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• How to set a key binding to make Emacs as transparent/opaque as I want?

  - by Vivi

  I want to have a command in Emacs to make it as opaque/transparent as I want (refer to the fabulous question that pointed out that transparency is possible in Emacs, and the EmacsWiki page linked there which has the code I am using below). The EmacsWiki code sets "C-c t" to toggle the previously set transparency on and off: ;;(set-frame-parameter (selected-frame) 'alpha '(<active> [<inactive>])) (set-frame-parameter (selected-frame) 'alpha '(85 50)) (add-to-list 'default-frame-alist '(alpha 85 50)) enter code here(eval-when-compile (require 'cl)) (defun toggle-transparency () (interactive) (if (/= (cadr (find 'alpha (frame-parameters nil) :key #'car)) 100) (set-frame-parameter nil 'alpha '(100 100)) (set-frame-parameter nil 'alpha '(85 60)))) (global-set-key (kbd "C-c t") 'toggle-transparency) What I would like to do is to be able to choose the % transparency when I am in Emacs. If possible, I would like a command where I type for example "C-c t N" (where N is the % opaqueness) for the active frame, and then "M-c t N" for the inactive window. If that can't be done like that, then maybe a command where if I type "C-c t" it asks me for the number which gives the opaqueness of the active window (and the same for the inactive window using "M-c t"). Thanks in advance for your time :) Below are just some comments that are not important to answer the question if you are not interested: I really want this because when I told my supervisor I was learning Emacs he said TexShop is much better and that I am using software from the 80's. I told him about the wonders of Emacs and he said TexShop has all of it and more. I matched everything he showed me except for the transparency (though he couldn't match the preview inside Emacs from preview-latex). I found the transparency thing by chance, and now I want to show him Emacs rules! I imagine this will be a piece of cake for some of you, and even though I could get it done if I spent enough time trying to learn lisp or reading around, I am not a programmer and I have only been using Emacs and a mac for a week. I am lost already as it is! So thanks in advance for your time and help - I will learn lisp eventually!

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• Sanity check on this idea for an Image Viewer in a web app

  - by Charlie Flowers

  I have an approach in mind for an image viewer in a web app, and want to get a sanity check and any thoughts you stackoverflowers might have. Here's the whirlwind nutshell summary: I'm working on an ASP.NET MVC application that will run in my company's retail stores. Even though it is a web application, we own the store machines and have control over them. We have a "windows agent" running on the store machine which we can talk to via http post (it is a WCF service, and our web app has permission to talk to it from the browser). One of the web pages needs to be an "image viewer" page with some common things like Rotate & Zoom. Now, there are some WebForms controls that offer Rotate and Zoom. However, they take up server resources and generate a good bit of traffic between the server and the browser. For example, the Rotate function would cause an ajax call to the server, which would then generate a new image written to a .NET Canvas object, which would then be written to a file on the server, which would then be returned from the ajax call and refreshed inside the browser. Normally, that's a pretty good way of doing things. But in our case, we have code running on the store machine that we can communicate with. This leads me to consider the following approach: When the user asks to view an image, we tell our "windows agent" to download it from our image server to the store machine. We then redirect our browser to our image viewer page, which will pull the image from the local file we just wrote to the store machine. When the user clicks "Rotate", we cause JavaScript code in the browser to call our "windows agent" software, asking it to perform the "Rotate" function. The "windows agent" does the rotation using the same kind of imaging control that would formerly have been used on the server, but it does so now on the store machine. Javascript in the browser then refreshes the image on the page to show the newly rotated image. Zoom and similar features would be implemented the same way. This seems to be much more efficient, scalable, and responsive for the end-users. However, I've never heard of anything like it being done, mostly because it's rare to have this combination of a web app plus a "windows agent" on the client machine. What do you think? Feasible? Reasonable? Any pitfalls I overlooked or improvements / suggestions you can see? Has anyone done anything like this who would like to offer the wisdom of experience? Thanks!

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• How to embed html table into the body of email

  - by Michael Mao

  Hi all: I am sending info to target email via PHP native mail() method right now. Everything else works fine but the table part troubles me the most. See sample output : Dear Michael Mao : Thank you for purchasing flight tickets with us, here is your receipt : Your tickets will be delivered by mail to the following address : Street Address 1 : sdfsdafsadf sdf Street Address 2 : N/A City : Sydney State : nsw Postcode : 2 Country : Australia Credit Card Number : *************1234 Your purchase details are recorded as : <table><tr><th class="delete">del?</th><th class="from_city">from</th><th class="to_city">to</th><th class="quantity">qty</th><th class="price">unit price</th><th class="price">total price</th></tr><tr class="evenrow" id="Sydney-Lima"><td><input name="isDeleting" type="checkbox"></td><td>Sydney</td><td>Lima</td><td>1</td><td>1030.00</td><td>1030</td></tr><tr class="oddrow" id="Sydney-Perth"><td><input name="isDeleting" type="checkbox"></td><td>Sydney</td><td>Perth</td><td>3</td><td>340.00</td><td>1020</td></tr><tr class="totalprice"><td colspan="5">Grand Total Price</td><td id="grandtotal">2050</td></tr></table> The source of table is directly taken from a webpage, exactly as the same. However, Gmail, Hotmail and most of other emails will ignore to render this as a table. So I am wondering, without using Outlook or other email sending agent software, how could I craft a embedded table for the PHP mail() method to send? Current code snippet corresponds to table generation : $purchaseinfo = $_POST["purchaseinfo"]; //if html tags are not to be filtered in the body of email $stringBuilder .= "<table>" .stripslashes($purchaseinfo) ."</table>"; //must send json response back to caller ajax request if(mail($email, 'Your purchase information on www.hardlyworldtravel.com', $emailbody, $headers)) echo json_encode(array("feedback"=>"successful")); else echo json_encode(array("feedback"=>"error")); Any hints and suggestions are welcomed, thanks a lot in advance.

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• Function Point Analysis -- a seriously over-estimating technique?

  - by kizzx2

  I know questions about FPA has been asked numerous times before, but this time I'm taking a more analytical angle at it, backed up with data. 1. First, some data This question is based on a tutorial. He had a "Sample Count" section where he demonstrated it step by step. You can see some screenshots of his sample application here. In the end, he calculated the unadjusted FP to be 99. There is another article on InformIT with industry data on typical hour/FP. It ranges from 2 hours/FP to 27.4 hours/FP. Let's try to stick with 2 for the moment (since SO readers are probably the more efficient crowd :p). 2. Reality check!? Now just check out the screenshots again. Do a little math here 99 * 2 = 198 hours 198 hours / 40 hours per week = 5 weeks Seriously? That sample application is going to take 5 weeks to implement? Is it just my feeling that it wouldn't take any decent programmer longer than one week to have it completed? Now let's try estimating the cost of the project. We'll use New York's minimum wage at the moment (Wikipedia), which is $7.25 198 * 7.25 = $1435.5 From what I could see from the screenshots, this application is a small excel-improvement app. I could have bought MS Office Pro for 200 bucks which gives me greater interoperability (.xls files) and flexibility (spreadsheets). (For the record, that same Web site has another article discussing productivity. It seems like they typically use 4.2 hours/FP, which gives us even more shocking stats: 99 * 4.2 = 415 hours = 10 weeks = almost 3 whopping months! 415 hours * $7.25 = $3000 zomg (That's even assuming that all our poor coders get the minimum wage!) 3. Am I missing something here? Right now, I could come up with several possible explanation: FPA is really only suited for bigger projects (1000+ FPs) so it becomes extremely inaccurate at smaller scale. The hours/FP metric fluctuates abruptly from team to team, project to project. For a small project like this, we could have used something like 0.5 hour/FP or something. (Now this kind of makes the whole estimation thing pointless, unless my firm does the same type of projects for several years with the same team, not really common.) From my experience with several software metrics, Function Point is really not a lightweight metric. If the hour/FP thing fluctuates so much, then what's the point, maybe I could have gone with User Story Points which is a lot faster to get and arguably almost as uncertain. What would be the FP experts' answers to this?

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• Recommendations for a free GIS library supporting raster images

  - by gspr

  Hi. I'm quite new to the whole field of GIS, and I'm about to make a small program that essentially overlays GPS tracks on a map together with some other annotations. I primarily need to allow scanned (thus raster) maps (although it would be nice to support proper map formats and something like OpenStreetmap in the long run). My first exploratory program uses Qt's graphics view framework and overlays the GPS points by simply projecting them onto the tangent plane to the WGS84 ellipsoid at a calibration point. This gives half-decent accuracy, and actually looks good. But then I started wondering. To get the accuracy I need (i.e. remove the "half" in "half-decent"), I have to correct for the map projection. While the math is not a problem in itself, supporting many map projection feels like needless work. Even though a few projections would probably be enough, I started thinking about just using something like the PROJ.4 library to do my projections. But then, why not take it all the way? Perhaps I might aswell use a full-blown map library such as Mapnik (edit: Quantum GIS also looks very nice), which will probably pay off when I start to want even more fancy annotations or some other symptom of featuritis. So, finally, to the question: What would you do? Would you use a full-blown map library? If so, which one? Again, it's important that it supports using (and zooming in and out with) raster maps and has pretty overlay features. Or would you just keep it simple, and go with Qt's own graphics view framework together with something like PROJ.4 to handle the map projections? I appreciate any feedback! Some technicalities: I'm writing in C++ with a Qt-based GUI, so I'd prefer something that plays relatively nicely with those. Also, the library must be free software (as in FOSS), and at least decently cross-platform (GNU/Linux, Windows and Mac, at least). Edit: OK, it seems I didn't do quite enough research before asking this question. Both Quantum GIS and Mapnik seem very well suited for my purpose. The former especially so since it's based on Qt.

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• Available Coroutine Libraries in Java

  - by JUST MY correct OPINION

  I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7? Edited to add: Just to ensure that confusion is contained, this is a related question to my other one, but not the same. This one is looking for an existing implementation in a bid to avoid reinventing the wheel unnecessarily. The other one is a question relating to how one would go about implementing coroutines in Java should this question prove unanswerable. The intent is to keep different questions on different threads.

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• Job queue manager with RPC interface

  - by admr

  I need a job queue manager that I can control over the Internet. It should be able to execute and stop processes, check on their status (ideally notice and execute some code when a process exits), respond to commands and also be able to report back to a server. Background: I have a GWT application that allows to create jobs to execute on a cloud instance (currently EC2). I want to push a "job packet" (data for a process to operate on etc) to S3, start a Linux EC2 instance (or use one that's already running), and tell a job manager on the instance to execute that job (possibly parallel to other jobs). It should then pull the "job packet" from S3, run a process that operates on that data and report back to the server that is running the server part of my GWT application with some information (e.g. exit code, stdout, stderr). If I have to write e.g. stdour/err to a file from the process and read that file, that's OK too. I would really like the manager to be "close" to the processes it runs, meaning I want to avoid using something like Runtime.exec from the JDK. It seems like I would have to do that if I used Quartz for example. I'm fine with the calls in both directions being asynchronous. I'm fine with any reasonable technology for the calls as long as I can easily build an interface for that in my GWT server side (e.g. HTTP requests to a servlet over SSL would be nice and trivial). The job manager does not need to have a very sophisticated queueing system. Running several processes either sequentially or in parallel should be fine. Determining how much compute time a process received during its lifetime would be nice (AFAIK, this might be challenging). I did not yet find any existing software that does this, including http://java-source.net/open-source/job-schedulers. I suspect I might have to build an RPC interface (with authentication etc, of course) around a job manager; maybe use something like Apache Commons Exec. In that case, I would prefer Java or Python for the job manager part. I would be happy to hear suggestions for either the former or latter scenario!

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• SQL efficiency argument, add a column or solvable by query?

  - by theTurk

  I am a recent college graduate and a new hire for software development. Things have been a little slow lately so I was given a db task. My db skills are limited to pet projects with Rails and Django. So, I was a little surprised with my latest task. I have been asked by my manager to subclass Person with a 'Parent' table and add a reference to their custodian in the Person table. This is to facilitate going from Parent to Form when the custodian, not the Parent, is the FormContact. Here is a simplified, mock structure of a sql-db I am working with. I would have drawn the relationship tables if I had access to Visio. We have a table 'Person' and we have a table 'Form'. There is a table, 'FormContact', that relates a Person to a Form, not all Persons are related to a Form. There is a relationship table for Person to Person relationships (Employer, Parent, etc.) I've asked, "Why this couldn't be handled by a query?" Response, Inefficient. (Really!?!) So, I ask, "Why not have a reference to the Form? That would be more efficient since you wouldn't be querying the FormContacts table with the reference from child/custodian." Response, this would essentially make the Parent is a FormContact. (Fair enough.) I went ahead an wrote a query to get from non-FormContact Parent to Form, and tested on the production server. The response time was instantaneous. *SOME_VALUE* is the Parent's fk ID. SELECT FormID FROM FormContact WHERE FormContact.ContactID IN (SELECT SourceContactID FROM ContactRelationship WHERE (ContactRelationship.RelatedContactID = *SOME_VALUE*) AND (ContactRelationship.Relationship = 'Parent')); If I am right, "This is an unnecessary change." What should I do, defend my position or should I concede to the managers request? If I am wrong. What is my error? Is there a better solution than the manager's?

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• Silverlight? WPF? or Windows Form?

  - by Amit

  After Silverlight 4.0 has been released with new WPF, I am kind of confused with these technologies: Silverlight? WPF? Windows Form? The main motive that we want to achieve for BIG business project is following: Performance Security And platform independent** If I consider all above three points then only Silverlight is the option as I don’t want people buying emulator on MacOS for WPF or Windows Form. Now how good the Silverlight is for Business applications, I was completely against when Silverlight 2.0 was in the market but now it is Silverlight 4.0 and they have provided many new features (but still basics) that is required in any challenging business applications. Comparing Silverlight and WPF -* Silverlight and WPF are very new technology and if I'd to compare from these two then I'd prefer WPF because it can be considered stable and mature. But it is not same as Windows Form. -* If I go with Silverlight then I am sure about keep updating to the latest version of Silverlight. I remembered when we were developing software for version 2.0 then we'd to create our own framework with dynamic loading DLL, and then Navigation concept. But everything was got changed once Silverlight 3.0 came. I don't want this to be happening with this new product. -* If we go with WPF then we don't get the platform independence. Now, why not we just focus on making WPF and then move to Silverlght. As someone (Tim?) from Microsoft has said that the idea is to make Silverlight as close as WPF. But if that is the case then why XAML structure is different; I will not be convinced with by saying that .Net framework for SL is too small.. well the difference is coming from the namespace ? I was searching on this subject and found "Microsoft WPF-Silverlight Comparison Whitepaper v1.1.pdf". This guide is very good that gives you ins-outs about how can we build common apps that runs on both. But again, it is comparing Silverlight 2 and not 4. I am sure many architect/ developers/ project managers must be facing similar kind of questions in their premises and wants to initiate this discussion, if it has not been :). We've still got 2 weeks to make this decision, so I'm expecting everyone to participate, gurus?

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• Container item implementation

  - by onurozcelik

  Hi, I am working in Train Traffic Controller software project. My responsibility in this project is to develop the visual railroad GUI. We are implementing the project with Qt. By now I am using QGraphicsLinearLayout to hold my items. I am using the layout because I do not want to calculate coordinates of each item. So far I wrote item classes to add the layout. For instance SwitchItem class symbolizes railroad switch in real world. Each item class is responsible for its own painting and events. So far so good. Now I need a composite item that can contain two or more item. This class is going to be responsible for painting the items contained in it. I need this class because I have to put two or more items inside same layout cell. If I don' t put them in same cell I can' t use layout. See the image below. BlockSegmentItem and SignalItem inside same cell. Here is my compositeitem implementation. #include "compositeitem.h" CompositeItem::CompositeItem(QString id,QList<FieldItem *> _children) { children = _children; } CompositeItem::~CompositeItem() { } QRectF CompositeItem::boundingRect() const { FieldItem *child; QRectF rect(0,0,0,0); foreach(child,children) { rect = rect.united(child->boundingRect()); } return rect; } void CompositeItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget ) { FieldItem *child; foreach(child,children) { child->paint(painter,option,widget); } } QSizeF CompositeItem::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const { QSizeF itsSize(0,0); FieldItem *child; foreach(child,children) { // if its size empty set first child size to itsSize if(itsSize.isEmpty()) itsSize = child->sizeHint(Qt::PreferredSize); else { QSizeF childSize = child->sizeHint(Qt::PreferredSize); if(itsSize.width() < childSize.width()) itsSize.setWidth(childSize.width()); itsSize.setHeight(itsSize.height() + childSize.height()); } } return itsSize; } void CompositeItem::contextMenuEvent(QGraphicsSceneContextMenuEvent *event) { qDebug()<<"Test"; } This code works good with painting but when it comes to item events it is problematic. QGraphicsScene treats the composite item like a single item which is right for layout but not for events. Because each item has its own event implementation.(e.g. SignalItem has its special context menu event.) I have to handle item events seperately. Also I need a composite item implementation for the layout. How can I overcome this dilemma?

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• MS Access MSChart.Graph.8 not printing

  - by Tanj

  Software: Microsoft Access 2007 SP2 Database File Version: Access 2000 I have an access program that I inherited from a previous employee. It uses forms for reports and since I don't have much experience in access I have continued to do this. I have created a copy of the program for another project and modified it to suit. I am having trouble getting more then one chart to print. All the charts display in form view, they all have the same properties (excepting data, position, etc.) For some reason they are not printing. They don't even show up in the print preview. I am thinking it must be something with the graphs themselves as they sometimes lose all information. I have to open the graphs in edit mode and change the data source from column to row and back again so that it gets redrawn. (Refresh doesn't fix it) So right now I don't even have a clue as to where to look so ideas are welcome. Edit #1 It seems to be a problem with linking to an unbound form. Subform Field Linker: Can't build a link between unbound forms. The query for the main form is SELECT tTest.ixTest, tMotorTypes.ixMotorType, tMotorTypes.asMotorType, tMotorTypes.fDeprecated, tTestType.asTest, tTest.asSerialNum, tTest.asOrderNum, tTest.asFrameNum, tTest.asRotorNum, tTest.asOperator, tTest.iStation, tTest.dtTestDate, tTest.ixTestType FROM tMotorTypes INNER JOIN (tTestType INNER JOIN tTest ON tTestType.ixTestType=tTest.ixTestType) ON tMotorTypes.ixMotorType=tTest.ixMotorType; The query for the chart is: SELECT qGraphRSTTemperatures.Frequency, qGraphRSTTemperatures.[Drive End], qGraphRSTTemperatures.[Non Drive End], qGraphRSTTemperatures.[Air In], qGraphRSTTemperatures.Core FROM qGraphRSTTemperatures ORDER BY qGraphRSTTemperatures.ixTemperature; Query qGraphRSTTemperatures: SELECT tElectricalData.dblFrequency AS Frequency, tTemperatures.dblDrvEnd AS [Drive End], tTemperatures.dblNonDrvEnd AS [Non Drive End], tTemperatures.dblAirIn AS [Air In], tTemperatures.dblCore AS Core, tSubTest.ixTest, tTemperatures.ixTemperature FROM (tSubTest INNER JOIN tElectricalData ON tSubTest.ixSubTest = tElectricalData.ixSubTest) LEFT JOIN tTemperatures ON tElectricalData.ixElectrical = tTemperatures.ixElectrical WHERE (((tSubTest.ixSubTestType)=5)) ORDER BY tSubTest.ixTest, tTemperatures.ixTemperature; So how come, in the form view it shows the graph with the correct data when linked thus: Child field: ixTest Master field: ixTest but won't print the graph. The graph will print if I remove the links, but then I have all the data from chart query as it is not limited by ixTest. edit #2 It seems to be a data retrieval/rendering issue in printing. Is there anything in printing that changes the context of records with respect to parent/child relationships?

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• C# Detect Localhost Port Usage

  - by ThaKidd

  In advance, thank you for your advice. I am currently working on a program which uses Putty to create a SSH connection with a server that uses local port forwarding to enable a client, running my software, to access the service behind the SSH server via localhost. IE: client:20100 - Internet - Remote SSH server exposed via router/firewall - Local Intranet - Intranet Web POP3 Server:110. Cmd Line: "putty -ssh -2 -P 22 -C -L 20100:intranteIP:110 -pw sshpassword sshusername@sshserver" Client would use putty to create a SSH connection with the SSH server specifying in the connection string that it would like to tie port 110 of the Intranet POP3 Server to port 20100 on the client system. Therefore the client would be able to open up a mail client to localhost:20100 and interact with the Internal POP3 server over the SSH tunnel. The above is a general description. I already know what I am trying to do will work without a problem so am not looking for debate on the above. The question is this...How can I ensure the local port (I cannot use dynamic ports, so it must be static) on localhost is not being used or listened to by any other application? I am currently executing this code in my C# app: private bool checkPort(int port) { try { //Create a socket on the current IPv4 address Socket TestSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); // Create an IP end point IPEndPoint localIP = new IPEndPoint(IPAddress.Parse("127.0.0.1"), port); // Bind that port TestSocket.Bind(localIP); // Cleanup TestSocket.Close(); return false; } catch (Exception e) { // Exception occurred. Port is already bound. return true; } } I am currently calling this function starting with a specific port in a for loop to get the 'false' return at the first available port. The first port I try is actually being listened to by uTorrent. The above code does not catch this and my connection fails. What is the best method to ensure a port is truly free? I do understand some other program may grab the port during/after I have tested it. I just need to find something that will ensure it is not currently in use AT ALL when the test is executed. If there is a way to truly reserve the localhost port during the test, I would love to hear about it.

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• java concurrency: many writers, one reader

  - by Janning

  I need to gather some statistics in my software and i am trying to make it fast and correct, which is not easy (for me!) first my code so far with two classes, a StatsService and a StatsHarvester public class StatsService { private Map<String, Long> stats = new HashMap<String, Long>(1000); public void notify ( String key ) { Long value = 1l; synchronized (stats) { if (stats.containsKey(key)) { value = stats.get(key) + 1; } stats.put(key, value); } } public Map<String, Long> getStats ( ) { Map<String, Long> copy; synchronized (stats) { copy = new HashMap<String, Long>(stats); stats.clear(); } return copy; } } this is my second class, a harvester which collects the stats from time to time and writes them to a database. public class StatsHarvester implements Runnable { private StatsService statsService; private Thread t; public void init ( ) { t = new Thread(this); t.start(); } public synchronized void run ( ) { while (true) { try { wait(5 * 60 * 1000); // 5 minutes collectAndSave(); } catch (InterruptedException e) { e.printStackTrace(); } } } private void collectAndSave ( ) { Map<String, Long> stats = statsService.getStats(); // do something like: // saveRecords(stats); } } At runtime it will have about 30 concurrent running threads each calling notify(key) about 100 times. Only one StatsHarvester is calling statsService.getStats() So i have many writers and only one reader. it would be nice to have accurate stats but i don't care if some records are lost on high concurrency. The reader should run every 5 Minutes or whatever is reasonable. Writing should be as fast as possible. Reading should be fast but if it locks for about 300ms every 5 minutes, its fine. I've read many docs (Java concurrency in practice, effective java and so on), but i have the strong feeling that i need your advice to get it right. I hope i stated my problem clear and short enough to get valuable help.

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• Autocomplete server-side implementation

  - by toluju

  What is a fast and efficient way to implement the server-side component for an autocomplete feature in an html input box? I am writing a service to autocomplete user queries in our web interface's main search box, and the completions are displayed in an ajax-powered dropdown. The data we are running queries against is simply a large table of concepts our system knows about, which matches roughly with the set of wikipedia page titles. For this service obviously speed is of utmost importance, as responsiveness of the web page is important to the user experience. The current implementation simply loads all concepts into memory in a sorted set, and performs a simple log(n) lookup on a user keystroke. The tailset is then used to provide additional matches beyond the closest match. The problem with this solution is that it does not scale. It currently is running up against the VM heap space limit (I've set -Xmx2g, which is about the most we can push on our 32 bit machines), and this prevents us from expanding our concept table or adding more functionality. Switching to 64-bit VMs on machines with more memory isn't an immediate option. I've been hesitant to start working on a disk-based solution as I am concerned that disk seek time will kill performance. Are there possible solutions that will let me scale better, either entirely in memory or with some fast disk-backed implementations? Edits: @Gandalf: For our use case it is important the the autocompletion is comprehensive and isn't just extra help for the user. As for what we are completing, it is a list of concept-type pairs. For example, possible entries are [("Microsoft", "Software Company"), ("Jeff Atwood", "Programmer"), ("StackOverflow.com", "Website")]. We are using Lucene for the full search once a user selects an item from the autocomplete list, but I am not yet sure Lucene would work well for the autocomplete itself. @Glen: No databases are being used here. When I'm talking about a table I just mean the structured representation of my data. @Jason Day: My original implementation to this problem was to use a Trie, but the memory bloat with that was actually worse than the sorted set due to needing a large number of object references. I'll read on the ternary search trees to see if it could be of use.

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• WMS authentication plugin

  - by roul

  Hi, I'm trying to create a custom authentication plugin for WMS 2009 in C#. I managed to implement something that for some reason blocks all requests... [ComVisible(true)] [Guid("C0A0B38C-C4FE-43B5-BE9E-C100A83BBCEE")] public class AuthenticationPlugin : IWMSBasicPlugin, IWMSAuthenticationPlugin, IWMSAuthenticationContext private const string SubKey = "SOFTWARE\\Microsoft\\Windows Media\\Server\\RegisteredPlugins\\Authentication\\{C0A0B38C-C4FE-43B5-BE9E-C100A83BBCEE}"; [ComRegisterFunction] public static void RegisterFunction(Type t) { try { RegistryKey regHKLM = Registry.LocalMachine; regHKLM = regHKLM.CreateSubKey(SubKey); regHKLM.SetValue(null, "UC WMS Authentication plugin"); RegistryKey regHKCR = Registry.ClassesRoot; regHKCR = regHKCR.CreateSubKey("CLSID\\{C0A0B38C-C4FE-43B5-BE9E-C100A83BBCEE}\\Properties"); regHKCR.SetValue("Name", CustomC WMS Authentication plugin"); regHKCR.SetValue("Author", "Me"); regHKCR.SetValue("CopyRight", "Copyright 2009. All rights reserved"); regHKCR.SetValue("Description", "Enables custom WMS authentication"); } catch (Exception error) { Console.WriteLine(error.Message, "Inside RegisterFunction(). Cannot Register."); } } [ComUnregisterFunction] public static void UnRegisterFunction(Type t) { try { RegistryKey regHKLM = Registry.LocalMachine; regHKLM.DeleteSubKey(SubKey); RegistryKey regHKCR = Registry.ClassesRoot; regHKCR.DeleteSubKeyTree("CLSID\\{C0A0B38C-C4FE-43B5-BE9E-C100A83BBCEE}"); regHKCR.DeleteSubKeyTree("CSEventTest.CSEventPlugin"); } catch (Exception error) { Console.WriteLine(error.Message, "Cannot delete a subkey."); } } #region IWMSBasicPlugin Members public void InitializePlugin(IWMSContext serverContext, WMSNamedValues namedValues, IWMSClassObject classFactory) { } public void ShutdownPlugin() { } public void EnablePlugin(ref int flags, ref int heartbeatPeriod) { } public void DisablePlugin() { } public object GetCustomAdminInterface() { return null; } public void OnHeartbeat() { } #endregion #region IWMSAuthenticationPlugin Members public IWMSAuthenticationContext CreateAuthenticationContext() { return (IWMSAuthenticationContext)this; } public int GetFlags() { return Convert.ToInt32(WMS_AUTHENTICATION_FLAGS.WMS_AUTHENTICATION_ANONYMOUS, CultureInfo.InvariantCulture); } public string GetPackageName() { return "Custom WMS Authentication"; } public string GetProtocolName() { return "Basic"; } #endregion #region IWMSAuthenticationContext Members public void Authenticate(object responseBlob, IWMSContext userContext, IWMSContext presentationContext, IWMSCommandContext commandContext, IWMSAuthenticationCallback callBack, object context) { callBack.OnAuthenticateComplete(WMS_AUTHENTICATION_RESULT.WMS_AUTHENTICATION_SUCCESS, null, context); } public IWMSAuthenticationPlugin GetAuthenticationPlugin() { return (IWMSAuthenticationPlugin)this; } public string GetImpersonationAccountName() { return String.Empty; } public int GetImpersonationToken() { return 0; } public string GetLogicalUserID() { return this.GetImpersonationAccountName(); } #endregion } Can anyone spot why this is happening? Also, is there any way I could have a look at the code for the standard Anonymous Authentication plugin already installed on the server? Is it in an assembly somewhere? Thanks.

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• Make a compiled binary run at native speed flawlessly without recompiling from source on a another system?

  - by unknownthreat

  I know that many people, at a first glance of the question, may immediately yell out "Java", but no, I know Java's qualities. Allow me to elaborate my question first. Normally, when we want our program to run at a native speed on a system, whether it be Windows, Mac OS X, or Linux, we need to compile from source codes. If you want to run a program of another system in your system, you need to use a virtual machine or an emulator. While these tools allow you to use the program you need on the non-native OS, they sometimes have problems of performance and glitches. We also have a newer compiler called "JIT Compiler", where the compiler will parse the bytecode program to native machine language before execution. The performance may increase to a very good extent with JIT Compiler, but the performance is still not the same as running it on a native system. Another program on Linux, WINE, is also a good tool for running Windows program on Linux system. I have tried running Team Fortress 2 on it, and tried experiment with some settings. I got ~40 fps on Windows at its mid-high setting on 1280 x 1024. On Linux, I need to turn everything low at 1280 x 1024 to get ~40 fps. There are 2 notable things though: Polygon model settings do not seem to affect framerate whether I set it low or high. When there are post-processing effects or some special effects that require manipulation of drawn pixels of the current frame, the framerate will drop to 10-20 fps. From this point, I can see that normal polygon rendering is just fine, but when it comes to newer rendering methods that requires graphic card to the job, it slows down to a crawl. Anyway, this question is rather theoretical. Is there anything we can do at all? I see that WINE can run STEAM and Team Fortress 2. Although there are flaws, they can run at lower setting. Or perhaps, I should also ask, "is it possible to translate one whole program on a system to another system without recompiling from source and get native speed?" I see that we also have AOT Compiler, is it possible to use it for something like this? Or there are so many constraints (such as DirectX call or differences in software architecture) that make it impossible to have a flawless and not native to the system program that runs at native speed?

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• Recommended textbook for machine-level programming?

  - by Norman Ramsey

  I'm looking at textbooks for an undergraduate course in machine-level programming. If the perfect book existed, this is what it would look like: Uses examples written in C or assembly language, or both. Covers machine-level operations such as two's-complement integer arithmetic, bitwise operations, and floating-point arithmetic. Explains how caches work and how they affect performance. Explains machine instructions or assembly instructions. Bonus if the example assembly language includes x86; triple bonus if it includes x86-64 (aka AMD64). Explains how C values and data structures are represented using hardware registers and memory. Explains how C control structures are translated into assembly language using conditional and unconditional branch instructions. Explains something about procedure calling conventions and how procedure calls are implemented at the machine level. Books I might be interested in would probably have the words "machine organization" or "computer architecture" in the title. Here are some books I'm considering but am not quite happy with: Computer Systems: A Programmer's Perspective by Randy Bryant and Dave O'Hallaron. This is quite a nice book, but it's a book for a broad, shallow course in systems programming, and it contains a great deal of material my students don't need. Also, it is just out in a second edition, which will make it expensive. Computer Organization and Design: The Hardware/Software Interface by Dave Patterson and John Hennessy. This is also a very nice book, but it contains way more information about how the hardware works than my students need. Also, the exercises look boring. Finally, it has a show-stopping bug: it is based very heavily on MIPS hardware and the use of a MIPS simulator. My students need to learn how to use DDD, and I can't see getting this to work on a simulator. Not to mention that I can't see them cross-compiling their code for the simulator, and so on and so forth. Another flaw is that the book mentions the x86 architecture only to sneer at it. I am entirely sympathetic to this point of view, but news flash! You guys lost! Write Great Code Vol I: Understanding the Machine by Randall Hyde. I haven't evaluated this book as thoroughly as the other two. It has a lot of what I need, but the translation from high-level language to assembler is deferred to Volume Two, which has mixed reviews. My students will be annoyed if I make them buy a two-volume series, even if the price of those two volumes is smaller than the price of other books. I would really welcome other suggestions of books that would help students in a class where they are to learn how C-language data structures and code are translated to machine-level data structures and code and where they learn how to think about performance, with an emphasis on the cache.

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• unable to install anything on ubuntu 9.10 with aptitude

  - by Srisa

  Hello, Earlier i could install software by using the 'sudo aptitude install ' command. Today when i tried to install rkhunter i am getting errors. It is not just rkhunter, i am not able to install anything. Here is the text output: user@server:~$ sudo aptitude install rkhunter ................ ................ 20% [3 rkhunter 947/271kB 0%] Get:4 http://archive.ubuntu.com karmic/universe unhide 20080519-4 [832kB] 40% [4 unhide 2955/832kB 0%] 100% [Working] Fetched 1394kB in 1s (825kB/s) Preconfiguring packages ... Selecting previously deselected package lsof. (Reading database ... ................ (Reading database ... 95% (Reading database ... 100% (Reading database ... 20076 files and directories currently installed.) Unpacking lsof (from .../lsof_4.81.dfsg.1-1_amd64.deb) ... dpkg: error processing /var/cache/apt/archives/lsof_4.81.dfsg.1-1_amd64.deb (--unpack): unable to create `/usr/bin/lsof.dpkg-new' (while processing `./usr/bin/lsof'): Permission denied dpkg-deb: subprocess paste killed by signal (Broken pipe) Selecting previously deselected package libmd5-perl. Unpacking libmd5-perl (from .../libmd5-perl_2.03-1_all.deb) ... Selecting previously deselected package rkhunter. Unpacking rkhunter (from .../rkhunter_1.3.4-5_all.deb) ... dpkg: error processing /var/cache/apt/archives/rkhunter_1.3.4-5_all.deb (--unpack): unable to create `/usr/bin/rkhunter.dpkg-new' (while processing `./usr/bin/rkhunter'): Permission denied dpkg-deb: subprocess paste killed by signal (Broken pipe) Selecting previously deselected package unhide. Unpacking unhide (from .../unhide_20080519-4_amd64.deb) ... dpkg: error processing /var/cache/apt/archives/unhide_20080519-4_amd64.deb (--unpack): unable to create `/usr/sbin/unhide-posix.dpkg-new' (while processing `./usr/sbin/unhide-posix'): Permission denied dpkg-deb: subprocess paste killed by signal (Broken pipe) Processing triggers for man-db ... Errors were encountered while processing: /var/cache/apt/archives/lsof_4.81.dfsg.1-1_amd64.deb /var/cache/apt/archives/rkhunter_1.3.4-5_all.deb /var/cache/apt/archives/unhide_20080519-4_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) A package failed to install. Trying to recover: Setting up libmd5-perl (2.03-1) ... Building dependency tree... 0% Building dependency tree... 50% Building dependency tree... 50% Building dependency tree Reading state information... 0% ........... .................... I have removed some lines to reduce the text. All the error messages are in here though. My experience with linux is limited and i am not sure what the problem is or how it is to be resolved. Thanks.

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• How to solve Python memory leak when using urrlib2?

  - by b_m

  Hi, I'm trying to write a simple Python script for my mobile phone to periodically load a web page using urrlib2. In fact I don't really care about the server response, I'd only like to pass some values in the URL to the PHP. The problem is that Python for S60 uses the old 2.5.4 Python core, which seems to have a memory leak in the urrlib2 module. As I read there's seems to be such problems in every type of network communications as well. This bug have been reported here a couple of years ago, while some workarounds were posted as well. I've tried everything I could find on that page, and with the help of Google, but my phone still runs out of memory after ~70 page loads. Strangely the Garbege Collector does not seem to make any difference either, except making my script much slower. It is said that, that the newer (3.1) core solves this issue, but unfortunately I can't wait a year (or more) for the S60 port to come. here's how my script looks after adding every little trick I've found: import urrlib2, httplib, gc while(true): url = "http://something.com/foo.php?parameter=" + value f = urllib2.urlopen(url) f.read(1) f.fp._sock.recv=None # hacky avoidance f.close() del f gc.collect() Any suggestions, how to make it work forever without getting the "cannot allocate memory" error? Thanks for advance, cheers, b_m update: I've managed to connect 92 times before it ran out of memory, but It's still not good enough. update2: Tried the socket method as suggested earlier, this is the second best (wrong) solution so far: class UpdateSocketThread(threading.Thread): def run(self): global data while 1: url = "/foo.php?parameter=%d"%data s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect(('something.com', 80)) s.send('GET '+url+' HTTP/1.0\r\n\r\n') s.close() sleep(1) I tried the little tricks, from above too. The thread closes after ~50 uploads (the phone has 50MB of memory left, obviously the Python shell has not.) UPDATE: I think I'm getting closer to the solution! I tried sending multiple data without closing and reopening the socket. This may be the key since this method will only leave one open file descriptor. The problem is: import socket s=socket.socket(socket.AF_INET, socket.SOCK_STREAM) socket.connect(("something.com", 80)) socket.send("test") #returns 4 (sent bytes, which is cool) socket.send("test") #4 socket.send("test") #4 socket.send("GET /foo.php?parameter=bar HTTP/1.0\r\n\r\n") #returns the number of sent bytes, ok socket.send("GET /foo.php?parameter=bar HTTP/1.0\r\n\r\n") #returns 0 on the phone, error on Windows7* socket.send("GET /foo.php?parameter=bar HTTP/1.0\r\n\r\n") #returns 0 on the phone, error on Windows7* socket.send("test") #returns 0, strange... *: error message: 10053, software caused connection abort Why can't I send multiple messages??

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• how Can we get the output format to CSV instead of HTML in Alfresco using webscripts?

  - by pavan123

  how Can we change the output format to CSV instead of HTML in Alfresco using webscripts? below are the my corresponding FTL and Webscript files recursive.get.html.ftl <#macro recurse_macro node depth> <#if node.isContainer> <tr> <td> ${node.properties.name} </td> <td></td> </tr> <#list node.children as child> <#if child.isContainer> <@recurse_macro node=child depth=depth+1/> <#list child.children as child2> <#if child2.isDocument> <tr><td></td><td>${child2.properties.name}</td></tr> </#if> </#list> </#if> </#list> </#if> </#macro> Recursive Listing of Spaces & Documents: Space Document recursive.get.desc.xml <webscript> <shortname>recurcive</shortname> <description>Recursive</description> <url>/sample/recursive/{recursive}</url> <format default="html">extension</format> <authentication>guest</authentication> </webscript> and html output is Recursive Listing of Spaces & Documents: Space Document Company Home Data Dictionary Space Templates Software Engineering Project Documentation Drafts Pending Approval Published Samples system-overview.html Discussions UI Design Presentations Quality Assurance Presentation Templates doc_info.ftl localizable.ftl my_docs.ftl my_spaces.ftl my_summary.ftl translatable.ftl recent_docs.ftl general_example.ftl my_docs_inline.ftl show_audit.ftl readme.ftl Email Templates notify_user_email.ftl invite_user_email.ftl RSS Templates RSS_2.0_recent_docs.ftl Saved Searches admin Scripts backup.js example test script.js backup and log.js append copyright.js alfresco docs.js test return value.js Web Scripts org alfresco sample blogsearch.get.js blogsearch.get.atom.ftl blogsearch.get.desc.xml blogsearch.get.html.ftl blogsearch.get.html.400.ftl blogsearch.get.atom.400.ftl categorysearch.get.js categorysearch.get.atom.ftl categorysearch.get.desc.xml categorysearch.get.html.ftl categorysearch.get.html.404.ftl categorysearch.get.atom.404.ftl folder.get.js folder.get.atom.ftl folder.get.desc.xml folder.get.html.ftl avmstores.get.desc.xml avmstores.get.html.ftl avmbrowse.get.js avmbrowse.get.desc.xml avmbrowse.get.html.ftl recursive.get.desc.xml recursive.get.html.ftl sgs.get.desc.xml sgs.get.csv.ftl sample1.get.desc.xml sample1.get.csv.ftl first.get.desc.xml first.get.text.ftl rag.get.html.ftl rag.get.desc.xml new1.get.desc.xml new1.get.html.ftl excel.get.html.ftl excel.get.desc.xml sgs1.get.desc.xml one.get.html.ftl one.get.desc.xml one.get.js readme.html Web Scripts Extensions readme.html Guest Home Alfresco-Tutorial.pdf User Homes isabel Users Home

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• Function Point Analysis -- a seriously overestimating technique?

  - by kizzx2

  I know questions about FPA has been asked numerous times before, but this time I'm taking a more analytical angle at it, backed up with data. 1. First, some data This question is based on a tutorial. He had a "Sample Count" section where he demonstrated it step by step. You can see some screenshots of his sample application here. In the end, he calculated the unadjusted FP to be 99. There is another article on InformIT with industry data on typical hour/FP. It ranges from 2 hours/FP to 27.4 hours/FP. Let's try to stick with 2 for the moment (since SO readers are probably the more efficient crowd :p). 2. Reality check!? Now just check out the screenshots again. Do a little math here 99 * 2 = 198 hours 198 hours / 40 hours per week = 5 weeks Seriously? That sample application is going to take 5 weeks to implement? Is it just my feeling that it wouldn't take any decent programmer longer than one week (I"m not even saying weekend) to have it completed? Now let's try estimating the cost of the project. We'll use New York's minimum wage at the moment (Wikipedia), which is $7.25 198 * 7.25 = $1435.5 From what I could see from the screenshots, this application is a small excel-improvement app. I could have bought MS Office Pro for 200 bucks which gives me greater interoperability (.xls files) and flexibility (spreadsheets). (For the record, that same Web site has another article discussing productivity. It seems like they typically use 4.2 hours/FP, which gives us even more shocking stats: 99 * 4.2 = 415 hours = 10 weeks = almost 3 whopping months! 415 hours * $7.25 = $3000 zomg (That's even assuming that all our poor coders get the minimum wage!) 3. Am I missing something here? Right now, I could come up with several possible explanation: FPA is really only suited for bigger projects (1000+ FPs) so it becomes extremely inaccurate at smaller scale. The hours/FP metric fluctuates abruptly from team to team, project to project. For a small project like this, we could have used something like 0.5 hour/FP or something. (Now this kind of makes the whole estimation thing pointless, unless my firm does the same type of projects for several years with the same team, not really common.) From my experience with several software metrics, Function Point is really not a lightweight metric. If the hour/FP thing fluctuates so much, then what's the point, maybe I could have gone with User Story Points which is a lot faster to get and arguably almost as uncertain. What would be the FP experts' answers to this?

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• Starting company and getting a good deal

  - by Dan

  Hi, I'm having the possibility to start a small company with someone else. I'm a software programmer and been working on a field where there isn't much competition, at least in the platform I'm developing, which is the one with highest market share. This other person comes from marketing so he would find / provide clients and be in charge of the business side. So initially it would be me, the tech guy with the knowledge to develop our product and products based on my development, and this person who would become CEO (basically a 50/50 share). The idea is getting a product on our own, but also perform projects for others in order to get some cash. The problem is that his idea is doing this without initial capital. He tells me that he could get some customers from past business (which is mostly true as he has been in the business for some time) and then with the money obtained from such development, we could hire some freelance developers and build our own platform. I've already discussed with him that I don't find this the best way, provided that we need to compete against other companies some of who are VC funded and have many developers working fulltime. But most of all, I'm thinking of whether this is a fair deal to do, provided that this person is not providing anything other than clients, and I'd be the one having to do the work and dedicate time, thus also taking most of the risks. In all fairness, I'd expect him to put some initial capital, given that initially I'm putting some of my code which in some way is money given the time I've dedicated to it. So the question here is, does this seem fair to you? Is this the way it is usually done? My only concern here is that I don't have previous experience with such deals, and I ignore whether this is the usual thing to do in other cases. Certainly having a marketing person helps a lot. As you probably know being a programmer doesn't make me the most indicated person for marketing ;-) but at the same time I'm not sure if this could be a good deal or I'd just be making a pretty inconvenient deal. Hope I made my point clear, but feel free to let me know if more details are needed. Thanks in advance

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• How do I debug a difficult-to-reproduce crash with no useful call stack?

  - by David M

  I am encountering an odd crash in our software and I'm having a lot of trouble debugging it, and so I am seeking SO's advice on how to tackle it. The crash is an access violation reading a NULL pointer: First chance exception at $00CF0041. Exception class $C0000005 with message 'access violation at 0x00cf0041: read of address 0x00000000'. It only happens 'sometimes' - I haven't managed to figure out any rhyme or reason, yet, for when - and only in the main thread. When it occurs, the call stack contains one incorrect entry: For the main thread, which this is, it should show a large stack full of other items. At this point, all other threads are inactive (mostly sitting in WaitForSingleObject or a similar function.) I have only seen this crash occur in the main thread. It always has the same call stack of one entry, in the same method at the same address. This method may or may not be related - we do use the VCL in our application. My bet, though, is that something (possibly quite a while ago) is corrupting the stack, and the address where it's crashing is effectively random. Note it has been the same address across several builds, though - it's probably not truly random. Here is what I've tried: Trying to reproduce it reliably at a certain point. I have found nothing that reproduces it every time, and a couple of things that occasionally do, or do not, for no apparent reason. These are not 'narrow' enough actions to narrow it down to a particular section of code. It may be timing related, but at the point the IDE breaks in, other threads are usually doing nothing. I can't rule out a threading problem, but think it's unlikely. Building with extra debugging statements (extra debug info, extra asserts, etc.) After doing so, the crash never occurs. Building with Codeguard enabled. After doing so, the crash never occurs and Codeguard shows no errors. My questions: 1. How do I find what code caused the crash? How do I do the equivalent of walking back up the stack? 2. What general advice do you have for how to trace the cause of this crash? I am using Embarcadero RAD Studio 2010 (the project mostly contains C++ Builder code and small amounts of Delphi.)

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• Overwhelmed by design patterns... where to begin?

  - by Pete

  I am writing a simple prototype code to demonstrate & profile I/O schemes (HDF4, HDF5, HDF5 using parallel IO, NetCDF, etc.) for a physics code. Since focus is on IO, the rest of the program is very simple: class Grid { public: floatArray x,y,z; }; class MyModel { public: MyModel(const int &nip1, const int &njp1, const int &nkp1, const int &numProcs); Grid grid; map<string, floatArray> plasmaVariables; }; Where floatArray is a simple class that lets me define arbitrary dimensioned arrays and do mathematical operations on them (i.e. x+y is point-wise addition). Of course, I could use better encapsulation (write accessors/setters, etc.), but that's not the concept I'm struggling with. For the I/O routines, I am envisioning applying simple inheritance: Abstract I/O class defines read & write functions to fill in the "myModel" object HDF4 derived class HDF5 HDF5 using parallel IO NetCDF etc... The code should read data in any of these formats, then write out to any of these formats. In the past, I would add an AbstractIO member to myModel and create/destroy this object depending on which I/O scheme I want. In this way, I could do something like: myModelObj.ioObj->read('input.hdf') myModelObj.ioObj->write('output.hdf') I have a bit of OOP experience but very little on the Design Patterns front, so I recently acquired the Gang of Four book "Design Patterns: Elements of Reusable Object-Oriented Software". OOP designers: Which pattern(s) would you recommend I use to integrate I/O with the myModel object? I am interested in answering this for two reasons: To learn more about design patterns in general Apply what I learn to help refactor an large old crufty/legacy physics code to be more human-readable & extensible. I am leaning towards applying the Decerator pattern to myModel, so I can attach the I/O responsibilities dynamically to myModel (i.e. whether to use HDF4, HDF5, etc.). However, I don't feel very confident that this is the best pattern to apply. Reading the Gang of Four book cover-to-cover before I start coding feels like a good way to develop an unhealthy caffeine addiction. What patterns do you recommend?

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• Question about Architecture for Viewing Images in ASP.NET MVC App

  - by Charlie Flowers

  I have an approach in mind for an image viewer in a web app, and want to get a sanity check and any thoughts you stackoverflowers might have. Here's the whirlwind nutshell summary: I'm working on an ASP.NET MVC application that will run in my company's retail stores. Even though it is a web application, we own the store machines and have control over them. We have a "windows agent" running on the store machine which we can talk to from the browser via javascript (it is a WCF service, and our web app has permission to talk to it from the browser). One of the web pages needs to be an "image viewer" page with some common things like Rotate & Zoom. Now, there are some WebForms controls that offer Rotate and Zoom. However, they take up server resources and generate a good bit of traffic between the server and the browser. For example, the Rotate function would cause an ajax call to the server, which would then generate a new image written to a .NET Canvas object, which would then be written to a file on the server, which would then be returned from the ajax call and refreshed inside the browser. Normally, that's a pretty good way of doing things. But in our case, we have code running on the store machine that we can communicate with. This leads me to consider the following approach: When the user asks to view an image, we tell our "windows agent" to download it from our image server to the store machine. We then redirect our browser to our image viewer page, which will pull the image from the local file we just wrote to the store machine. When the user clicks "Rotate", we cause JavaScript code in the browser to call our "windows agent" software, asking it to perform the "Rotate" function. The "windows agent" does the rotation using the same kind of imaging control that would formerly have been used on the server, but it does so now on the store machine. Javascript in the browser then refreshes the image on the page to show the newly rotated image. Zoom and similar features would be implemented the same way. This seems to be much more efficient, scalable, and responsive for the end-users. However, I've never heard of anything like it being done, mostly because it's rare to have this combination of a web app plus a "windows agent" on the client machine. What do you think? Feasible? Reasonable? Any pitfalls I overlooked or improvements / suggestions you can see? Has anyone done anything like this who would like to offer the wisdom of experience? Thanks!

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