Introduces Cocoa_GetWindowDisplayIndex. This enable a proper management for dpi when switching between retina and non-retina displays.

[misl6]

Description

The generic SDL_GetWindowDisplayIndex doesn't provide the real window positioning on macOS.

On macOS, displays may have separate Spaces (by default, it can be changed via System Preferences > Mission Control > Displays have separate Spaces)

This means that even if the window is placed by 99% on "SCREEN B", the focus is kept on "SCREEN A", the window belongs to the "SCREEN A".

These changes introduce Cocoa_GetWindowDisplayIndex, which takes into account NSWindow.screen.

That makes possible to select the right display density only when the window really switches the display is attached to. (As an example when moving the window from a non-retina display and a retina one or vice-versa)

Existing Issue(s)

[sezero]

I got the following error when building against 10.8 SDM from an old clang version:

src/video/cocoa/SDL_cocoawindow.m:2213:12: error: initializing 'CGRect' (aka 'struct CGRect') with an expression of incompatible type 'NSRect' (aka 'struct _NSRect')
    CGRect displayframe = data->nswindow.screen.frame;
           ^              ~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
make: *** [build/SDL_cocoawindow.lo] Error 1
make: *** Waiting for unfinished jobs....

[misl6]

I got the following error when building against 10.8 SDM from an old clang version:

src/video/cocoa/SDL_cocoawindow.m:2213:12: error: initializing 'CGRect' (aka 'struct CGRect') with an expression of incompatible type 'NSRect' (aka 'struct _NSRect')
    CGRect displayframe = data->nswindow.screen.frame;
           ^              ~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
make: *** [build/SDL_cocoawindow.lo] Error 1
make: *** Waiting for unfinished jobs....

I guess this is due to: When building for 64 bit systems, or building 32 bit like 64 bit, NSRect is typedef’d to CGRect. Reference: https://developer.apple.com/documentation/foundation/nsrect?language=objc

Will submit a patch ASAP.

[sezero]

I was indeed building for i686

[misl6]

I was indeed building for i686

Can you confirm that https://github.com/libsdl-org/SDL/pull/5576/files fixes the issue?

[sezero]

Yes, it does. Thanks!