincidence and not by political membership. There might be basic rules applying to all European countries. etc.) Let's assume that there are similarities between an Asian country and an African country. Moving the common part to a central place will cause problems. What happens if one of the countries changes its rules? Or - more likely - what happens if users of one country complain about an error in the calculation? If there is shared code, it is very risky to change it, even for a bugfix. It is hard to find requirements to be repeated by coincidence. Then there is not much you can do against the repetition of the code. What you really should consider is to make coding of the rules as simple as possible. So this independent knowledge "Tax Rules in Timbuktu" or wherever should be as pure as possible, without much overhead and stuff that does not belong to it. So you can write every independent requirement short and clean. DRYing try-catch and using Blocks This is a technical issue. Blocks like try-catch or using (e.g. in C#) are very hard to DRY. Imagine a complex exception handling, including several catch blocks. When the contents of the try block as well as the contents of the individual catch block are trivial, but the whole structure is repeated on many places in the code, there is almost no reasonable way to DRY it. try { // trivial code here using (Thingy thing = new thingy) { //trivial, but always different line of code } } catch(FooException foo) { // trivial foo handling } catch (BarException bar) { // trivial bar handling } catch { // trivial common handling } finally { // trivial finally block } The key here is that every block is trivial, so there is nothing to just move into a separate method. The only part that differs from case to case is the line of code in the body of the using block (or any other block). The situation is especially interesting if the many occurrences of this structure are completely independent: they appear in classes with no common base class, they don't aggregate each other and so on. Let's assume that this is a common pattern in service methods within the whole system. Examples of Evil DRYing in this situation: Put a if or switch statement into the method to choose the line of code to execute. There are several reasons why this is not a good idea: The close coupling of the formerly independent implementation is the strongest. Also the readability of the code and the use of a parameter to control the logic. Put everything into a method which takes a delegate as argument to call. The caller just passes his "specific line of code" to this method. The code will be very unreadable. The same maintainability problems apply as for any "Code Repetition by Coincidence" situations. Enforce a base class to all the classes where this pattern appears and use the template method pattern. It's the same readability and maintainability problem as above, but additionally complex and tightly coupled because of the base class. I would call this "Inheritance by Coincidence" which will not lead to great software design. What can you do against it: Ideally, the individual line of code is a call to a class or interface, which could be made individual by inheritance. If this would be the case, it wouldn't be a problem at all. I assume that it is no such a trivial case. Consider to refactor the error concept to make error handling easier. The last but not worst option is to keep the replications. Some pattern of code must be maintained in consistency, there is nothing we can do against it. And no reason to make it unreadable. Conclusion The DRY-principle is an important and basic principle every software developer should master. The key is to identify the "pieces of knowledge". There is code which can't be reused easily because of technical reasons. This requires quite a bit flexibility and creativity to make code simple and maintainable. It's not the problem of the principle, it is the problem of blindly applying a principle without understanding the problem it should solve. The result is mostly much worse then ignoring the principle.

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• Metro: Dynamically Switching Templates with a WinJS ListView

  - by Stephen.Walther

  Imagine that you want to display a list of products using the WinJS ListView control. Imagine, furthermore, that you want to use different templates to display different products. In particular, when a product is on sale, you want to display the product using a special “On Sale” template. In this blog entry, I explain how you can switch templates dynamically when displaying items with a ListView control. In other words, you learn how to use more than one template when displaying items with a ListView control. Creating the Data Source Let’s start by creating the data source for the ListView. Nothing special here – our data source is a list of products. Two of the products, Oranges and Apples, are on sale. (function () { "use strict"; var products = new WinJS.Binding.List([ { name: "Milk", price: 2.44 }, { name: "Oranges", price: 1.99, onSale: true }, { name: "Wine", price: 8.55 }, { name: "Apples", price: 2.44, onSale: true }, { name: "Steak", price: 1.99 }, { name: "Eggs", price: 2.44 }, { name: "Mushrooms", price: 1.99 }, { name: "Yogurt", price: 2.44 }, { name: "Soup", price: 1.99 }, { name: "Cereal", price: 2.44 }, { name: "Pepsi", price: 1.99 } ]); WinJS.Namespace.define("ListViewDemos", { products: products }); })(); The file above is saved with the name products.js and referenced by the default.html page described below. Declaring the Templates and ListView Control Next, we need to declare the ListView control and the two Template controls which we will use to display template items. The markup below appears in the default.html file: <!-- Templates --> <div id="productItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div id="productOnSaleTemplate" data-win-control="WinJS.Binding.Template"> <div class="product onSale"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> </div> <!-- ListView --> <div id="productsListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.products.dataSource, layout: { type: WinJS.UI.ListLayout } }"> </div> In the markup above, two Template controls are declared. The first template is used when rendering a normal product and the second template is used when rendering a product which is on sale. The second template, unlike the first template, includes the text “(On Sale!)”. The ListView control is bound to the data source which we created in the previous section. The ListView itemDataSource property is set to the value ListViewDemos.products.dataSource. Notice that we do not set the ListView itemTemplate property. We set this property in the default.js file. Switching Between Templates All of the magic happens in the default.js file. The default.js file contains the JavaScript code used to switch templates dynamically. Here’s the entire contents of the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll().then(function () { var productsListView = document.getElementById("productsListView"); productsListView.winControl.itemTemplate = itemTemplateFunction; });; } }; function itemTemplateFunction(itemPromise) { return itemPromise.then(function (item) { // Select either normal product template or on sale template var itemTemplate = document.getElementById("productItemTemplate"); if (item.data.onSale) { itemTemplate = document.getElementById("productOnSaleTemplate"); }; // Render selected template to DIV container var container = document.createElement("div"); itemTemplate.winControl.render(item.data, container); return container; }); } app.start(); })(); In the code above, a function is assigned to the ListView itemTemplate property with the following line of code: productsListView.winControl.itemTemplate = itemTemplateFunction;   The itemTemplateFunction returns a DOM element which is used for the template item. Depending on the value of the product onSale property, the DOM element is generated from either the productItemTemplate or the productOnSaleTemplate template. Using Binding Converters instead of Multiple Templates In the previous sections, I explained how you can use different templates to render normal products and on sale products. There is an alternative approach to displaying different markup for normal products and on sale products. Instead of creating two templates, you can create a single template which contains separate DIV elements for a normal product and an on sale product. The following default.html file contains a single item template and a ListView control bound to the template. <!-- Template --> <div id="productItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="product" data-win-bind="style.display: onSale ListViewDemos.displayNormalProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> <div class="product onSale" data-win-bind="style.display: onSale ListViewDemos.displayOnSaleProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> </div> <!-- ListView --> <div id="productsListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.products.dataSource, itemTemplate: select('#productItemTemplate'), layout: { type: WinJS.UI.ListLayout } }"> </div> The first DIV element is used to render a normal product: <div class="product" data-win-bind="style.display: onSale ListViewDemos.displayNormalProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> The second DIV element is used to render an “on sale” product: <div class="product onSale" data-win-bind="style.display: onSale ListViewDemos.displayOnSaleProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> Notice that both templates include a data-win-bind attribute. These data-win-bind attributes are used to show the “normal” template when a product is not on sale and show the “on sale” template when a product is on sale. These attributes set the Cascading Style Sheet display attribute to either “none” or “block”. The data-win-bind attributes take advantage of binding converters. The binding converters are defined in the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll(); } }; WinJS.Namespace.define("ListViewDemos", { displayNormalProduct: WinJS.Binding.converter(function (onSale) { return onSale ? "none" : "block"; }), displayOnSaleProduct: WinJS.Binding.converter(function (onSale) { return onSale ? "block" : "none"; }) }); app.start(); })(); The ListViewDemos.displayNormalProduct binding converter converts the value true or false to the value “none” or “block”. The ListViewDemos.displayOnSaleProduct binding converter does the opposite; it converts the value true or false to the value “block” or “none” (Sadly, you cannot simply place a NOT operator before the onSale property in the binding expression – you need to create both converters). The end result is that you can display different markup depending on the value of the product onSale property. Either the contents of the first or second DIV element are displayed: Summary In this blog entry, I’ve explored two approaches to displaying different markup in a ListView depending on the value of a data item property. The bulk of this blog entry was devoted to explaining how you can assign a function to the ListView itemTemplate property which returns different templates. We created both a productItemTemplate and productOnSaleTemplate and displayed both templates with the same ListView control. We also discussed how you can create a single template and display different markup by using binding converters. The binding converters are used to set a DIV element’s display property to either “none” or “block”. We created a binding converter which displays normal products and a binding converter which displays “on sale” products.

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• Weird CSS-behaviour [migrated]

  - by WMRKameleon

  <!DOCTYPE html> <html> <head> <title>PakHet</title> <link rel="stylesheet" type="text/css" href="css/basis.css" /> </head> <body> <div class="wrapper"> <div id='cssmenu'> <ul> <li class="active"><a href='index.html'><span>Start</span></a></li> <li><a href='pakhet.html'><span>Over PakHet</span></a></li> <li><a href='overons.html'><span>Over Ons</span></a></li> <li class='has-sub '><a href='#'><span>Uw pakket</span></a> <ul> <li><a href='aanmelden.php'><span>Aanmelden</span></a></li> <li><a href='traceren.php'><span>Traceren</span></a></li> </ul> </li> </ul> </div> <div class="header"> <h1>Hier komt de titel van de website</h1> </div> <div class="content"> <p>Dit is de tekst van de content. Dit is de indexpagina.</p> </div> </div> </body> </html> And this is the CSS: /* CSS RESET */ html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td, article, aside, canvas, details, embed, figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary, time, mark, audio, video, *{ margin: 0; padding: 0; border: 0; vertical-align: baseline; } table { border-collapse: collapse; border-spacing: 0; } /* Einde CSS RESET, nu echte code */ html, body{ background:url(../images/bg_picture.jpg) fixed no-repeat; } .wrapper{ margin:0 auto; } .header{ margin:0 auto; background-color:rgba(0, 0, 0, 0.4); } .content{ background-color:rgba(0, 0, 0, 0.4); width:600px; margin:0 auto; margin-top:50px; } .content p{ color:white; text-shadow:1px 1px 0 rgba(0,0,0, 0.5); font-family:"Lucida Grande", sans-serif; } #cssmenu{ height:37px; display:block; padding:0; margin: 0; border:1px solid; } #cssmenu > ul {list-style:inside none; padding:0; margin:0;} #cssmenu > ul > li {list-style:inside none; padding:0; margin:0; float:left; display:block; position:relative;} #cssmenu > ul > li > a{ outline:none; display:block; position:relative; padding:12px 20px; font:bold 13px/100% "Lucida Grande", Helvetica, sans-serif; text-align:center; text-decoration:none; text-shadow:1px 1px 0 rgba(0,0,0, 0.4); } #cssmenu > ul > li:first-child > a{border-radius:5px 0 0 5px;} #cssmenu > ul > li > a:after{ content:''; position:absolute; border-right:1px solid; top:-1px; bottom:-1px; right:-2px; z-index:99; } #cssmenu ul li.has-sub:hover > a:after{top:0; bottom:0;} #cssmenu > ul > li.has-sub > a:before{ content:''; position:absolute; top:18px; right:6px; border:5px solid transparent; border-top:5px solid #fff; } #cssmenu > ul > li.has-sub:hover > a:before{top:19px;} #cssmenu ul li.has-sub:hover > a{ background:#3f3f3f; border-color:#3f3f3f; padding-bottom:13px; padding-top:13px; top:-1px; z-index:999; } #cssmenu ul li.has-sub:hover > ul, #cssmenu ul li.has-sub:hover > div{display:block;} #cssmenu ul li.has-sub > a:hover{background:#3f3f3f; border-color:#3f3f3f;} #cssmenu ul li > ul, #cssmenu ul li > div{ display:none; width:auto; position:absolute; top:38px; padding:10px 0; background:#3f3f3f; border-radius:0 0 5px 5px; z-index:999; } #cssmenu ul li > ul{width:200px;} #cssmenu ul li > ul li{display:block; list-style:inside none; padding:0; margin:0; position:relative;} #cssmenu ul li > ul li a{ outline:none; display:block; position:relative; margin:0; padding:8px 20px; font:10pt "Lucida Grande", Helvetica, sans-serif; color:#fff; text-decoration:none; text-shadow:1px 1px 0 rgba(0,0,0, 0.5); } #cssmenu, #cssmenu > ul > li > ul > li a:hover{ background:#333333; background:-moz-linear-gradient(top, #333333 0%, #222222 100%); background:-webkit-gradient(linear, left top, left bottom, color-stop(0%,#333333), color-stop(100%,#222222)); background:-webkit-linear-gradient(top, #333333 0%,#222222 100%); background:-o-linear-gradient(top, #333333 0%,#222222 100%); background:-ms-linear-gradient(top, #333333 0%,#222222 100%); background:linear-gradient(top, #333333 0%,#222222 100%); filter:progid:DXImageTransform.Microsoft.gradient( startColorstr='#333333', endColorstr='#222222',GradientType=0 ); } #cssmenu{border-color:#000;} #cssmenu > ul > li > a{border-right:1px solid #000; color:#fff;} #cssmenu > ul > li > a:after{border-color:#444;} #cssmenu > ul > li > a:hover{background:#111;} #cssmenu > ul > li.active > a{ color:orange; } .header{ clear:both; } The problem is that, whenever I hover on the dropdown-menu, that a 1px margin appears in between the menu and the header. Can I solve that? I can't seem to find the solution.

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• Minecraft-style player-gound collision detection

  - by khyperia

  The title pretty much says it all... (Minecraft is a game consisting of evenly-spaced cubes for terrain, like voxels) Note: I am using C# XNA. I am pretty sure AABB is the way to go, yet I don't know how to implement it. I admit, I'm almost looking for code, but theories/ideas are very welcome. Important capabilities of my code: I have a function that can get a block anywhere in the world, and get a BoundingBox for that cube. Hence, I have created a BoundingBox for the player to collide with those cubes. My idea was to get the blocks around the player (maybe 4x6x4) and test against those. The problems I have been having: Say the world is a flat plane. If I use the method of go the shortest distance out, then if the player is slightly clipped into the ground (from gravity), but even slighter into the next block over, then the player will be pushed sideways (and so cannot walk along ground). Of course, this is assuming I react to every block intersected. Another problem is knowing which direction to go (aka negative x or positive). That takes me to my final problem- Getting the amount of intersection, in the correct direction (+ or -) has been tough for me. I hope I haven't been too hard to understand, I'm not too good at explaining things... And if this question has already been asked, I'm sorry, I looked for it... for 3 days straight. One last thing, if someone knows exactly how minecraft does it, or has source (I know MC modders have the source, how else would they mod), please point me to it.

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• How do I align my partition table properly?

  - by Jorge Castro

  I am in the process of building my first RAID5 array. I've used mdadm to create the following set up: root@bondigas:~# mdadm --detail /dev/md1 /dev/md1: Version : 00.90 Creation Time : Wed Oct 20 20:00:41 2010 Raid Level : raid5 Array Size : 5860543488 (5589.05 GiB 6001.20 GB) Used Dev Size : 1953514496 (1863.02 GiB 2000.40 GB) Raid Devices : 4 Total Devices : 4 Preferred Minor : 1 Persistence : Superblock is persistent Update Time : Wed Oct 20 20:13:48 2010 State : clean, degraded, recovering Active Devices : 3 Working Devices : 4 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 64K Rebuild Status : 1% complete UUID : f6dc829e:aa29b476:edd1ef19:85032322 (local to host bondigas) Events : 0.12 Number Major Minor RaidDevice State 0 8 16 0 active sync /dev/sdb 1 8 32 1 active sync /dev/sdc 2 8 48 2 active sync /dev/sdd 4 8 64 3 spare rebuilding /dev/sde While that's going I decided to format the beast with the following command: root@bondigas:~# mkfs.ext4 /dev/md1p1 mke2fs 1.41.11 (14-Mar-2010) /dev/md1p1 alignment is offset by 63488 bytes. This may result in very poor performance, (re)-partitioning suggested. Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=16 blocks, Stripe width=48 blocks 97853440 inodes, 391394047 blocks 19569702 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=0 11945 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 102400000, 214990848 Writing inode tables: ^C 27/11945 root@bondigas:~# ^C I am unsure what to do about "/dev/md1p1 alignment is offset by 63488 bytes." and how to properly partition the disks to match so I can format it properly.

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• Page_BlockSubmit - reset it to False, if there is a scenario when page doesn't postback on validation error

  - by Vipin

  Recently, I was facing a problem where if there was a validation error, and if I changed the state of checkbox it won't postback on first attempt. But when I uncheck and check again , it postbacks on second attempt...this is some quirky behaviour in .ASP.Net platform. The solution was to reset Page_BlockSubmit flag to false and it works fine. The following explanation is from http://lionsden.co.il/codeden/?p=137&cpage=1#comment-143   Submit button on the page is a member of vgMain, so automatically it will only run the validation on that group. A solution is needed that will run validation on multiple groups and block the postback if needed. Solution Include the following function on the page: function DoValidation() { //validate the primary group var validated = Page_ClientValidate('vgPrimary ');   //if it is valid if (validated) { //valid the main group validated = Page_ClientValidate('vgMain'); }   //remove the flag to block the submit if it was raised Page_BlockSubmit = false;   //return the results return validated; } Call the above function from the submit button’s OnClientClick event. <asp:Button runat="server" ID="btnSubmit" CausesValidation="true" ValidationGroup="vgMain" Text="Next" OnClick="btnSubmit_Click" OnClientClick="return DoValidation();" /> What is Page_BlockSubmit When the user clicks on a button causing a full post back, after running Page_ClientValidate ASP.NET runs another built in function ValidatorCommonOnSubmit. Within Page_ClientValidate, Page_BlockSubmit is set based on the validation. The postback is then blocked in ValidatorCommonOnSubmit if Page_BlockSubmit is true. No matter what, at the end of the function Page_BlockSubmit is always reset back to false. If a page does a partial postback without running any validation and Page_BlockSubmit has not been reset to false, the partial postback will be blocked. In essence the above function, RunValidation, acts similar to ValidatorCommonOnSubmit. It runs the validation and then returns false to block the postback if needed. Since the built in postback is never run, we need to reset Page_BlockSubmit manually before returning the validation result.

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• Metro: Dynamically Switching Templates with a WinJS ListView

  - by Stephen.Walther

  Imagine that you want to display a list of products using the WinJS ListView control. Imagine, furthermore, that you want to use different templates to display different products. In particular, when a product is on sale, you want to display the product using a special “On Sale” template. In this blog entry, I explain how you can switch templates dynamically when displaying items with a ListView control. In other words, you learn how to use more than one template when displaying items with a ListView control. Creating the Data Source Let’s start by creating the data source for the ListView. Nothing special here – our data source is a list of products. Two of the products, Oranges and Apples, are on sale. (function () { "use strict"; var products = new WinJS.Binding.List([ { name: "Milk", price: 2.44 }, { name: "Oranges", price: 1.99, onSale: true }, { name: "Wine", price: 8.55 }, { name: "Apples", price: 2.44, onSale: true }, { name: "Steak", price: 1.99 }, { name: "Eggs", price: 2.44 }, { name: "Mushrooms", price: 1.99 }, { name: "Yogurt", price: 2.44 }, { name: "Soup", price: 1.99 }, { name: "Cereal", price: 2.44 }, { name: "Pepsi", price: 1.99 } ]); WinJS.Namespace.define("ListViewDemos", { products: products }); })(); The file above is saved with the name products.js and referenced by the default.html page described below. Declaring the Templates and ListView Control Next, we need to declare the ListView control and the two Template controls which we will use to display template items. The markup below appears in the default.html file: <!-- Templates --> <div id="productItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div id="productOnSaleTemplate" data-win-control="WinJS.Binding.Template"> <div class="product onSale"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> </div> <!-- ListView --> <div id="productsListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.products.dataSource, layout: { type: WinJS.UI.ListLayout } }"> </div> In the markup above, two Template controls are declared. The first template is used when rendering a normal product and the second template is used when rendering a product which is on sale. The second template, unlike the first template, includes the text “(On Sale!)”. The ListView control is bound to the data source which we created in the previous section. The ListView itemDataSource property is set to the value ListViewDemos.products.dataSource. Notice that we do not set the ListView itemTemplate property. We set this property in the default.js file. Switching Between Templates All of the magic happens in the default.js file. The default.js file contains the JavaScript code used to switch templates dynamically. Here’s the entire contents of the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll().then(function () { var productsListView = document.getElementById("productsListView"); productsListView.winControl.itemTemplate = itemTemplateFunction; });; } }; function itemTemplateFunction(itemPromise) { return itemPromise.then(function (item) { // Select either normal product template or on sale template var itemTemplate = document.getElementById("productItemTemplate"); if (item.data.onSale) { itemTemplate = document.getElementById("productOnSaleTemplate"); }; // Render selected template to DIV container var container = document.createElement("div"); itemTemplate.winControl.render(item.data, container); return container; }); } app.start(); })(); In the code above, a function is assigned to the ListView itemTemplate property with the following line of code: productsListView.winControl.itemTemplate = itemTemplateFunction;   The itemTemplateFunction returns a DOM element which is used for the template item. Depending on the value of the product onSale property, the DOM element is generated from either the productItemTemplate or the productOnSaleTemplate template. Using Binding Converters instead of Multiple Templates In the previous sections, I explained how you can use different templates to render normal products and on sale products. There is an alternative approach to displaying different markup for normal products and on sale products. Instead of creating two templates, you can create a single template which contains separate DIV elements for a normal product and an on sale product. The following default.html file contains a single item template and a ListView control bound to the template. <!-- Template --> <div id="productItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="product" data-win-bind="style.display: onSale ListViewDemos.displayNormalProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> <div class="product onSale" data-win-bind="style.display: onSale ListViewDemos.displayOnSaleProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> </div> <!-- ListView --> <div id="productsListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.products.dataSource, itemTemplate: select('#productItemTemplate'), layout: { type: WinJS.UI.ListLayout } }"> </div> The first DIV element is used to render a normal product: <div class="product" data-win-bind="style.display: onSale ListViewDemos.displayNormalProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> The second DIV element is used to render an “on sale” product: <div class="product onSale" data-win-bind="style.display: onSale ListViewDemos.displayOnSaleProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> Notice that both templates include a data-win-bind attribute. These data-win-bind attributes are used to show the “normal” template when a product is not on sale and show the “on sale” template when a product is on sale. These attributes set the Cascading Style Sheet display attribute to either “none” or “block”. The data-win-bind attributes take advantage of binding converters. The binding converters are defined in the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll(); } }; WinJS.Namespace.define("ListViewDemos", { displayNormalProduct: WinJS.Binding.converter(function (onSale) { return onSale ? "none" : "block"; }), displayOnSaleProduct: WinJS.Binding.converter(function (onSale) { return onSale ? "block" : "none"; }) }); app.start(); })(); The ListViewDemos.displayNormalProduct binding converter converts the value true or false to the value “none” or “block”. The ListViewDemos.displayOnSaleProduct binding converter does the opposite; it converts the value true or false to the value “block” or “none” (Sadly, you cannot simply place a NOT operator before the onSale property in the binding expression – you need to create both converters). The end result is that you can display different markup depending on the value of the product onSale property. Either the contents of the first or second DIV element are displayed: Summary In this blog entry, I’ve explored two approaches to displaying different markup in a ListView depending on the value of a data item property. The bulk of this blog entry was devoted to explaining how you can assign a function to the ListView itemTemplate property which returns different templates. We created both a productItemTemplate and productOnSaleTemplate and displayed both templates with the same ListView control. We also discussed how you can create a single template and display different markup by using binding converters. The binding converters are used to set a DIV element’s display property to either “none” or “block”. We created a binding converter which displays normal products and a binding converter which displays “on sale” products.

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• Strange if-else branching behavior in a fragment shader

  - by Winged

  In my fragment shader I have passed an uniform int uLightType variable, which indicates what type of light is in usage right now. The problem is that if-else branching does not work correctly - the fragment shader performs instructions in every if statement block. if (uLightType == 1) { // Spotlight light type vec3 depthTextureCoord = vDepthPosition.xyz / vDepthPosition.w; shadowDepth = unpack(texture2D(uDepthMapSampler, depthTextureCoord.xy)); } else if (uLightType == 2) { // Omni-directional light type shadowDepth = unpack(textureCube(uDepthCubemapSampler, -lightVec)); } In the case when uLightType equals 1, unless I comment out the content of the second if block, it assigns an another value to shadowDepth. Also while uLightType equals 1, when I remove the second 'if' block and change == to != like in the sample code below, nothing happens (which means that uLightType really equals 1). if (uLightType != 1) { // Spotlight light type vec3 depthTextureCoord = vDepthPosition.xyz / vDepthPosition.w; shadowDepth = unpack(texture2D(uDepthMapSampler, depthTextureCoord.xy)); } Also, when I manually create an int variable (which is not an uniform) like this: var lightType = 1; and replace uLightType with it in the if-else branch, everything works fine, so I guess it have something to do with the fact that uLightType is the uniform.

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• GetContactList stops reporting collisions on welded bodies

  - by Henrique Jung

  I have some strange problem with my game which uses Box2D as physics engine and I'm out of ideas on what I can do to solve it. My game is a class assignment where I need to build a simple game where the main character moves in a 2D environment while square blocks comes from below him. Each time a collision occurs, that block is attached to the character using a weld joint, when three blocks of the same colors are together, they annihilate themselves(an effect similar to Bejeweled). I'm using a recursive function to iterate through all the attached blocks of a given block to see if there are enough blocks for them to be deleted. I'm using GetContactList function to iterate through the list of contacts to see which blocks are adjacent to each other. The results are quite disappointing, the blocks only get annihilated in few cases. After a lot of debugging, I found the issue, but I still don't know how to solve. My issue is: after some time, GetContactList STOPS returning contacts (return NULL) to blocks that were already attached for some time. I spent some time reading the Box2D manual as well as some tutorials and still didn't find any clue of what is happening. Below there's some simplified version of the code that I wrote. for(int a = 0; a < blocksList.size(); a++) { blocksList[a].BuildConnections(); } And on BuildConnections b2ContactEdge* edge = body->GetContactList(); while(edge != NULL) { if (long_check_to_see_if_there's_a_block_nearby) { // add itself to the list to be anihilated globalList.push_back(this); //if there's, call BuildConnections again on the adjacent block adjacentBody->GetUserData()->BuildConnections; } edge = edge->next; } I know that there's another issue related to circular inclusions, but I fairly sure that this problem isn't causing the problem with the collisions. You can download my entire code from this page if you'd like http://code.google.com/p/fellz/source/list

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• Implmenting RLE into a tilemap or how to create a large 3D array?

  - by Smallbro

  Currently I've been using a 3D array for my tiles in a 2D world but the 3D side comes in when moving down into caves and whatnot. Now this is not memory efficient and I switched over to a 2D array and can now have much larger maps. The only issue I'm having now is that it seems that my tiles cannot occupy the same space as a tile on the same z level. My current structure means that each block has its own z variable. This is what it used to look like: map.blockData[x][y][z] = new Block(); however now it works like this map.blockData[x][y] = new Block(z); I'm not sure why but if I decide to use the same space on say the floor below it wont allow me to. Does anyone have any ideas on how I can add a z-axis to my 2D array? I'm using java but I reckon the concept carries across different languages. Edit: As Will posted, RLE sounds like the best method for achieving a fast 3D array. However I'm struggling to understand how I would even start to implement it? Would I create a 4D array the 4th being something which controls how many to skip? Or would the x-axis simply change altogether and have large gaps in between - for example [5][y][z] would skip 5 tiles? Is there something really obvious here which I am missing? The number of z levels I'm trying to have is around 66, it would be preferably that I can have up to or more than 1000 in x and y.

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• Android Game Development problem with Speed = Distance / Time

  - by Charlton Santana

  I have been coding speed for an object. I have made it so the object will move from one end of the screen to another at a speed depending on the screen size, at the monemt I have made it so it will take one second to pass the screen. So i have worked out the speed in code but when I go to assign the speed it tells me to force close and i do not understand why. Here is the code: MainGame Code: @Override protected void onDraw(Canvas canvas) { setBlockSpeed(getWidth()); } private int blockSpeed; private void setBlockSpeed(int screenWidth){ Log.d(TAG, "screenWidth " + screenWidth); blockSpeed = screenWidth / 100; // 100 is the FPS.. i want it to take 1 second to pass the screen Math.round(blockSpeed); // to make it a whole number block.speed = blockSpeed; // this is line 318!! if i put eg block.speed = 8; it still tells me to force close } Block.java Code: public int speed; public void draw(Canvas canvas) { canvas.drawBitmap(bitmap, x - (bitmap.getWidth() / 2), y - (bitmap.getHeight() / 2), null); if(dontmove == 0){ this.x -= speed; // if it was eg this.x -= 18; it would not have an error } } The exception 06-08 13:22:34.315: E/AndroidRuntime(2801): FATAL EXCEPTION: Thread-11 06-08 13:22:34.315: E/AndroidRuntime(2801): java.lang.NullPointerException 06-08 13:22:34.315: E/AndroidRuntime(2801): at com.charltonsantana.game.MainGame.setBlockSpeed(MainGame.java:318) 06-08 13:22:34.315: E/AndroidRuntime(2801): at com.charltonsantana.game.MainGame.onDraw(MainGame.java:351) 06-08 13:22:34.315: E/AndroidRuntime(2801): at com.charltonsantana.game.MainThread.run(MainThread.java:64)

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• Using a permutation table for simplex noise without storing it

  - by J. C. Leitão

  Generating Simplex noise requires a permutation table for randomisation (e.g. see this question or this example). In some applications, we need to persist the state of the permutation table. This can be done by creating the table, e.g. using def permutation_table(seed): table_size = 2**10 # arbitrary for this question l = range(1, table_size + 1) random.seed(seed) # ensures the same shuffle for a given seed random.shuffle(l) return l + l # see shared link why l + l; is a detail and storing it. Can we avoid storing the full table by generating the required elements every time they are required? Specifically, currently I store the table and call it using table[i] (table is a list). Can I avoid storing it by having a function that computes the element i, e.g. get_table_element(seed, i). I'm aware that cryptography already solved this problem using block cyphers, however, I found it too complex to go deep and implement a block cypher. Does anyone knows a simple implementation of a block cypher to this problem?

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• Why does my player stop when stepping onto a new tile?

  - by user220631

  Me and my friend are creating a game from scratch. He is in charge of art design and I am in charge of coding. I have done well so far with the code, but I have a collision detection problem when the character moves right: Once the player moves right, whenever a new block is encountered, the player stops. I don't know if this is a problem with collision or the player but I can't work around it. Here is the collision code: this.IsColliding = function(obj) { if(this.X > obj.X + obj.Width) return false; else if(this.X + this.Width < obj.X) return false; else if(this.Y > obj.Y + obj.Height) return false; else if(this.Y + this.Height < obj.Y) return false; else return true; } I also wanted to see if there as a way to make the player collide with the bottom of the block and the right side of the block instead of running through it.

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• How to improve Minecraft-esque voxel world performance?

  - by SomeXnaChump

  After playing Minecraft I marveled a bit at its large worlds but at the same time I found them extremely slow to navigate, even with a quad core and meaty graphics card. Now I assume Minecraft is fairly slow because: A) It's written in Java, and as most of the spatial partitioning and memory management activities happen in there, it would naturally be slower than a native C++ version. B) It doesn't partition its world very well. I could be wrong on both assumptions; however it got me thinking about the best way to manage large voxel worlds. As it is a true 3D world, where a block can exist in any part of the world, it is basically a big 3D array [x][y][z], where each block in the world has a type (i.e BlockType.Empty = 0, BlockType.Dirt = 1 etc.) Now, I am assuming to make this sort of world perform well you would need to: A) Use a tree of some variety (oct/kd/bsp) to split all the cubes out; it seems like an oct/kd would be the better option as you can just partition on a per cube level not a per triangle level. B) Use some algorithm to work out which blocks can currently be seen, as blocks closer to the user could obfuscate the blocks behind, making it pointless to render them. C) Keep the block object themselves lightweight, so it is quick to add and remove them from the trees. I guess there is no right answer to this, but I would be interested to see peoples' opinions on the subject. How would you improve performance in a large voxel-based world?

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• UFW blocking random packets on 443

  - by s2jcpete

  All, I have UFW setup to allow traffic on port 443. It works as expected, though I have a large amount of UFW Block log entries. To Action From -- ------ ---- 80 ALLOW Anywhere 443 ALLOW Anywhere 22222 ALLOW Anywhere 80 ALLOW Anywhere (v6) 443 ALLOW Anywhere (v6) 22222 ALLOW Anywhere (v6) However in my syslog file I see this: [UFW BLOCK] IN=eth0 OUT= MAC=XXX SRC=<foreignip> DST=<serverip> LEN=40 TOS=0x00 PREC=0x00 TTL=116 ID=22025 DF PROTO=TCP SPT=49622 DPT=443 WINDOW=0 RES=0x00 ACK RST URGP=0 About 30 or so seconds later pound (which I'm using for SSL decryption and port redirection) throws a connection timed out messsage. I'm assuming this is because UFW is blocking the packet. I'm at a loss as to an explination. Could the packet be malformed or something, is this normal? Edit - I have since changed the /etc/defaults/ufw and set ipv6=no, so the v6 rules are no longer in the mix. The server is still showing the block / connection timed out behavior though. The new ufw status output is: Status: active Logging: on (low) Default: deny (incoming), allow (outgoing) New profiles: skip To Action From -- ------ ---- 80 ALLOW IN Anywhere 443 ALLOW IN Anywhere 22222 ALLOW IN Anywhere

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• Collision detection between a sprite and rectangle in canvas

  - by Andy

  I'm building a Javascript + canvas game which is essentially a platformer. I have the player all set up and he's running, jumping and falling, but I'm having trouble with the collision detection between the player and blocks (the blocks will essentially be the platforms that the player moves on). The blocks are stored in an array like this: var blockList = [[50, 400, 100, 100]]; And drawn to the canvas using this: this.draw = function() { c.fillRect(blockList[0][0], blockList[0][1], 100, 100); } I'm checking for collisions using something along these lines in the player object: this.update = function() { // Check for collitions with blocks for(var i = 0; i < blockList.length; i++) { if((player.xpos + 34) > blockList[i][0] && player.ypos > blockList[i][1]) { player.xpos = blockList[i][0] - 28; return false; } } // Other code to move the player based on keyboard input etc } The idea is if the player will collide with a block in the next game update (the game uses a main loop running at 60Htz), the function will return false and exit, thus meaning the player won't move. Unfortunately, that only works when the player hits the left side of the block, and I can't work out how to make it so the player stops if it hits any side of the block. I have the properties player.xpos and player.ypos to help here.

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• Movement on the X an Z axis are combined?

  - by Magicaxis

  This is probably a stupid question, but I'm trying to simply move a 3D object up, down, left, and right (Not forward or backward). The Y axis works fine, but when I increment the object's X position, the object moves BOTH right and backwards! when I decrement X, left and forwards! setPosition(getPosition().X + 2/*times deltatime*/, getPosition().Y, getPosition().Z); I was astonished that XNA doesnt have its own setPosition function, so I made a parent class for all objects with a setPosition and Draw function. Setposition simply edits a variable "mPosition" and passes it to the common draw function: // Copy any parent transforms. Matrix[] transforms = new Matrix[block.Bones.Count]; block.CopyAbsoluteBoneTransformsTo(transforms); // Draw the model. A model can have multiple meshes, so loop. foreach (ModelMesh mesh in block.Meshes) { // This is where the mesh orientation is set, as well // as our camera and projection. foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.World = transforms[mesh.ParentBone.Index] * Matrix.CreateRotationY(MathHelper.ToRadians(mOrientation.Y)) * Matrix.CreateTranslation(mPosition); effect.View = game1.getView(); effect.Projection = game1.getProjection(); } // Draw the mesh, using the effects set above. mesh.Draw(); } I tried to work it out by attempting to increment and decrement the Z axis, but nothing happens?! So using the X axis changes the objects x and z axis', but changing the Z does nothing. Great. So how do I seperate the X and Z axis movement?

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• What is the best way to manage large 3d worlds (i.e minecraft style)?

  - by SomeXnaChump

  After playing minecraft I was marvelling a bit at their large worlds but at the same time finding it extremely slow to navigate, even with a quad core and meaty graphics card. Now I assume its fairly slow because: A) Its written in Java, and as most of the actual spatial partitioning and other memory management activities happen in there it would be slower than a native C++ version. B) They are not partitioning their world very well I could be wrong on both assumptions, however it got me thinking about the best way to manage large worlds. As it is more of a true 3d world, where a block can exist in any part of the world, it is basically a big 3d array [x][y][z], where each block in the world has a type (i.e BlockType.Empty = 0, BlockType.Dirt = 1 etc). Now I am assuming to make this sort of world performant you would need to: a) Use a tree of some variety (oct/kd/bsp) to split all the cubes out, it seems like an oct/kd would be the better option as you can just partition on a per cube level not a per triangle level. b) Use some algorithm to work out if the blocks within the scene can currently be seen, as blocks closer to the user could obfuscate the blocks behind, making it pointless to render them. c) Keep the block object themselves lightweight, so it is quick to add and remove them from the trees I guess there is no right answer to this, but I would be interested to see peoples opinions on the subject.

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• GWB | 30 Posts in 60 Days Update

  - by Staff of Geeks

  One month after the contest started, we definitely have some leaders and one blogger who has reached the mark.  Keep up the good work guys, I have really enjoyed the content being produced by our bloggers. Current Winners: Enrique Lima (37 posts) - http://geekswithblogs.net/enriquelima Almost There: Stuart Brierley (28 posts) - http://geekswithblogs.net/StuartBrierley Dave Campbell (26 posts) - http://geekswithblogs.net/WynApseTechnicalMusings Eric Nelson (23 posts) - http://geekswithblogs.net/iupdateable Coming Along: Liam McLennan (17 posts) - http://geekswithblogs.net/liammclennan Christopher House (13 posts) - http://geekswithblogs.net/13DaysaWeek mbcrump (13 posts) - http://geekswithblogs.net/mbcrump Steve Michelotti (10 posts) - http://geekswithblogs.net/michelotti Michael Freidgeim (9 posts) - http://geekswithblogs.net/mnf MarkPearl (9 posts) - http://geekswithblogs.net/MarkPearl Brian Schroer (8 posts) - http://geekswithblogs.net/brians Chris Williams (8 posts) - http://geekswithblogs.net/cwilliams CatherineRussell (7 posts) - http://geekswithblogs.net/CatherineRussell Shawn Cicoria (7 posts) - http://geekswithblogs.net/cicorias Matt Christian (7 posts) - http://geekswithblogs.net/CodeBlog James Michael Hare (7 posts) - http://geekswithblogs.net/BlackRabbitCoder John Blumenauer (7 posts) - http://geekswithblogs.net/jblumenauer Scott Dorman (7 posts) - http://geekswithblogs.net/sdorman   Technorati Tags: Standings,Geekswithblogs,30 in 60

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• Django - I got TemplateSyntaxError when I try open the admin page. (http://DOMAIN_NAME/admin)

  - by user140827

  I use grappelly plugin. When I try open the admin page (/admin) I got TemplateSyntaxError. It says 'get_generic_relation_list' is invalid block tag. TemplateSyntaxError at /admin/ Invalid block tag: 'get_generic_relation_list', expected 'endblock' Request Method: GET Request URL: http://DOMAIN_NAME/admin/ Django Version: 1.4 Exception Type: TemplateSyntaxError Exception Value: Invalid block tag: 'get_generic_relation_list', expected 'endblock' Exception Location: /opt/python27/django/1.4/lib/python2.7/site-packages/django/template/base.py in invalid_block_tag, line 320 Python Executable: /opt/python27/django/1.4/bin/python Python Version: 2.7.0 Python Path: ['/home/vhosts/DOMAIN_NAME/httpdocs/media', '/home/vhosts/DOMAIN_NAME/private/new_malinnikov/lib', '/home/vhosts/DOMAIN_NAME/httpdocs/', '/home/vhosts/DOMAIN_NAME/private/new_malinnikov', '/home/vhosts/DOMAIN_NAME/private/new_malinnikov', '/home/vhosts/DOMAIN_NAME/private', '/opt/python27/django/1.4', '/home/vhosts/DOMAIN_NAME/httpdocs', '/opt/python27/django/1.4/lib/python2.7/site-packages/setuptools-0.6c12dev_r88846-py2.7.egg', '/opt/python27/django/1.4/lib/python2.7/site-packages/pip-0.8.1-py2.7.egg', '/opt/python27/django/1.4/lib/python27.zip', '/opt/python27/django/1.4/lib/python2.7', '/opt/python27/django/1.4/lib/python2.7/plat-linux2', '/opt/python27/django/1.4/lib/python2.7/lib-tk', '/opt/python27/django/1.4/lib/python2.7/lib-old', '/opt/python27/django/1.4/lib/python2.7/lib-dynload', '/opt/python27/lib/python2.7', '/opt/python27/lib/python2.7/plat-linux2', '/opt/python27/lib/python2.7/lib-tk', '/opt/python27/django/1.4/lib/python2.7/site-packages', '/opt/python27/lib/python2.7/site-packages/setuptools-0.6c11-py2.7.egg', '/opt/python27/lib/python2.7/site-packages/flup-1.0.3.dev_20100525-py2.7.egg', '/opt/python27/lib/python2.7/site-packages/virtualenv-1.5.1-py2.7.egg', '/opt/python27/lib/python2.7/site-packages/SQLAlchemy-0.6.4-py2.7.egg', '/opt/python27/lib/python2.7/site-packages/SQLObject-0.14.1-py2.7.egg', '/opt/python27/lib/python2.7/site-packages/FormEncode-1.2.3dev-py2.7.egg', '/opt/python27/lib/python2.7/site-packages/MySQL_python-1.2.3-py2.7-linux-x86_64.egg', '/opt/python27/lib/python2.7/site-packages/psycopg2-2.2.2-py2.7-linux-x86_64.egg', '/opt/python27/lib/python2.7/site-packages/pysqlite-2.6.0-py2.7-linux-x86_64.egg', '/opt/python27/lib/python2.7/site-packages', '/opt/python27/lib/python2.7/site-packages/PIL'] Server time: ???, 7 ??? 2012 04:19:42 +0700 Error during template rendering In template /home/vhosts/DOMAIN_NAME/httpdocs/templates/grappelli/admin/base.html, error at line 28 Invalid block tag: 'get_generic_relation_list', expected 'endblock' 18 <!--[if lt IE 8]> 19 <script src="http://ie7-js.googlecode.com/svn/version/2.0(beta3)/IE8.js" type="text/javascript"></script> 20 <![endif]--> 21 {% block javascripts %} 22 <script type="text/javascript" src="{% admin_media_prefix %}jquery/jquery-1.3.2.min.js"></script> 23 <script type="text/javascript" src="{% admin_media_prefix %}js/admin/Bookmarks.js"></script> 24 <script type="text/javascript"> 25 // Admin URL 26 var ADMIN_URL = "{% get_admin_url %}"; 27 // Generic Relations 28 {% get_generic_relation_list %} 29 // Get Bookmarks 30 $(document).ready(function(){ 31 $.ajax({ 32 type: "GET", 33 url: '{% url grp_bookmark_get %}', 34 data: "path=" + escape(window.location.pathname + window.location.search), 35 dataType: "html", 36 success: function(data){ 37 $('ul#bookmarks').replaceWith(data); 38 }

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• Troubles with list "dropdowns" and which list item gets the dropdown

  - by Andrew

  I'm working on a project for an MMO "guild" that gives members of the guild randomly generated tasks for the game. They can "block" three tasks from being assigned. The lists will look something like this: <ul> <li class="blocked">Task that is blocked</li> <li class="blocked-open">Click to block a task</li> <li class="blocked-open">Click to block a task</li> </ul> The blocked-open class means they haven't chosen a task to block yet. The blocked task means they've already blocked a task. When they click the list item, I want this to appear: <ul class="tasks-dropdown no-display"> <li><h1>Click a Task to Block</h1></li> <ul class="task-dropdown-inner"> <?php //output all tasks foreach($tasks as $task) { echo '<li class="blocked-option"><span id="'.$task.'">'.$task.'</span></li>'; } ?> <br class="clear" /> </ul> </ul> I don't quite know how, when the user clicks the .blocked-open line-item, to show that dropdown under only the one they clicked. My jQuery looked like this before I became confused. $("li.blocked-open").click(function() { $("ul.no-display").slideToggle("900"); }); $(".blocked-option span").click(function() { var task = $(this).attr('id'); alert("You have blocked: " + task); location.reload(true); }); I tested it by putting the dropdown under a line item in the code, and it worked fine, but when I have more than one dropdown in the code, clicking on one line item toggles all the dropdowns. I'm not sure what to do. :-p.

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• How to calculate the time difference between two time fields , with respect to the date changes

  - by Tiru

  I want to calculate the time difference.I have three EditTexts , I want to input the times in the first two edittexts in HH:MM format. And then calculate the time difference and the result will show on third edittext field in same format. If the date changes, the time difference will calculate according that, i.e If first time = 23:00 and second time = 01:00 then, the time difference = 02:00 hours public class TimeCalculate extends Activity { private String mBlock; private String mBlockoff; private String mBlockon ; // String mHours, mMinutes; Date date1, date2; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); EditText blockoff = (EditText) findViewById(R.id.blockoff); mBlockoff = blockoff.getText().toString(); EditText blockon = (EditText) findViewById(R.id.blockon); mBlockon = blockon.getText().toString(); SimpleDateFormat simpleDateFormat = new SimpleDateFormat("hh:mm"); try { date1 = simpleDateFormat.parse(mBlockoff); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } try { date2 = simpleDateFormat.parse(mBlockon); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } mBlock = getDifference(date1, date2); EditText block = (EditText) findViewById(R.id.block); block.setText(mBlock.toString()); } public static String getDifference(Date startTime, Date endTime) { if (startTime == null) return "corrupted"; Calendar startDateTime = Calendar.getInstance(); startDateTime.setTime(startTime); Calendar endDateTime = Calendar.getInstance(); endDateTime.setTime(endTime); long milliseconds1 = startDateTime.getTimeInMillis(); long milliseconds2 = endDateTime.getTimeInMillis(); long diff = milliseconds2 - milliseconds1; /*int hours = (int)diff / (60 * 60 * 1000); int minutes = (int) (diff / (60 * 1000)); minutes = minutes - 60 * hours; long seconds = diff / (1000); */ //timeDiff = DateUtils.formatElapsedTime(seconds); SimpleDateFormat simpleDateFormat = new SimpleDateFormat("HH:MM"); Date date = new Date(diff); return simpleDateFormat.format(date); } } I executed this code ,but gives error as Source not found.I think error at getDifference method.Please give any other logic

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• make img height 100% of td

  - by kristina childs

  I'm creating an HTML email and since background images can't be used on anything but <body> thought I could get around this by making a border image 100% height within a cell. Perhaps it was wishful thinking? I've searched at the solutions that worked in the past no longer work in modern browsers. Is there any special trick to making this happen without setting a hard height for the cell? Here are the things I've tried so far: <td width="25" style="margin:0; padding:0;"> <img src="http://www.mysite.com/images/side-left.jpg" width="25" height="100%" alt="border" style="margin:0; padding:0; display: block;" /> </td> stretches the image to 100% height of the entire table (even though the table is nested in a <td width="25" height="100%" style="margin:0; padding:0;"> <div style="height:100%; diplay: block;"> <img src="http://www.mysite.com/images/side-left.jpg" width="25" height="100%" alt="border" style="margin:0; padding:0; display: block;" /> </div> </td> ditto <td width="25" height="1" style="margin:0; padding:0;"> <div style="height:100%; diplay: block;"> <img src="http://www.mysite.com/images/side-left.jpg" width="25" height="100%" alt="border" style="margin:0; padding:0; display: block;" /> </div> </td> setting a smaller td size does not force it to strectch as expected. bummer.

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