evdev: Add middle button scrolling for trackpoints

Most trackpoint users want to be able to scroll using the trackpoint with
the middle button pressed, add support for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

include/linux/input.h

@@ -163,6 +163,7 @@ struct input_keymap_entry {
 #define INPUT_PROP_BUTTONPAD		0x02	/* has button(s) under pad */
 #define INPUT_PROP_SEMI_MT		0x03	/* touch rectangle only */
 #define INPUT_PROP_TOPBUTTONPAD		0x04	/* softbuttons at top of pad */
+#define INPUT_PROP_POINTING_STICK	0x05	/* is a pointing stick */
 
 #define INPUT_PROP_MAX			0x1f
 #define INPUT_PROP_CNT			(INPUT_PROP_MAX + 1)

src/evdev.c

@@ -41,6 +41,7 @@
 #include "libinput-private.h"
 
 #define DEFAULT_AXIS_STEP_DISTANCE 10
+#define DEFAULT_MIDDLE_BUTTON_SCROLL_TIMEOUT 200
 
 enum evdev_key_type {
 	EVDEV_KEY_TYPE_NONE,
@@ -203,6 +204,15 @@ evdev_flush_pending_event(struct evdev_device *device, uint64_t time)
 		device->rel.dx = 0;
 		device->rel.dy = 0;
 
+		/* Use unaccelerated deltas for pointing stick scroll */
+		if (device->scroll.has_middle_button_scroll &&
+		    hw_is_key_down(device, BTN_MIDDLE)) {
+			if (device->scroll.middle_button_scroll_active)
+				evdev_post_scroll(device, time,
+						  motion.dx, motion.dy);
+			break;
+		}
+
 		/* Apply pointer acceleration. */
 		filter_dispatch(device->pointer.filter, &motion, device, time);
 
@@ -345,6 +355,37 @@ get_key_type(uint16_t code)
 	return EVDEV_KEY_TYPE_NONE;
 }
 
+static void
+evdev_middle_button_scroll_timeout(uint64_t time, void *data)
+{
+	struct evdev_device *device = data;
+
+	device->scroll.middle_button_scroll_active = true;
+}
+
+static void
+evdev_middle_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);
+	} else {
+		libinput_timer_cancel(&device->scroll.timer);
+		if (device->scroll.middle_button_scroll_active) {
+			evdev_stop_scroll(device, time);
+			device->scroll.middle_button_scroll_active = false;
+		} else {
+			/* If the button is released quickly enough emit the
+			 * button press/release events. */
+			evdev_pointer_notify_button(device, time, BTN_MIDDLE,
+					LIBINPUT_BUTTON_STATE_PRESSED);
+			evdev_pointer_notify_button(device, time, BTN_MIDDLE,
+					LIBINPUT_BUTTON_STATE_RELEASED);
+		}
+	}
+}
+
 static void
 evdev_process_touch_button(struct evdev_device *device,
 			   uint64_t time, int value)
@@ -405,6 +446,12 @@ evdev_process_key(struct evdev_device *device,
 				   LIBINPUT_KEY_STATE_RELEASED);
 		break;
 	case EVDEV_KEY_TYPE_BUTTON:
+		if (device->scroll.has_middle_button_scroll &&
+		    e->code == BTN_MIDDLE) {
+			evdev_middle_button_scroll_button(device, time,
+							  e->value);
+			break;
+		}
 		evdev_pointer_notify_button(
 			device,
 			time,
@@ -946,6 +993,15 @@ evdev_configure_device(struct evdev_device *device)
 			device->mt.slot = active_slot;
 		}
 	}
+
+	if (libevdev_has_property(evdev, INPUT_PROP_POINTING_STICK)) {
+		libinput_timer_init(&device->scroll.timer,
+				    device->base.seat->libinput,
+				    evdev_middle_button_scroll_timeout,
+				    device);
+		device->scroll.has_middle_button_scroll = true;
+	}
+
 	if (libevdev_has_event_code(evdev, EV_REL, REL_X) ||
 	    libevdev_has_event_code(evdev, EV_REL, REL_Y))
 		has_rel = 1;

src/evdev.h

@@ -26,10 +26,12 @@
 
 #include "config.h"
 
+#include <stdbool.h>
 #include "linux/input.h"
 #include <libevdev/libevdev.h>
 
 #include "libinput-private.h"
+#include "timer.h"
 
 enum evdev_event_type {
 	EVDEV_NONE,
@@ -96,6 +98,9 @@ struct evdev_device {
 	} rel;
 
 	struct {
+		struct libinput_timer timer;
+		bool has_middle_button_scroll;
+		bool middle_button_scroll_active;
 		double threshold;
 		uint32_t direction;
 	} scroll;

test/litest-trackpoint.c

@@ -49,6 +49,8 @@ static int events[] = {
 	EV_KEY, BTN_MIDDLE,
 	EV_REL, REL_X,
 	EV_REL, REL_Y,
+	INPUT_PROP_MAX, INPUT_PROP_POINTER,
+	INPUT_PROP_MAX, INPUT_PROP_POINTING_STICK,
 	-1, -1,
 };
 

test/pointer.c

@@ -132,7 +132,9 @@ START_TEST(pointer_button)
 		test_button_event(dev, BTN_RIGHT, 0);
 	}
 
-	if (libevdev_has_event_code(dev->evdev, EV_KEY, BTN_MIDDLE)) {
+	/* Skip middle button test on trackpoints (used for scrolling) */
+	if (!libevdev_has_property(dev->evdev, INPUT_PROP_POINTING_STICK) &&
+	    libevdev_has_event_code(dev->evdev, EV_KEY, BTN_MIDDLE)) {
 		test_button_event(dev, BTN_MIDDLE, 1);
 		test_button_event(dev, BTN_MIDDLE, 0);
 	}