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  • Winforms: calling entry form function from a different class

    - by samy
    I'm kinda new to programming and got a question on what is a good practice. I created a class that represents a ball and it has a function Jump() that use 2 timers and get the ball up and down. I know that in Winforms you got to call Invalidate() every time you want to repaint the screen, or part of it. I didn't find a good way to do that, so I reference the form in my class, and called Invalidate() inside my ball class every time I need to repaint to ball movement. (this works but I got a feeling that this is not a good practice) Here is the class I created: public class Ball { public Form1 parent;//----> here is the reference to the form public Rectangle ball; Size size; public Point p; Timer timerBallGoUp = new Timer(); Timer timerBallGDown = new Timer(); public int ballY; public Ball(Size _size, Point _p) { size = _size; p = _p; ball = new Rectangle(p, size); } public void Jump() { ballY = p.Y; timerBallGDown.Elapsed += ballGoDown; timerBallGDown.Interval = 50; timerBallGoUp.Elapsed += ballGoUp; timerBallGoUp.Interval = 50; timerBallGoUp.Start(); } private void ballGoUp(object obj,ElapsedEventArgs e) { p.Y++; ball.Location = new Point(ball.Location.X, p.Y); if (p.Y >= ballY + 50) { timerBallGoUp.Stop(); timerBallGDown.Start(); } parent.Invalidate(); // here i call parent.Invalidate() 1 } private void ballGoDown(object obj, ElapsedEventArgs e) { p.Y--; ball.Location = new Point(ball.Location.X, p.Y); if (p.Y <= ballY) { timerBallGDown.Stop(); timerBallGoUp.Start(); } parent.Invalidate(); // here i call parent.Invalidate() 2 } } I'm wondring if there is a better way to do that? (sorry for my english)

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  • Tomcat - Redirect to Error Page when ServletContextListener fails

    - by Vic
    When Tomcat starts it calls my ServletContextListener to obtain a database connection, which I will later use in other servlets with getServletContext(). It is called in my web.xml as: listener listener-class org.ppdc.database.DBCPoolingListener /listener-class /listener (I removed the < because they wouldn't display properly in this message. If I cannot connect to the database when Tomcat starts up I get a 404 error, because Tomcat cannot start the application. How can I redirect the user to a custom error page at this point? I tried the following in my web.xml (I have the < brackets in the original): (error-page) (error-code404/error-code) (location/file_not_found.html/location) (/error-page) Any ideas on how to redirect a user to one of my error pages when Tomcat tries to start the application? Thanks Vic

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  • Array of previous weeks

    - by azz0r
    Hello, I am trying to create an array of weeks for users to select to view stats week on week. What I'm looking for is an array that has the timestamp of week start (monday 00.00 to sunday 11.59) that I can then use in MYSQL queries. Has anyone got an code that might assist? I was thinking of doing something like: $number_of_weeks = 4; $week_array = array(); foreach ($number_of_weeks as $week) { $number_of_weeks--; $value = $number_of_weeks * 604800; $StartOfLastWeek = 6 + date("w",mktime()); $week_array[$number_of_week]['start'] = date('Y-m-d', strtotime("-$StartOfLastWeek day"), $value); $week_array[$number_of_week]['end'] = date('Y-m-d', strtotime("-$StartOfLastWeek day"), $value+ 604800); }

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  • how to create a rounded transparent rectangle by using cocoa touch ?

    - by srikanth rongali
    Hi, I need to create a rounded rectangular box in which there will be 6 buttons in iPhone application. And the rectangular box is transparent. Each button have an image and text. And they are also transparent. ( Here transparent means we can see the background image of the box. Sorry for my vocabulary.) I could not get how to start it. I thought of the following one but, By using core graphics draw the outside rounded rectangle and then draw inside rectangles like 2x3 grid. Can I make with this ? Are there any good and easy methods than this. Please give me some idea how to start over with ? Thank you.

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  • Streaming Audio from A URL in Android using MediaPlayer?

    - by Sena Gbeckor-Kove
    Hi, I've been trying to stream mp3's over http using Android's built in MediaPlayer class. The documentation would suggest to me that this should be as easy as : MediaPlayer mp = new MediaPlayer(); mp.setDataSource(URL_OF_FILE); mp.prepare(); mp.start(); However I am getting the following repeatedly. I have tried different URLs as well. Please don't tell me that streaming doesn't work on mp3's. E/PlayerDriver( 31): Command PLAYER_SET_DATA_SOURCE completed with an error or info PVMFErrNotSupported W/PlayerDriver( 31): PVMFInfoErrorHandlingComplete E/MediaPlayer( 198): error (1, -4) E/MediaPlayer( 198): start called in state 0 E/MediaPlayer( 198): error (-38, 0) E/MediaPlayer( 198): Error (1,-4) E/MediaPlayer( 198): Error (-38,0) Any help much appreciated, thanks S

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  • Problem with memory leaks

    - by user191723
    Sorry, having difficulty formattin code to appear correct here??? I am trying to understand the readings I get from running instruments on my app which are telling me I am leaking memory. There are a number, quite a few in fact, that get reported from inside the Foundation, AVFoundation CoreGraphics etc that I assume I have no control over and so should ignore such as: Malloc 32 bytes: 96 bytes, AVFoundation, prepareToRecordQueue or Malloc 128 bytes: 128 bytes, CoreGraphics, open_handle_to_dylib_path Am I correct in assuming these are something the system will resolve? But then there are leaks that are reported that I believe I am responsible for, such as: This call reports against this line leaks 2.31KB [self createAVAudioRecorder:frameAudioFile]; Immediately followed by this: -(NSError*) createAVAudioRecorder: (NSString *)fileName { // flush recorder to start afresh [audioRecorder release]; audioRecorder = nil; // delete existing file to ensure we have clean start [self deleteFile: fileName]; VariableStore *singleton = [VariableStore sharedInstance]; // get full path to target file to create NSString *destinationString = [singleton.docsPath stringByAppendingPathComponent: fileName]; NSURL *destinationURL = [NSURL fileURLWithPath: destinationString]; // configure the recording settings NSMutableDictionary *recordSettings = [[NSMutableDictionary alloc] initWithCapacity:6]; //****** LEAKING 384 BYTES [recordSettings setObject:[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey: AVFormatIDKey]; //***** LEAKING 32 BYTES float sampleRate = 44100.0; [recordSettings setObject:[NSNumber numberWithFloat: sampleRate] forKey: AVSampleRateKey]; //***** LEAKING 48 BYTES [recordSettings setObject:[NSNumber numberWithInt:2] forKey:AVNumberOfChannelsKey]; int bitDepth = 16; [recordSettings setObject: [NSNumber numberWithInt:bitDepth] forKey:AVLinearPCMBitDepthKey]; //***** LEAKING 48 BYTES [recordSettings setObject:[NSNumber numberWithBool:YES] forKey:AVLinearPCMIsBigEndianKey]; [recordSettings setObject:[NSNumber numberWithBool: NO]forKey:AVLinearPCMIsFloatKey]; NSError *recorderSetupError = nil; // create the new recorder with target file audioRecorder = [[AVAudioRecorder alloc] initWithURL: destinationURL settings: recordSettings error: &recorderSetupError]; //***** LEAKING 1.31KB [recordSettings release]; recordSettings = nil; // check for erros if (recorderSetupError) { UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Can't record" message: [recorderSetupError localizedDescription] delegate: nil cancelButtonTitle: @"OK" otherButtonTitles: nil]; [alert show]; [alert release]; alert = nil; return recorderSetupError; } [audioRecorder prepareToRecord]; //***** LEAKING 512 BYTES audioRecorder.delegate = self; return recorderSetupError; } I do not understand why there is a leak as I release audioRecorder at the start and set to nil and I release recordSettings and set to nil? Can anyone enlighten me please? Thanks

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  • Windows GUI application when user is not logged in?

    - by Tiax
    I've written a Autoit script that starts a GUI application, when the application starts there is a login form. The scripts fills the login form and tries to log in. Then it records the time it took to login to the application and shuts the application down afterwards, writes a output file with the time it took. The thing is, I can't get the application to start unless Im logged in as the user the Scheduled task is running on. So my question is: Is there any way to start a GUI application even though the user isn't logged in? Or is the only way to have a user always logged in?

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  • What would you recommend to do simple 2D Graphics?

    - by Tom Ritter
    I want to build a program that will (as part of what it's doing) display lines organically growing and interacting horizontally across the screen. Here's a sample image, just imagine the lines sprouting from the left and growing to the right: The lines would look like the lines used on Google Maps Transit Overlay or OnNYTurf's transit pages. It's a personal project, so I'm open to just about any language and library combination. But I don't know where to start. What have you used in the past to create graphics that are similar to this? What would you recommend? I want it to run on Windows without any extras needed (.Net is fine), and it doesn't have to run elsewhere. I needs to run as an actual program, not javascript in the browser. There's obviously no 'right' answer to this, but the purpose isn't to start an argument about X better than Y but rather just find a list of graphics toolkits that do simple 2D graphics that people recommend because of their ease of use or community or whatever.

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  • JPanel Layout Image Cutoff

    - by Trizicus
    I am adding images to a JPanel but the images are getting cut off. I was originally trying BorderLayout but that only worked for one image and adding others added image cut-off. So I switched to other layouts and the best and closest I could get was BoxLayout however that adds a very large cut-off which is not acceptable either. So basically; How can I add images (from a custom JComponent) to a custom JPanel without bad effects such as the one present in the code. Custom JPanel: import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import javax.swing.BoxLayout; import javax.swing.JPanel; import javax.swing.Timer; public class GraphicsPanel extends JPanel implements MouseListener { private Entity test; private Timer timer; private long startTime = 0; private int numFrames = 0; private float fps = 0.0f; GraphicsPanel() { test = new Entity("test.png"); Thread t1 = new Thread(test); t1.start(); Entity ent2 = new Entity("images.jpg"); ent2.setX(150); ent2.setY(150); Thread t2 = new Thread(ent2); t2.start(); Entity ent3 = new Entity("test.png"); ent3.setX(0); ent3.setY(150); Thread t3 = new Thread(ent3); t3.start(); //ESSENTIAL setLayout(new BoxLayout(this, BoxLayout.X_AXIS)); add(test); add(ent2); add(ent3); //GAMELOOP timer = new Timer(30, new Gameloop(this)); timer.start(); addMouseListener(this); } @Override public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D) g.create(); g2.setClip(0, 0, getWidth(), getHeight()); g2.setColor(Color.BLACK); g2.drawString("FPS: " + fps, 1, 15); } public void getFPS() { ++numFrames; if (startTime == 0) { startTime = System.currentTimeMillis(); } else { long currentTime = System.currentTimeMillis(); long delta = (currentTime - startTime); if (delta > 1000) { fps = (numFrames * 1000) / delta; numFrames = 0; startTime = currentTime; } } } public void mouseClicked(MouseEvent e) {} public void mousePressed(MouseEvent e) {} public void mouseReleased(MouseEvent e) {} public void mouseEntered(MouseEvent e) { } public void mouseExited(MouseEvent e) { } class Gameloop implements ActionListener { private GraphicsPanel gp; Gameloop(GraphicsPanel gp) { this.gp = gp; } public void actionPerformed(ActionEvent e) { try { gp.getFPS(); gp.repaint(); } catch (Exception ez) { } } } } Main class: import java.awt.EventQueue; import javax.swing.JFrame; public class MainWindow { public static void main(String[] args) { new MainWindow(); } private JFrame frame; private GraphicsPanel gp = new GraphicsPanel(); MainWindow() { EventQueue.invokeLater(new Runnable() { public void run() { frame = new JFrame("Graphics Practice"); frame.setSize(680, 420); frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.add(gp); } }); } } Custom JComponent import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.image.BufferedImage; import javax.imageio.ImageIO; import javax.swing.JComponent; public class Entity extends JComponent implements Runnable { private BufferedImage bImg; private int x = 0; private int y = 0; private int entityWidth, entityHeight; private String filename; Entity(String filename) { this.filename = filename; } public void run() { bImg = loadBImage(filename); entityWidth = bImg.getWidth(); entityHeight = bImg.getHeight(); setPreferredSize(new Dimension(entityWidth, entityHeight)); } @Override public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g.create(); g2d.drawImage(bImg, x, y, null); g2d.dispose(); } public BufferedImage loadBImage(String filename) { try { bImg = ImageIO.read(getClass().getResource(filename)); } catch (Exception e) { } return bImg; } public int getEntityWidth() { return entityWidth; } public int getEntityHeight() { return entityHeight; } public int getX() { return x; } public int getY() { return y; } public void setX(int x) { this.x = x; } public void setY(int y) { this.y = y; } }

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  • Mercurial in Windows doesn't see .hgignore - why?

    - by AP257
    Windows fails to pick up my .hgignore file. I'm running Mercurial from the command line, and "hg status" shows lots of files in the ignored directories. The .hgignore file looks like this (there's no whitespace at the start of the file, or at the start of each line). I've put it in the root directory of the repository. \.pyc$ \.pyo$ \.DS_Store \.Python \.installed.cfg ^bin$ ^build$ ^develop-eggs$ ^eggs$ ^include$ ^lib$ ^parts$ ^pip-log.txt$ ^web/localsettings.py$ I've tried saving the file in ANSI and UTF-8, and it doesn't seem to make a difference. I know the file is working OK on Linux, is there anything different about the paths in Windows?

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  • 2D Platform Games in Java

    - by breno.inojosa
    I'm not new in Java, but I know nothing about tools and APIs related to games. So now I have decided to create a few games but I don't know where to start. I could buy a book but I don't think that's the best choice. So.. What do you guys suggest? What should I learn first, are there any Complete tutorials? What further reading do you recommend? Better: Where should I start? Need help. Thanks =D

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  • Recommend a PHP framework for new PHP programmer

    - by webworm
    Hi All, I am fairly new to PHP but not programming in general. I was hoping I could get some suggestions on the best type of PHP framework to start with considering my basic experience with PHP. I have a .NET and ASP.NET background and I am familiar with the MVC design pattern. I would prefer to start with a framework that makes logical design easier but does not generate all the code for you. I have read some like the Zend framework for this. Opinions?

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  • How to use Haar wavelet to detect LINES on an image?

    - by Ole Jak
    So I have Image like this I want to get something like this (I hevent drawn all lines I want but I hope you can get my idea) I want to use SURF ( (Speeded Up Robust Features) is a robust image descriptor, first presented by Herbert Bay et al. in 2006 ) or something that is based on sums of 2D Haar wavelet responses and makes an efficient use of integral images for finding all straight lines on image. I want to get relative to picture pixel coords start and end points of lines. So on this picture to find all lines between tiles and thouse 2 black lines on top. Is there any such Code Example (with lines search capability) to start from? I love C and C++ but any other readable code will probably work for me=)

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  • jquery datepicker: select date as back as 6 months

    - by Abu Hamzah
    Start date: user can select start date as back as 6 months. example: if today is 04/23/2010 then i can go back up to 11/23/2009 but not more than 6 months. <script type="text/javascript"> $(document).ready(function () { $('#endDate').datepicker({ showOn: 'button', buttonImage: '../images/Calendar.png', buttonImageOnly: true, onSelect: function () { }, onClose: function () { $(this).focus(); } }); $('#startDate').datepicker({ showOn: 'button', buttonImage: '../images/Calendar.png', buttonImageOnly: true, onSelect: function (dateText, inst) { $('#endDate').datepicker("option", 'minDate', new Date(dateText)); } , onClose: function () { $(this).focus(); } }); }); update code: var currentDate = new Date(); var currentMonth = currentDate.getMonth() + 1; var sixMonths = currentMonth + 6 currentDate.setMonth(currentDate.currentMonth, sixMonths); var myNewCurrentDate = new Date(currentDate) $('#startDate').datepicker('option', { minDate: myNewCurrentDate }); i am getting currentDate = NaN

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  • More GCC link time issues: undefined reference to main

    - by vikramtheone
    Hi Guys, I'm writing software for a Cortex-A8 processor and I have to write some ARM assembly code to access specific registers. I'm making use of the gnu compilers and related tool chains, these tools are installed on the processor board(Freescale i.MX515) with Ubuntu. I make a connection to it from my host PC(Windows) using WinSCP and the PuTTY terminal. As usual I started with a simple C project having main.c and functions.s. I compile the main.c using GCC, assemble the functions.s using as and link the generated object files using once again GCC, but I get strange errors during this process. An important finding - Meanwhile, I found out that my assembly code may have some issues because when I individually assemble it using the command as -o functions.o functions.s and try running the generated functions.o using ./functions.o command, the bash shell is failing to recognize this file as an executable(on pressing tab functions.o is not getting selected/PuTTY is not highlighting the file). Can anyone suggest whats happening here? Are there any specific options I have to send, to GCC during the linking process? The errors I see are strange and beyond my understanding, I don't understand to what the GCC is referring. I'm pasting here the contents of main.c, functions.s, the Makefile and the list of errors. Help, please!!! Vikram main.c #include <stdio.h> #include <stdlib.h> int main(void) { puts("!!!Hello World!!!"); /* prints !!!Hello World!!! */ return EXIT_SUCCESS; } functions.s * Main program */ .equ STACK_TOP, 0x20000800 .text .global _start .syntax unified _start: .word STACK_TOP, start .type start, function start: movs r0, #10 movs r1, #0 .end Makefile all: hello hello: main.o functions.o gcc -o main.o functions.o main.o: main.c gcc -c -mcpu=cortex-a8 main.c functions.o: functions.s as -mcpu=cortex-a8 -o functions.o functions.s Errors ubuntu@ubuntu-desktop:~/Documents/Project/Others/helloworld$ make gcc -c -mcpu=cortex-a8 main.c as -mcpu=cortex-a8 -o functions.o functions.s gcc -o main.o functions.o functions.o: In function `_start': (.text+0x0): multiple definition of `_start' /usr/lib/gcc/arm-linux-gnueabi/4.3.3/../../../crt1.o:init.c:(.text+0x0): first defined here /usr/lib/gcc/arm-linux-gnueabi/4.3.3/../../../crt1.o: In function `_start': init.c:(.text+0x30): undefined reference to `main' collect2: ld returned 1 exit status make: *** [hello] Error 1

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  • Grouping Months of a particular Time span together using DateTime.

    - by Calibre2010
    public static string TimeLine2(this HtmlHelper helper, string myString2) { StringBuilder myString3 = new StringBuilder(); DateTime start = new DateTime(2010, 1, 1); DateTime end = new DateTime(2011, 12, 12); myString3.Append("<table>"); myString3.Append("<tr>"); for (DateTime date = start; date <= end; date = date.AddDays(1)) { DayOfWeek dw = date.DayOfWeek; var g = date.Month; var sun = " "; switch (dw) { case DayOfWeek.Sunday: sun = "S"; break; case DayOfWeek.Monday: sun = "M"; break; case DayOfWeek.Tuesday: sun = "T"; break; case DayOfWeek.Wednesday: sun = "W"; break; case DayOfWeek.Thursday: sun = "T"; break; case DayOfWeek.Friday: sun = "F"; break; case DayOfWeek.Saturday: sun = "S"; break; } myString3.Append("<td>" + sun + " " + g + "</td>"); } myString3.Append("</tr>"); myString3.Append("<tr>"); for (DateTime date = start; date <= end; date = date.AddDays(1)) { var f = date.Day; myString3.Append("<td>" + f + "</td>"); } myString3.Append("</tr>"); myString3.Append("</table>"); return myString3.ToString(); } Basically, what I have here is a few loops showing all the days of the week and also all the days in a month. This is all placed inside of a table, so you get MTWTFSSMT W T F S S M M TWTFSSM 12345678910 11 12 13 14 + + to 31 1234567 I'm trying to code a way in which I can split all of these days of the week and days in months so that my code returns each month with all its days in the month and all its days of the week, not just all my months between my timeSpan but splits them so MAY MTWTFSSMTWTFSSMTWTFSSMTWTFSSMTWTF 12345678 JUNE MTWTFSSMTWTFSSMTWTFSSMTWTFSSMTWTF 123456789

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  • How do you use kate? Tips/Tricks/Workflow

    - by Roman A. Taycher
    We all seen a bunch of these? Mostly for IDE's but also for vim and emacs. Kate is (only) a text editor (an awesome one) but it has a ton of options plus a number of plugins, so its hard to know all of it well. How do use the Kate text editor? Please share your workflow and help me and others learn some of the cool tricks you use. I'll start I use the built in terminal a lot opening files quickly, and using it as an enhanced haskell repl with ghci (since ghci doesn't allow you all to just put in all kinds of haskell code). Also use split views to quickly compare files (especially different versions of the same file). Also the auto-complete maybe simple(more use for saving typing time then remembering functions) but it works really well for that. Also if You highlight something and hit a start [/{/( it puts it in between brackets rather then replacing it with a bracket(why the hell do a lot of IDEs not have this feature).

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  • After I've installed it, NUnit doesn't appear in VS2008

    - by Richard77
    Hello, I downloaded and installed NUnit successfuly (or so I was told by the installer). Now, when I start a project, I don't see NUnit in the 'Create UnitTest' prompt as one the choice I'm givven to. All I can see are (i) VS Unit Test and (ii) Mb Unit v3 as choices. In fact, I downloaded today the MbB Unit. After, installing it, I was able to see it right away in the prompt. What happen to the NUnit? Althought, I can see it when I do Start - All Programs Or maybe NUnit dosn't need to appear in the prompt as choice since it has its own GUI. Thanks for helping

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  • jquery plugin with multiple functions

    - by tcurdt
    According to the developer documentation jquery plugins are supposed to have only one namespace for all functions they make available. Which is straight forward as long as you only expose a single function per context (static/element). (function($){ var state_a = 0, $.myplugin = function(in_options) { // static return this; } $.fn.myplugin = function(in_options) { // element return this; } })(jQuery); This makes calls like this possible: $("elem").myplugin(options); jQuery.myplugin(options); What's the best approach if you have more than one function and need to share state? I would like to call into my plugin like this: $("elem").myplugin.start(options); $("elem").myplugin.stop(); jQuery.myplugin.start(options); jQuery.myplugin.stop();

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  • Running a Windows Forms app. from a service.

    - by RemotecUk
    Hi, I have a strange application in that for development and testing I need a windows forms application so that I can monitor what it is doing. For production, the application will be started from a service and no visible UI is needed. I dont really want to re-write the app. once it is completed into a console app so I would like to leave it as it but start it from the service. My question is will this application work fine from a service? At the moment it has UI elements and I have been able to successfully start the application from a service using the Process class (System.Diagnostics). Could anything go wrong with this approach?

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  • Oracle Hash Cluster Overflow Blocks

    - by Andrew
    When inserting a large number of rows into a single table hash cluster in Oracle, it will fill up the block with any values that hash to that hash-value and then start using overflow blocks. These overflow blocks are listed as chained off the main block, but I can not find detailed information on the way in which they are allocated or chained. When an overflow block is allocated for a hash value, is that block exclusively allocated to that hash value, or are the overflow blocks used as a pool and different hash values can then start using the same overflow block. How is the free space of the chain monitored - in that, as data is continued to be inserted, does it have to traverse the entire chain to find out if it has some free space in the current overflow chain, and then if it finds none, it then chooses to allocate a new block?

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  • Scala actors: receive vs react

    - by jqno
    Let me first say that I have quite a lot of Java experience, but have only recently become interested in functional languages. Recently I've started looking at Scala, which seems like a very nice language. However, I've been reading about Scala's Actor framework in Programming in Scala, and there's one thing I don't understand. In chapter 30.4 it says that using react instead of receive makes it possible to re-use threads, which is good for performance, since threads are expensive in the JVM. Does this mean that, as long as I remember to call react instead of receive, I can start as many Actors as I like? Before discovering Scala, I've been playing with Erlang, and the author of Programming Erlang boasts about spawning over 200,000 processes without breaking a sweat. I'd hate to do that with Java threads. What kind of limits am I looking at in Scala as compared to Erlang (and Java)? Also, how does this thread re-use work in Scala? Let's assume, for simplicity, that I have only one thread. Will all the actors that I start run sequentially in this thread, or will some sort of task-switching take place? For example, if I start two actors that ping-pong messages to each other, will I risk deadlock if they're started in the same thread? According to Programming in Scala, writing actors to use react is more difficult than with receive. This sounds plausible, since react doesn't return. However, the book goes on to show how you can put a react inside a loop using Actor.loop. As a result, you get loop { react { ... } } which, to me, seems pretty similar to while (true) { receive { ... } } which is used earlier in the book. Still, the book says that "in practice, programs will need at least a few receive's". So what am I missing here? What can receive do that react cannot, besides return? And why do I care? Finally, coming to the core of what I don't understand: the book keeps mentioning how using react makes it possible to discard the call stack to re-use the thread. How does that work? Why is it necessary to discard the call stack? And why can the call stack be discarded when a function terminates by throwing an exception (react), but not when it terminates by returning (receive)? I have the impression that Programming in Scala has been glossing over some of the key issues here, which is a shame, because otherwise it's a truly excellent book.

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  • ubuntu programming

    - by Apache
    hi experts, i start learning using ubuntu 9.10 OS, if i want to retrieve all available wifi on ubuntu, how this can be done programitcally, can anyone give example please, thanks

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  • SDK for writing DVD's

    - by Matt Warren
    I need to add DVD writing functionality to an application I'm working on. However it needs to be able to write out files that are being grabbed "live" from a camera, over a long period of time. I can't wait until all the files are captured before I start writing them to the DVD, I need to write them out in chunks as I go along. I've looked at IMAPI v2, but the main problems seems to be that you need to point it to all the files you plan to write out to disk before you start the burning process. I know it has to concept of "sessions", which means you can write to the DVD in several parts, before you finally "close" it. But I was wondering if there were any other DVD writing SDK's that allow you to be constantly writing files to a DVD and in particular files that are only in memory. It would be more efficient if I didn't have to write the captured images out to hard before they are burned to DVD. The solution needs to work under .NET on Windows XP and vista

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  • Best way to handle SQL Server fulltext index updates

    - by tlianza
    Hi all, I have a fulltext index which doesn't need to be immediately up-to-date, I'd like to spare myself the I/O (when I do bulk updates, I see a ton of I/O related to the index) and do the index updates during low usage times (nightly, perhaps even weekly). It seems there are two ways to go about this: Turn off change tracking (SET CHANGE_TRACKING OFF) and add a timestamp field to the indexed table, so that you can run alter fulltext index on <table> start INCREMENTAL population, or Enable change tracking, but set it to MANUAL, so that you can run alter fulltext index on <table> start UPDATE population when you need it updated. Is there a preferred method? I couldn't tell from this overview if there was a performance benefit one way or the other. Tom

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