fix: correct hidpi rendering on macos

[53053]

edit: it seems this project may be inactive at the moment, though this patch has been working correctly in my own use so i’ll keep the PR up in case it helps someone else.

there are also some forks like yigithanyigit/lldbg that appear to include additional fixes and improvements.

if development resumes here in the future, i’d still be glad to help and contribute 🙂

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fix: correct retina/hidpi rendering on macos

details

• Fixes blurry rendering on retina/high-dpi displays by consistently separating logical window coordinates from physical framebuffer sizes.

• Fonts are now scaled using the window content scale, glviewport uses framebuffer dimensions, and resize/layout calculations stay in logical coordinates as expected by imgui.

should be effectively a no-op on 1x displays, tested mainly on macos retina.

screenshots

zoom-in anywhere to notice.

before (retina, 2x scale):

after:

tested on apple silicon, macos, 2x retina. imgui 1.90.9.

related

• High DPI, Retina Mac ocornut/imgui#3757 - canonical description of the glViewport/1/4-framebuffer bug and blurry fonts on macOS retina (SDL backend, same root cause)
• High DPI scaling on Mac OS and glfw ocornut/imgui#5081 - same stack: imgui + glfw + opengl3, apple silicon M1, GLFW_COCOA_RETINA_FRAMEBUFFER, same fix pattern
• imgui official glfw+opengl3 example uses glfwGetFramebufferSize for glViewport: https://github.com/ocornut/imgui/blob/master/examples/example_glfw_opengl3/main.cpp
• imgui FAQ DPI section: https://github.com/ocornut/imgui/blob/master/docs/FAQ.md