Change mouse buttons to x11 map and libevdev names

This modifies the way mouse bindings are parsed. Instead of adding to
BTN_LEFT, which results in button numbers that may not be expected,
buttons will be parsed in one of the following ways:

1. `button[1-9]` will now map to their x11 equivalents. This is already
the case for bar bindings. This adds support for binding to axis events,
which was not possible in the previous approach.

2. Anything that starts with `BTN_` will be parsed as an event code name
using `libevdev_event_code_from_name`. This allows for any button to be
mapped to instead of limiting usage to the ones near BTN_LEFT. This also
adds a dependency on libevdev, but since libevdev is already a dependency
of libinput, this should be fine. If needed, this option can have dependency
guards added.

Binding changes:
- button1: BTN_LEFT -> BTN_LEFT
- button2: BTN_RIGHT -> BTN_MIDDLE
- button3: BTN_MIDDLE -> BTN_RIGHT
- button4: BTN_SIDE -> SWAY_SCROLL_UP
- button5: BTN_EXTRA -> SWAY_SCROLL_DOWN
- button6: BTN_FORWARD -> SWAY_SCROLL_LEFT
- button7: BTN_BACK -> SWAY_SCROLL_RIGHT
- button8: BTN_TASK -> BTN_SIDE
- button9: BTN_JOYSTICK -> BTN_EXTRA

Since the axis events need to be mapped to an event code, this uses the
following mappings to avoid any conflicts:
- SWAY_SCROLL_UP: KEY_MAX + 1
- SWAY_SCROLL_DOWN: KEY_MAX + 2
- SWAY_SCROLL_LEFT: KEY_MAX + 3
- SWAY_SCROLL_RIGHT: KEY_MAX + 4

include/sway/input/cursor.h

@@ -5,6 +5,11 @@
 
 #define SWAY_CURSOR_PRESSED_BUTTONS_CAP 32
 
+#define SWAY_SCROLL_UP KEY_MAX + 1
+#define SWAY_SCROLL_DOWN KEY_MAX + 2
+#define SWAY_SCROLL_LEFT KEY_MAX + 3
+#define SWAY_SCROLL_RIGHT KEY_MAX + 4
+
 struct sway_cursor {
 	struct sway_seat *seat;
 	struct wlr_cursor *cursor;

meson.build

@@ -46,6 +46,7 @@ pango          = dependency('pango')
 pangocairo     = dependency('pangocairo')
 gdk_pixbuf     = dependency('gdk-pixbuf-2.0', required: false)
 pixman         = dependency('pixman-1')
+libevdev       = dependency('libevdev')
 libinput       = dependency('libinput', version: '>=1.6.0')
 libpam         = cc.find_library('pam', required: false)
 crypt          = cc.find_library('crypt', required: false)

sway/commands/bind.c

@@ -1,4 +1,5 @@
 #define _POSIX_C_SOURCE 200809L
+#include <libevdev/libevdev.h>
 #ifdef __linux__
 #include <linux/input-event-codes.h>
 #elif __FreeBSD__
@@ -10,6 +11,7 @@
 #include <strings.h>
 #include "sway/commands.h"
 #include "sway/config.h"
+#include "sway/input/cursor.h"
 #include "sway/ipc-server.h"
 #include "list.h"
 #include "log.h"
@@ -102,9 +104,26 @@ static struct cmd_results *identify_key(const char* name, bool first_key,
 
 		// Check for mouse binding
 		uint32_t button = 0;
-		if (strncasecmp(name, "button", strlen("button")) == 0 &&
-				strlen(name) == strlen("button0")) {
-			button = name[strlen("button")] - '1' + BTN_LEFT;
+		if (strncasecmp(name, "button", strlen("button")) == 0) {
+			// Map to x11 mouse buttons
+			button = name[strlen("button")] - '0';
+			if (button < 1 || button > 9 || strlen(name) > strlen("button0")) {
+				return cmd_results_new(CMD_INVALID, "bindsym",
+						"Only buttons 1-9 are supported. For other mouse "
+						"buttons, use the name of the event code.");
+			}
+			uint32_t buttons[] = {BTN_LEFT, BTN_MIDDLE, BTN_RIGHT,
+				SWAY_SCROLL_UP, SWAY_SCROLL_DOWN, SWAY_SCROLL_LEFT,
+				SWAY_SCROLL_RIGHT, BTN_SIDE, BTN_EXTRA};
+			button = buttons[button - 1];
+		} else if (strncmp(name, "BTN_", strlen("BTN_")) == 0) {
+			// Get event code
+			int code = libevdev_event_code_from_name(EV_KEY, name);
+			if (code == -1) {
+				return cmd_results_new(CMD_INVALID, "bindsym",
+						"Invalid event code name %s", name);
+			}
+			button = code;
 		}
 
 		if (*type == BINDING_KEYSYM) {

sway/input/cursor.c

@@ -1,5 +1,6 @@
 #define _POSIX_C_SOURCE 200809L
 #include <math.h>
+#include <libevdev/libevdev.h>
 #ifdef __linux__
 #include <linux/input-event-codes.h>
 #elif __FreeBSD__
@@ -982,6 +983,18 @@ static void handle_cursor_button(struct wl_listener *listener, void *data) {
 	transaction_commit_dirty();
 }
 
+static uint32_t wl_axis_to_button(struct wlr_event_pointer_axis *event) {
+	switch (event->orientation) {
+	case WLR_AXIS_ORIENTATION_VERTICAL:
+		return event->delta < 0 ? SWAY_SCROLL_UP : SWAY_SCROLL_DOWN;
+	case WLR_AXIS_ORIENTATION_HORIZONTAL:
+		return event->delta < 0 ? SWAY_SCROLL_LEFT : SWAY_SCROLL_RIGHT;
+	default:
+		wlr_log(WLR_DEBUG, "Unknown axis orientation");
+		return 0;
+	}
+}
+
 static void dispatch_cursor_axis(struct sway_cursor *cursor,
 		struct wlr_event_pointer_axis *event) {
 	struct sway_seat *seat = cursor->seat;
@@ -998,11 +1011,32 @@ static void dispatch_cursor_axis(struct sway_cursor *cursor,
 	enum wlr_edges edge = cont ? find_edge(cont, cursor) : WLR_EDGE_NONE;
 	bool on_border = edge != WLR_EDGE_NONE;
 	bool on_titlebar = cont && !on_border && !surface;
+	bool on_contents = cont && !on_border && surface;
 	float scroll_factor =
 		(ic == NULL || ic->scroll_factor == FLT_MIN) ? 1.0f : ic->scroll_factor;
 
-	// Scrolling on a tabbed or stacked title bar
-	if (on_titlebar) {
+	bool handled = false;
+
+	// Gather information needed for mouse bindings
+	struct wlr_keyboard *keyboard = wlr_seat_get_keyboard(seat->wlr_seat);
+	uint32_t modifiers = keyboard ? wlr_keyboard_get_modifiers(keyboard) : 0;
+	struct wlr_input_device *device = input_device->wlr_device;
+	char *dev_id = device ? input_device_get_identifier(device) : strdup("*");
+	uint32_t button = wl_axis_to_button(event);
+
+	// Handle mouse bindings - x11 mouse buttons 4-7 - press event
+	struct sway_binding *binding = NULL;
+	state_add_button(cursor, button);
+	binding = get_active_mouse_binding(cursor,
+		config->current_mode->mouse_bindings, modifiers, false,
+		on_titlebar, on_border, on_contents, dev_id);
+	if (binding) {
+		seat_execute_command(seat, binding);
+		handled = true;
+	}
+
+	// Scrolling on a tabbed or stacked title bar (handled as press event)
+	if (!handled && on_titlebar) {
 		enum sway_container_layout layout = container_parent_layout(cont);
 		if (layout == L_TABBED || layout == L_STACKED) {
 			struct sway_node *tabcontainer = node_get_parent(node);
@@ -1029,13 +1063,26 @@ static void dispatch_cursor_axis(struct sway_cursor *cursor,
 				seat_set_raw_focus(seat, new_focus);
 				seat_set_raw_focus(seat, old_focus);
 			}
-			return;
+			handled = true;
 		}
 	}
 
+	// Handle mouse bindings - x11 mouse buttons 4-7 - release event
+	binding = get_active_mouse_binding(cursor,
+		config->current_mode->mouse_bindings, modifiers, true,
+		on_titlebar, on_border, on_contents, dev_id);
+	state_erase_button(cursor, button);
+	if (binding) {
+		seat_execute_command(seat, binding);
+		handled = true;
+	}
+	free(dev_id);
+
+	if (!handled) {
 		wlr_seat_pointer_notify_axis(cursor->seat->wlr_seat, event->time_msec,
 			event->orientation, scroll_factor * event->delta,
 			round(scroll_factor * event->delta_discrete), event->source);
+	}
 }
 
 static void handle_cursor_axis(struct wl_listener *listener, void *data) {

sway/meson.build

@@ -174,6 +174,7 @@ sway_deps = [
 	cairo,
 	gdk_pixbuf,
 	jsonc,
+	libevdev,
 	libinput,
 	math,
 	pango,

sway/sway.5.scd

@@ -288,6 +288,13 @@ runtime.
 	overwrite a binding, swaynag will give you a warning. To silence this, use
 	the _--no-warn_ flag.
 
+	Mouse buttons can either be specified in the form _button[1-9]_ or by using
+	the name of the event code (ex _BTN\_LEFT_ or _BTN\_RIGHT_). For the former
+	option, the buttons will be mapped to their values in X11 (1=left, 2=middle,
+	3=right, 4=scroll up, 5=scroll down, 6=scroll left, 7=scroll right, 8=back,
+	9=forward). For the latter option, you can find the event names using
+	_libinput debug-events_.
+
 	Example:
 ```
 		# Execute firefox when alt, shift, and f are pressed together