Hi all,
I'm tying to understand the exact definition of the Cocoa drawing and event
coordinate system on macOS. In particular the exact location of 0,0 and
subpixel accuracy.
I know 0,0 is the bottom-left, but is it:
- the centre of the bottom-left pixel?
- the bottom-left corner of the bottom-left pixel?
I made a custom NSView and implemented mouseDown:
- (void)mouseDown:(NSEvent*)inEvent {
NSPoint viewPoint = [self convertPoint:[inEvent locationInWindow]
fromView:nil];
I then use Pixie.app at max magnification and click the bottom-left pixel,
yielding results like:
(lldb) p viewPoint
(NSPoint) $3 = (x = 0.15234375, y = 0.90625)
So it's giving fractional values, but they are hard to interpret without
knowing where 0,0 is exactly.
Then there's the 'locationInWindow' docs, that say "Note: The y coordinate in
the returned point starts from a base of 1, not 0." That's quite odd. Why?
Does anyone know the exact details here?
Thanks,
--
____________________________________________________________
Sean McBride, B. Eng [email protected]
Rogue Research www.rogue-research.com
Mac Software Developer Montréal, Québec, Canada
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