x11: fix refresh rate reported as 0 for high pixel-clock modes#15888
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francisdb wants to merge 1 commit into
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x11: fix refresh rate reported as 0 for high pixel-clock modes#15888francisdb wants to merge 1 commit into
francisdb wants to merge 1 commit into
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CalculateXRandRRefreshRate assigned the XRandR mode's dotClock (unsigned long) directly into the int numerator. For high pixel-clock modes (e.g. 4K@240Hz the pixel clock exceeds INT_MAX) the numerator overflowed to a negative value, so SDL_GetDesktopDisplayMode reported a refresh rate of 0. Compute the fraction in 64-bit and scale it down to fit the int numerator and denominator while preserving the ratio.
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, including code generated by a Large Language Model ("AI")If the AI code completion part is a problem consider this an issue an let somebody else come up with a fix.
Description
On X11,
SDL_GetDesktopDisplayMode()reports a refresh rate of0for high pixel-clock modes such as 4K@240Hz, while lower-clock modes on the same machine (4K@60, 1080p) are fine.The X11 refresh-rate calculation overflows for those high pixel clocks and falls back to 0. It is a regression from when the calculation moved to the numerator/denominator representation, which dropped the wide-integer handling the earlier path had (#8933).
Testing
Reproduced with a small program calling
SDL_GetDesktopDisplayMode()per display on a dual-monitor setup (a 4K@240Hz DP-1 and a 4K@60Hz portrait DP-4), and cross-checked againstxrandr:0.000(num=0)239.980(num=1626625000)239.98240.00059.98059.98059.9860.000Note: this surfaced while running an SDL app under Xwayland, but it is not Xwayland-specific - the same overflow applies to any high pixel-clock mode on a native X server.