[news.eclipse.platform.swt] Re: How to avoid paint merging ?

["Veronika Irvine" <veronika_irvine@xxxxxxx>]

You should not be loading the data in the UI thread.  Start a separate 
thread to load the data and from the second thread damage the canvas to 
draw.

 Canvas control = new Control(Display.getCurrent(), SWT.NO.BACKGROUND)
 control.addPaintListener(new PaintListener(){
    public void paintControl(PaintEvent event){
          //paint data on event.gc
          //paint elements that are already loaded
          //paint placeholders for the remaining elements
 }

Thread newThread = new Thread() {
        public void run() {
                Display display = Display.getDefault();
                for(int i=0;i<10;i++){
                        //load a chunk of data
                        display.syncExec(new Runnable() {
                                public void run() {
                                        if (!canvas.isDisposed()) 
canvas.redraw();
                                }
                        });
                }
        }
};
newThread.start();

"Yves Harms" <user@xxxxxxxxxxxxxx> wrote in message 
news:dmeud4$msg$1@xxxxxxxxxxxxxxxxxxx
>I need to display large amount of data on a custom widget (subclassed from 
>canvas) , loading the data from database takes a considerable amount of 
>time. So I want to fetch the data in smaller bunches while displaying 
>placeholders fo all elements that are not loaded yet.
> On windows everythings works ok, but on MacOSX the paint requests seem to 
> get merged, the os just waits until everything is loaded (which makes the 
> app feel very slow).
>
> How can I avoid that ?
>
> control.update() and display.update() both have no effect.
>
>
> Short snippet to illustrate what i want to do :
>
> Canvas control = new Control(Display.getCurrent(), SWT.NO.BACKGROUND)
> control.addPaintListener(new PaintListener(){
>    public void paintControl(PaintEvent event){
>      for(int i=0;i<10;i++){
> //load data
> ..
> //paint data on event.gc
> //paint elements that are already loaded
> ...
> //paint placeholders for the remaining elements
> ...
> //Paint requests must be procesed NOW
> this.update(); //no effect ?!
> }
>
>      }
> });
>
> Regards,
> Yves Harms