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Is this an issue in my code or in my Linux distro?
(lemmy.world)
Display of OpenGL context works fine on Windows, no issues with resizing. Function glViewport works as intended.
It only has issues with X11 on Linux (no plans yet to implement Wayland due to lack of free time). Resizing breaks everything, and it doesn't really work the way you expect (point of triangle moves down if you make it taller, etc). I cannot find anything on if I should call anything else besides glViewport, only that "you should use [insert already existing library], which will take care of this behavior". Others are suggesting me that it's an issue with my distro, but I cannot find any OpenGL testcase that is small enough to test on my VM or my Raspberry Pi to actually test whether that's the case.
On a past OpenGL project where I supported resizing, I used GLFW and responded to its framebuffer size callback by calling
glViewportand resetting the projection matrix (in my case withglLoadIdentityfollowed byglOrtho-- it's not fresh in my memory any more, but I don't think that project used shaders at all). I also calledglClearwithGL_COLOR_BUFFER_BITas part of my regular redraw. That worked fine for my needs.It looks like what GLFW was doing under the hood to trigger that callback was looking for an
XEventfrom X11 (viaXNextEventin a loop with a condition based on the result of callingXQLength) withtypeset toConfigureNotifyand which had anxconfigureentry with a width or height that differed from what was tracked directly by GLFW on its own window structure. When it saw an event like that, it would call the callback. After processing the event queue, GLFW calledXFlushon the display.See x11_window.c in GLFW's source code for more detail: https://github.com/glfw/glfw/blob/master/src/x11_window.c
Direct link to raw code, if you prefer: https://raw.githubusercontent.com/glfw/glfw/master/src/x11_window.c
Hopefully comparing with what GLFW did can help you debug your own implementation. Good luck!
It seems like the issue was setting the
ResizeRedirectFlagin the event configuration, since the whole documentation on event configurations were scarce.Did you mean
ResizeRedirectMask?Xlib docs for that say:
which definitely sounds like it could cause misbehavior.
Glad to hear you've made progress, and good luck on the rest of your project!