Add mouse button bindings

Adds support for bindings like:

bindsym button3 floating toggle
bindsym $mod+button3 floating toggle

sway/commands/bind.c

@@ -1,7 +1,9 @@
 #include <xkbcommon/xkbcommon.h>
 #include <xkbcommon/xkbcommon-names.h>
+#include <strings.h>
 #include "sway/commands.h"
 #include "sway/config.h"
+#include "sway/input_state.h"
 #include "list.h"
 #include "log.h"
 #include "stringop.h"
@@ -52,6 +54,12 @@ struct cmd_results *cmd_bindsym(int argc, char **argv) {
 		// Check for xkb key
 		xkb_keysym_t sym = xkb_keysym_from_name(split->items[i],
 				XKB_KEYSYM_CASE_INSENSITIVE);
+
+		// Check for mouse binding
+		if (strncasecmp(split->items[i], "button", strlen("button")) == 0 &&
+				strlen(split->items[i]) == strlen("button0")) {
+			sym = ((char *)split->items[i])[strlen("button")] - '1' + M_LEFT_CLICK;
+		}
 		if (!sym) {
 			free_sway_binding(binding);
 			free_flat_list(split);

sway/handlers.c

@@ -917,6 +917,26 @@ static bool handle_pointer_button(wlc_handle view, uint32_t time, const struct w
 	// Update view pointer is on
 	pointer_state.view = container_under_pointer();
 
+	struct sway_mode *mode = config->current_mode;
+	// handle bindings
+	for (int i = 0; i < mode->bindings->length; ++i) {
+		struct sway_binding *binding = mode->bindings->items[i];
+		if ((modifiers->mods ^ binding->modifiers) == 0) {
+			switch (state) {
+				case WLC_BUTTON_STATE_PRESSED: {
+					if (!binding->release && handle_bindsym(binding, button, 0)) {
+						return EVENT_HANDLED;
+					}
+				}
+				case WLC_BUTTON_STATE_RELEASED:
+					if (binding->release && handle_bindsym(binding, button, 0)) {
+						return EVENT_HANDLED;
+					}
+				break;
+			}
+		}
+	}
+
 	// Update pointer_state
 	switch (button) {
 	case M_LEFT_CLICK: