MacOS framebuffer size and window content scale incorrect on external display without high dpi

[xiaozhuai]

When move the window to external display. the framebuffer size is incorrect. On retina display, it works fine.
Window size: 600x600
Framebuffer size: 600x600 (Actually 1200x1200)
Content scale: 1.0, 1.0 (Actually 2.0, 2.0)

My external display resolution is 2560x1440

It also works if I enable hidpi on external display https://github.com/xzhih/one-key-hidpi

[xiaozhuai]

Any progress on this issue?

[elmindreda]

This seems related to #1897 and I cannot reproduce it on macOS 10.15. If this issue occurs only on macOS 11 then I cannot currently fix this as I don't have a machine capable of running it.

[xiaozhuai]

@elmindreda It occurs on 10.15. I can reproduce it , and what should I do to help?

[elmindreda]

Oh, that's great! Does it happen with any of the examples in GLFW, or do you have a minimal program that reproduces it?

[xiaozhuai]

Here is a minimal demo code which reproduce it.
glfw_demo.zip

This code use angle instead of OpenGL Desktop on MacOS.

angle prebuilt libraries from https://github.com/xiaozhuai/angle_builds

Build & Run

cmake -B build .
cmake --build build
./build/glfw_demo

On my macbook screen

On external screen

[elmindreda]

It looks like you're only retrieving the framebuffer size at the start of the program. The framebuffer size will change when the window moves to a monitor with a different content scale, even if the window size remains the same.

The simplest fix is to retrieve the framebuffer size each frame. If you instead want to be notified when it changes, see the framebuffer size callback.

If you don't want the framebuffer to change size independent of the window size, you can disable it with the GLFW_COCOA_RETINA_FRAMEBUFFER window hint. The framebuffer will then always behave as if the content scale was 1.

[xiaozhuai]

@elmindreda Oh, this is my mistake. But I'm sure this is not the point of the problem.
I didn't move window between monitor.
I tried to move this get framebuffer size code into render loop, and got same results.