Hi Fred,
Andreas Höschler wrote:
Hi all,
I have a view subclass with
- (void)mouseDown:(NSEvent *)theEvent
{
NSPoint locA = [self convertPoint:[theEvent locationInWindow]
fromView:nil];
BOOL shiftPressed = (([theEvent modifierFlags] & NSShiftKeyMask) >
0);
BOOL keepOn = YES;
BOOL hasDragged = NO;
while (keepOn)
{
theEvent = [[self window]
nextEventMatchingMask:NSLeftMouseUpMask | NSLeftMouseDraggedMask];
switch ([theEvent type])
{
case NSLeftMouseDragged:
{
NSPoint locB = [self convertPoint:[theEvent
locationInWindow] fromView:nil];
NSSize offset = NSMakeSize(locB.x - locA.x, locB.y -
locA.y);
NSRect oldRect = _selectionRect;
_selectionRect.origin = locA;
if (offset.width < 0)
{
_selectionRect.origin.x = locB.x;
offset.width = -offset.width;
}
if (offset.height < 0)
{
_selectionRect.origin.y = locB.y;
offset.height = -offset.height;
}
_selectionRect.size = offset;
_selecting = YES;
[self setNeedsDisplayInRect:NSUnionRect(_selectionRect,
oldRect)];
hasDragged = YES;
}
break;
case NSLeftMouseUp:
{
keepOn = NO;
}
break;
default:
break;
}
}
}
- (void)drawRect:(NSRect)rect
{
[super drawRect:rect];
if (_selecting)
{
[[NSColor grayColor] set];
NSFrameRect(_selectionRect);
}
}
This draws a rectangle following the mouse until the user releases
the mouse button. On MacOSX the rectangle follows the mouse
instantly. Under GNUstep I see a significant delay. Dragging
rectangles makes no fun there. Any idea why this is so slow? This of
course has nothing to do with rectangles in special but with slow
drawing code in general. In my app I want to drag objects around with
the mouse. This works under GNUstep and MacOX but on GNustep it is
almost too slow to be usable. Is this a known (may be even already
improved) issue? My GNUstep tree is already a year old. :-)
Most likely the slow drawing speed you see in GNUstep has nothing to
do with the drawing itself, but with the event handling in GNUstep.
The window will just not get a chance to redraw itself.
One possible reason for this may be that in
[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] we
handle an expiration date of nil different from Cocoa. There
distantPast is used while we use distantFuture, resulting in the loop
to wait until the next event happens.
As I am no expert in this area, I would like to get some comments from
other developers before changing this code. That change may result in
the need to adopt a lot of places that rely on the old behaviour.
For a qick test I changed all occurances of distantFuture to
distantPast in NSApplication.m. This had no obvious effect, neither
good nor bad. Drawing (event handling) is still (far too) slow!? Any
more ideas?
Thanks a lot!
Regards,
Andreas
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