c# - Why does this single line of code cause Visual Studio to crash? -

-

with 1 line of code, can cause vs2012 crash consistently. (by "crash" mean when hit build, visual studio hangs indefinitely , have kill task manager.) here's code (in custom user control):

public class transparentpanel : system.windows.forms.panel {     protected override void onpaintbackground(painteventargs pe)     {         this.invalidate(); //this offending line     } }

to reproduce problem, create control based on above code , add windows form; try build solution. "build started..." displayed in status bar , vs , permanently freeze up. tried troubleshooting, using devenv /log, activity log displayed no errors or warnings. question is, why code fatal c# compiler? (it causes problems in ide too. example, after adding transparent control, properties pane becomes frozen whenever form designer open.)

side question: should bug reported microsoft? if so, how? (i tried submit bug on the ms connect site, apparently accepting bugs vs2013.)

[if want know background of why trying use line, read on.]

i created custom (windows forms) control application. (i trying create control partially transparent image, location changed through mouse interactions.) used following code, gave me image (on panel) transparency looking for:

public class transparentpanel : system.windows.forms.panel {     public image image { get; set; }      protected override void onpaint(painteventargs pe)     {         rectangle rect = new rectangle(this.location, this.size);         if (image != null)             pe.graphics.drawimage(image, this.displayrectangle);     }      protected override void onpaintbackground(painteventargs pe)     {         //this.invalidate();         brush brush = new solidbrush(color.fromargb(0, 0, 0, 0));         pe.graphics.fillrectangle(brush, pe.cliprectangle);     }      protected override createparams createparams     {                 {             createparams cp = base.createparams;             cp.exstyle |= 0x20; // ws_ex_transparent                    return cp;         }     } }

however, transparency doesn't "stick". when control relocated, example event handler:

    private void transparentpanel1_mouseclick(object sender, mouseeventargs e)     {         int y = this.transparentpanel1.location.y ;         int x = this.transparentpanel1.location.x ;         this.transparentpanel1.location = new system.drawing.point(x-5, y-5);     }

...the transparent portion of control retains same background had when first painted. (this can seen if control placed behind it. sorry, hard describe.) attempting use invalidate() repaint control, , therefore, repaint transparent portion match whatever behind control after relocation. when vs bug appeared. (actually didn't notice bug right away, rather excruciating isolate offending line of code.)

public class transparentpanel : system.windows.forms.panel {     protected override void onpaintbackground(painteventargs pe)     {         this.invalidate(); //this offending line     } }

that akin infinite loop.

when panel repaints, handler called... , tell invalidate itself... causes repaint... calls handler... etc.

the designer loses mind. don't need or want invalidate control within onpaintbackground, unless conditional (still rare).


Comments

Post a Comment

Popular posts from this blog

c++ - OpenCV Error: Assertion failed <scn == 3 ::scn == 4> in unknown function, -

-
i read alot other solution still confused should mine... #include <opencv2/objdetect/objdetect.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> #include <stdio.h> using namespace std; using namespace cv; int main(int argc, const char** argv) { //create cascade classifier object used face detection cascadeclassifier face_cascade; //use haarcascade_frontalface_alt.xml library face_cascade.load("haarcascade_frontalface_alt.xml"); //setup video capture device , link first capture device videocapture capturedevice; capturedevice.open(0); //setup image files used in capture process mat captureframe; mat grayscaleframe; //create window present results namedwindow("outputcapture", 1); //create loop capture , find faces while (true) { //capture new image frame capturedevice >> captureframe; ...
Read more

php - render data via PDO::FETCH_FUNC vs loop -

-
i've been using 2 methods render data. the first one: function name($id,$name){ return '<div id="'.$id.'">'.$name.'</div>'; } echo implode($pdo->query("select id,name user")->fetchall(pdo::fetch_func,'name')); the second one: $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); foreach($users $user){ echo name($user->id,$user->name); } i don't understand how pdo::fetch_func works. tried figure out. however, not well-documented. could please explain fetch mode? , also, 1 performs better? thank you. both methods wrong , have learn how use templates , how separate business logic presentation logic. $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); tpl::assign('users', $users); is code business logic part. then in template <?php foreach $users $row): ?> <div id="<?=$...
Read more

The canvas has been tainted by cross-origin data in chrome only -

-
uncaught securityerror: failed execute 'getimagedata' on 'canvasrenderingcontext2d': canvas has been tainted cross-origin data i getting above error in chrome. code(following) works fine in mozilla. have not corss domain issue. why above error in chrome? var wheel_canvas, wheel_context, can_w, can_h, wheel_grd; var large_radius = 160; var small_radius = 120; var wheel_canvas = document.getelementbyid('wheel_canvas'); var wheel_context = wheel_canvas.getcontext('2d'); var can_w = $(wheel_canvas).width(); var can_h = $(wheel_canvas).height(); var centerx = can_w / 2, centery = can_h / 2; var wheel_grd = null; test('#ff0000'); function test(hex) { $('#clrpicker').css({'left': 210, 'top': 210 }); inverted = hexbw(hex); $('#color_val_show').val(hex); current_color_hex_val_selected = hex; $('#color_val_show').css({'color':inverted,'background':hex}); fillgradient...
Read more