Strange behaviour on Retina Macs

lefty · September 12, 2023, 9:50am

I am testing my game on a Mac with a resolution of 2560 x1600 and am getting some strange behaviour. The frame buffer size reported by glfwGetFramebufferSize is always 1650 x 1050, regardless of which resolution I set with glfwCreateWindow, or if I set GLFW_COCOA_RETINA_FRAMEBUFFER or not.
I do not understand why the frame buffer is 1650 x 1050. It should either be 2560x1600, or 1280 x 800 depending if retina is enabled.

The GLFW_COCOA_RETINA_FRAMEBUFFER setting seems to have no effect at all. The performance of the game is equally bad, if it’s enabled or disabled.

dougbinks · September 15, 2023, 3:37pm

There appear to be a number of issues related to retina displays with the recent ARM Mac hardware (M1 etc.).

lefty · September 15, 2023, 4:02pm

Thanks for the answer.
The mac that I am having problems with is actually Intel, not ARM

dougbinks · September 15, 2023, 5:06pm

What version of OSX are you on, and what version of GLFW are you using?

If you haven’t yet tried using the latest from Github, then it would potentially be worth trying that.

However it looks like your issue is related to:

github.com/glfw/glfw

glfwGetFramebufferSize wrong values on mac

opened 06:59PM - 31 Oct 20 UTC

songsofsyx

macOS High DPI

Hello! I'm rendering a bunch of stuff to a FBO and when I'm done I'm blitting… to the default FB. This works smooth, except for some mac users. Behavior seems a bit erratic. The problem is I'm not getting the correct framebuffer size glfwGetFramebufferSize. They are doubled. glBlitFramebuffer(0, 0, offlineW, offlineH, 0, 0, defaultFBW, defaultFBH, GL_COLOR_BUFFER_BIT, GL_NEAREST); where defaultFB is the values from glfwGetFramebufferSize. On my IMac listed as (Retina 4K, 21.5-inch, 2017), the display is stated to be 4096 x2304. glfwGetVideoModes(glfwGetPrimaryMonitor()) returns resolutions from 640x480 -> 4096x2304 If I launch a windowed window with any resolution, I get the same size framebuffer. The blit is working as expected. If I launch a full screen window, glfwGetFramebufferSize gives me double the numbers. I.e. window = 4096x2304, FB = double, window = 2304x1296, FB = 4096x2304 and the result is the lower-left quadrant of the offline FBO on the whole screen. I can solve this by: glfwWindowHint(GLFW_COCOA_RETINA_FRAMEBUFFER, GL11.GL_FALSE); But this sadly doesn't solve it for some other mac users. So, I'm thinking, as a layman... Should glfwGetVideoModes(glfwGetPrimaryMonitor()) really return displaymodes > 2304x1296 for me? Maybe they should, but I'm still getting too big framebuffers sizes. The x2 factor is consistent on every full screen resolution I'm picking. I hope this explains it. I'm using lwjgl, so I'm tied to their latest wrapper. I'm also interested if there is a potential workaround. I've tried dividing with glfwGetWindowSize and stuff like that, but getting inconsistent results with different macs, so I stopped. And thanks for your great work!

It might be worth reporting your OS, Mac hardware and test results there.

lefty · September 19, 2023, 12:04am

I am using latest release GLFW and OSX 12 something. Unfortunately, I only had temporary access to a friend’s machine, so I can’t really test it fully.

dougbinks · September 19, 2023, 12:46pm

I only have macOS 10.13 and no retina display, so cannot investigate this issue myself. From what I recall there were changes in macOS 11+ which broke some features of GLFW, and this may be one of them.