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Bug 3709

Summary: Assertion failure in WIN_GetDisplayUsableBounds on highdpi display
Product: SDL Reporter: Eric Wasylishen <ewasylishen>
Component: videoAssignee: Sam Lantinga <slouken>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: sezeroz
Version: HG 2.1   
Hardware: x86_64   
OS: Windows 10   

Description Eric Wasylishen 2017-07-21 23:21:06 UTC 
1. have a monitor with scaling set in Windows display settings. I have 2880x1800 with 200% scaling.
2. run testgl2 with "--info all". You should get the SDL_assert(hmon != NULL); assertion failing in WIN_GetDisplayUsableBounds.

Unfortunately I think the code in SDL_windowsmodes.c is fundamentally broken wherever it attempts to convert coordinates in the DEVMODE struct (which are always in pixels, even under DPI virtualization) to virtual screen coordinates (what MonitorFromPoint takes).
I think the only correct fix is to get a HMONITOR by doing a EnumDisplayMonitors and looking for a monitor name matching the DEVMODE.dmDeviceName , but I'm not sure about this as the msdn docs don't seem to say how to get a HMONITOR from a DEVMODE.

Tested on SDL2 7cfe088fafba, Windows 10 1703, build 15063.447
Comment 1 Eric Wasylishen 2017-08-11 07:22:33 UTC 
The patch I added in https://bugzilla.libsdl.org/show_bug.cgi?id=3714 fixes this.
Comment 2 Sam Lantinga 2017-08-11 17:19:45 UTC 
Fixed, thanks!
https://hg.libsdl.org/SDL/rev/0060bcf673e8