[PATCH libinput] evdev: Activate button scrolling only after pointer movement

[Norwin Hanghuhn]

Currently, a timer is used to discriminate between button clicks and
button scrolling. Therefore, button clicks must finalize before and
scrolling can only start after the timer has elapsed.

This patch changes the behaviour such that scrolling starts
immediately after the scroll button is pressed and button events
are released consistently if no scrolling takes place after all.

Signed-off-by: Norwin Hanghuhn <norwinhanghuhn at gmail.com>
---
 src/evdev.c | 34 +++++++++++-----------------------
 src/evdev.h |  5 +++--
 2 files changed, 14 insertions(+), 25 deletions(-)

diff --git a/src/evdev.c b/src/evdev.c
index 8f0a607..515baff 100644
--- a/src/evdev.c
+++ b/src/evdev.c
@@ -44,7 +44,6 @@
 #include "libinput-private.h"
 
 #define DEFAULT_WHEEL_CLICK_ANGLE 15
-#define DEFAULT_MIDDLE_BUTTON_SCROLL_TIMEOUT ms2us(200)
 
 enum evdev_key_type {
 	EVDEV_KEY_TYPE_NONE,
@@ -273,13 +272,12 @@ evdev_post_trackpoint_scroll(struct evdev_device *device,
 			     uint64_t time)
 {
 	if (device->scroll.method != LIBINPUT_CONFIG_SCROLL_ON_BUTTON_DOWN ||
-	    !hw_is_key_down(device, device->scroll.button))
+	    !device->scroll.button_down)
 		return false;
 
-	if (device->scroll.button_scroll_active)
-		evdev_post_scroll(device, time,
-				  LIBINPUT_POINTER_AXIS_SOURCE_CONTINUOUS,
-				  &unaccel);
+	evdev_post_scroll(device, time,
+			  LIBINPUT_POINTER_AXIS_SOURCE_CONTINUOUS,
+			  &unaccel);
 
 	return true;
 }
@@ -481,30 +479,20 @@ get_key_type(uint16_t code)
 }
 
 static void
-evdev_button_scroll_timeout(uint64_t time, void *data)
-{
-	struct evdev_device *device = data;
-
-	device->scroll.button_scroll_active = true;
-}
-
-static void
 evdev_button_scroll_button(struct evdev_device *device,
 			   uint64_t time, int is_press)
 {
 	if (is_press) {
-		libinput_timer_set(&device->scroll.timer,
-				   time + DEFAULT_MIDDLE_BUTTON_SCROLL_TIMEOUT);
+		device->scroll.button_down = true;
 		device->scroll.button_down_time = time;
 	} else {
-		libinput_timer_cancel(&device->scroll.timer);
-		if (device->scroll.button_scroll_active) {
+		device->scroll.button_down = false;
+
+		if (device->scroll.button_scroll_started) {
 			evdev_stop_scroll(device, time,
 					  LIBINPUT_POINTER_AXIS_SOURCE_CONTINUOUS);
-			device->scroll.button_scroll_active = false;
 		} else {
-			/* If the button is released quickly enough emit the
-			 * button press/release events. */
+			/* If no scrolling was done, always emit the events */
 			evdev_pointer_notify_physical_button(device,
 					device->scroll.button_down_time,
 					device->scroll.button,
@@ -1186,8 +1174,6 @@ static int
 evdev_init_button_scroll(struct evdev_device *device,
 			 void (*change_scroll_method)(struct evdev_device *))
 {
-	libinput_timer_init(&device->scroll.timer, device->base.seat->libinput,
-			    evdev_button_scroll_timeout, device);
 	device->scroll.config.get_methods = evdev_scroll_get_methods;
 	device->scroll.config.set_method = evdev_scroll_set_method;
 	device->scroll.config.get_method = evdev_scroll_get_method;
@@ -2539,6 +2525,7 @@ evdev_start_scrolling(struct evdev_device *device,
 	       axis == LIBINPUT_POINTER_AXIS_SCROLL_VERTICAL);
 
 	device->scroll.direction |= AS_MASK(axis);
+	device->scroll.button_scroll_started = true;
 }
 
 void
@@ -2636,6 +2623,7 @@ evdev_stop_scroll(struct evdev_device *device,
 	device->scroll.buildup.x = 0;
 	device->scroll.buildup.y = 0;
 	device->scroll.direction = 0;
+	device->scroll.button_scroll_started = false;
 }
 
 void
diff --git a/src/evdev.h b/src/evdev.h
index 02b5112..f5daaf1 100644
--- a/src/evdev.h
+++ b/src/evdev.h
@@ -154,7 +154,6 @@ struct evdev_device {
 	struct device_coords rel;
 
 	struct {
-		struct libinput_timer timer;
 		struct libinput_device_config_scroll_method config;
 		/* Currently enabled method, button */
 		enum libinput_config_scroll_method method;
@@ -167,7 +166,9 @@ struct evdev_device {
 		uint32_t want_button;
 		/* Checks if buttons are down and commits the setting */
 		void (*change_scroll_method)(struct evdev_device *device);
-		bool button_scroll_active;
+		bool button_down;
+		bool button_scroll_started;
+
 		double threshold;
 		double direction_lock_threshold;
 		uint32_t direction;
-- 
2.6.2