dix: if we run out of space for new touch events, resize the queue

Co-authored-by: Daniel Stone <daniel@fooishbar.org>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

2 files changed, 117 insertions, 1 deletions

diff --git a/dix/touch.c b/dix/touch.c
index 8fdd3449b..dd0f7eced 100644
--- a/dix/touch.c
+++ b/dix/touch.c
@@ -34,6 +34,9 @@
 #include "eventstr.h"
 #include "exevents.h"
 
+/* If a touch queue resize is needed, the device id's bit is set. */
+static unsigned char resize_waiting[(MAXDEVICES + 7)/8];
+
 /**
  * Some documentation about touch points:
  * The driver submits touch events with it's own (unique) touch point ID.
@@ -54,6 +57,60 @@
  */
 
 /**
+ * Check which devices need a bigger touch event queue and grow their
+ * last.touches by half it's current size.
+ *
+ * @param client Always the serverClient
+ * @param closure Always NULL
+ *
+ * @return Always True. If we fail to grow we probably will topple over soon
+ * anyway and re-executing this won't help.
+ */
+static Bool
+TouchResizeQueue(ClientPtr client, pointer closure)
+{
+    int i;
+
+    OsBlockSignals();
+
+    /* first two ids are reserved */
+    for (i = 2; i < MAXDEVICES; i++)
+    {
+        DeviceIntPtr dev;
+        DDXTouchPointInfoPtr tmp;
+        size_t size;
+
+        if (!BitIsOn(resize_waiting, i))
+            continue;
+
+        ClearBit(resize_waiting, i);
+
+        /* device may have disappeared by now */
+        dixLookupDevice(&dev, i, serverClient, DixWriteAccess);
+        if (!dev)
+            continue;
+
+        /* Need to grow the queue means dropping events. Grow sufficiently so we
+         * don't need to do it often */
+        size = dev->last.num_touches + dev->last.num_touches/2 + 1;
+
+        tmp = realloc(dev->last.touches, size *  sizeof(*dev->last.touches));
+        if (tmp)
+        {
+            int i;
+            dev->last.touches = tmp;
+            for (i = dev->last.num_touches; i < size; i++)
+                TouchInitDDXTouchPoint(dev, &dev->last.touches[i]);
+            dev->last.num_touches = size;
+        }
+
+    }
+    OsReleaseSignals();
+
+    return TRUE;
+}
+
+/**
  * Given the DDX-facing ID (which is _not_ DeviceEvent::detail.touch), find the
  * associated DDXTouchPointInfoRec.
  *
@@ -133,7 +190,15 @@ TouchBeginDDXTouch(DeviceIntPtr dev, uint32_t ddx_id)
         return ti;
     }
 
-    /* If we get here, then we've run out of touches, drop the event */
+    /* If we get here, then we've run out of touches and we need to drop the
+     * event (we're inside the SIGIO handler here) schedule a WorkProc to
+     * grow the queue for us for next time. */
+    ErrorF("%s: not enough space for touch events. Dropping this event.\n", dev->name);
+    if (!BitIsOn(resize_waiting, dev->id)) {
+        SetBit(resize_waiting, dev->id);
+        QueueWorkProc(TouchResizeQueue, serverClient, NULL);
+    }
+
     return NULL;
 }
 
diff --git a/test/touch.c b/test/touch.c
index 5b8e567cc..1ea8f0ca5 100644
--- a/test/touch.c
+++ b/test/touch.c
@@ -29,6 +29,56 @@
 #include "inputstr.h"
 #include "assert.h"
 
+static void touch_grow_queue(void)
+{
+    DeviceIntRec dev;
+    ValuatorClassRec val;
+    TouchClassRec touch;
+    size_t size, new_size;
+    int i;
+
+    memset(&dev, 0, sizeof(dev));
+    dev.id = 2;
+    dev.valuator = &val;
+    val.numAxes = 5;
+    dev.touch = &touch;
+    inputInfo.devices = &dev;
+
+    size = 5;
+
+    dev.last.num_touches = size;
+    dev.last.touches = calloc(dev.last.num_touches, sizeof(*dev.last.touches));
+    assert(dev.last.touches);
+    for (i = 0; i < size; i++) {
+        dev.last.touches[i].active = TRUE;
+        dev.last.touches[i].ddx_id = i;
+        dev.last.touches[i].client_id = i * 2;
+    }
+
+    /* no more space, should've scheduled a workproc */
+    assert(TouchBeginDDXTouch(&dev, 1234) == NULL);
+    ProcessWorkQueue();
+
+    new_size = size + size/2 + 1;
+    assert(dev.last.num_touches == new_size);
+
+    /* make sure we haven't touched those */
+    for (i = 0; i < size; i++) {
+        DDXTouchPointInfoPtr t = &dev.last.touches[i];
+        assert(t->active == TRUE);
+        assert(t->ddx_id == i);
+        assert(t->client_id == i * 2);
+    }
+
+    /* make sure those are zero-initialized */
+    for (i = size; i < new_size; i++) {
+        DDXTouchPointInfoPtr t = &dev.last.touches[i];
+        assert(t->active == FALSE);
+        assert(t->client_id == 0);
+        assert(t->ddx_id == 0);
+    }
+}
+
 static void touch_find_ddxid(void)
 {
     DeviceIntRec dev;
@@ -142,6 +192,7 @@ static void touch_begin_ddxtouch(void)
 
 int main(int argc, char** argv)
 {
+    touch_grow_queue();
     touch_find_ddxid();
     touch_begin_ddxtouch();