[PATCH synaptics v2] Don't count fingers twice when guessing distance (#48316)

[Peter Hutterer]

A finger may be closer than the required distance to more than one finger.
e.g. for fingers A, B, C, AB, AC and BC may trigger the check and count
C twice -resulting in a 4 finger click.

Avoid double-counting by marking those fingers already close enough to a
previous finger to avoid overcounting.

X.Org Bug 48316 <http://bugs.freedesktop.org/show_bug.cgi?id=48316>

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
Changes to v1:
- new algorithm. for each pair closer than the distance, mark both points.
  then count the number of points marked.

 src/synaptics.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/synaptics.c b/src/synaptics.c
index 918dc6f..3681b41 100644
--- a/src/synaptics.c
+++ b/src/synaptics.c
@@ -2624,7 +2624,10 @@ clickpad_guess_clickfingers(SynapticsPrivate *priv, struct SynapticsHwState *hw)
 {
     int nfingers = 0;
 #if HAVE_MULTITOUCH
+    char close_point[SYNAPTICS_MAX_TOUCHES] = {0}; /* 1 for each point close
+                                                      to another one */
     int i, j;
+
     for (i = 0; i < hw->num_mt_mask - 1; i++) {
         ValuatorMask *f1;
 
@@ -2655,14 +2658,18 @@ clickpad_guess_clickfingers(SynapticsPrivate *priv, struct SynapticsHwState *hw)
              * you'll need to find a touchpad that doesn't lie about it's
              * size. Good luck. */
             if (abs(x1 - x2) < (priv->maxx - priv->minx) * .3 &&
-                abs(y1 - y2) < (priv->maxy - priv->miny) * .3)
-                nfingers++;
+                abs(y1 - y2) < (priv->maxy - priv->miny) * .3) {
+                close_point[j] = 1;
+                close_point[i] = 1;
+            }
         }
     }
+
+    for (i = 0; i < SYNAPTICS_MAX_TOUCHES; i++)
+        nfingers += close_point[i];
 #endif
 
-    /* 1 doesn't make sense */
-    return nfingers ? nfingers + 1 : 0;
+    return nfingers;
 }
 
 
-- 
1.7.10