From e3a734d081ebda4460e6c1eb7dcdd0f7c10ba9b4 Mon Sep 17 00:00:00 2001
From: "Jasper St. Pierre" <jstpierre@mecheye.net>
Date: Sat, 24 Nov 2012 21:42:56 -0500
Subject: [PATCH] barriers: Add a couple pixels of elbow room for the hit
 detection

Pointers (and the hands that drive them) aren't very precise, and the
slightest amount of nudging to either side might be enough to reset
the event ID, making clients think they have an entirely new hit. Allow
for a slightly bigger "hit box" before these barriers get reset.

Signed-off-by: Jasper St. Pierre <jstpierre@mecheye.net>
Reviewed-by: Jasper St. Pierre <jstpierre@mecheye.net>
---
 Xi/xibarriers.c | 40 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 5 deletions(-)

diff --git a/Xi/xibarriers.c b/Xi/xibarriers.c
index ac94927bf..95a62ae32 100644
--- a/Xi/xibarriers.c
+++ b/Xi/xibarriers.c
@@ -79,7 +79,7 @@ struct PointerBarrierClient {
     int barrier_event_id;
     int release_event_id;
     Bool hit;
-    Bool last_hit;
+    Bool seen;
 };
 
 typedef struct _BarrierScreen {
@@ -220,6 +220,35 @@ barrier_is_blocking(const struct PointerBarrier * barrier,
     return rc;
 }
 
+#define HIT_EDGE_EXTENTS 2
+static BOOL
+barrier_inside_hit_box(struct PointerBarrier *barrier, int x, int y)
+{
+    int x1, x2, y1, y2;
+    int dir;
+
+    x1 = barrier->x1;
+    x2 = barrier->x2;
+    y1 = barrier->y1;
+    y2 = barrier->y2;
+    dir = ~(barrier->directions);
+
+    if (barrier_is_vertical(barrier)) {
+        if (dir & BarrierPositiveX)
+            x1 -= HIT_EDGE_EXTENTS;
+        if (dir & BarrierNegativeX)
+            x2 += HIT_EDGE_EXTENTS;
+    }
+    if (barrier_is_horizontal(barrier)) {
+        if (dir & BarrierPositiveY)
+            y1 -= HIT_EDGE_EXTENTS;
+        if (dir & BarrierNegativeY)
+            y2 += HIT_EDGE_EXTENTS;
+    }
+
+    return x >= x1 && x <= x2 && y >= y1 && y <= y2;
+}
+
 static BOOL
 barrier_blocks_device(struct PointerBarrierClient *client,
                       DeviceIntPtr dev)
@@ -267,7 +296,7 @@ barrier_find_nearest(BarrierScreenPtr cs, DeviceIntPtr dev,
         struct PointerBarrier *b = &c->barrier;
         double distance;
 
-        if (c->hit)
+        if (c->seen)
             continue;
 
         if (!barrier_is_blocking_direction(b, dir))
@@ -388,8 +417,9 @@ input_constrain_cursor(DeviceIntPtr dev, ScreenPtr screen,
     }
 
     xorg_list_for_each_entry(c, &cs->barriers, entry) {
-        c->last_hit = c->hit;
-        c->hit = FALSE;
+        c->seen = FALSE;
+        if (c->hit && !barrier_inside_hit_box(&c->barrier, x, y))
+            c->hit = FALSE;
     }
 
  out:
@@ -459,7 +489,7 @@ CreatePointerBarrierClient(ClientPtr client,
     ret->barrier_event_id = 0;
     ret->release_event_id = 0;
     ret->hit = FALSE;
-    ret->last_hit = FALSE;
+    ret->seen = FALSE;
     ret->barrier.x1 = min(stuff->x1, stuff->x2);
     ret->barrier.x2 = max(stuff->x1, stuff->x2);
     ret->barrier.y1 = min(stuff->y1, stuff->y2);