input_cmd_scroll_button: utilize mouse btn helpers

This modifies `input_cmd_scroll_button` to utilize the mouse button
helper `get_mouse_button` when parsing the button. x11 axis buttons are
not supported with this command and `CMD_INVALID` will be returned, but
all other x11 buttons, button event names, and button event codes should
be working

sway/commands/input/scroll_button.c

@@ -1,9 +1,7 @@
-#include <string.h>
-#include <strings.h>
-#include <errno.h>
+#include <libevdev/libevdev.h>
 #include "sway/config.h"
 #include "sway/commands.h"
-#include "sway/input/input-manager.h"
+#include "sway/input/cursor.h"
 
 struct cmd_results *input_cmd_scroll_button(int argc, char **argv) {
 	struct cmd_results *error = NULL;
@@ -16,22 +14,26 @@ struct cmd_results *input_cmd_scroll_button(int argc, char **argv) {
 			"No input device defined.");
 	}
 
-	errno = 0;
-	char *endptr;
-	int scroll_button = strtol(*argv, &endptr, 10);
-	if (endptr == *argv && scroll_button == 0) {
-		return cmd_results_new(CMD_INVALID, "scroll_button",
-				"Scroll button identifier must be an integer.");
+	if (strcmp(*argv, "disable") == 0) {
+		ic->scroll_button = 0;
+		return cmd_results_new(CMD_SUCCESS, NULL, NULL);
 	}
-	if (errno == ERANGE) {
+
+	char *message = NULL;
+	uint32_t button = get_mouse_button(*argv, &message);
+	if (message) {
+		error = cmd_results_new(CMD_INVALID, "scroll_button", message);
+		free(message);
+		return error;
+	} else if (button == SWAY_SCROLL_UP || button == SWAY_SCROLL_DOWN
+			|| button == SWAY_SCROLL_LEFT || button == SWAY_SCROLL_RIGHT) {
 		return cmd_results_new(CMD_INVALID, "scroll_button",
-				"Scroll button identifier out of range.");
-	}
-	if (scroll_button < 0) {
+				"X11 axis buttons are not supported for scroll_button");
+	} else if (!button) {
 		return cmd_results_new(CMD_INVALID, "scroll_button",
-				"Scroll button identifier cannot be negative.");
+				"Unknown button %s", *argv);
 	}
-	ic->scroll_button = scroll_button;
+	ic->scroll_button = button;
 
 	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
 }

sway/input/cursor.c

@@ -1593,7 +1593,7 @@ uint32_t get_mouse_bindcode(const char *name, char **error) {
 
 uint32_t get_mouse_button(const char *name, char **error) {
 	uint32_t button = get_mouse_bindsym(name, error);
-	if (!button && !error) {
+	if (!button && !*error) {
 		button = get_mouse_bindcode(name, error);
 	}
 	return button;

sway/sway-input.5.scd

@@ -105,10 +105,11 @@ The following commands may only be used in the configuration file.
 *input* <identifier> repeat\_rate <characters per second>
 	Sets the frequency of key repeats once the repeat\_delay has passed.
 
-*input* <identifier> scroll\_button <button\_identifier>
-	Sets button used for scroll\_method on\_button\_down. The button identifier
-	can be obtained from `libinput debug-events`.
-	If set to 0, it disables the scroll\_button on\_button\_down.
+*input* <identifier> scroll\_button disable|button[1-3,8,9]|<event-code-or-name>
+	Sets the button used for scroll\_method on\_button\_down. The button can
+	be given as an event name or code, which can be obtained from `libinput
+	debug-events`, or as a x11 mouse button (button[1-3,8,9]). If set to
+	_disable_, it disables the scroll\_method on\_button\_down.
 
 *input* <identifier> scroll\_factor <floating point value>
 	Changes the scroll factor for the specified input device. Scroll speed will