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Trouble using swt GLCanvas on linux [message #1022304] Thu, 21 March 2013 16:37 Go to next message
Steven Reynolds is currently offline Steven ReynoldsFriend
Messages: 2
Registered: March 2013
Junior Member

I am having trouble using the swt GLCanvas while on linux. If I use the provided Snippet209

I get 100% CPU utilization. The code is clearly structured to cause this high utilitzation. It does (from the main method)

display.asyncExec(new Runnable() {
int rot = 0;
public void run() {
// draw stuff

Which means that it busy loops drawing as fast as it can.

When I try to convert the snippet to draw on PaintEvents, the opengl drawing that I do is immediatedly klobbered with something that draws plain black.

Does anyone have any luck using the swt GLCanvas on linux? Busy looping won't work for my application, most of the time, the display should be static and not consume CPU.

I've attached the PaintEvent version as DemoSWT2.


Re: Trouble using swt GLCanvas on linux [message #1022372 is a reply to message #1022304] Thu, 21 March 2013 19:10 Go to previous message
Steven Reynolds is currently offline Steven ReynoldsFriend
Messages: 2
Registered: March 2013
Junior Member
Oh, I have a solution. It looks like the swt GLCanvas is doing GTK double buffering. The associated gtk buffer swap hammered my drawing. With the following change, the code seems fine now

retrieving revision 1.7
retrieving revision 1.8
diff -u -r1.7 -r1.8
--- 20 Mar 2013 22:13:41 -0000 1.7
+++ 21 Mar 2013 18:49:58 -0000 1.8
@@ -9,6 +9,7 @@
+import org.eclipse.swt.internal.gtk.OS;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.opengl.GLCanvas;
import org.eclipse.swt.opengl.GLData;
@@ -83,7 +84,11 @@
GLData data = new GLData ();
data.doubleBuffer = true;
final GLCanvas canvas = new GLCanvas(comp, SWT.NONE, data);
+ if (SWT.getPlatform().equals("gtk")) {
+ System.out.printf("Disabling GTK double buffering\n");
+ // TODO invoke reflectively?
+ OS.gtk_widget_set_double_buffered(canvas.handle,false);
+ }
final GLContext context = GLDrawableFactory.getFactory().createExternalGLContext();

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