dix: fix scale_to_desktop for edge ABS events

Scale_to_desktop() converts ABS events from device coordinates
to screen coordinates:
[dev_X_min, dev_X_max]  -> [screen_X_min, screen_X_max]
[dev_Y_min, dev_Y_max]  -> [screen_Y_min, screen_Y_max]

An edge ABS event with X = dev_X_max (e.g., generated from the
edge of a touchscreen) will be converted to have screen X value
= screen_X_max, which, however, will be filterd out when xserver
tries to find proper Window to receive the event, because the
range check for a Window to receive events is
       window_X_min <= event_screen_X < window_X_max
Events with event_screen_X = screen_X_max will fail the test get
and rejected by the Window.

To fix this, we change the device to screen coordinates mapping to
[dev_X_min, dev_X_max]  -> [screen_X_min, screen_X_max-1]
[dev_Y_min, dev_Y_max]  -> [screen_Y_min, screen_Y_max-1]

Reviewed-by: Chase Douglas <chase.douglas@canonical.com>
Reviewed-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>
Signed-off-by: Yufeng Shen <miletus@chromium.org>
Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/dix/getevents.c b/dix/getevents.c
index 4e62507aa..71d83c4ba 100644
--- a/dix/getevents.c
+++ b/dix/getevents.c
@@ -896,9 +896,9 @@ scale_to_desktop(DeviceIntPtr dev, ValuatorMask *mask,
 
     /* scale x&y to desktop coordinates */
     *screenx = rescaleValuatorAxis(x, dev->valuator->axes + 0, NULL,
-                                   screenInfo.x, screenInfo.width);
+                                   screenInfo.x, screenInfo.width - 1);
     *screeny = rescaleValuatorAxis(y, dev->valuator->axes + 1, NULL,
-                                   screenInfo.y, screenInfo.height);
+                                   screenInfo.y, screenInfo.height - 1);
 
     *devx = x;
     *devy = y;