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  • XML to be validated against multiple xsd schemas

    - by Michael Rusch
    I'm writing the xsd and the code to validate, so I have great control here. I would like to have an upload facility that adds stuff to my application based on an xml file. One part of the xml file should be validated against different schemas based on one of the values in the other part of it. Here's an example to illustrate: <foo> <name>Harold</name> <bar>Alpha</bar> <baz>Mercury</baz> <!-- ... more general info that applies to all foos ... --> <bar-config> <!-- the content here is specific to the bar named "Alpha" --> </bar-config> <baz-config> <!-- the content here is specific to the baz named "Mercury" --> </baz> </foo> In this case, there is some controlled vocabulary for the content of <bar>, and I can handle that part just fine. Then, based on the bar value, the appropriate xml schema should be used to validate the content of bar-config. Similarly for baz and baz-config. The code doing the parsing/validation is written in Java. Not sure how language-dependent the solution will be. Ideally, the solution would permit the xml author to declare the appropriate schema locations and what-not so that s/he could get the xml validated on the fly in a sufficiently smart editor. Also, the possible values for <bar> and <baz> are orthogonal, so I don't want to do this by extension for every possible bar/baz combo. What I mean is, if there are 24 possible bar values/schemas and 8 possible baz values/schemas, I want to be able to write 1 + 24 + 8 = 33 total schemas, instead of 1 * 24 * 8 = 192 total schemas. Also, I'd prefer to NOT break out the bar-config and baz-config into separate xml files if possible. I realize that might make all the problems much easier, as each xml file would have a single schema, but I'm trying to see if there is a good single-xml-file solution.

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  • Exposing model object using bindings in custom NSCell of NSTableView

    - by Hooligancat
    I am struggling trying to perform what I would think would be a relatively common task. I have an NSTableView that is bound to it's array via an NSArrayController. The array controller has it's content set to an NSMutableArray that contains one or more NSObject instances of a model class. What I don't know how to do is expose the model inside the NSCell subclass in a way that is bindings friendly. For the purpose of illustration, we'll say that the object model is a person consisting of a first name, last name, age and gender. Thus the model would appear something like this: @interface PersonModel : NSObject { NSString * firstName; NSString * lastName; NSString * gender; int * age; } Obviously the appropriate setters, getters init etc for the class. In my controller class I define an NSTableView, NSMutableArray and an NSArrayController: @interface ControllerClass : NSObject { IBOutlet NSTableView * myTableView; NSMutableArray * myPersonArray; IBOutlet NSArrayController * myPersonArrayController; } Using Interface Builder I can easily bind the model to the appropriate columns: myPersonArray --> myPersonArrayController --> table column binding This works fine. So I remove the extra columns, leaving one column hidden that is bound to the NSArrayController (this creates and keeps the association between each row and the NSArrayController) so that I am down to one visible column in my NSTableView and one hidden column. I create an NSCell subclass and put the appropriate drawing method to create the cell. In my awakeFromNib I establish the custom NSCell subclass: PersonModel * aCustomCell = [[[PersonModel alloc] init] autorelease]; [[myTableView tableColumnWithIdentifier:@"customCellColumn"] setDataCell:aCustomCell]; This, too, works fine from a drawing perspective. I get my custom cell showing up in the column and it repeats for every managed object in my array controller. If I add an object or remove an object from the array controller the table updates accordingly. However... I was under the impression that my PersonModel object would be available from within my NSCell subclass. But I don't know how to get to it. I don't want to set each NSCell using setters and getters because then I'm breaking the whole model concept by storing data in the NSCell instead of referencing it from the array controller. And yes I do need to have a custom NSCell, so having multiple columns is not an option. Where to from here? In addition to the Google and StackOverflow search, I've done the obligatory walk through on Apple's docs and don't seem to have found the answer. I have found a lot of references that beat around the bush but nothing involving an NSArrayController. The controller makes life very easy when binding to other elements of the model entity (such as a master/detail scenario). I have also found a lot of references (although no answers) when using Core Data, but Im not using Core Data. As per the norm, I'm very grateful for any assistance that can be offered!

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  • Psychology researcher wants to learn new language

    - by user273347
    I'm currently considering R, matlab, or python, but I'm open to other options. Could you help me pick the best language for my needs? Here are the criteria I have in mind (not in order): Simple to learn. I don't really have a lot of free time, so I'm looking for something that isn't extremely complicated and/or difficult to pick up. I know some C, FWIW. Good for statistics/psychometrics. I do a ton of statistics and psychometrics analysis. A lot of it is basic stuff that I can do with SPSS, but I'd like to play around with the more advanced stuff too (bootstrapping, genetic programming, data mining, neural nets, modeling, etc). I'm looking for a language/environment that can help me run my simpler analyses faster and give me more options than a canned stat package like SPSS. If it can even make tables for me, then it'll be perfect. I also do a fair bit of experimental psychology. I use a canned experiment "programming" software (SuperLab) to make most of my experiments, but I want to be able to program executable programs that I can run on any computer and that can compile the data from the experiments in a spreadsheet. I know python has psychopy and pyepl and matlab has psychtoolbox, but I don't know which one is best. If R had something like this, I'd probably be sold on R already. I'm looking for something regularly used in academe and industry. Everybody else here (including myself, so far) uses canned stat and experiment programming software. One of the reasons I'm trying to learn a programming language is so that I can keep up when I move to another lab. Looking forward to your comments and suggestions. Thank you all for your kind and informative replies. I appreciate it. It's still a tough choice because of so many strong arguments for each language. Python - Thinking about it, I've forgotten so much about C already (I don't even remember what to do with an array) that it might be better for me to start from scratch with a simple program that does what it's supposed to do. It looks like it can do most of the things I'll need it to do, though not as cleanly as R and MATLAB. R - I'm really liking what I'm reading about R. The packages are perfect for my statistical work now. Given the purpose of R, I don't think it's suited to building psychological experiments though. To clarify, what I mean is making a program that presents visual and auditory stimuli to my specifications (hundreds of them in a preset and/or randomized sequence) and records the response data gathered from participants. MATLAB - It's awesome that cognitive and neuro folk are recommending MATLAB, because I'm preparing for the big leap from social and personality psychology to cognitive neuro. The problem is the Uni where I work doesn't have MATLAB licenses (and 3750 GBP for a compiler license is not an option for me haha). Octave looks like a good alternative. PsychToolbox is compatible with Octave, thankfully. SQL - Thanks for the tip. I'll explore that option, too. Python will be the least backbreaking and most useful in the short term. R is well suited to my current work. MATLAB is well suited to my prospective work. It's a tough call, but I think I am now equipped to make a more well-informed decision about where to go next. Thanks again!

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  • WPF: Updating visibility of controls not updating the screen

    - by Brad McBride
    I will preface this by stating that I am new to WPF programming and may be making multiple errors. Any insight that can be provided to help me improve in my skills are greatly appreciated. I am working with a WPF application and am looping through a list of objects that contain properties that describe a document that should be built on the fly and automatically printed. I am attempting to display a small grid in the interface that shows the document being built before it is printed. This serves two purposes: one, it allows the user to see work being done by the application. Two, it renders the items on the screen so that I can then have something to actually print since WPF appears to not be able to load an image for printing dynamicaly without displaying it on the screen. In my code, I am setting the various elements in the grid and setting the visibility to visible. However, the UI is not updating and the printed document doesn't look as intended since the image never shows up on the screen. Here is the XAML that I have set up <Grid x:Name="LayoutRoot" Background="Black"> <Grid Name="previewGrid" Grid.Row="1" Grid.Column="1" Background="White" Visibility="Hidden"> <Canvas Name="pageCanvas" HorizontalAlignment="Center" VerticalAlignment="Center"> <Grid Name="pageGrid" Width="163" Height="211"> <Grid.ColumnDefinitions> <ColumnDefinition Width="81.5"></ColumnDefinition> <ColumnDefinition Width="81.5"></ColumnDefinition> </Grid.ColumnDefinitions> <TextBlock Grid.Column="0" Name="copyright" TextAlignment="Center" HorizontalAlignment="Center" VerticalAlignment="Bottom"></TextBlock> <Image Name="pageImage" Grid.Column="1" HorizontalAlignment="Center" VerticalAlignment="Center"></Image> </Grid> </Canvas> .....canvas for pages 2-4 not shown but structure is the same as for pageGrid..... </Grid> </Grid> </Window> Here is the code behind that is supposed to set the elements. previewGrid.Visibility = Windows.Visibility.Visible pageURI = New Uri(pageCollection(i).iamgeURL, UriKind.Absolute) pageGrid.Visibility = Windows.Visibility.Visible bmp.BeginInit() bmp.StreamSource = getCachedURLStream(cardURI) bmp.EndInit() pageImage.Source = bmp copyright.Text = copyrightText cardPreviewGrid.UpdateLayout() ' More code that prints the visual element pageGrid previewGrid.Visibility = Windows.Visibility.Hidden The code in codebehind loops through a number of times depending on how many different documents the user prints. Basically it builds a visual element for a page, prints an XPS version of it and then builds the next page and prints it, etc. Once all pages have been processed, the job is actually sent to the printer. The only purpose of this application is to let the user print these documents so there is not other task that they can do in the application while the documents print. I thought that putting this task in a background thread would help to update the UI but since I am trying to manipulate items directly on the UI thread it would appear that this option won't work for me. What am I doing wrong here and how can I improve the code so that I can get the behavior that I am trying to achieve?

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  • How can I anchor a textbox in wpf ?

    - by csuporj
    I have a window with tabs. On one of the tabs, I have a layout like below. (In fact it is more complicated, I have 4 text boxes in a row, and I have more rows.) How can I make the 3rd textbox have the width of the label + the width of the text box above, that is, to have them properly aligned ? The problem is that WPF widens the 3rd textbox, when I type text into it. Using hardcoded numbers for the sizes defeats the whole purpose of WPF. I could do that way 10 times faster in Windows Forms than in WPF. Is there a better way, than using a grid for each set of consecutive small text boxes, having to skip the large ones from the grid, because putting them in messes up everything. <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <Window.Resources> <Style TargetType="{x:Type Label}"> <Setter Property="VerticalAlignment" Value="Center"/> </Style> <Style TargetType="{x:Type TextBox}"> <Setter Property="VerticalAlignment" Value="Center"/> <Setter Property="Margin" Value="3"/> </Style> <Style x:Key="SmallTextBox" TargetType="{x:Type TextBox}" BasedOn="{StaticResource {x:Type TextBox}}"> <Setter Property="Width" Value="50"/> </Style> </Window.Resources> <StackPanel VerticalAlignment="Top" HorizontalAlignment="Left" Width="{Binding ElementName=grid,Path=ActualWidth}" Grid.IsSharedSizeScope="True"> <Grid Name="grid" HorizontalAlignment="Left"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" SharedSizeGroup="c1"/> <ColumnDefinition Width="Auto" SharedSizeGroup="c2"/> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="Auto"/> <RowDefinition Height="Auto"/> </Grid.RowDefinitions> <Label Content="Foo:"/> <TextBox Grid.Column="1" Style="{StaticResource SmallTextBox}"/> <Label Grid.Row="1" Content="Foobar:"/> <TextBox Grid.Row="1" Grid.Column="1" Style="{StaticResource SmallTextBox}"/> </Grid> <TextBox Grid.Row="1"/> <Grid Name="grid2" HorizontalAlignment="Left"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" SharedSizeGroup="c1"/> <ColumnDefinition Width="Auto" SharedSizeGroup="c2"/> </Grid.ColumnDefinitions> <Label Content="Bar:"/> <TextBox Grid.Column="1" Style="{StaticResource SmallTextBox}"/> </Grid> </StackPanel> </Window>

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  • Use bug tracker to get things done and manage personal tasks?

    - by Frank
    This is slightly off-topic, but can only be answered by programmers and is useful to many programmers: Do you think it is useful to use a bug tracking system to keep track of personal todo items and to Get Things Done? I have not tried that; in fact, I don't have much experience with bug tracking systems. For my todo lists, I have played around with Google Tasks and Remember The Milk, but both of them have shortcomings: Google Tasks: I like that you can create todo lists easily, can reorder items in the list and easily create hierarchies. But it is way too simplistic and does not allow to tag tasks or move tasks from one list to another. Remember The Milk: It is nice and sleek, but you cannot create hierarchies of tasks, cannot arbitrarily reorder tasks and cannot set dependencies of tasks. That's where a bug tracking system should come in: Since I think (maybe too much?) like a programmer, my tasks have a natural hierarchy and a tree of dependencies, like in a Makefile. Here are two examples: The task of writing my thesis is done when several milestones are done. Some of these milestones can run in parallel (writing background chapter, running experiments A, running experiments B), others depend on each other (writing main chapter depends on first getting results from experiments A). The same is true for more personal goals: I want to host a dinner party, which requires finding a good date, finishing the guest list, making invitations, finding nice recipes, cooking, ... For me, all these tasks involve hierarchical dependencies and milestones that bug tracking systems should be able to handle? Here is an article that explains how to do advanced GTD with Remember The Milk, but he has to use several workarounds: (1) add a general tag 'wait' to tasks that are waiting for others to be completed but you cannot enter the IDs of the tasks that they are waiting for, (2) starting some special tasks with "." so that they are at the top of the alphabetically sorted list and signal that others are 'below' it as subgoals. Bug tracking systems should be able to handle these things much more naturally? Does anyone have experience and can recommend a lightweight bug tracking system that might be good for this? Other requirements: Should run as web app, should allow me to tag a task with several tags (like 'work', 'fun', 'short-task', 'errands', ...).

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  • SQLAlchemy session management in long-running process

    - by codeape
    Scenario: A .NET-based application server (Wonderware IAS/System Platform) hosts automation objects that communicate with various equipment on the factory floor. CPython is hosted inside this application server (using Python for .NET). The automation objects have scripting functionality built-in (using a custom, .NET-based language). These scripts call Python functions. The Python functions are part of a system to track Work-In-Progress on the factory floor. The purpose of the system is to track the produced widgets along the process, ensure that the widgets go through the process in the correct order, and check that certain conditions are met along the process. The widget production history and widget state is stored in a relational database, this is where SQLAlchemy plays its part. For example, when a widget passes a scanner, the automation software triggers the following script (written in the application server's custom scripting language): ' wiget_id and scanner_id provided by automation object ' ExecFunction() takes care of calling a CPython function retval = ExecFunction("WidgetScanned", widget_id, scanner_id); ' if the python function raises an Exception, ErrorOccured will be true ' in this case, any errors should cause the production line to stop. if (retval.ErrorOccured) then ProductionLine.Running = False; InformationBoard.DisplayText = "ERROR: " + retval.Exception.Message; InformationBoard.SoundAlarm = True end if; The script calls the WidgetScanned python function: # pywip/functions.py from pywip.database import session from pywip.model import Widget, WidgetHistoryItem from pywip import validation, StatusMessage from datetime import datetime def WidgetScanned(widget_id, scanner_id): widget = session.query(Widget).get(widget_id) validation.validate_widget_passed_scanner(widget, scanner) # raises exception on error widget.history.append(WidgetHistoryItem(timestamp=datetime.now(), action=u"SCANNED", scanner_id=scanner_id)) widget.last_scanner = scanner_id widget.last_update = datetime.now() return StatusMessage("OK") # ... there are a dozen similar functions My question is: How do I best manage SQLAlchemy sessions in this scenario? The application server is a long-running process, typically running months between restarts. The application server is single-threaded. Currently, I do it the following way: I apply a decorator to the functions I make avaliable to the application server: # pywip/iasfunctions.py from pywip import functions def ias_session_handling(func): def _ias_session_handling(*args, **kwargs): try: retval = func(*args, **kwargs) session.commit() return retval except: session.rollback() raise return _ias_session_handling # ... actually I populate this module with decorated versions of all the functions in pywip.functions dynamically WidgetScanned = ias_session_handling(functions.WidgetScanned) Question: Is the decorator above suitable for handling sessions in a long-running process? Should I call session.remove()? The SQLAlchemy session object is a scoped session: # pywip/database.py from sqlalchemy.orm import scoped_session, sessionmaker session = scoped_session(sessionmaker()) I want to keep the session management out of the basic functions. For two reasons: There is another family of functions, sequence functions. The sequence functions call several of the basic functions. One sequence function should equal one database transaction. I need to be able to use the library from other environments. a) From a TurboGears web application. In that case, session management is done by TurboGears. b) From an IPython shell. In that case, commit/rollback will be explicit. (I am truly sorry for the long question. But I felt I needed to explain the scenario. Perhaps not necessary?)

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  • ListView: convertView / holder getting confused

    - by Steve H
    I'm working with a ListView, trying to get the convertView / referenceHolder optimisation to work properly but it's giving me trouble. (This is the system where you store the R.id.xxx pointers in as a tag for each View to avoid having to call findViewById). I have a ListView populated with simple rows of an ImageView and some text, but the ImageView can be formatted either for portrait-sized images (tall and narrow) or landscape-sized images (short and wide). It's adjusting this formatting for each row which isn't working as I had hoped. The basic system is that to begin with, it inflates the layout for each row and sets the ImageView's settings based on the data, and includes an int denoting the orientation in the tag containing the R.id.xxx values. Then when it starts reusing convertViews, it checks this saved orientation against the orientation of the new row. The theory then is that if the orientation is the same, then the ImageView should already be set up correctly. If it isn't, then it sets the parameters for the ImageView as appropriate and updates the tag. However, I found that it was somehow getting confused; sometimes the tag would get out of sync with the orientation of the ImageView. For example, the tag would still say portrait, but the actual ImageView would still be in landscape layout. I couldn't find a pattern to how or when this happened; it wasn't consistent by orientation, position in the list or speed of scrolling. I can solve the problem by simply removing the check about convertView's orientation and simply always set the ImageView's parameters, but that seems to defeat the purpose of this optimisation. Can anyone see what I've done wrong in the code below? static LinearLayout.LayoutParams layoutParams; (...) public View getView(int position, View convertView, ViewGroup parent){ ReferenceHolder holder; if (convertView == null){ convertView = inflater.inflate(R.layout.pick_image_row, null); holder = new ReferenceHolder(); holder.getIdsAndSetTag(convertView, position); if (data[position][ORIENTATION] == LANDSCAPE) { // Layout defaults to portrait settings, so ImageView size needs adjusting. // layoutParams is modified here, with specific values for width, height, margins etc holder.image.setLayoutParams(layoutParams); } holder.orientation = data[position][ORIENTATION]; } else { holder = (ReferenceHolder) convertView.getTag(); if (holder.orientation != data[position][ORIENTATION]){ //This is the key if statement for my question switch (image[position][ORIENTATION]) { case PORTRAIT: // layoutParams is reset to the Portrait settings holder.orientation = data[position][ORIENTATION]; break; case LANDSCAPE: // layoutParams is reset to the Landscape settings holder.orientation = data[position][ORIENTATION]; break; } holder.image.setLayoutParams(layoutParams); } } // and the row's image and text is set here, using holder.image.xxx // and holder.text.xxx return convertView; } static class ReferenceHolder { ImageView image; TextView text; int orientation; void getIdsAndSetTag(View v, int position){ image = (ImageView) v.findViewById(R.id.pickImageImage); text = (TextView) v.findViewById(R.id.pickImageText); orientation = data[position][ORIENTATION]; v.setTag(this); } } Thanks!

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  • Daylight saving time and Timezone best practices

    - by Oded
    I am hoping to make this question and the answers to it the definitive guide to dealing with daylight saving time, in particular for dealing with the actual change overs. If you have anything to add, please do Many systems are dependent on keeping accurate time, the problem is with changes to time due to daylight savings - moving the clock forward or backwards. For instance, one has business rules in an order taking system that depend on the time of the order - if the clock changes, the rules might not be as clear. How should the time of the order be persisted? There is of course an endless number of scenarios - this one is simply an illustrative one. How have you dealt with the daylight saving issue? What assumptions are part of your solution? (looking for context here) As important, if not more so: What did you try that did not work? Why did it not work? I would be interested in programming, OS, data persistence and other pertinent aspects of the issue. General answers are great, but I would also like to see details especially if they are only available on one platform. Summary of answers and other data: (please add yours) Do: Always persist time according to a unified standard that is not affected by daylight savings. GMT and UTC have been mentioned by different people. Include the local time offset (including DST offset) in stored timestamps. Remember that DST offsets are not always an integer number of hours (e.g. Indian Standard Time is UTC+05:30). If using Java, use JodaTime. - http://joda-time.sourceforge.net/ Create a table TZOffsets with three columns: RegionClassId, StartDateTime, and OffsetMinutes (int, in minutes). See answer Check if your DBMS needs to be shutdown during transition. Business rules should always work on civil time. Internally, keep timestamps in something like civil-time-seconds-from-epoch. See answer Only convert to local times at the last possible moment. Don't: Do not use javascript date and time calculations in web apps unless you ABSOLUTELY have to. Testing: When testing make sure you test countries in the Western and Eastern hemispheres, with both DST in progress and not and a country that does not use DST (6 in total). Reference: Olson database, aka Tz_database - ftp://elsie.nci.nih.gov/pub Sources for Time Zone and DST - http://www.twinsun.com/tz/tz-link.htm ISO format (ISO 8601) - http://en.wikipedia.org/wiki/ISO_8601 Mapping between Olson database and Windows TimeZone Ids, from the Unicode Consortium - http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/windows_tzid.html TimeZone page on WikiPedia - http://en.wikipedia.org/wiki/Tz_database StackOverflow questions tagged dst - http://stackoverflow.com/questions/tagged/dst StackOverflow questions tagged timezone - http://stackoverflow.com/questions/tagged/timezone Other: Lobby your representative to end the abomination that is DST. We can always hope...

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  • Servlet/JSP Flow Control: Enums, Exceptions, or Something Else?

    - by Christopher Parker
    I recently inherited an application developed with bare servlets and JSPs (i.e.: no frameworks). I've been tasked with cleaning up the error-handling workflow. Currently, each <form> in the workflow submits to a servlet, and based on the result of the form submission, the servlet does one of two things: If everything is OK, the servlet either forwards or redirects to the next page in the workflow. If there's a problem, such as an invalid username or password, the servlet forwards to a page specific to the problem condition. For example, there are pages such as AccountDisabled.jsp, AccountExpired.jsp, AuthenticationFailed.jsp, SecurityQuestionIncorrect.jsp, etc. I need to redesign this system to centralize how problem conditions are handled. So far, I've considered two possible solutions: Exceptions Create an exception class specific to my needs, such as AuthException. Inherit from this class to be more specific when necessary (e.g.: InvalidUsernameException, InvalidPasswordException, AccountDisabledException, etc.). Whenever there's a problem condition, throw an exception specific to the condition. Catch all exceptions via web.xml and route them to the appropriate page(s) with the <error-page> tag. enums Adopt an error code approach, with an enum keeping track of the error code and description. The descriptions can be read from a resource bundle in the finished product. I'm leaning more toward the enum approach, as an authentication failure isn't really an "exceptional condition" and I don't see any benefit in adding clutter to the server logs. Plus, I'd just be replacing one maintenance headache with another. Instead of separate JSPs to maintain, I'd have separate Exception classes. I'm planning on implementing "error" handling in a servlet that I'm writing specifically for this purpose. I'm also going to eliminate all of the separate error pages, instead setting an error request attribute with the error message to display to the user and forwarding back to the referrer. Each target servlet (Logon, ChangePassword, AnswerProfileQuestions, etc.) would add an error code to the request and redirect to my new servlet in the event of a problem. My new servlet would look something like this: public enum Error { INVALID_PASSWORD(5000, "You have entered an invalid password."), ACCOUNT_DISABLED(5002, "Your account has been disabled."), SESSION_EXPIRED(5003, "Your session has expired. Please log in again."), INVALID_SECURITY_QUESTION(5004, "You have answered a security question incorrectly."); private final int code; private final String description; Error(int code, String description) { this.code = code; this.description = description; } public int getCode() { return code; } public String getDescription() { return description; } }; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String sendTo = "UnknownError.jsp"; String message = "An unknown error has occurred."; int errorCode = Integer.parseInt((String)request.getAttribute("errorCode"), 10); Error errors[] = Error.values(); Error error = null; for (int i = 0; error == null && i < errors.length; i++) { if (errors[i].getCode() == errorCode) { error = errors[i]; } } if (error != null) { sendTo = request.getHeader("referer"); message = error.getDescription(); } request.setAttribute("error", message); request.getRequestDispatcher(sendTo).forward(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } Being fairly inexperienced with Java EE (this is my first real exposure to JSPs and servlets), I'm sure there's something I'm missing, or my approach is suboptimal. Am I on the right track, or do I need to rethink my strategy?

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  • How to show server errors in Rails 2.3.5 with JSON and jQuery

    - by Fortuity
    I've got in-place editing on a page in my app (using Rails 2.3.5 and jQuery). I want to know how to display an error on the page when the update fails. I'm using ajax (an XMLHttpRequest) to save an update to a Comment object. The controller has an update method like this: def update @comment = Comment.find(params[:id]) respond_to do |format| # if @comment.update_attributes!(params[:comment]) if false #deliberately forcing a fail here to see what happens format.json { render :nothing => true } else format.json { render :json => @comment.errors, :status => :unprocessable_entity } end end end In Firebug, I can see the server returns a "422" (an appropriate validation error status code). But it's a response to an XMLHttpRequest so there is no redirect to an error page. I think I actually want to do this: format.json { render :json => @comment.errors} or maybe this: format.json {render :json => { :status => :error, :message => "Could not be saved" }.to_json, :status => 400 } and trigger some Javascript function that iterates through (and displays) any errors. I'm using a rails plugin http://github.com/janv/rest_in_place/ to implement the in-place editing. It doesn't appear to have any callback function to handle a failure. What are my options? Can I write some Javascript to respond to a failure condition without hacking the plugin? Do I have to hack the rest_in_place plugin to handle a failure condition? Is there a better plugin (for Rails or jQuery) that handles in-place editing, including failure conditions? UPDATE This post from Peter Bui (http://paydrotalks.com/posts/45-standard-json-response-for-rails-and-jquery) was helpful in showing how to handle an error message from the server using XMLHttpRequest.status. I looked at his implementation of a blog using ajax (http://github.com/paydro/talks). I'm surprised at the complexity required to handle a simple error condition. Usually Rails has all the goodness baked in but it seems server errors with JSON are out of scope. Can that be? I also looked at grimen's validatious-on-rails (http://github.com/grimen/validatious-on-rails/) which accommodates models validations when ajax XMLHttpRequest is used. It's not clear to me how I'd use it to handle the general case of a "save" failing when validations succeed. P.S. Please vote me up... so I can use more than one HTML link when I ask my question :-)

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  • CommandBinding broken in inner Custom Control when nesting two Custom Controls of the same type.

    - by Fredrik Eriksson
    I've done a Custom Control in form of a GroupBox but with an extra header which purpose is to hold a button or a stackpanel with buttons at the other side. I've added the a Dependency Property to hold the extra header and I've connected the customized template. Everything works fine until I put one of these controls in another one. Now the wierd stuff begins(at least in my eyes xP), the command binding in the inner control simply isn't set. I tried to use Snoop to gather some data, the see if the inherits is broken and when I clicked on the buttons which isn't doing what I want it to, boom, breakpoint triggered. So in some wierd way the Command isn't set until something that I don't know what it is, happens, which snoops triggers. I've also tried to put the buttons in the regular Header property and that works fine, but not with my own made. I could just switch places with them to make it like I want but now I'm curious to know where the problem lies... Now I wonder, what can I've missed? The control class: public class TwoHeaderedGroupBox : GroupBox { static TwoHeaderedGroupBox() { DefaultStyleKeyProperty.OverrideMetadata(typeof(TwoHeaderedGroupBox), new FrameworkPropertyMetadata(typeof(TwoHeaderedGroupBox))); } public static DependencyProperty HeaderTwoProperty = DependencyProperty.Register("HeaderTwo", typeof(object), typeof(TwoHeaderedGroupBox), new FrameworkPropertyMetadata()); public object HeaderTwo { get { return (object)GetValue(HeaderTwoProperty); } set { SetValue(HeaderTwoProperty, value);} } } And here is the Template (which by the way is created by blend from the beginning): <ControlTemplate TargetType="{x:Type Controls:TwoHeaderedGroupBox}"> <Grid SnapsToDevicePixels="true"> <Grid.ColumnDefinitions> <ColumnDefinition Width="6"/> <ColumnDefinition Width="Auto"/> <ColumnDefinition Width="*"/> <ColumnDefinition Width="6"/> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition Height="Auto"/> <RowDefinition Height="Auto"/> <RowDefinition Height="*"/> <RowDefinition Height="6"/> </Grid.RowDefinitions> <Border BorderBrush="Transparent" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.ColumnSpan="4" Grid.Column="0" CornerRadius="4" Grid.Row="1" Grid.RowSpan="3"/> <Border x:Name="Header" Grid.Column="1" Padding="3,1,3,0" Grid.Row="0" Grid.RowSpan="2" VerticalAlignment="Center"> <ContentControl Content="{TemplateBinding Header}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/> </Border> <ContentPresenter Grid.ColumnSpan="2" Grid.Column="1" Margin="{TemplateBinding Padding}" Grid.Row="2" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/> <Border BorderBrush="White" BorderThickness="{TemplateBinding BorderThickness}" Grid.ColumnSpan="4" CornerRadius="4" Grid.Row="1" Grid.RowSpan="3"> <Border.OpacityMask> <MultiBinding ConverterParameter="7" Converter="{StaticResource BorderGapMaskConverter}"> <Binding ElementName="Header" Path="ActualWidth"/> <Binding Path="ActualWidth" RelativeSource="{RelativeSource Self}"/> <Binding Path="ActualHeight" RelativeSource="{RelativeSource Self}"/> </MultiBinding> </Border.OpacityMask> <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="3"> <Border BorderBrush="White" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="2"/> </Border> </Border> <Border x:Name="HeaderTwo" Grid.Column="2" Padding="3,5,3,5" Grid.Row="0" Grid.RowSpan="2" HorizontalAlignment="Right"> <ContentControl Content="{TemplateBinding HeaderTwo}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" DataContext="{TemplateBinding DataContext}"/> </Border> </Grid> </ControlTemplate>

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  • From a 3D modeler to an iPhone app - what are best practices?

    - by bonkey
    I am quite new in 3D programming on iPhone and I would like to ask for hints about organizing a work between designers and programmers on that platform. Most of all: what kind of tools, libraries or plugins cooperate the best on both sides. Although I consider the question as looking for general best-practices advice I would like to find a solution for my current situation which I describe further, too. I've already done some research and found following libraries: SIO2 Khronos OpenGL ES 1.x SDK for PowerVR MBX Unity3D Oolong Game Engine I've checked modellers or plugins to them giving output formats readable by those tools: obj2opengl Wavefront OBJ to plain header file converter Blender with SIO2 exporter iphonewavefrontloader Cheetah3D PVRGeoPOD for 3DS / Maya Unfortunately I still have no clear vision how to combine any of that tools to get a desinger's work in an application. I look for a way of getting it in the most possible complete way: models, lights, scenes, textures, maybe some simple animations (but rather no game-like physics), but I still got nothing. And here comes my situation: I would like to find right way to present few (but quite complicated) models from a single scene. The designers mostly use 3DS Max 9, sometimes 10 (which partly prevents using PVRGeoPOD) and are rather reluctant to switch to something else but if there's no other choice I suppose it would be possible. The basic rule I've already found in some places "use Wavefront OBJ" not always works. I haven't got any acceptable results with production files, actually. The only things worked fine were some mere examples. Some of my models did imported incomplete, sometimes exporters hung or generated enormous files not really useful on an iPhone, sometimes enabling textures (with GL_TEXTURE_2D) just crashed an app. I know it might be a problem with too complicated models or my mistakes coming from inexeperience but I am not able to find any guidelines for that process to have streamlined cooperation with designers. I am even willing to write some things from scratch in pure OpenGL-ES if it's necessary, but I would like to avoid what might be avoided and get the most from the model files. The best would be the effect I saw on some SIO2 tutorials: export, build & go. But at that moment I've got only "import, wrong", "import, where are textures?", "import, that almost looks fine, export, hang" and so on... Is it really so much frustrating or I am just missed something obvious? Can anybody share his/her experience in that field and tell what kind of software uses for "making things happen"?

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  • How to Practice Unix Programming in C?

    - by danben
    After five years of professional Java (and to a lesser extent, Python) programming and slowly feeling my CS education slip away, I decided I wanted to broaden my horizons / general usefulness to the world and do something that feels more (to me) like I really have an influence over the machine. I chose to learn C and Unix programming since I feel like that is where many of the most interesting problems are. My end goal is to be able to do this professionally, if for no other reason than the fact that I have to spend 40-50 hours per week on work that pays the bills, so it may as well also be the type of coding I want to get better at. Of course, you don't get hired to do things you haven't dont before, so for now I am ramping up on my own. To this end, I started with K&R, which was a great resource in part due to the exercises spread throughout each chapter. After that I moved on to Computer Systems: A Programmer's Perspective, followed by ten chapters of Advanced Programming in the Unix Environment. When I am done with this book, I will read Unix Network Programming. What I'm missing in the Stevens books is the lack of programming problems; they mainly document functionality and provide examples, with a few end-of-chapter questions following. I feel that I would benefit much more from being challenged to use the knowledge in each chapter ala K&R. I could write some test program for each function, but this is a less desirable method as (1) I would probably be less motivated than if I were rising to some external challenge, and (2) I will naturally only think to use the function in the ways that have already occurred to me. So, I'd like to get some recommendations on how to practice. Obviously, my first choice would be to find some resource that has Unix programming challenges. I have also considered finding and attempting to contribute to some open source C project, but this is a bit daunting as there would be some overhead in learning to use the software, then learning the codebase. The only open-source C project I can think of that I use regularly is Python, and I'm not sure how easy that would be to get started on. That said, I'm open to all kinds of suggestions as there are likely things I haven't even thought of.

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  • Advice on displaying and allowing editing of data using ASP.NET MVC?

    - by Remnant
    I am embarking upon my first ASP.NET MVC project and I would like to get some input on possible ways to display database data and general best practice. In short, the body of my webpage will show data from my database in a table like format, with each table row showing similar data. For example: Name Age Position Date Joined Jon Smith 23 Striker 18th Mar 2005 John Doe 38 Defender 3rd Jan 1988 In terms of functionality, primarily I’d like to give the user the ability to edit the data and, after the edit, commit the edit to the database and refresh the view.The reason I want to refresh the view is because the data is date ordered and I will need to re-sort if the user edits a date field. My main question is what architecture / tools would be best suited to this fulfil my requirements at a high level? From the research I have done so far my initial conclusions were: ADO.NET for data retrieval. This is something I have used before and feel comfortable with. I like the look of LINQ to SQL but don’t want to make the learning curve any steeper for my first outing into MVC land just yet. Partial Views to create a template and then iterate through a datatable that I have pulled back from my database model. jQuery to allow the user to edit data in the table, error check edited data entries etc. Also, my intial view was that caching the data would not be a key requirement here. The only field a user will be able to update is the field and, if they do, I will need to commit that data to the database immediately and then refresh the view (as the data is date sorted). Any thoughts on this? Alternatively, I have seen some jQuery plug-ins that emulate a datagrid and provide associated functionality. My first thoughts are that I do not need all the functionality that comes with these plug-ins (e.g. zebra striping, ability to sort by column using sort glyph in column headers etc .) and I don’t really see any benefit to this over and above the solution I have outlined above. Again, is there reason to reconsider this view? Finally, when a user edits a date , I will need to refresh the view. In order to do this I had been reading about Html.RenderAction and this seemed like it may be a better option than using Partial Views as I can incorporate application logic into the action method. Am I right to consider Html.RenderAction or have I misunderstood its usage? Hope this post is clear and not too long. I did consider separate posts for each topic (e.g. Partial View vs. Html.RenderAction, when to use jQury datagrid plug-in) but it feels like these issues are so intertwined that they need to be dealt with in contect of each other. Thanks

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  • Create a screen like the iPhone home screen with Scrollview and Buttons

    - by Anthony Chan
    Hi, I'm working on a project and need to create a screen similar to the iPhone home screen: A scrollview with multiple pages A bunch of icons When not in edit mode, swipe through different pages (even I started the touch on an icon) When not in edit mode, tap an icon to do something When in edit mode, drag the icon to swap places, and even swap to different pages When in edit mode, tap an icon to remove it Previously I read from several forums that I have to subclass UIScrollview in order to have touch input for the UIViews on top of it. So I subclassed it overriding the methods to handle touches: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { //If not dragging, send event to next responder if (!self.dragging) [self.nextResponder touchesBegan:touches withEvent:event]; else [super touchesBegan:touches withEvent:event]; } In general I've override the touchesBegan:, touchesMoved: and touchesEnded: methods similarly. Then in the view controller, I added to following code: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; UIView *hitView = (UIView *)touch.view; if ([hitView isKindOfClass:[UIView class]]) { [hitView doSomething]; NSLog(@"touchesBegan"); } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { // Some codes to move the icons NSLog(@"touchesMoved"); } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"touchesEnded"); } When I run the app, I have the touchesBegan method detected correctly. However, when I tried to drag the icon, the icon just moved a tiny bit and then the page started to scroll. In console, it logged with 2 or 3 "touchesMoved" message only. However, I learned from another project that it should logged tonnes of "touchesMoved" message as long as I'm still dragging on the screen. (I'm suspecting I have the delaysContentTouches set to YES, so it delays a little bit when I tried to drag the icons. After that minor delay, it sends to signal back to the scrollview to scroll through the page. Please correct me if I'm wrong.) So if any help on the code to perform the above tasks would be greatly appreciated. I've stuck in this place for nearly a week with no hope. Thanks a lot.

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  • Challenge: Neater way of currying or partially applying C#4's string.Join

    - by Damian Powell
    Background I recently read that .NET 4's System.String class has a new overload of the Join method. This new overload takes a separator, and an IEnumerable<T> which allows arbitrary collections to be joined into a single string without the need to convert to an intermediate string array. Cool! That means I can now do this: var evenNums = Enumerable.Range(1, 100) .Where(i => i%2 == 0); var list = string.Join(",",evenNums); ...instead of this: var evenNums = Enumerable.Range(1, 100) .Where(i => i%2 == 0) .Select(i => i.ToString()) .ToArray(); var list = string.Join(",", evenNums); ...thus saving on a conversion of every item to a string, and then the allocation of an array. The Problem However, being a fan of the functional style of programming in general, and method chaining in C# in particular, I would prefer to be able to write something like this: var list = Enumerable.Range(1, 100) .Where(i => i%2 == 0) .string.Join(","); This is not legal C# though. The closest I've managed to get is this: var list = Enumerable.Range(1, 100) .Where(i => i%2 == 0) .ApplyTo( Functional.Curry<string, IEnumerable<object>, string> (string.Join)(",") ); ...using the following extension methods: public static class Functional { public static TRslt ApplyTo<TArg, TRslt>(this TArg arg, Func<TArg, TRslt> func) { return func(arg); } public static Func<T1, Func<T2, TResult>> Curry<T1, T2, TResult>(this Func<T1, T2, TResult> func) { Func<Func<T1, T2, TResult>, Func<T1, Func<T2, TResult>>> curried = f => x => y => f(x, y); return curried(func); } } This is quite verbose, requires explicit definition of the parameters and return type of the string.Join overload I want to use, and relies upon C#4's variance features because we are defining one of the arguments as IEnumerable rather than IEnumerable. The Challenge Can you find a neater way of achieving this using the method-chaining style of programming?

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  • Is Ogre's use of Exceptions a good way of using them?

    - by identitycrisisuk
    I've managed to get through my C++ game programming career so far virtually never touching exceptions but recently I've been working on a project with the Ogre engine and I'm trying to learn properly. I've found a lot of good questions and answers here on the general usage of C++ exceptions but I'd like to get some outside opinions from here on whether Ogre's usage is good and how best to work with them. To start with, quoting from Ogre's documentation of it's own Exception class: OGRE never uses return values to indicate errors. Instead, if an error occurs, an exception is thrown, and this is the object that encapsulates the detail of the problem. The application using OGRE should always ensure that the exceptions are caught, so all OGRE engine functions should occur within a try{} catch(Ogre::Exception& e) {} block. Really? Every single Ogre function could throw an exception and be wrapped in a try/catch block? At present this is handled in our usage of it by a try/catch in main that will show a message box with the exception description before exiting. This can be a bit awkward for debugging though as you don't get a stack trace, just the function that threw the error - more important is the function from our code that called the Ogre function. If it was an assert in Ogre code then it would go straight to the code in the debugger and I'd be able to find out what's going on much easier - I don't know if I'm missing something that would allow me to debug exceptions already? I'm starting to add a few more try/catch blocks in our code now, generally thinking about whether it matters if the Ogre function throws an exception. If it's something that will stop everything working then let the main try/catch handle it and exit the program. If it's not of great importance then catch it just after the function call and let the program continue. One recent example of this was building up a vector of the vertex/fragment program parameters for materials applied to an entity - if a material didn't have any parameters then it would throw an exception, which I caught and then ignored as it didn't need to add to my list of parameters. Does this seem like a reasonable way of dealing with things? Any specific advice for working with Ogre is much appreciated.

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  • Moving from Linear Probing to Quadratic Probing (hash collisons)

    - by Nazgulled
    Hi, My current implementation of an Hash Table is using Linear Probing and now I want to move to Quadratic Probing (and later to chaining and maybe double hashing too). I've read a few articles, tutorials, wikipedia, etc... But I still don't know exactly what I should do. Linear Probing, basically, has a step of 1 and that's easy to do. When searching, inserting or removing an element from the Hash Table, I need to calculate an hash and for that I do this: index = hash_function(key) % table_size; Then, while searching, inserting or removing I loop through the table until I find a free bucket, like this: do { if(/* CHECK IF IT'S THE ELEMENT WE WANT */) { // FOUND ELEMENT return; } else { index = (index + 1) % table_size; } while(/* LOOP UNTIL IT'S NECESSARY */); As for Quadratic Probing, I think what I need to do is change how the "index" step size is calculated but that's what I don't understand how I should do it. I've seen various pieces of code, and all of them are somewhat different. Also, I've seen some implementations of Quadratic Probing where the hash function is changed to accommodated that (but not all of them). Is that change really needed or can I avoid modifying the hash function and still use Quadratic Probing? EDIT: After reading everything pointed out by Eli Bendersky below I think I got the general idea. Here's part of the code at http://eternallyconfuzzled.com/tuts/datastructures/jsw_tut_hashtable.aspx: 15 for ( step = 1; table->table[h] != EMPTY; step++ ) { 16 if ( compare ( key, table->table[h] ) == 0 ) 17 return 1; 18 19 /* Move forward by quadratically, wrap if necessary */ 20 h = ( h + ( step * step - step ) / 2 ) % table->size; 21 } There's 2 things I don't get... They say that quadratic probing is usually done using c(i)=i^2. However, in the code above, it's doing something more like c(i)=(i^2-i)/2 I was ready to implement this on my code but I would simply do: index = (index + (index^index)) % table_size; ...and not: index = (index + (index^index - index)/2) % table_size; If anything, I would do: index = (index + (index^index)/2) % table_size; ...cause I've seen other code examples diving by two. Although I don't understand why... 1) Why is it subtracting the step? 2) Why is it diving it by 2?

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  • Is this (Lock-Free) Queue Implementation Thread-Safe?

    - by Hosam Aly
    I am trying to create a lock-free queue implementation in Java, mainly for personal learning. The queue should be a general one, allowing any number of readers and/or writers concurrently. Would you please review it, and suggest any improvements/issues you find? Thank you. import java.util.concurrent.atomic.AtomicReference; public class LockFreeQueue<T> { private static class Node<E> { E value; volatile Node<E> next; Node(E value) { this.value = value; } } private AtomicReference<Node<T>> head, tail; public LockFreeQueue() { // have both head and tail point to a dummy node Node<T> dummyNode = new Node<T>(null); head = new AtomicReference<Node<T>>(dummyNode); tail = new AtomicReference<Node<T>>(dummyNode); } /** * Puts an object at the end of the queue. */ public void putObject(T value) { Node<T> newNode = new Node<T>(value); Node<T> prevTailNode = tail.getAndSet(newNode); prevTailNode.next = newNode; } /** * Gets an object from the beginning of the queue. The object is removed * from the queue. If there are no objects in the queue, returns null. */ public T getObject() { Node<T> headNode, valueNode; // move head node to the next node using atomic semantics // as long as next node is not null do { headNode = head.get(); valueNode = headNode.next; // try until the whole loop executes pseudo-atomically // (i.e. unaffected by modifications done by other threads) } while (valueNode != null && !head.compareAndSet(headNode, valueNode)); T value = (valueNode != null ? valueNode.value : null); // release the value pointed to by head, keeping the head node dummy if (valueNode != null) valueNode.value = null; return value; }

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  • Why does Process Explorer cause highly targeted failure of some applications / basic UI functions in a high-power EC2 Windows instance?

    - by Dan Nissenbaum
    Update: I have determined that Process Explorer itself - the program I am using to debug a performance issue - seems to be the cause of the issue. See note, with updated question, at end. I am running a high-power (cc2.8xlarge) Amazon AWS EC2 Windows instance off of a boot EBS volume, provisioned at 2500 PIOPS, which was created from a snapshot of a previous boot volume. My purpose with the instance is to use it as a development workstation with many developer tools installed, such as Visual Studio, a local XAMPP stack, etc. I have upwards of 40 programs installed on the machine. The usability of the instance as a development machine often works quite well. The RDP lag is adequately small. I have used it for hours on end without problems for some of my most intense development tasks. As a result, I have just purchased a reserved instance, and I opted to rebuild my development machine starting from scratch with a Windows Server 2012 AMI. After having installed all of my desired/required applications for development over this past week, again the machine seems to often work well and I have worked for up to an hour at a time without problems doing heavy development work. However, I continue to run into catastrophic OS usability issues that may prevent me from being able to rely on this machine as a development machine. I would like to track down the source of the problem, if there is an easily identifiable source. (Update: I have tracked down the source to be Process Explorer, the very program I was using to debug the problem. See update at end.) The issues are as follows. (These are some primary examples) Some applications, after a period of adequate responsiveness, suddenly begin to respond very, very slowly to basic user interface actions such as clicking on menus and pressing Ctrl-Tab to switch between open documents. Two examples are UltraEdit and PhpEd. It typically takes ~2 seconds for a menu to appear, and ~4 seconds to switch between open documents. Additionally, insertion point motion in the editor is lagged by upwards of ~2 seconds. Process Explorer, which I am using to help debug the problem, seems to run acceptably for a couple of minutes, but on multiple occasions Process Explorer itself hangs completely. It hangs at the same time as the problems noted above. When it hangs, it is 100% unresponsive. Clicking on its taskbar icon neither causes it to come to the top or go behind, and its viewable area is filled with nothing but a region partially containing pure white and partially containing incomplete windows widgets that are unreadable, and that never change. Waiting 10 minutes does not clear the problem. Attempting to force-quit Process Explorer by right-clicking on its taskbar icon and choosing "Close Window" takes about 5 full minutes to exit (Process Explorer itself can't be used to exit Process Explorer, and it is registered as a Task Manager substitute). Other programs work just fine during this time. For example, Chrome tabs flip very quickly back and forth, menus pop open instantly, web pages load quickly, and typing in forms/web applications inside the browser works promptly. Another example of an application that works crisply is Filemaker - its menus open instantly, and switching views in this application occurs promptly. Other applications also work without issue. Also, switching between applications occurs promptly as well. It is only a handful of applications that exhibit the problem, with some primary examples given above. At first I thought that EBS IOPS might be a problem. Therefore, I ran Performance Monitor, and watched the "Disk Transfers/sec" monitor in real time. At no point did this measure come anywhere close to hitting the 2500 PIOPS provisioned for the EBS volume. The RAM was also well under the limit (~10 GB used out of 60 GB). I did notice that one CPU core (out of 32 logical cores) was fully thrashing at 100% (i.e., ~3.1%) during the problematic periods. This seems to indicate that a single CPU core is handling the menus / flipping between open documents (for some applications only) / managing the Process Explorer user interface, and that this single core was hosed for some reason during the problematic periods. Also note that I have a desktop workstation (Windows 7) that I also use as a development machine, via a remote connection, with a nearly identical set of programs installed, and this desktop workstation does not exhibit any of the problems I've discussed above. I have been using it heavily for well over a year now. Any suggestions regarding either the source of the problem, or steps I might take to investigate the source of the problem, would be appreciated. Thanks. Note: After extensive testing & investigation, I have noticed that when I quit Process Explorer, the problem vanishes and the system performance returns to normal, and then reappears quickly when I run Process Explorer again (note: again, the performance problems only appear for a subset of applications - other applications work perfectly fine during the same period). My question is therefore (thankfully) more specific: Why does Process Explorer cause highly targeted failure of some applications (including itself) and basic UI functions, in a high-power EC2 Windows instance?

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  • Faster Matrix Multiplication in C#

    - by Kyle Lahnakoski
    I have as small c# project that involves matrices. I am processing large amounts of data by splitting it into n-length chunks, treating the chucks as vectors, and multiplying by a Vandermonde** matrix. The problem is, depending on the conditions, the size of the chucks and corresponding Vandermonde** matrix can vary. I have a general solution which is easy to read, but way too slow: public byte[] addBlockRedundancy(byte[] data) { if (data.Length!=numGood) D.error("Expecting data to be just "+numGood+" bytes long"); aMatrix d=aMatrix.newColumnMatrix(this.mod, data); var r=vandermonde.multiplyBy(d); return r.ToByteArray(); }//method This can process about 1/4 megabytes per second on my i5 U470 @ 1.33GHz. I can make this faster by manually inlining the matrix multiplication: int o=0; int d=0; for (d=0; d<data.Length-numGood; d+=numGood) { for (int r=0; r<numGood+numRedundant; r++) { Byte value=0; for (int c=0; c<numGood; c++) { value=mod.Add(value, mod.Multiply(vandermonde.get(r, c), data[d+c])); }//for output[r][o]=value; }//for o++; }//for This can process about 1 meg a second. (Please note the "mod" is performing operations over GF(2^8) modulo my favorite irreducible polynomial.) I know this can get a lot faster: After all, the Vandermonde** matrix is mostly zeros. I should be able to make a routine, or find a routine, that can take my matrix and return a optimized method which will effectively multiply vectors by the given matrix, but faster. Then, when I give this routine a 5x5 Vandermonde matrix (the identity matrix), there is simply no arithmetic to perform, and the original data is just copied. ** Please note: What I use the term "Vandermonde", I actually mean an Identity matrix with some number of rows from the Vandermonde matrix appended (see comments). This matrix is wonderful because of all the zeros, and because if you remove enough rows (of your choosing) to make it square, it is an invertible matrix. And, of course, I would like to use this same routine to convert any one of those inverted matrices into an optimized series of instructions. How can I make this matrix multiplication faster? Thanks! (edited to correct my mistake with Vandermonde matrix)

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  • What are the Open Source alternatives to WPF/XAML?

    - by Evan Plaice
    If we've learned anything from HTML/CSS it's that, declarative languages (like XML) work best to describe User Interfaces because: It's easy to build code preprocessors that can template the code effectively. The code is in a well defined well structured (ideally) format so it's easy to parse. The technology to effectively parse or crawl an XML based source file already exists. The UIs scripted code becomes much simpler and easier to understand. It simple enough that designers are able to design the interface themselves. Programmers suck at creating UIs so it should be made easy enough for designers. I recently took a look at the meat of a WPF application (ie. the XAML) and it looks surprisingly familiar to the declarative language style used in HTML. It's apparent to me that the current state of desktop UI development is largely fractionalized, otherwise there wouldn't be so much duplicated effort in the domain of graphical user interface design (IE. GTK, XUL, Qt, Winforms, WPF, etc). There are 45 GUI platforms for Python alone It's seems reasonable to me that there should be a general purpose, open source, standardized, platform independent, markup language for designing desktop GUIs. Much like what the W3C made HTML/CSS into. WPF, or more specifically XAML seems like a pretty likely step in the right direction. Now that the 'browser wars' are over should we look forward to a future of 'desktop gui wars?' Note: This topic is relatively subjective in the attempt to be 'future-thinking.' I think that desktop GUI development in its current state sucks ((really)hard) and, even though WPF is still in it's infancy, it presents a likely solution to the problem. Update: Thanks a lot for the info, keep it comin'. Here's are the options I've gathered from the comments and answers. GladeXML Editor: Glade Interface Designer OS Platforms: All GUI Platform: GTK+ Languages: C (libglade), C++, C# (Glade#), Python, Ada, Pike, Perl, PHP, Eiffel, Ruby XRC (XML Resource) Editors: wxGlade, XRCed, wxDesigner, DialogBlocks (non-free) OS Platforms: All GUI Platform: wxWidgets Languages: C++, Python (wxPython), Perl (wxPerl), .NET (wx.NET) XML based formats that are either not free, not cross-platform, or language specific XUL Editor: Any basic text editor OS Platforms: Any OS running a browser that supports XUL GUI Platform: Gecko Engine? Languages: C++, Python, Ruby as plugin languages not base languages Note: I'm not sure if XUL deserves mentioning in this list because it's less of a desktop GUI language and more of a make-webapps-run-on-the-desktop language. Plus, it requires a browser to run. IE, it's 'DHTML for the desktop.' CookSwing Editor: Eclipse via WindowBuilder, NetBeans 5.0 (non-free) via Swing GUI Builder aka Matisse OS Platforms: All GUI Platform: Java Languages: Java only XAML (Moonlight) Editor: MonoDevelop OS Platforms: Linux and other Unix/X11 based OSes only GUI Platforms: GTK+ Languages: .NET Note: XAML is not a pure Open Source format because Microsoft controls its terms of use including the right to change the terms at any time. Moonlight can not legally be made to run on Windows or Mac. In addition, the only platform that is exempt from legal action is Novell. See this for a full description of what I mean.

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  • CSS/JavaScript/hacking: Detect :visited styling on a link *without* checking it directly OR do it fa

    - by Sai Emrys
    This is for research purposes on http://cssfingerprint.com Consider the following code: <style> div.csshistory a { display: none; color: #00ff00;} div.csshistory a:visited { display: inline; color: #ff0000;} </style> <div id="batch" class="csshistory"> <a id="1" href="http://foo.com">anything you want here</a> <a id="2" href="http://bar.com">anything you want here</a> [etc * ~2000] </div> My goal is to detect whether foo has been rendered using the :visited styling. I want to detect whether foo.com is visited without directly looking at $('1').getComputedStyle (or in Internet Explorer, currentStyle), or any other direct method on that element. The purpose of this is to get around a potential browser restriction that would prevent direct inspection of the style of visited links. For instance, maybe you can put a sub-element in the <a> tag, or check the styling of the text directly; etc. Any method that does not directly or indierctly rely on $('1').anything is acceptable. Doing something clever with the child or parent is probably necessary. Note that for the purposes of this point only, the scenario is that the browser will lie to JavaScript about all properties of the <a> element (but not others), and that it will only render color: in :visited. Therefore, methods that rely on e.g. text size or background-image will not meet this requirement. I want to improve the speed of my current scraping methods. The majority of time (at least with the jQuery method in Firefox) is spent on document.body.appendChild(batch), so finding a way to improve that call would probably most effective. See http://cssfingerprint.com/about and http://cssfingerprint.com/results for current speed test results. The methods I am currently using can be seen at http://github.com/saizai/cssfingerprint/blob/master/public/javascripts/history_scrape.js To summarize for tl;dr, they are: set color or display on :visited per above, and check each one directly w/ getComputedStyle put the ID of the link (plus a space) inside the <a> tag, and using jQuery's :visible selector, extract only the visible text (= the visited link IDs) FWIW, I'm a white hat, and I'm doing this in consultation with the EFF and some other fairly well known security researchers. If you contribute a new method or speedup, you'll get thanked at http://cssfingerprint.com/about (if you want to be :-P), and potentially in a future published paper. ETA: The bounty will be rewarded only for suggestions that can, on Firefox, avoid the hypothetical restriction described in point 1 above, or perform at least 10% faster, on any browser for which I have sufficient current data, than my best performing methods listed in the graph at http://cssfingerprint.com/about In case more than one suggestion fits either criterion, the one that does best wins.

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  • TabHost / TabWidget - Scale Background Image ?

    - by user359519
    I need to scale my TabWidget background images so they maintain aspect ratio. I am using a TabHost with a TabWidget. I am then using setBackgroundDrawable to set the images. I found a close answer here - Background in tab widget ignore scaling. However, I'm not sure just where to add the new Drawable code. (Working with the HelloTabWidget example, none of my modules use RelativeLayout, and I don't see any layout for "tabcontent".) I also found this thread - Android: Scale a Drawable or background image?. According to it, it sounds like I would have to pre-scale my images, which defeats the whole purpose of making them scaleable. I also found another thread where someone subclassed the Drawable class so it would either not scale, or it would scale properly. I can't find it now, but that seems like a LOT to go through when you should just be able to do something simple like mTab.setScaleType(centerInside). Here's my code: main.xml: <?xml version="1.0" encoding="utf-8"?> <TabHost xmlns:android="http://schemas.android.com/apk/res/android" android:id="@android:id/tabhost" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@drawable/main_background"> <LinearLayout android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <FrameLayout android:id="@android:id/tabcontent" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1"/> <TabWidget android:id="@android:id/tabs" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_weight="0"/> </LinearLayout> </TabHost> main activity: tabHost.setOnTabChangedListener(new OnTabChangeListener() { TabHost changedTabHost = getTabHost(); TabWidget changedTabWidget = getTabWidget(); View changedView = changedTabHost.getTabWidget().getChildAt(0); public void onTabChanged(String tabId) { int selectedTab = changedTabHost.getCurrentTab(); TabWidget tw = getTabWidget(); if(selectedTab == 0) { //setTitle("Missions Timeline"); View tempView = tabHost.getTabWidget().getChildAt(0); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_timeline_on)); tempView = tabHost.getTabWidget().getChildAt(1); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_map_off)); tempView = tabHost.getTabWidget().getChildAt(2); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_search_off)); tempView = tabHost.getTabWidget().getChildAt(3); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_news_off)); tempView = tabHost.getTabWidget().getChildAt(4); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_license_off)); //ImageView iv = (ImageView)tabHost.getTabWidget().getChildAt(0).findViewById(android.R.id.icon); //iv.setImageDrawable(getResources().getDrawable(R.drawable.tab_timeline_on)); //iv = (ImageView)tabHost.getTabWidget().getChildAt(1).findViewById(android.R.id.icon); //iv.setImageDrawable(getResources().getDrawable(R.drawable.tab_map_off)); } else if (selectedTab == 1) { //setTitle("Spinoffs Around You"); View tempView = tabHost.getTabWidget().getChildAt(0); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_timeline_off)); tempView = tabHost.getTabWidget().getChildAt(1); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_map_on)); tempView = tabHost.getTabWidget().getChildAt(2); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_search_off)); tempView = tabHost.getTabWidget().getChildAt(3); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_news_off)); tempView = tabHost.getTabWidget().getChildAt(4); tempView.setBackgroundDrawable(getResources().getDrawable(R.drawable.tab_license_off)); } I also tried 9patch images, but they wind up being too small. So, what's the best way to go about this?

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