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  • How do I catch the error from my printer with PrintDocument?

    - by Scottie
    I am using the PrintDocument class to print to my Brother label printer. When I execute the Print() method, the printer starts flashing a red error light, but everything else returns successful. I can run this same code on my laser printer and everything works fine. How can I see what is causing the error on my label printer? Code: public class Test { private Font printFont; private List<string> _documentLinesToPrint = new List<string>(); public void Run() { _documentLinesToPrint.Add("Test1"); _documentLinesToPrint.Add("Test2"); printFont = new Font("Arial", 10); var pd = new PrintDocument(); pd.DefaultPageSettings.Margins = new Margins(25, 25, 25, 25); pd.DefaultPageSettings.PaperSize = new PaperSize("Label", 400, 237); var printerSettings = new System.Drawing.Printing.PrinterSettings(); printerSettings.PrinterName ="Brother QL-570 LE"; pd.PrinterSettings = printerSettings; pd.PrinterSettings.Copies = 1; pd.PrintPage += new PrintPageEventHandler(this.pd_PrintPage); pd.Print(); } // The PrintPage event is raised for each page to be printed. private void pd_PrintPage(object sender, PrintPageEventArgs ev) { float linesPerPage = 0; float yPos = 0; int count = 0; float leftMargin = ev.MarginBounds.Left; float topMargin = ev.MarginBounds.Top; string line = null; // Calculate the number of lines per page. linesPerPage = ev.MarginBounds.Height / printFont.GetHeight(ev.Graphics); // Print each line of the file. while ((count < linesPerPage) && (count < _documentLinesToPrint.Count)) { line = _documentLinesToPrint[count]; yPos = topMargin + (count * printFont.GetHeight(ev.Graphics)); ev.Graphics.DrawString(line, printFont, Brushes.Black, leftMargin, yPos, new StringFormat()); line = null; count++; } // If more lines exist, print another page. if (line != null) ev.HasMorePages = true; else ev.HasMorePages = false; } }

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  • Custom event loop and UIKit controls. What extra magic Apple's event loop does?

    - by tequilatango
    Does anyone know or have good links that explain what iPhone's event loop does under the hood? We are using a custom event loop in our OpenGL-based iPhone game framework. It calls our game rendering system, calls presentRenderbuffer and pumps events using CFRunLoopRunInMode. See the code below for details. It works well when we are not using UIKit controls (as a proof, try Facetap, our first released game). However, when using UIKit controls, everything almost works, but not quite. Specifically, scrolling of UIKit controls doesn't work properly. For example, let's consider following scenario. We show UIImagePickerController on top of our own view. UIImagePickerController covers our custom view We also pause our own rendering, but keep on using the custom event loop. As said, everything works, except scrolling. Picking photos works. Drilling down to photo albums works and transition animations are smooth. When trying to scroll photo album view, the view follows your finger. Problem: when scrolling, scrolling stops immediately after you lift your finger. Normally, it continues smoothly based on the speed of your movement, but not when we are using the custom event loop. It seems that iPhone's event loop is doing some magic related to UIKit scrolling that we haven't implemented ourselves. Now, we can get UIKit controls to work just fine and dandy together with our own system by using Apple's event loop and calling our own rendering via NSTimer callbacks. However, I'd still like to understand, what is possibly happening inside iPhone's event loop that is not implemented in our custom event loop. - (void)customEventLoop { OBJC_METHOD; float excess = 0.0f; while(isRunning) { animationInterval = 1.0f / openGLapp->ticks_per_second(); // Calculate the target time to be used in this run of loop float wait = max(0.0, animationInterval - excess); Systemtime target = Systemtime::now().after_seconds(wait); Scope("event loop"); NSAutoreleasePool* pool = [[ NSAutoreleasePool alloc] init]; // Call our own render system and present render buffer [self drawView]; // Pump system events [self handleSystemEvents:target]; [pool release]; excess = target.seconds_to_now(); } } - (void)drawView { OBJC_METHOD; // call our own custom rendering bool bind = openGLapp->app_render(); // bind the buffer to be THE renderbuffer and present its contents if (bind) { opengl::bind_renderbuffer(renderbuffer); [context presentRenderbuffer:GL_RENDERBUFFER_OES]; } } - (void) handleSystemEvents:(Systemtime)target { OBJC_METHOD; SInt32 reason = 0; double time_left = target.seconds_since_now(); if (time_left <= 0.0) { while((reason = CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, TRUE)) == kCFRunLoopRunHandledSource) {} } else { float dt = time_left; while((reason = CFRunLoopRunInMode(kCFRunLoopDefaultMode, dt, FALSE)) == kCFRunLoopRunHandledSource) { double time_left = target.seconds_since_now(); if (time_left <= 0.0) break; dt = (float) time_left; } } }

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  • Unhandled Exception in c#

    - by nightcoder1
    Hello i am currently trying to run a web crawler through the terminal. it compiles fine and the debug does not find any errors, however i get the following error which i do not understand. any ideas on how to get rid of this error would be much appreciated Unhandled Exception: System.ArgumentOutOfRangeException: startIndex + length > this.length Parameter name: length at System.String.Substring (Int32 startIndex, Int32 length) [0x00000] at OpenWebSpiderCS.mysql.executeSQLQuery (System.String SQL) [0x00000] at OpenWebSpiderCS.db.startIndexThisSite (OpenWebSpiderCS.page p) [0x00000] at OpenWebSpiderCS.ows.startCrawling () [0x00000] at OpenWebSpiderCS.mainClass.Main (System.String[] args) [0x00000] thank you

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  • Is there a reason Image.FromFile throws an OutOfMemoryException for an invalid image format?

    - by Arc
    I am writing code that catches this OutOfMemoryException and throws a new, more intuitive exception: /// ... /// <exception cref="FormatException">The file does not have a valid image format.</exception> public static Image OpenImage( string filename ) { try { return Image.FromFile( filename, ); } catch( OutOfMemoryException ex ) { throw new FormatException( "The file does not have a valid image format.", ex ); } } Is this code acceptable to its user, or is OutOfMemoryException intentionally being thrown for a particular reason?

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  • Should I throw my own ArgumentOutOfRangeException or let one bubble up from below?

    - by Neil N
    I have a class that wraps List< I have GetValue by index method: public RenderedImageInfo GetValue(int index) { list[index].LastRetrieved = DateTime.Now; return list[index]; } If the user requests an index that is out of range, this will throw an ArgumentOutOfRangeException . Should I just let this happen or check for it and throw my own? i.e. public RenderedImageInfo GetValue(int index) { if (index >= list.Count) { throw new ArgumentOutOfRangeException("index"); } list[index].LastRetrieved = DateTime.Now; return list[index]; } In the first scenario, the user would have an exception from the internal list, which breaks mt OOP goal of the user not needing to know about the underlying objects. But in the second scenario, I feel as though I am adding redundant code. Edit: And now that I think of it, what about a 3rd scenario, where I catch the internal exception, modify it, and rethrow it?

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  • Why does this C# event handler not respond to this event in this Silverlight application?

    - by Edward Tanguay
    Can anyone tell me why the following code successfully executes this event: OnLoadingComplete(this, null); but never executes this event handler? void initialDataLoader_OnLoadingComplete(object obj, DataLoaderArgs args) CODE: using System; using System.Collections.Generic; using System.Linq; using System.Windows.Controls; using System.Diagnostics; namespace TestEvent22928 { public partial class MainPage : UserControl { public MainPage() { InitializeComponent(); DataLoader initialDataLoader = new DataLoader("initial"); initialDataLoader.RegisterText("test1", "http://test:111/testdata/test1.txt"); initialDataLoader.RegisterText("test2", "http://test:111/testdata/test2.txt"); initialDataLoader.BeginLoading(); initialDataLoader.OnLoadingComplete += new DataLoader.LoadingComplete(initialDataLoader_OnLoadingComplete); } void initialDataLoader_OnLoadingComplete(object obj, DataLoaderArgs args) { Debug.WriteLine("loading complete"); //WHY DOES EXECUTION NEVER GET HERE? } } public class DataManager { public DataLoader CreateDataloader(string dataloaderIdCode) { DataLoader dataLoader = new DataLoader(dataloaderIdCode); return dataLoader; } } public class DataLoader { public string IdCode { get; set; } public List<DataItem> DataItems { get; set; } public delegate void LoadingComplete(object obj, DataLoaderArgs args); public event LoadingComplete OnLoadingComplete = delegate { }; private int dataItemCurrentlyLoadingIndex; public DataLoader(string idCode) { IdCode = idCode; DataItems = new List<DataItem>(); dataItemCurrentlyLoadingIndex = -1; } public void RegisterText(string idCode, string absoluteSourceUrl) { DataItem dataItem = new DataItem { IdCode = idCode, AbsoluteSourceUrl = absoluteSourceUrl, Kind = DataItemKind.Text }; DataItems.Add(dataItem); } public void BeginLoading() { LoadNext(); } private void LoadNext() { dataItemCurrentlyLoadingIndex++; if (dataItemCurrentlyLoadingIndex < DataItems.Count()) { DataItem dataItem = DataItems[dataItemCurrentlyLoadingIndex]; Debug.WriteLine("loading " + dataItem.IdCode + "..."); LoadNext(); } else { OnLoadingComplete(this, null); //EXECUTION GETS HERE } } } public class DataItem { public string IdCode { get; set; } public string AbsoluteSourceUrl { get; set; } public DataItemKind Kind { get; set; } public object DataObject { get; set; } } public enum DataItemKind { Text, Image } public class DataLoaderArgs : EventArgs { public string Message { get; set; } public DataItem DataItem { get; set; } public DataLoaderArgs(string message, DataItem dataItem) { Message = message; DataItem = dataItem; } } }

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  • File Encoding handling in Eclipse 3.5

    - by Cédric Girard
    Hi, I use Eclipse 3.5 on Windows, with PDT and Subclipse plugins, with both legacy projects using ISO-8859-1 encoding (latin-1), and newers ones wich use UTF-8. I configured my workspace to use UTF-8, and I configured old projects to use latin-1. But every time I open an old project, it use UTF-8. With a workspace using latin-1 by default, I have the same problem with utf-8 projects edited as iso-8859-1. My encoding choice is written in the file .settings/org.eclipse.core.resources.prefs but seems to be never read. The only solution for now is to have a latin1 workspace, and an utf8 one. Any better idea? Regards, Cédric

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  • Why is there no assertError() function in FlexUnit?

    - by lorennorman
    It seems that most XUnit testing frameworks provide assertions for the times when you want to assert that a given operation will thrown an exception (or an Error in AS3 parlance.) Is there some "standard" way of doing this that I am overlooking, which would explain the absence of an assertError() assertion included with FlexUnit? I know HOW to implement such a thing, and I will probably add it to my FlexUnit (go open source!), but it seems like such a glaring omission that I'm left wondering if I'm just doing it wrong. Anyone have thoughts on this?

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  • Handling inverse kinematics: animation blending or math?

    - by meds
    I've been working for the past four days on inverse kinematics for my game engine. I'm working on a game with a shoestring budget so when the idea of inverse kinematics came up I knew I had to make it such that the 3D models bones would be mathematically changed to appear to be stepping on objects. This is causing some serious problems with my animation, after it was technically implemented the animations started looking quite bad when the character was wlaking up inclines or steps even though mathematically the stepping was correct and was even smoothly interpolating. So I was wondering, is it actually possible to get a smooth efficient inverse kinematic system based exclusively on math where bones are changed or is this just a wild goose chase and I should either solve the inverse kinematics problem with animation blending or don't do it at all?

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  • Handling Special char such as ^ÛY, ^ÛR in java

    - by RJ
    Hi, Has anybody encountered special char such as ^ÛY, ^ÛR ? Q1. How do I do an ftp of the files containing these chars? The chars are not seen once I do a ftp on AIX (bi or ascii) and hence I am unable to see my program to replace these, working. Q2. My java program doesn't seem to recognise these or replace these if I search for these explicitly (^ÛY, ^ÛR ) in the file however a replace using regular expression seems to work (I could only see the difference in the length of the string). My program is executed on AIX. Any insights why java cannot recognise these? Q3. Does the Oracle database recognise these chars? An update is failing where my program indicates the string to be of lesser length and without these characters but the db complains "value too large for column" as the string to be updated contains these chars and hence longer. thanks in advance, RJ

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  • controlling if exceptions are swallowed by a static boolean

    - by sandis
    So we are a few guys developing this product that is communicating with a really unstable server. It often returns very strange and corrupt data. During testing we want the resulting crashes to be loud, so we discover them. But every other day we need to demonstrate our product for a potential customer. To the customer the errors will go undiscovered if we just swallow them. I am thinking about implementing something like this around all server communication to quickly switch between swallowing exceptions and crashing: try { apiCall(); } catch (Exception e) { if(!SWALLOW_EXCEPTION) { throw e; } } Is this an awesome idea, or can it be done in a better way?

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  • Throw a long list of exceptions vs throw an Exception vs throw custom exception?

    - by athena
    I have an application which uses two methods of an API. Both these methods throw more than five exceptions each. So, if I just add a throws declaration then it becomes a list of more than ten. (My method cannot handle any of the ten exceptions) I have read that throwing a long list of exceptions is a bad practice. Also throwing (the umbrella) Exception is a bad practice. So, what should I do? Add a try catch block, and log and exit in the catch block? (Current approach) Create a custom exception class, wrap every exception and throw the custom exception? Add a throws declaration for all exceptions? Throw Exception?

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  • Unable to catch exception from Activator.CreateInstance.

    - by Patrik Hägne
    OK, I admit it this code will just look weird to you, and that's because it is weird. This is just code to reproduce the behavior, not code I want to use. class Program { static void Main(string[] args) { try { Activator.CreateInstance(typeof(Func<int>), new object[] { new object(), IntPtr.Zero }); } catch { Console.WriteLine("This won't print!"); } Console.Write("Actually this will not print either!"); Console.ReadLine(); } } No matter what exception type I try to catch (the actual exception thrown is an ArgumentException as far as I can tell) the code inside the catch block will not execute. Actually execution will just stop at the Activator.CreateInstance-line.

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  • Stream (.NET) handling best-practices

    - by Jader Dias
    The question is entitled with the word "Stream" because the question below is a concrete example of a more generic doubt I have about Streams: I have a problem that accepts two solutions and I want to know the best one: I download a file, save it to disk (2 min), read it and write the contents to the DB (+ 2 min). I download a file and write the contents directly to the DB (3 min). If the write to DB fails I'll have to download again in the second case, but not in the first case. Which is best? Which would you use?

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  • ASP.NET MVC: Returning a view with querystring in tact

    - by ajbeaven
    I'm creating a messaging web app in ASP.NET and are having some problems when displaying an error message to the user if they go to send a message and there is something wrong. A user can look through profiles of people and then click, 'send a message'. The following action is called (url is /message/create?to=username) and shows them a page where they can enter their message and send it: public ActionResult Create(string to) { ViewData["recipientUsername"] = to; return View(); } On the page that is displayed, the username is entered in to a hidden input field. When the user clicks 'send': [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(string message, string to) { try { //do message stuff that errors out } catch { ModelState.AddModelErrors(message.GetRuleViolations()); //adding errors to modelstate } return View(); } So now the error message is displayed to the user fine, however the url is changed in that it no longer has the querystring (/message/create). Again, this would be fine except that when the user clicks the refresh button, the page errors out as the Create action no longer has the 'to' parameter. So I'm guessing that I need to maintain my querystring somehow. Is there any way to do this or do I need to use a different method altogether?

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  • Graceful handling of server timeout in BlazeDS

    - by Rydell
    I have a flex client that makes service calls to a tomcat server running BlazeDS. I would like to gracefully handle server session timeouts in this environment. I do have security constraints on the service, so the client authenticates against a remote object by initializing a ChannelSet based on the destination, and then logging in using that ChannelSet. After the user is authenticated, if they go get a (long) cup of coffee, their session will inevitably time out. I would like the client to detect the timeout, and return the user back to the login page, with the appropriate informational messages. But I am having difficulty finding the best way to detect this timeout from the client. Is it possible, or must I have the server throw an error when the timeout occurs? Thanks!

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  • PHP autoloader: ignoring non-existing include

    - by Bart van Heukelom
    I have a problem with my autoloader: public function loadClass($className) { $file = str_replace(array('_', '\\'), '/', $className) . '.php'; include_once $file; } As you can see, it's quite simple. I just deduce the filename of the class and try to include it. I have a problem though; I get an exception when trying to load a non-existing class (because I have an error handler which throws exceptions). This is inconvenient, because it's also fired when you use class_exists() on a non-existing class. You don't want an exception there, just a "false" returned. I fixed this earlier by putting an @ before the include (supressing all errors). The big drawback with this, though, is that any parser/compiler errors (that are fatal) in this include won't show up (not even in the logs), resulting in a hard to find bug. What would be the best way to solve both problems at once? The easiest way would be to include something like this in the autoloader (pseudocode): foreach (path in the include_path) { if (is_readable(the path + the class name)) readable = true; } if (!readable) return; But I worry about the performance there. Would it hurt a lot? (Solved) Made it like this: public function loadClass($className) { $file = str_replace(array('_', '\\'), '/', $className) . '.php'; $paths = explode(PATH_SEPARATOR, get_include_path()); foreach ($paths as $path) { if (is_readable($path . '/' . $file)) { include_once $file; return; } } }

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  • Handling Errors in PHP

    - by Mike
    I have a custom class that, when called, will redirect to a page and send a 'message_type' and 'message' variable via GET. When the page opens it checks for these variables and displays a 'success', 'warning', or 'error' message depending on the 'message_type' variable. I made it so the user thinks they stay on the same page. It also allows for other variables to be passed along with the message. Is this good practice, or should I just start using exceptions? Example: //Call a static function that will redirect to a page, with an error message RedirectWithMessage::go('somepage.php', MessageType::ERROR, 'Error message here.'); The following checkMessage() function is an include file: function checkMessage() { if((isset($_GET['message_type']) && strlen($_GET['message_type'])) && (isset($_GET['message']) && strlen($_GET['message_type']))) { DisplayMessage::display($_GET['message_type'], $_GET['message']); return true; } return false; } On the page that is redirected to, call checkMessage(); //If a message is received, display it. If not, do nothing checkMessage(); I know this might be vague, and I can supply more code if necessary. I guess the issue is that I don't have much experience using exceptions, but I think they seem cumbersome (writing try-catch blocks everywhere). Please let me know if I am making this more difficult for myself or if there is a better solution. Thanks! Mike

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  • Logging and Error handling in asp.net

    - by parminder
    Hi Experts, I have a website running now. I have to implement some logging routines as well as some handler for unhandeled exceptions. I was looking at ELMAH also which seems good to me. I need something very light and easy to use. Can someone recommend any other option I can choose from. Thanks Parminder

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  • Squid handling of concurrent cache misses

    - by Oliver H-H
    We're using a Squid cache to off-load traffic from our web servers, ie. it's setup as a reverse-proxy responding to inbound requests before they hit our web servers. When we get blitzed with concurrent requests for the same request that's not in the cache, Squid proxies all the requests through to our web ("origin") servers. For us, this behavior isn't ideal: our origin servers gets bogged down trying to fulfill N identical requests concurrently. Instead, we'd like the first request to proxy through to the origin server, the rest of the requests to queue at the Squid layer, and then all be fulfilled by Squid when the origin server has responded to that first request. Does anyone know how to configure Squid to do this? We've read through the documentation multiple times and thoroughly web-searched the topic, but can't figure out how to do it. We use Akamai too and, interestingly, this is its default behavior. (However, Akamai has so many nodes that we still see lots of concurrent requests in certain traffic spike scenarios, even with Akamai's super-node feature enabled.) This behavior is clearly configurable for some other caches, eg. the Ehcache documentation offers the option "Concurrent Cache Misses: A cache miss will cause the filter chain, upstream of the caching filter to be processed. To avoid threads requesting the same key to do useless duplicate work, these threads block behind the first thread." Some folks call this behavior a "blocking cache," since the subsequent concurrent requests block behind the first request until it's fulfilled or timed-out. Thx for looking over my noob question! Oliver

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  • Neural Network: Handling unavailable inputs (missing or incomplete data)

    - by Mike
    Hopefully the last NN question you'll get from me this weekend, but here goes :) Is there a way to handle an input that you "don't always know"... so it doesn't affect the weightings somehow? Soo... if I ask someone if they are male or female and they would not like to answer, is there a way to disregard this input? Perhaps by placing it squarely in the centre? (assuming 1,0 inputs at 0.5?) Thanks

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  • Why should I not wrap every block in "try"-"catch"?

    - by Konrad
    I have always been of the belief that if a method can throw an exception then it is reckless not to protect this call with a meaningful try block. I just posted 'You should ALWAYS wrap calls that can throw in try, catch blocks.' to this question and was told that it was 'remarkably bad advice' - I'd like to understand why. Thanks!

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