Fixed bug 3134 - CalculateXRandRRefreshRate() returns incorrect refresh 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.

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