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Bug 4255

Summary: SDL_GetGlobalMouseState() returns incorrect Y on secondary display
Product: SDL Reporter: Julian Raschke <julian>
Component: videoAssignee: Sam Lantinga <slouken>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: rasky, sezeroz
Version: 2.0.8   
Hardware: x86_64   
OS: macOS 10.13   
Attachments: Fix for the bug on OSX

Description Julian Raschke 2018-09-09 09:49:45 UTC 
I use an open Mac laptop with an additional external monitor. The coordinate spaces from SDL_GetGlobalMouseState() and SDL_GetWindowPosition() match on the primary display, but not on the secondary display.

Cocoa window coordinates are vertically flipped in relation to the primary display:

https://github.com/spurious/SDL-mirror/blob/release-2.0.8/src/video/cocoa/SDL_cocoawindow.m#L219-L222

However, Cocoa_GetGlobalMouseState inverts the cursor Y coordinate per-display:

https://github.com/spurious/SDL-mirror/blob/release-2.0.8/src/video/cocoa/SDL_cocoamouse.m#L320-L323

Suggested fix: Replace the for-loop with this simpler calculation:

    *x = (int) cocoaLocation.x;
    *y = (int) (CGDisplayPixelsHigh(kCGDirectMainDisplay) - cocoaLocation.y);

Related ticket:

https://bugzilla.libsdl.org/show_bug.cgi?id=2655
Comment 1 Giovanni Bajo 2018-12-13 15:14:13 UTC 
Created attachment 3545 [details]
Fix for the bug on OSX

I have the same problem: SDL_GetGlobalMouseState() is wrong on double monitor setups on OSX.

The fix suggested in this bug perfectly works. I'm attaching a patch that allows me to use SDL_GetGlobalMouseState() on double-monitor setups correctly. Please apply the fix.
Comment 2 Giovanni Bajo 2018-12-30 08:22:57 UTC 
Ping! Can we get this applied?
Comment 3 Sam Lantinga 2019-01-05 06:09:57 UTC 
Patch added, thanks!
https://hg.libsdl.org/SDL/rev/74e8ace1b2c3