Reconsider need for macOS 10.14-specific DisplayLink vsync workaround?

[follower]

During research for #33116 I encountered suggestions that the underlying V-Sync issue was fixed in a subsequent minor OS point release. [1]

This made me wonder if the workaround added via b53f2d1 was still required.

My primary reason for asking is that I have suspicions that the DisplayLink-based workaround may be causing Godot editor and/or games to hang (when V-Sync is enabled) when my MacBook Pro on Mac OS X 10.9.5 goes to sleep automatically.

I did some preliminary investigations which suggested the DisplayLink thread may not survive the sleep/wake cycle but haven't had the chance to investigate properly.

Next steps:

• Someone may wish to test if the DisplayLink patch is still necessary for 10.14+
• At some point I may be able to dig deeper into the sleep issue I observed.

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[1] e.g.

• ofVerticalSync(true) broken on macOS 10.14 + XCode 10.0 openframeworks/openFrameworks#6146 (comment)
• https://twitter.com/FlohOfWoe/status/1103296098834305026
• ofVerticalSync(true) broken on macOS 10.14 + XCode 10.0 openframeworks/openFrameworks#6146 (comment)
• Vsync doesn't work on macOS 10.14 (Mojave) glfw/glfw#1337 (comment)
• Stuttering movement and black screen on macOS 10.14 & Xcode 10 cocos2d/cocos2d-x#19080 (comment)
• https://stackoverflow.com/questions/52938516/opengl-not-rendering-on-macos-mojave#52938517
• https://hg.libsdl.org/SDL/rev/73f3ca85ac0e

[2] Here are some other recent Mac OpenGL patches I noticed in other projects in case we encounter the same issues at some point:

• Override NSOpenGLView::openGLContext to prevent it from creating a context wxWidgets/wxWidgets#1617 & "wxGLCanvas macOS texture issues with 10.13 and lower"
• [OSX] wxGLCanvas resize fix on macOS 10.14.5 wxWidgets/wxWidgets#1354
• qt/qtbase@f39230f

[3] Random other semi-related links I encountered:

• https://stackoverflow.com/questions/20083027/nsopenglview-and-cvdisplaylink-no-default-frame-buffer#44301471
• https://stackoverflow.com/questions/54891914/nsopenglview-drops-its-nsopenglcontext-on-macos-10-9

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Edit: Link to Mac OS sleep-related issue which might be related: #28039

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cc: @BastiaanOlij due to being author of the original patch

[bruvzg]

SDL have removed it in https://hg.libsdl.org/SDL/rev/1b6f67e84802

[BastiaanOlij]

If Apple fixed the issue I don't see any reason why we shouldn't undo the DisplayLink fix. It really was just a bandaid imho.

[follower]

BTW in the unlikely case this information is useful to someone in future, as noted in the above issue, at some point I discovered that almost no CVDisplayLink implementations correctly handle a situation that can occur (via Fast User Switching) where the link is destroyed & then a new link created later:

"In macOS 10.4 and later, the display link thread is automatically stopped if the user employs Fast User Switching. The display link is restarted when switching back to the original user. "

-- https://developer.apple.com/documentation/corevideo/1457281-cvdisplaylinkstop?language=objc

As I understand it this was the cause of a Godot hang I encountered (at the time) of uncertain origin but turned out to be related to the use of Fast User Switching while Godot was running.