Reset hw->x/y to INT_MIN and skip HandleState until we have x/y events

The driver assumes x/y is always valid but after coming from a resume we may
get a few events with either ABS_X or ABS_Y (not both). Thus we process with
hw->x == 0 and hw->y == somevalue, causing cursor jumps when calculating
deltas whenver the real hw->x comes in.

Fix this by resetting hw->x/y to INT_MIN and skip state processing until
both axes are available.

For clickpads, this means handling of data will be delayed until we get
at least one motion on each axis. Button presses won't be recognised either
until that happens. It requires some skill to not trigger motion on both
axes, even more to press a button without doing so.

For non-clickpads, handling of motion events will be delayed likewise. If a
physical button is pressed immediately after resume we have to assume deltas
of x/y.
- If the next event is a new touch, it will have ABS_X/ABS_Y set anyway
- If the finger was already down, a button event is generated, and the
  finger has generated ABS_X or ABS_Y only before the event, the next event
  containing the missing data will cause a jump. The fix for this is more
  invasive and this is quite a corner-case.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Chase Douglas <chase.douglas@canonical.com>
(cherry picked from commit cd569377cda9b5a4ee00c0137db14f625c76c40f)

2 files changed, 15 insertions, 2 deletions

diff --git a/src/synaptics.c b/src/synaptics.c
index 78660f4..cd9f936 100644
--- a/src/synaptics.c
+++ b/src/synaptics.c
@@ -3278,6 +3278,19 @@ HandleState(InputInfoPtr pInfo, struct SynapticsHwState *hw, CARD32 now,
         return delay;
     }
 
+    /* We need both and x/y, the driver can't handle just one of the two
+     * yet. But since it's possible to hit a phys button on non-clickpads
+     * without ever getting motion data first, we must continue with 0/0 for
+     * that case. */
+    if (hw->x == INT_MIN || hw->y == INT_MAX) {
+        if (para->clickpad)
+            return delay;
+        else if (hw->left || hw->right || hw->middle) {
+            hw->x = (hw->x == INT_MIN) ? 0 : hw->x;
+            hw->y = (hw->y == INT_MIN) ? 0 : hw->y;
+        }
+    }
+
     /* If a physical button is pressed on a clickpad, use cumulative relative
      * touch movements for motion */
     if (para->clickpad && (hw->left || hw->right || hw->middle)) {
diff --git a/src/synproto.c b/src/synproto.c
index d6e8c65..0c8a066 100644
--- a/src/synproto.c
+++ b/src/synproto.c
@@ -134,8 +134,8 @@ void
 SynapticsResetHwState(struct SynapticsHwState *hw)
 {
     hw->millis = 0;
-    hw->x = 0;
-    hw->y = 0;
+    hw->x = INT_MIN;
+    hw->y = INT_MIN;
     hw->z = 0;
     hw->cumulative_dx = 0;
     hw->cumulative_dy = 0;