[PATCH] dix: Untwist transformAbsolute logic, eliminate uninitialized value warnings

[Keith Packard]

tranformAbsolute has a pretty simple job, that of running the X/Y
values from a device through the transformation matrix. The tricky bit
comes when the current device state doesn't include one of the
values. In that case, the last delivered value is back-converted to
device space and used instead.

The logic was twisted though, confusing GCC's uninitialized value
detection logic and emitting warnings.

This has been fixed by changing the code to:

 1) Detect whether the ValuatorMask includes X/Y values
 2) If either are missing, back-convert the current values into ox/oy
 3) When X/Y are present, set ox/oy to the current value
 4) Transform
 5) Store X/Y values if changed or if they were set before.

Signed-off-by: Keith Packard <keithp at keithp.com>
Cc: Peter Hutterer <peter.hutterer at who-t.net>
---
 dix/getevents.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/dix/getevents.c b/dix/getevents.c
index ffa89fa..dd96265 100644
--- a/dix/getevents.c
+++ b/dix/getevents.c
@@ -1248,8 +1248,8 @@ transformAbsolute(DeviceIntPtr dev, ValuatorMask *mask)
     double x, y, ox, oy;
     int has_x, has_y;
 
-    has_x = valuator_mask_fetch_double(mask, 0, &ox);
-    has_y = valuator_mask_fetch_double(mask, 1, &oy);
+    has_x = valuator_mask_isset(mask, 0);
+    has_y = valuator_mask_isset(mask, 1);
 
     if (!has_x && !has_y)
         return;
@@ -1263,23 +1263,23 @@ transformAbsolute(DeviceIntPtr dev, ValuatorMask *mask)
 
         pixman_f_transform_invert(&invert, &dev->scale_and_transform);
         transform(&invert, &ox, &oy);
-
-        x = ox;
-        y = oy;
     }
 
-    if (valuator_mask_isset(mask, 0))
-        ox = x = valuator_mask_get_double(mask, 0);
+    if (has_x)
+        ox = valuator_mask_get_double(mask, 0);
 
-    if (valuator_mask_isset(mask, 1))
-        oy = y = valuator_mask_get_double(mask, 1);
+    if (has_y)
+        oy = valuator_mask_get_double(mask, 1);
+
+    x = ox;
+    y = oy;
 
     transform(&dev->scale_and_transform, &x, &y);
 
-    if (valuator_mask_isset(mask, 0) || ox != x)
+    if (has_x || ox != x)
         valuator_mask_set_double(mask, 0, x);
 
-    if (valuator_mask_isset(mask, 1) || oy != y)
+    if (has_y || oy != y)
         valuator_mask_set_double(mask, 1, y);
 }
 
-- 
2.1.1