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Resizing works, but scrolling "smears" image. [message #1053444]

Mon, 06 May 2013 01:53

Robert Adamson

Messages: 9
Registered: March 2013

Junior Member

I am writing an application which loads .jpg files as images and then allows users to place "marks" on the image. I'm using code similar to that of snipped #48. When I re-size the image the marks are retained. However, when I scroll the screen, the marks (small green circles) are "smeared across the image. Resizing again will restore the image and the marks to the "correct" state. I have attached screen shots to illustrate, the first one is what the file looks like with the green circles,
index.php/fa/14655/0/

the second one shows what happens when I scroll the screen.
index.php/fa/14656/0/

I looked at the javadoc for the Scroll event and one section of the description for scroll event stood out as the probable cause of the code not behaving as I want. Either that or I just don't understand the implication of what it says:
" ... In addition, all outstanding paint events are flushed before the source area is copied to ensure that the contents of the canvas are drawn correctly. "

The actual code which redraws the green circles is in the paint event handler.

So it seems like if the javadoc description was accurate it would finish scrolling before it reapplied my green circles. But obviously it's redrawing them at very small increments as the scrolling is taking place.

Any ideas would be appreciated.

And I'm using SWT 3.7.2 64 bit, on Windows 7 64 bit, in Indigo 3.7.2.

Attachment: Normal Map with marks.jpg
(Size: 363.92KB, Downloaded 440 times)
Attachment: Smear Event.jpg
(Size: 428.74KB, Downloaded 443 times)

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Re: Resizing works, but scrolling "smears" image. [message #1053685 is a reply to message #1053444]

Tue, 07 May 2013 08:44

Vijay Raj

Messages: 608
Registered: July 2009

Senior Member

It depends on how you are painting those green circles...
could you please share a snippet to represent what you are doing there(paint code)..

---------------------
why, mr. Anderson, why, why do you persist?
Because I Choose To.
Regards,
Vijay

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Re: Resizing works, but scrolling "smears" image. [message #1057499 is a reply to message #1053685]

Wed, 08 May 2013 12:33

Robert Adamson

Messages: 9
Registered: March 2013

Junior Member

Thanks for Responding, here is the code for the Paint Event.

// Handle Paint event.s
canvas.addListener (SWT.Paint, new Listener () {
public void handleEvent (Event e) {
GC gc = e.gc;
gc.drawImage (image, origin.x, origin.y);
Rectangle rect = image.getBounds ();
Rectangle client = canvas.getClientArea ();
int marginWidth = client.width - rect.width;
if (marginWidth > 0) {
gc.fillRectangle (rect.width, 0, marginWidth, client.height);
}
int marginHeight = client.height - rect.height;
if (marginHeight > 0) {
gc.fillRectangle (0, rect.height, client.width, marginHeight);
}
// TODO is this where we can tell it to repaint our plotted hexes ???

// redraw any plotted hexes.
// Need to iterate though the list and mark the map again.

if (currUnit != null && plotting) {
Collection<PlottedHex> tempList = currUnit.getListValues();
PlottedHex[] ph = tempList.toArray( new PlottedHex[20] );

PlottedHex tempHex = null;

int i=0;
while ( (i < ph.length) && (ph[i] != null) ) {

tempHex = ph[i];
// now mark hex once we have the X and Y

GC myGC = new GC(canvas);
;
Color frgdColor = new Color(display, 0, 180, 10); // bright green
Color oldFrgd = myGC.getForeground(); // save setting.
myGC.setForeground(frgdColor);
myGC.setLineWidth(2);
myGC.drawOval(tempHex.getX() - 10, tempHex.getY(), 10, 10);
myGC.setForeground(oldFrgd); // restore it.
myGC.dispose();

i++;

}
}

}
});

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