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Bug 4373

Summary: SDL_WINDOW_ALLOW_HIGHDPI flag is not unset on failure
Product: SDL Reporter: Caleb Cornett <spydog>
Component: videoAssignee: Sam Lantinga <slouken>
Status: NEW --- QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: amaranth72, sezeroz
Version: 2.0.9   
Hardware: x86_64   
OS: Mac OS X (All)   

Description Caleb Cornett 2018-11-09 02:58:31 UTC 
On macOS, if SDL cannot create a high-DPI window (e.g. because of an insufficient screen resolution), the SDL_WINDOW_ALLOW_HIGHDPI window flag is never turned off. This makes it difficult to determine at runtime if high-dpi window creation has been successful.

The snippet responsible for this behavior (or lack thereof) appears to be this:
https://hg.libsdl.org/SDL/file/a4d730631698/src/video/cocoa/SDL_cocoawindow.m#l1360

What's the best way to fix this? I suspect there's a simple solution, but I'm not familiar with Cocoa so I have no idea what it would be.
Comment 1 Alex Szpakowski 2018-11-09 12:11:21 UTC 
As the flag's name implies, it just makes SDL windows capable of being high-dpi, it isn't really meant to fail to create the window if it isn't high dpi - you can use SDL_GL_GetDrawableSize (if you're using OpenGL directly), or SDL_GetRendererOutputSize (if you're using SDL_Render) and compare that to SDL_GetWindowSize, to determine if the window is currently high dpi.