evdev: Only send the events at synchronization time.

Instead of just posting the button/key press/release events to the
server as soon as they arrive, add them to an internal queue and post
them once we receive an EV_SYN synchronization event.

The motion events are always sent first, followed by the queued events.
There will be one motion event and possibly many queued button/key
events posted every EV_SYN event.

Note that the size of the event queue (EVDEV_MAXQUEUE) is arbitrary and
you may change it. If we receive more events than the queue can handle,
those events are dropped and a warning message printed.

Tested on my Lenovo T400 using evdev for all input devices; keyboard,
touchpad, and trackpoint.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/evdev.h b/src/evdev.h
index 5b95369..23ee003 100644
--- a/src/evdev.h
+++ b/src/evdev.h
@@ -54,6 +54,7 @@
 #endif
 
 #define EVDEV_MAXBUTTONS 32
+#define EVDEV_MAXQUEUE 32
 
 #if GET_ABI_MAJOR(ABI_XINPUT_VERSION) >= 3
 #define HAVE_PROPERTIES 1
@@ -87,6 +88,16 @@ typedef struct {
     int traveled_distance;
 } WheelAxis, *WheelAxisPtr;
 
+/* Event queue used to defer keyboard/button events until EV_SYN time. */
+typedef struct {
+    enum {
+        EV_QUEUE_KEY,	/* xf86PostKeyboardEvent() */
+        EV_QUEUE_BTN,	/* xf86PostButtonEvent() */
+    } type;
+    int key;		/* May be either a key code or button number. */
+    int val;		/* State of the key/button; pressed or released. */
+} EventQueueRec, *EventQueuePtr;
+
 typedef struct {
     const char *device;
     int grabDevice;         /* grab the event device? */
@@ -103,6 +114,9 @@ typedef struct {
     BOOL invert_x;
     BOOL invert_y;
 
+    int delta[REL_CNT];
+    unsigned int abs, rel;
+
     /* XKB stuff has to be per-device rather than per-driver */
 #if GET_ABI_MAJOR(ABI_XINPUT_VERSION) < 5
     XkbComponentNamesRec    xkbnames;
@@ -159,6 +173,10 @@ typedef struct {
 
     /* minor/major number */
     dev_t min_maj;
+
+    /* Event queue used to defer keyboard/button events until EV_SYN time. */
+    int                     num_queue;
+    EventQueueRec           queue[EVDEV_MAXQUEUE];
 } EvdevRec, *EvdevPtr;
 
 unsigned int EvdevUtilButtonEventToButtonNumber(EvdevPtr pEvdev, int code);