config: mouse-bindings: verify button isn't already mapped

A button may only be mapped to a single action. Detect when the user
tried to map the same button to multiple actions and error out.

To clear a binding (for example, to free up a button from the default
bindings), one can set the action it is bound to to
`NONE` (e.g. `primary-paste=NONE`).

config.c

@@ -49,6 +49,7 @@ static const uint32_t default_bright[] = {
 };
 
 static const char *binding_action_map[] = {
+    [BIND_ACTION_NONE] = NULL,
     [BIND_ACTION_SCROLLBACK_UP] = "scrollback-up",
     [BIND_ACTION_SCROLLBACK_DOWN] = "scrollback-down",
     [BIND_ACTION_CLIPBOARD_COPY] = "clipboard-copy",
@@ -454,6 +455,9 @@ parse_section_key_bindings(
     const char *path, unsigned lineno)
 {
     for (enum binding_action action = 0; action < BIND_ACTION_COUNT; action++) {
+        if (binding_action_map[action] == NULL)
+            continue;
+
         if (strcmp(key, binding_action_map[action]) != 0)
             continue;
 
@@ -488,9 +492,17 @@ parse_section_mouse_bindings(
     const char *path, unsigned lineno)
 {
     for (enum binding_action action = 0; action < BIND_ACTION_COUNT; action++) {
+        if (binding_action_map[action] == NULL)
+            continue;
+
         if (strcmp(key, binding_action_map[action]) != 0)
             continue;
 
+        if (strcmp(value, "NONE") == 0) {
+            conf->bindings.mouse[action] = (struct mouse_binding){0, 0, BIND_ACTION_NONE};
+            return true;
+        }
+
         const char *map[] = {
             [BTN_LEFT] = "BTN_LEFT",
             [BTN_RIGHT] = "BTN_RIGHT",
@@ -506,7 +518,19 @@ parse_section_mouse_bindings(
             if (map[i] == NULL || strcmp(map[i], value) != 0)
                 continue;
 
-            conf->bindings.mouse[action] = (struct mouse_binding){i, 1, action};
+            const int count = 1;
+
+            /* Make sure button isn't already mapped to another action */
+            for (enum binding_action j = 0; j < BIND_ACTION_COUNT; j++) {
+                const struct mouse_binding *collision = &conf->bindings.mouse[j];
+                if (collision->button == i && collision->count == count) {
+                    LOG_ERR("%s:%d: %s already mapped to %s", path, lineno,
+                            value, binding_action_map[collision->action]);
+                    return false;
+                }
+            }
+
+            conf->bindings.mouse[action] = (struct mouse_binding){i, count, action};
             return true;
         }
 

doc/foot.5.scd

@@ -151,15 +151,15 @@ component.
 
 This section lets you override the default key bindings.
 
-The general format is *action*=*combo1*...*comboN*. That is, each
+The general format is _action_=_combo1_..._comboN_. That is, each
 action may have one or more key combinations, space separated. Each
-combination is on the form *mod1*+*mod2*+*key*. The names of the
+combination is on the form _mod1_+_mod2_+_key_. The names of the
 modifiers and the key *must* be a valid XKB key name.
 
 Note that if *Shift* is one of the modifiers, the _key_ *must* be in
 upper case.
 
-Note that _Alt_ is usually called *Mod1*.
+Note that *Alt* is usually called *Mod1*.
 
 *scrollback-up*
 	Scrolls up/back in history. Default: _Shift+Page_Up_.
@@ -207,10 +207,16 @@ Note that _Alt_ is usually called *Mod1*.
 
 This section lets you override the default mouse bindings.
 
-The general format is *action*=*BTN\_<name>*, where *BTN\_<name>* is
+The general format is _action_=_BTN\_<name>_, where _BTN\_<name>_ is
 the name of the event code (e.g. *BTN\_LEFT*, *BTN\_RIGHT*). You can
 find the event names using *libinput debug-events*.
 
+A button can only be mapped to *one* action. Lets say you want to bind
+*BTN\_MIDDLE* to *fullscreen*. Since *BTN\_MIDDLE* is the default
+binding for *primary-paste*, you first need to unmap the default
+binding. This can be done by setting _action_=*NONE*;
+e.g. *primary-paste*=*NONE*.
+
 *primary-paste*
 	Pastes from the _primary selection_. Default: _BTN_MIDDLE_.
 

input.c

@@ -38,6 +38,9 @@ input_execute_binding(struct terminal *term, enum binding_action action,
                       uint32_t serial)
 {
     switch (action) {
+    case BIND_ACTION_NONE:
+        break;
+
     case BIND_ACTION_SCROLLBACK_UP:
         cmd_scrollback_up(term, term->rows);
         break;
@@ -1168,6 +1171,7 @@ wl_pointer_button(void *data, struct wl_pointer *wl_pointer,
                     }
 
                     input_execute_binding(term, binding->action, serial);
+                    break;
                 }
                 selection_cancel(term);
             }

wayland.h

@@ -42,6 +42,7 @@ struct monitor {
 };
 
 enum binding_action {
+    BIND_ACTION_NONE,
     BIND_ACTION_SCROLLBACK_UP,
     BIND_ACTION_SCROLLBACK_DOWN,
     BIND_ACTION_CLIPBOARD_COPY,