Fixed bug 3134 - CalculateXRandRRefreshRate() returns incorrect refre…

…sh rate due to floating point truncation. Michael In SDL_x11modes.c the CalculateXRandRRefreshRate() function performs integer math on values that may return fractional results. This causes a value that would be calculated as 59.99972... to be returned as 59. In Linux the xrandr command returns 60Hz for this particular display mode yet SDL returns 59Hz. I suggest this function be updated to correctly round the result of the calculation instead of truncating the result.
libsdl-org · Oct 1, 2016 · 0250eb3 · 0250eb3
1 parent 7543092
commit 0250eb3
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/src/video/x11/SDL_x11modes.c b/src/video/x11/SDL_x11modes.c
@@ -264,8 +264,8 @@ CheckXRandR(Display * display, int *major, int *minor)
 static int
 CalculateXRandRRefreshRate(const XRRModeInfo *info)
 {
-    return (info->hTotal
-            && info->vTotal) ? (info->dotClock / (info->hTotal * info->vTotal)) : 0;
+    return (info->hTotal && info->vTotal) ?
+        round(((double)info->dotClock / (double)(info->hTotal * info->vTotal))) : 0;
 }
 
 static SDL_bool