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• What is a de-compiler how does it work?

  - by thyrgle

  So is a decompiler really a thing that gives gives the source of a compiled/interpreted piece of code? Because to me that sounds impossible. How would you get the names of the functions, variables, classes, etc if it is compiled. Or am I misinterpreting the definition? How does it work? And what is the general principal behind making one?

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• Javascript self contained sandbox events and client side stack

  - by amnon

  I'm in the process of moving a JSF heavy web application to a REST and mainly JS module application . I've watched "scalable javascript application architecture" by Nicholas Zakas on yui theater (excellent video) and implemented much of the talk with good success but i have some questions : I found the lecture a little confusing in regards to the relationship between modules and sandboxes , on one had to my understanding modules should not be effected by something happening outside of their sandbox and this is why they publish events via the sandbox (and not via the core as they do access the core for hiding base libary) but each module in the application gets a new sandbox ? , shouldn't the sandbox limit events to the modoules using it ? or should events be published cross page ? e.g. : if i have two editable tables but i want to contain each one in a different sandbox and it's events effect only the modules inside that sandbox something like messabe box per table which is a different module/widget how can i do that with sandbox per module , ofcourse i can prefix the events with the moduleid but that creates coupling that i want to avoid ... and i don't want to package modules toghter as one module per combination as i already have 6-7 modules ? while i can hide the base library for small things like id selector etc.. i would still like to use the base library for module dependencies and resource loading and use something like yui loader or dojo.require so in fact i'm hiding the base library but the modules themself are defined and loaded by the base library ... seems a little strange to me libraries don't return simple js objects but usualy wrap them e.g. : u can do something like $$('.classname').each(.. which cleans the code alot , it makes no sense to wrap the base and then in the module create a dependency for the base library by executing .each but not using those features makes a lot of code written which can be left out ... and implemnting that functionality is very bug prone does anyonen have any experience with building a front side stack of this order ? how easy is it to change a base library and/or have modules from different libraries , using yui datatable but doing form validation with dojo ... ? some what of a combination of 2+4 if u choose to do something like i said and load dojo form validation widgets for inputs via yui loader would that mean dojocore is a module and the form module is dependant on it ? Thanks .

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• SpringBatch Jaxb2Marshaller: different name of class and xml attribute

  - by user588961

  I try to read an xml file as input for spring batch: Java Class: package de.example.schema.processes.standardprocess; @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "Process", namespace = "http://schema.example.de/processes/process", propOrder = { "input" }) public class Process implements Serializable { @XmlElement(namespace = "http://schema.example.de/processes/process") protected ProcessInput input; public ProcessInput getInput() { return input; } public void setInput(ProcessInput value) { this.input = value; } } SpringBatch dev-job.xml: <bean id="exampleReader" class="org.springframework.batch.item.xml.StaxEventItemReader" scope="step"> <property name="fragmentRootElementName" value="input" /> <property name="resource" value="file:#{jobParameters['dateiname']}" /> <property name="unmarshaller" ref="jaxb2Marshaller" /> </bean> <bean id="jaxb2Marshaller" class="org.springframework.oxm.jaxb.Jaxb2Marshaller"> <property name="classesToBeBound"> <list> <value>de.example.schema.processes.standardprocess.Process</value> <value>de.example.schema.processes.standardprocess.ProcessInput</value> ... </list> </property> </bean> Input file: <?xml version="1.0" encoding="UTF-8"?> <process:process xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:process="http://schema.example.de/processes/process"> <process:input> ... </process:input> </process:process> It fires the following exception: [javax.xml.bind.UnmarshalException: unexpected element (uri:"http://schema.example.de/processes/process", local:"input"). Expected elements are <<{http://schema.example.de/processes/process}processInput] at org.springframework.oxm.jaxb.JaxbUtils.convertJaxbException(JaxbUtils.java:92) at org.springframework.oxm.jaxb.AbstractJaxbMarshaller.convertJaxbException(AbstractJaxbMarshaller.java:143) at org.springframework.oxm.jaxb.Jaxb2Marshaller.unmarshal(Jaxb2Marshaller.java:428) If I change to in xml it work's fine. Unfortunately I can change neither the xml nor the java class. Is there a possibility to make Jaxb2Marshaller map the element 'input' to the class 'ProcessInput'?

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• Calling methods in super class constructor of subclass constructor?

  - by deamon

  Calling methods in super class constructor of subclass constructor? Passing configuration to the __init__ method which calls register implicitely: class Base: def __init__(self, *verbs=("get", "post")): self._register(verbs) def _register(self, *verbs): pass class Sub(Base): def __init__(self): super().__init__("get", "post", "put") Or calling register explicitely in the subclass' __init__ method: class Base: def __init__(self): self._register("get", "post") def _register(self, *verbs): pass class Sub(Base): def __init__(self): _register("get", "post", "put") What is better or more pythonic? Or is it only a matter of taste?

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• How can I inherit an ASP.NET MVC controller and change only the view?

  - by AlexWalker

  I have a controller that's inheriting from a base controller, and I'm wondering how I can utilize all of the logic from the base controller, but return a different view than the base controller uses. The base controller populates a model object and passes that model object to its view, but I'm not sure how I can access that model object in the child controller so that I can pass it to the child controller's view.

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• HTML/CSS: Keep the same height between the backgrounds of a term-description pair in a table-like de

  - by peroyomas

  I want to format a definition list in HTML as if it were a table with th in a column and td in another, with a background that alternates per row (although a background for the dt and another for the dd also fits for the problem), so I have this CSS: dl { font-family: Verdana, Geneva, sans-serif; font-size: 0.6em; overflow: hidden; width: 200px;; } dl dt { font-weight: bold; float: left; clear: left; padding-right: 1%; width: 48%; } dl dt:nth-of-type(odd), dl dd:nth-of-type(odd) { background-color: #EEE; } dl dt:nth-of-type(even), dl dd:nth-of-type(even) { background-color: #DDD; } dl dd { float: left; width: 50%; padding-left: 1%; margin-left: 0; } Example HTML: <dl> <dt>Key 1</dt> <dd>Value 1</dd> <dt>Very very very long key 2 </dt> <dd>Value 2</dd> <dt>Key 3</dt> <dd>Value 3 with<br /> line breaks</dd> <dt>Key 4</dt> <dd>Value 4</dd> </dl> The problem is that, due to the eventual height dissimilarity, "holes" with no background appears in the list: Is there a way to fix that?

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• No more memory available in Mathematica, Fit the parameters of system of differential equation

  - by user1058051

  I encountered a memory problem in Mathematica, when I tried to process my experimental data. It's a system of two differential equations and I need to find most suitable parameters. Unfortunately I am not a Pro in Mathematica, so the program used a lot of memory, when the parameter epsilon is more than 0.4. When it less than 0.4, the program work properly. The command 'historylength = 0' and attempts to reduce the Accuracy Goal and WorkingPrecision didn`t help. I can't use ' clear Cache ', because there isnt a circle. I'm trying to understand what mistakes I made, and how I may limit the memory usage. I have already bought extra-RAM, now its 4GB, and now I haven't free memory-slots in motherboard Remove["Global`*"]; T=13200; L = 0.085; e = 0.41; v = 0.000557197; q = 0.1618; C0 = 0.0256; R = 0.00075; data = {{L,600,0.141124587},{L,1200,0.254134509},{L,1800,0.342888644}, {L,2400,0.424476295},{L,3600,0.562844542},{L,4800,0.657111356}, {L,6000,0.75137817},{L,7200,0.815876516},{L,8430,0.879823594}, {L,9000,0.900771775},{L,13200,1}}; model[(De_)?NumberQ, (Kf_)?NumberQ, (Y_)?NumberQ] := model[De, Kf, Y] = yeld /.Last[Last[ NDSolve[{ v (Ci^(1,0))[z,t]+(Ci^(0,1))[z,t]== -((3 (1-e) Kf (Ci[z,t]-C0))/ (R e (1-(R Kf (1-R/r[z,t]))/De))), (r^(0,1))[z,t]== (R^2 Kf (Ci[z,t]-C0))/ (q r[z,t]^2 (1-(R Kf (1-R/r[z,t]))/De)), (yeld^(0,1))[z,t]== Y*(v e Ci[z,t])/(L q (1-e)), r[z,0]==R, Ci[z,0]==0, Ci[0,t]==0, yeld[z,0]==0}, {r[z,t],Ci[z,t],yeld},{z,0,L},{t,0,T}]]] fit = FindFit[data, {model[De, Kf, Y][z, t], {Y > 0.97, Y < 1.03, Kf > 10^-6, Kf < 10^-4, De > 10^-13, De < 10^-9}}, {{De,7*10^-13}, {Kf, 10^-5}, {Y, 1}}, {z, t}, Method -> NMinimize] data = {{600,0.141124587},{1200,0.254134509},{1800,0.342888644}, {2400,0.424476295},{3600,0.562844542},{4800,0.657111356}, {6000,0.75137817},{7200,0.815876516},{8430,0.879823594}, {9000,0.900771775},{13200,1}}; YYY = model[ De /. fit[[1]], Kf /. fit[[2]], Y /. fit[[3]]]; Show[Plot[Evaluate[YYY[L,t]],{t,0,T},PlotRange->All], ListPlot[data,PlotStyle->Directive[PointSize[Medium],Red]]] the link on the .nb file http://www.4shared.com/folder/249TSjlz/_online.html

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• Is there a standard SQL Table design for overriding 'big picture' default values with lower level de

  - by RichardHowells

  Here's an example. Suppose we are trying to calculate a service charge. Say sales in the USA attract a 10 dollar charge, sales in the UK attract a 20 dollar charge So far it's easy - we are starting to imagine a table that lists charges by country. Now lets assume that Alaska and Hawaii are treated as special cases they are both 15 dollars That suggests a table with states, Alaska and Hawaii are charged at 15, but presumably we need 48 (redundant) rows all saying 10. This gives us a maintainance problem, our user only wants to type 10 once NOT 48 times. It does not sit well with the UK either. The UK does not have states. Suppose we throw in another couple of cross cutting rules. If you order by phone there is a 10% supplement on the charge. If you order via the web there is a 10% discount. But for some reason best known to the owners of the business the web/phone supplement/discount are not applied in Hawaii. It seems to me that this is quite a common kind of problem and there is probably a well known arrangement of tables to store the data. Most cases get handled by broad brush answers, but there are some very detailed low level variations that give rise to a huge number of theoretical combinations, most of which are not used.

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• Why de methods contains(), indexOf() in a Java Collection use o.equals(e) and not e.equals(0)?

  - by Fernando

  anyone know the reasons of that??

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• T-SQL 2005 - Divide by zero error encountered

  - by Grant

  Hi, I am trying to get some percentage data from a stored procedure using code similar to the line below. Obviously this is going to cause a (Divide by zero error encountered) problem when base.[XXX_DataSetB] returns 0 which may happen some of the time. Does anyone know how i can deal with this in the most efficient manner? Note: There would be about 20+ lines looking like the one below... cast((base.[XXX_DataSetB] - base.[XXX_DataSetA]) as decimal) / base.[XXX_DataSetB] as [XXX_Percentage]

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• ListView Final Column Autosize creates scrollbar

  - by Courtney de Lautour

  Hi There, I am implementing a custom control which derives from ListView. I would like for the final column to fill the remaining space (Quite a common task), I have gone about this via overriding the OnResize method: protected override void OnResize(EventArgs e) { base.OnResize(e); if (Columns.Count == 0) return; Columns[Columns.Count - 1].Width = -2; // -2 = Fill remaining space } or via another method: protected override void OnResize(EventArgs e) { base.OnResize(e); if (!_autoFillLastColumn) return; if (Columns.Count == 0) return; int TotalWidth = 0; int i = 0; for (; i < Columns.Count - 1; i++) { TotalWidth += Columns[i].Width; } Columns[i].Width = this.DisplayRectangle.Width - TotalWidth; } Edit: This works fine until I dock the ListView into a parent container and resize via that control. Every second time the control size shrinks (IE, drag the the border one pixel), I get a scroll bar on the bottom which can't move at all (not even one pixel). The result of which is when I drag the size of the parent I am left with a flickering scroll bar in the ListView, and a 50% chance it will be there when the dragging stops.

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• Call a dynamically generated method on a ILGenerator on the same type

  - by Thiado de Arruda

  Normally, when I want to call a dynamic method in another ILGenerator object that is writing a method on the same type I do the following : generator.Emit(OpCodes.Ldarg_0); // reference to the current object generator.Emit(OpCodes.Ldstr, "someArgument"); generator.Emit(OpCodes.Call, methodBuilder); //this methodbuilder is also defined on this dynamic type. However, I faced the following problem: I cant have a reference to the methodbuilder of the method I want to call, because it is generated by another framework(I only get a reference to the current TypeBuilder). This method is defined as protected virtual(and overriden on the methodbuilder I cant get a reference to) in the base class of the current dynamic type and I can get a reference to it by doing this : generator.Emit(OpCodes.Ldarg_0); // reference to the current object generator.Emit(OpCodes.Ldstr, "someArgument"); generator.Emit(OpCodes.Call, baseType.GetMethod("SomeMethodDefinedInBaseClassThatWasOverridenInThisDynamicType")); The problem is that this calls the method on the base type and not the overriden method. Is there any way I can get a reference to a methodbuilder only having a reference to the typebuilder that defined it? Or is there a way to call a method using ILGenerator without having to pass the 'MethodInfo' object to it?

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• How To Clear An Alert - Part 2

  - by werner.de.gruyter

  There were some interesting comments and remarks on the original posting, so I decided to do a follow-up and address some of the issues that got raised... Handling Metric Errors First of all, there is a significant difference between an 'error' and an 'alert'. An 'alert' is the violation of a condition (a threshold) specified for a given metric. That means that the Agent is collecting and gathering the data for the metric, but there is a situation that requires the attention of an administrator. An 'error' on the other hand however, is a failure to collect metric data: The Agent is throwing the error because it cannot determine the value for the metric Whereas the 'alert' guarantees continuity of the metric data, an 'error' signals a big unknown. And the unknown aspect of all this is what makes an error a lot more serious than a regular alert: If you don't know what the current state of affairs is, there could be some serious issues brewing that nobody is aware of... The life-cycle of a Metric Error Clearing a metric error is pretty much the same workflow as a metric 'alert': The Agent signals the error after it failed to execute the metric The error is uploaded to the OMS/repository, where it becomes visible in the Console The error will remain active until the Agent is able to execute the metric successfully. Even though the metric is still getting scheduled and executed on a regular basis, the error will remain outstanding as long as the Agent is not capable of executing the metric correctly Knowing this, the way to fix the metric error should be obvious: Take the 'problem' away, and as soon as the metric is executed again (based on the frequency of the metric), the error will go away. The same tricks used to clear alerts can be used here too: Wait for the next scheduled execution. For those metrics that are executed regularly (like every 15 minutes or so), it's just a matter of waiting those minutes to see the updates. The 'Reevaluate Alert' button can be used to force a re-execution of the metric. In case a metric is executed once a day, this will be a better way to make sure that the underlying problem has been solved. And if it has been, the metric error will be removed, and the regular data points will be uploaded to the repository. And just in case you have to 'force' the issue a little: If you disable and re-enable a metric, it will get re-scheduled. And that means a new metric execution, and an update of the (hopefully) fixed problem. Database server-generated alerts and problem checkers There are various ways the Agent can collect metric data: Via a script or a SQL statement, reading a log file, getting a value from an SNMP OID or listening for SNMP traps or via the DBMS_SERVER_ALERTS mechanism of an Oracle database. For those alert which are generated by the database (like tablespace metrics for 10g and above databases), the Agent just 'waits' for the database to report any new findings. If the Agent has lost the current state of the server-side metrics (due to an incomplete recovery after a disaster, or after an improper use of the 'emctl clearstate' command), the Agent might be still aware of an alert that the database no longer has (or vice versa). The same goes for 'problem checker' alerts: Those metrics that only report data if there is a problem (like the 'invalid objects' metric) will also have a problem if the Agent state has been tampered with (again, the incomplete recovery, and after improper use of 'emctl clearstate' are the two main causes for this). The best way to deal with these kinds of mismatches, is to simple disable and re-enable the metric again: The disabling will clear the state of the metric, and the re-enabling will force a re-execution of the metric, so the new and updated results can get uploaded to the repository. Starting 10gR5, the Agent performs additional checks and verifications after each restart of the Agent and/or each state change of the database (shutdown/startup or failover in case of DataGuard) to catch these kinds of mismatches.

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• index.html redirecting to cgi-sys/defaultwebpage.cgi

  - by Andrew De Forest

  This problem has been persisting over the last couple of days. I thought I fixed it Friday only to get in on Monday morning and see that cPanel is still giving me issues. On Friday, all incoming traffic to my index.html page were being redirected to cgi-sys/defaultwebpage.cgi. Upon further investigation, I found that my entire index.html code had been overwritten and contained only a single meta tag, which was causing the aforementioned redirect. I re-uploaded the original index page and overwrote the one that was causing the redirects and it seemed to have fixed the problem. Fast forward to Monday. The problem began happening again and I took the same steps as before to fix it, but now I'm wondering how to permanently stop this from happening. From what I've found, it's related to cPanel. I personally did not make any changes to the server, but there are a few people with access who might have. I'm on a VPS with my own dedicated IP address. I've been hosting fine for a few months without this problem. The server is runs a traditional LAMP stack.

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• Abstracting away the type of a property

  - by L. De Leo

  In Python luckily most of the times you don't have to write getters and setters to get access to class properties. That said sometimes you'll have to remember that a certain property is a list or whatnot and a property would save you there by abstracting the type and providing a setter to add something to such list for example rather than exposing the list directly. Where do you draw the line between exposing the type directly or wrapping its access in a property? What's the general "pythonic" advice?

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• Pyglet vs. PyQt

  - by L. De Leo

  I need to implement a really simple card game. As the game logic is written in Python I chose to stick with some Python framework even if my goal is to develop a Windows only version. I also don't like to work with .NET so I ruled out Iron Python + WPF. I tried to write a simple prototype with Pyglet but soon discovered that I will have to do a lot of stuff by hand: things like detecting mouseover events and finding which card was clicked on and moving it, etc... very low level and unnecessary for my use-case. So I thought it might be easier to do things in PyQt. Do you reckon it would be feasible to use PyQt for implementing a simple card game? Will I have higher level events I can work with?

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• black screen after waking up from suspend

  - by Daniel De Leon

  running 11.10 and on wake up after being suspended (for a long time or 2 seconds, doesn't matter) I am presented with a black screen that just has a purple bar (about the size of the top menu bar). As far as I can tell the system is unresponsive to anything outside of a manual restart by pressing the power button on the tower, after which it starts normally. using the most up to date graphics driver, also tried switching to a different version, nothing. just switched back to Linux and this is really giving me a headache, I would really like this to work. Any help would be greatly appreciated.

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• Something to add to your library...

  - by werner.de.gruyter

  There is a new book in town: The Grid Control Handbook. Featuring an in-depth discussion of what Grid Control is and what Grid Control can do for your IT environment. It starts right at the beginning, and guides you through the all steps of a typical deployment: From the planning phase, to installing, to the strengthening of the environment and finally (most importantly) the maintenance and daily-use of the product. And there are quite a few tips, tricks, workshops and best practices along the way to help you with some very practical day-to-day challenges. For all those using Grid Control, something definitely worth checking out!

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• Can find any /.ecryptfs dir to retrieve my encrypted home dir

  - by Roberto de Armas

  At firs sorry for my english, it isn't my native languaje. I've readed some questions similar but no the exactly whith the same problem. I've moved my home directory to a separated partitión (Ubuntu 11.10) following this tutorial http://www.ubuntu-es.org/node/58233 After checking that they were all my files and folders (forgetting that one of dirs was encrypted by ecryptfs) i've installed fedora 16. Well, suprised when in my home folder was an Readme.txt advising me that my folder was unmounted for security reasons and proposing to type in comand line "ecryptfs-mount-Private" (din't work) or make click on labeled icon "acces your private data desktop" (neither din't work). After three days reading all i could find on the internet, i follow The Dustin Kirkland tutorial in http://blog.dustinkirkland.com/2011/04/introducing-ecryptfs-recover-private.html, but any /.ecryptfs was found. I'm sure that the data are somewere (the size of the moved dir is identical to the original one). Any help would by greatly appreciated. Thaks a lot.

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• Should devs, testers and business users have one unified test script?

  - by Carlos Jaime C. De Leon

  In development, I would normally have my own test scripts that would document the data, scenarios and execution steps that I plan to test; this is my dev test plan. When the functionality has been deployed to Test, testers test it using their own test script that they wrote. In UAT, the business user then tests using their own test plan. In retrospect, it looks like this provides a better coverage, with dev tests having a mix of black and white box testing, while testers and business users focus on black box testing. But on the other hand, this brings up distinct test cases that only are executed per stage (ie. some cases which testers thought of are only executed on Test stage) and it would like the dev missed it, which makes it a finding/bug. Is it worth consolidating the test scripts from the start? Thus using one unified test script, or is it abit difficult to do this upfront?

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• Why is Adobe Air so underrated for building mobile apps?

  - by Marcelo de Assis

  I worked with Adobe Flash related technologies for the last 5 years, although not being a big fan of Adobe. I see some little bugs happening in some apps, but I cannot imagine why a lot of big companies do not even think to use use Adobe Air as a good technology for their mobile apps. I see a lot of mobile developer positions asking for experts in Android or iOS , but very much less positions asking for Adobe Air, even when Adobe Air apps have the advantage of being multi-plataform, with the same app working in Blackberry, iOS and Android. Is so much easier to develop a game using Flash, than using Android SDK, for example. It really have flaws (that I never saw) or it is just some kind of mass prejudgement? I also would like to hear what a project manager or a indie developer takes when choosing a plataform for building apps.

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• Connect to new wireless network

  - by Shawn de Wet

  Wireless networking was working perfectly on my old adsl router. Then I moved to a new home that does not have adsl, and the router has been replaced with a new 3G one. I have worked through the following links: Connecting to a wireless network and http://ubuntuforums.org/showthread.php?t=571188 I have set the router from it's default WPA-PSK encryption to WEP encryption and also to No Encryption. But when I get to dhclient -wlan0, I keep getting No DHCPOFFERS received. Yet the 2 windows machines in my home connect fine to this wirelesss network (in all encryption settings). If I try iwlist scan I can see that the wireless network is indeed visible. Where do I start scratching to see where the problem may lie.

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• Firefox ignore GTK theme for localhost stuff

  - by Mario De Schaepmeester

  I know this is pretty much a duplicate of How can one make firefox ignore my GTK theme entirely?, but the answers on that one are no permanent solution. It works by launching firefox from the terminal. I would like to know a solution that works for every instance of firefox no matter how it was created. There is the possibility to edit the userContent.css file, but the settings you make randomly do not apply to some sites or in some situations, strangely, even with the !important added... I have a dark GTK theme and this results in some textboxes having a black background with black text with a userContent.css that has input, textarea { color: black !important; background-color: white !important; } Update I changed a setting in about:config from true to false, namely browser.display.use_system_colors. Everything appears normal and well now, for one exception: everything that runs on localhost. This includes PHPMyAdmin and a website I am making. I would like to know if there is a solution to this.

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• Accessing host LVM partition from Windows XP through Virt.manager 0.8.5 / Qemu / KVM

  - by Nico de Smidt

  Hi, requested use case is having a Windows XP SP3 guest running in 64bit Ubuntu. (Linux pcs 2.6.35-22-server #35-Ubuntu SMP Sat Oct 16 22:02:33 UTC 2010 x86_64 GNU/Linux) I want this guest to access an LVM LV on the Ubuntu disk. I've setup the following LVM config: --- Logical volume --- LV Name /dev/storage/sdc1 VG Name storage LV UUID Zg5IMC-OlqB-prL5-fgg4-3A9A-OgKP-oZ0QkJ LV Write Access read/write LV Status available # open 0 LV Size 1.01 GiB Current LE 259 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 251:3 -- 1) I've setup a storage pool for /dev/storage 2) I've mkfs.vfat /dev/storage/sdc1 3) and made a virtual IDE disk in the virt-manager setup for the guest. Target device: IDE Disk 2 Source path: /dev/storage/sdc1 -- Now when running XP (guest) Windows sees a new disk in Disk Manager and want's to install a partition on it, since it believes the drive is empty. After formatting from within Windows I can put data on the new disk volume. -- Back in Ubuntu however I cannot access this this any more since it created a partition within an LVM Logical Volume. Running fdisk -l shows the following: root@pcs:/media# fdisk -l /dev/storage/sdc1 Disk /dev/storage/sdc1: 1086 MB, 1086324736 bytes 32 heads, 63 sectors/track, 1052 cylinders Units = cylinders of 2016 * 512 = 1032192 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x8d72e4f4 Device Boot Start End Blocks Id System /dev/storage/sdc1p1 1 1050 1058368+ c W95 FAT32 (LBA) -- which seems fine to me, but when trying to mount /dev/storage/sdc1p1 I get the following error: mount /dev/storage/sdc1p1 /media/xp mount: special device /dev/storage/sdc1p1 does not exist which makes sense since in lvdisplay sdc1p1 does not exist Main question: I want to mount the vfat partition in both Ubuntu and XP What am I missing here????? regards, and thanks for your consideration. Nico

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• Ball bouncing at a certain angle and efficiency computations

  - by X Y

  I would like to make a pong game with a small twist (for now). Every time the ball bounces off one of the paddles i want it to be under a certain angle (between a min and a max). I simply can't wrap my head around how to actually do it (i have some thoughts and such but i simply cannot implement them properly - i feel i'm overcomplicating things). Here's an image with a small explanation . One other problem would be that the conditions for bouncing have to be different for every edge. For example, in the picture, on the two small horizontal edges i do not want a perfectly vertical bounce when in the middle of the edge but rather a constant angle (pi/4 maybe) in either direction depending on the collision point (before the middle of the edge, or after). All of my collisions are done with the Separating Axes Theorem (and seem to work fine). I'm looking for something efficient because i want to add a lot of things later on (maybe polygons with many edges and such). So i need to keep to a minimum the amount of checking done every frame. The collision algorithm begins testing whenever the bounding boxes of the paddle and the ball intersect. Is there something better to test for possible collisions every frame? (more efficient in the long run,with many more objects etc, not necessarily easy to code). I'm going to post the code for my game: Paddle Class public class Paddle : Microsoft.Xna.Framework.DrawableGameComponent { #region Private Members private SpriteBatch spriteBatch; private ContentManager contentManager; private bool keybEnabled; private bool isLeftPaddle; private Texture2D paddleSprite; private Vector2 paddlePosition; private float paddleSpeedY; private Vector2 paddleScale = new Vector2(1f, 1f); private const float DEFAULT_Y_SPEED = 150; private Vector2[] Normals2Edges; private Vector2[] Vertices = new Vector2[4]; private List<Vector2> lst = new List<Vector2>(); private Vector2 Edge; #endregion #region Properties public float Speed { get {return paddleSpeedY; } set { paddleSpeedY = value; } } public Vector2[] Normal2EdgesVector { get { NormalsToEdges(this.isLeftPaddle); return Normals2Edges; } } public Vector2[] VertexVector { get { return Vertices; } } public Vector2 Scale { get { return paddleScale; } set { paddleScale = value; NormalsToEdges(this.isLeftPaddle); } } public float X { get { return paddlePosition.X; } set { paddlePosition.X = value; } } public float Y { get { return paddlePosition.Y; } set { paddlePosition.Y = value; } } public float Width { get { return (Scale.X == 1f ? (float)paddleSprite.Width : paddleSprite.Width * Scale.X); } } public float Height { get { return ( Scale.Y==1f ? (float)paddleSprite.Height : paddleSprite.Height*Scale.Y ); } } public Texture2D GetSprite { get { return paddleSprite; } } public Rectangle Boundary { get { return new Rectangle((int)paddlePosition.X, (int)paddlePosition.Y, (int)this.Width, (int)this.Height); } } public bool KeyboardEnabled { get { return keybEnabled; } } #endregion private void NormalsToEdges(bool isLeftPaddle) { Normals2Edges = null; Edge = Vector2.Zero; lst.Clear(); for (int i = 0; i < Vertices.Length; i++) { Edge = Vertices[i + 1 == Vertices.Length ? 0 : i + 1] - Vertices[i]; if (Edge != Vector2.Zero) { Edge.Normalize(); //outer normal to edge !! (origin in top-left) lst.Add(new Vector2(Edge.Y, -Edge.X)); } } Normals2Edges = lst.ToArray(); } public float[] ProjectPaddle(Vector2 axis) { if (Vertices.Length == 0 || axis == Vector2.Zero) return (new float[2] { 0, 0 }); float min, max; min = Vector2.Dot(axis, Vertices[0]); max = min; for (int i = 1; i < Vertices.Length; i++) { float p = Vector2.Dot(axis, Vertices[i]); if (p < min) min = p; else if (p > max) max = p; } return (new float[2] { min, max }); } public Paddle(Game game, bool isLeftPaddle, bool enableKeyboard = true) : base(game) { contentManager = new ContentManager(game.Services); keybEnabled = enableKeyboard; this.isLeftPaddle = isLeftPaddle; } public void setPosition(Vector2 newPos) { X = newPos.X; Y = newPos.Y; } public override void Initialize() { base.Initialize(); this.Speed = DEFAULT_Y_SPEED; X = 0; Y = 0; NormalsToEdges(this.isLeftPaddle); } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); paddleSprite = contentManager.Load<Texture2D>(@"Content\pongBar"); } public override void Update(GameTime gameTime) { //vertices array Vertices[0] = this.paddlePosition; Vertices[1] = this.paddlePosition + new Vector2(this.Width, 0); Vertices[2] = this.paddlePosition + new Vector2(this.Width, this.Height); Vertices[3] = this.paddlePosition + new Vector2(0, this.Height); // Move paddle, but don't allow movement off the screen if (KeyboardEnabled) { float moveDistance = Speed * (float)gameTime.ElapsedGameTime.TotalSeconds; KeyboardState newKeyState = Keyboard.GetState(); if (newKeyState.IsKeyDown(Keys.Down) && Y + paddleSprite.Height + moveDistance <= Game.GraphicsDevice.Viewport.Height) { Y += moveDistance; } else if (newKeyState.IsKeyDown(Keys.Up) && Y - moveDistance >= 0) { Y -= moveDistance; } } else { if (this.Y + this.Height > this.GraphicsDevice.Viewport.Height) { this.Y = this.Game.GraphicsDevice.Viewport.Height - this.Height - 1; } } base.Update(gameTime); } public override void Draw(GameTime gameTime) { spriteBatch.Begin(SpriteSortMode.Texture,null); spriteBatch.Draw(paddleSprite, paddlePosition, null, Color.White, 0f, Vector2.Zero, Scale, SpriteEffects.None, 0); spriteBatch.End(); base.Draw(gameTime); } } Ball Class public class Ball : Microsoft.Xna.Framework.DrawableGameComponent { #region Private Members private SpriteBatch spriteBatch; private ContentManager contentManager; private const float DEFAULT_SPEED = 50; private float speedIncrement = 0; private Vector2 ballScale = new Vector2(1f, 1f); private const float INCREASE_SPEED = 50; private Texture2D ballSprite; //initial texture private Vector2 ballPosition; //position private Vector2 centerOfBall; //center coords private Vector2 ballSpeed = new Vector2(DEFAULT_SPEED, DEFAULT_SPEED); //speed #endregion #region Properties public float DEFAULTSPEED { get { return DEFAULT_SPEED; } } public Vector2 ballCenter { get { return centerOfBall; } } public Vector2 Scale { get { return ballScale; } set { ballScale = value; } } public float SpeedX { get { return ballSpeed.X; } set { ballSpeed.X = value; } } public float SpeedY { get { return ballSpeed.Y; } set { ballSpeed.Y = value; } } public float X { get { return ballPosition.X; } set { ballPosition.X = value; } } public float Y { get { return ballPosition.Y; } set { ballPosition.Y = value; } } public Texture2D GetSprite { get { return ballSprite; } } public float Width { get { return (Scale.X == 1f ? (float)ballSprite.Width : ballSprite.Width * Scale.X); } } public float Height { get { return (Scale.Y == 1f ? (float)ballSprite.Height : ballSprite.Height * Scale.Y); } } public float SpeedIncreaseIncrement { get { return speedIncrement; } set { speedIncrement = value; } } public Rectangle Boundary { get { return new Rectangle((int)ballPosition.X, (int)ballPosition.Y, (int)this.Width, (int)this.Height); } } #endregion public Ball(Game game) : base(game) { contentManager = new ContentManager(game.Services); } public void Reset() { ballSpeed.X = DEFAULT_SPEED; ballSpeed.Y = DEFAULT_SPEED; ballPosition.X = Game.GraphicsDevice.Viewport.Width / 2 - ballSprite.Width / 2; ballPosition.Y = Game.GraphicsDevice.Viewport.Height / 2 - ballSprite.Height / 2; } public void SpeedUp() { if (ballSpeed.Y < 0) ballSpeed.Y -= (INCREASE_SPEED + speedIncrement); else ballSpeed.Y += (INCREASE_SPEED + speedIncrement); if (ballSpeed.X < 0) ballSpeed.X -= (INCREASE_SPEED + speedIncrement); else ballSpeed.X += (INCREASE_SPEED + speedIncrement); } public float[] ProjectBall(Vector2 axis) { if (axis == Vector2.Zero) return (new float[2] { 0, 0 }); float min, max; min = Vector2.Dot(axis, this.ballCenter) - this.Width/2; //center - radius max = min + this.Width; //center + radius return (new float[2] { min, max }); } public void ChangeHorzDirection() { ballSpeed.X *= -1; } public void ChangeVertDirection() { ballSpeed.Y *= -1; } public override void Initialize() { base.Initialize(); ballPosition.X = Game.GraphicsDevice.Viewport.Width / 2 - ballSprite.Width / 2; ballPosition.Y = Game.GraphicsDevice.Viewport.Height / 2 - ballSprite.Height / 2; } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); ballSprite = contentManager.Load<Texture2D>(@"Content\ball"); } public override void Update(GameTime gameTime) { if (this.Y < 1 || this.Y > GraphicsDevice.Viewport.Height - this.Height - 1) this.ChangeVertDirection(); centerOfBall = new Vector2(ballPosition.X + this.Width / 2, ballPosition.Y + this.Height / 2); base.Update(gameTime); } public override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.Draw(ballSprite, ballPosition, null, Color.White, 0f, Vector2.Zero, Scale, SpriteEffects.None, 0); spriteBatch.End(); base.Draw(gameTime); } } Main game class public class gameStart : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; public gameStart() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; this.Window.Title = "Pong game"; } protected override void Initialize() { ball = new Ball(this); paddleLeft = new Paddle(this,true,false); paddleRight = new Paddle(this,false,true); Components.Add(ball); Components.Add(paddleLeft); Components.Add(paddleRight); this.Window.AllowUserResizing = false; this.IsMouseVisible = true; this.IsFixedTimeStep = false; this.isColliding = false; base.Initialize(); } #region MyPrivateStuff private Ball ball; private Paddle paddleLeft, paddleRight; private int[] bit = { -1, 1 }; private Random rnd = new Random(); private int updates = 0; enum nrPaddle { None, Left, Right }; private nrPaddle PongBar = nrPaddle.None; private ArrayList Axes = new ArrayList(); private Vector2 MTV; //minimum translation vector private bool isColliding; private float overlap; //smallest distance after projections private Vector2 overlapAxis; //axis of overlap #endregion protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); paddleLeft.setPosition(new Vector2(0, this.GraphicsDevice.Viewport.Height / 2 - paddleLeft.Height / 2)); paddleRight.setPosition(new Vector2(this.GraphicsDevice.Viewport.Width - paddleRight.Width, this.GraphicsDevice.Viewport.Height / 2 - paddleRight.Height / 2)); paddleLeft.Scale = new Vector2(1f, 2f); //scale left paddle } private bool ShapesIntersect(Paddle paddle, Ball ball) { overlap = 1000000f; //large value overlapAxis = Vector2.Zero; MTV = Vector2.Zero; foreach (Vector2 ax in Axes) { float[] pad = paddle.ProjectPaddle(ax); //pad0 = min, pad1 = max float[] circle = ball.ProjectBall(ax); //circle0 = min, circle1 = max if (pad[1] <= circle[0] || circle[1] <= pad[0]) { return false; } if (pad[1] - circle[0] < circle[1] - pad[0]) { if (Math.Abs(overlap) > Math.Abs(-pad[1] + circle[0])) { overlap = -pad[1] + circle[0]; overlapAxis = ax; } } else { if (Math.Abs(overlap) > Math.Abs(circle[1] - pad[0])) { overlap = circle[1] - pad[0]; overlapAxis = ax; } } } if (overlapAxis != Vector2.Zero) { MTV = overlapAxis * overlap; } return true; } protected override void Update(GameTime gameTime) { updates += 1; float ftime = 5 * (float)gameTime.ElapsedGameTime.TotalSeconds; if (updates == 1) { isColliding = false; int Xrnd = bit[Convert.ToInt32(rnd.Next(0, 2))]; int Yrnd = bit[Convert.ToInt32(rnd.Next(0, 2))]; ball.SpeedX = Xrnd * ball.SpeedX; ball.SpeedY = Yrnd * ball.SpeedY; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; } else { updates = 100; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; } //autorun :) paddleLeft.Y = ball.Y; //collision detection PongBar = nrPaddle.None; if (ball.Boundary.Intersects(paddleLeft.Boundary)) { PongBar = nrPaddle.Left; if (!isColliding) { Axes.Clear(); Axes.AddRange(paddleLeft.Normal2EdgesVector); //axis from nearest vertex to ball's center Axes.Add(FORMULAS.NormAxisFromCircle2ClosestVertex(paddleLeft.VertexVector, ball.ballCenter)); } } else if (ball.Boundary.Intersects(paddleRight.Boundary)) { PongBar = nrPaddle.Right; if (!isColliding) { Axes.Clear(); Axes.AddRange(paddleRight.Normal2EdgesVector); //axis from nearest vertex to ball's center Axes.Add(FORMULAS.NormAxisFromCircle2ClosestVertex(paddleRight.VertexVector, ball.ballCenter)); } } if (PongBar != nrPaddle.None && !isColliding) switch (PongBar) { case nrPaddle.Left: if (ShapesIntersect(paddleLeft, ball)) { isColliding = true; if (MTV != Vector2.Zero) ball.X += MTV.X; ball.Y += MTV.Y; ball.ChangeHorzDirection(); } break; case nrPaddle.Right: if (ShapesIntersect(paddleRight, ball)) { isColliding = true; if (MTV != Vector2.Zero) ball.X += MTV.X; ball.Y += MTV.Y; ball.ChangeHorzDirection(); } break; default: break; } if (!ShapesIntersect(paddleRight, ball) && !ShapesIntersect(paddleLeft, ball)) isColliding = false; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; //check ball movement if (ball.X > paddleRight.X + paddleRight.Width + 2) { //IncreaseScore(Left); ball.Reset(); updates = 0; return; } else if (ball.X < paddleLeft.X - 2) { //IncreaseScore(Right); ball.Reset(); updates = 0; return; } base.Update(gameTime); } protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.Aquamarine); spriteBatch.Begin(SpriteSortMode.BackToFront, BlendState.AlphaBlend); spriteBatch.End(); base.Draw(gameTime); } } And one method i've used: public static Vector2 NormAxisFromCircle2ClosestVertex(Vector2[] vertices, Vector2 circle) { Vector2 temp = Vector2.Zero; if (vertices.Length > 0) { float dist = (circle.X - vertices[0].X) * (circle.X - vertices[0].X) + (circle.Y - vertices[0].Y) * (circle.Y - vertices[0].Y); for (int i = 1; i < vertices.Length;i++) { if (dist > (circle.X - vertices[i].X) * (circle.X - vertices[i].X) + (circle.Y - vertices[i].Y) * (circle.Y - vertices[i].Y)) { temp = vertices[i]; //memorize the closest vertex dist = (circle.X - vertices[i].X) * (circle.X - vertices[i].X) + (circle.Y - vertices[i].Y) * (circle.Y - vertices[i].Y); } } temp = circle - temp; temp.Normalize(); } return temp; } Thanks in advance for any tips on the 4 issues. EDIT1: Something isn't working properly. The collision axis doesn't come out right and the interpolation also seems to have no effect. I've changed the code a bit: private bool ShapesIntersect(Paddle paddle, Ball ball) { overlap = 1000000f; //large value overlapAxis = Vector2.Zero; MTV = Vector2.Zero; foreach (Vector2 ax in Axes) { float[] pad = paddle.ProjectPaddle(ax); //pad0 = min, pad1 = max float[] circle = ball.ProjectBall(ax); //circle0 = min, circle1 = max if (pad[1] < circle[0] || circle[1] < pad[0]) { return false; } if (Math.Abs(pad[1] - circle[0]) < Math.Abs(circle[1] - pad[0])) { if (Math.Abs(overlap) > Math.Abs(-pad[1] + circle[0])) { overlap = -pad[1] + circle[0]; overlapAxis = ax * (-1); } //to get the proper axis } else { if (Math.Abs(overlap) > Math.Abs(circle[1] - pad[0])) { overlap = circle[1] - pad[0]; overlapAxis = ax; } } } if (overlapAxis != Vector2.Zero) { MTV = overlapAxis * Math.Abs(overlap); } return true; } And part of the Update method: if (ShapesIntersect(paddleRight, ball)) { isColliding = true; if (MTV != Vector2.Zero) { ball.X += MTV.X; ball.Y += MTV.Y; } //test if (overlapAxis.X == 0) //collision with horizontal edge { } else if (overlapAxis.Y == 0) //collision with vertical edge { float factor = Math.Abs(ball.ballCenter.Y - paddleRight.Y) / paddleRight.Height; if (factor > 1) factor = 1f; if (overlapAxis.X < 0) //left edge? ball.Speed = ball.DEFAULTSPEED * Vector2.Normalize(Vector2.Reflect(ball.Speed, (Vector2.Lerp(new Vector2(-1, -3), new Vector2(-1, 3), factor)))); else //right edge? ball.Speed = ball.DEFAULTSPEED * Vector2.Normalize(Vector2.Reflect(ball.Speed, (Vector2.Lerp(new Vector2(1, -3), new Vector2(1, 3), factor)))); } else //vertex collision??? { ball.Speed = -ball.Speed; } } What seems to happen is that "overlapAxis" doesn't always return the right one. So instead of (-1,0) i get the (1,0) (this happened even before i multiplied with -1 there). Sometimes there isn't even a collision registered even though the ball passes through the paddle... The interpolation also seems to have no effect as the angles barely change (or the overlapAxis is almost never (-1,0) or (1,0) but something like (0.9783473, 0.02743843)... ). What am i missing here? :(

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