dix: fix axis scaling.

For two axes [a, b] and [x, y] (inclusive), the formula to scale point P(ab)
to (x,y) is:
    (P - a)/(b - a) * (y - x) + x

And the whole end result rounded of course to get the integer we need.

1 files changed, 6 insertions, 2 deletions

diff --git a/dix/getevents.c b/dix/getevents.c
index f2086e8d6..ed7bf7ffa 100644
--- a/dix/getevents.c
+++ b/dix/getevents.c
@@ -175,8 +175,12 @@ rescaleValuatorAxis(int coord, AxisInfoPtr from, AxisInfoPtr to,
 
     if(fmin == tmin && fmax == tmax)
         return coord;
-    return (int)(((float)(coord - fmin)) * (tmax - tmin + 1) /
-                 (fmax - fmin + 1)) + tmin;
+
+    if(fmax == fmin) /* avoid division by 0 */
+        return 0;
+
+    return roundf(((float)(coord - fmin)) * (tmax - tmin) /
+                 (fmax - fmin)) + tmin;
 }
 
 /**