config, doc, changelog: move selection-override-modifiers to [mouse-bindings] and validate other case

specifically, check for conflicts both when mouse bindings are set and when the selection-override-modifiers setting itself is set

CHANGELOG.md

@@ -38,9 +38,9 @@
 ## Unreleased
 ### Added
 
-* `[mouse].selection-override-modifiers` option, specifying which modifiers
-  to hold to override mouse grabs by client applications and force selection
-  instead.
+* `[mouse-bindings].selection-override-modifiers` option, specifying
+  which modifiers to hold to override mouse grabs by client
+  applications and force selection instead.
 
 
 ### Changed

config.c

@@ -1349,13 +1349,6 @@ parse_section_mouse(struct context *ctx)
     else if (strcmp(key, "alternate-scroll-mode") == 0)
         return value_to_bool(ctx, &conf->mouse.alternate_scroll_mode);
 
-    else if (strcmp(key, "selection-override-modifiers") == 0) {
-        if (!parse_modifiers(ctx, ctx->value, strlen(ctx->value), &conf->mouse.selection_override_modifiers)) {
-            LOG_CONTEXTUAL_ERR("%s: invalid modifiers '%s'", key, ctx->value);
-            return false;
-        }
-    }
-
     else {
         LOG_CONTEXTUAL_ERR("not a valid option: %s", key);
         return false;
@@ -2166,6 +2159,37 @@ parse_section_mouse_bindings(struct context *ctx)
     const char *key = ctx->key;
     const char *value = ctx->value;
 
+    if (strcmp(ctx->key, "selection-override-modifiers") == 0) {
+        if (!parse_modifiers(ctx, ctx->value, strlen(ctx->value),
+            &conf->mouse.selection_override_modifiers)) {
+            LOG_CONTEXTUAL_ERR("%s: invalid modifiers '%s'", key, ctx->value);
+            return false;
+        }
+
+        /* Ensure no existing bindings use these modifiers */
+        for (size_t i = 0; i < conf->bindings.mouse.count; i++) {
+            const struct config_mouse_binding *binding = &conf->bindings.mouse.arr[i];
+            struct key_combo combo = {
+                .modifiers = binding->modifiers,
+                .m = {
+                    .button = binding->button,
+                    .count = binding->count,
+                },
+            };
+
+            struct key_combo_list key_combos = {
+                .count = 1,
+                .combos = &combo,
+            };
+
+            if (selection_override_interferes_with_mouse_binding(ctx, &key_combos)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     struct argv pipe_argv;
 
     ssize_t pipe_remove_len = pipe_argv_from_value(ctx, &pipe_argv);

doc/foot.ini.5.scd

@@ -470,16 +470,6 @@ applications can change these at runtime.
 	
 	Default: _yes_.
 
-*selection-override-modifiers*
-	Modifiers. The set of modifiers which, when held, will override
-	attempts by programs running in the terminal to capture mouse
-	input.
-	
-	Any modifiers in this set cannot be used for mouse bindings
-	themselves.
-	
-	Default: Shift
-
 
 # SECTION: colors
 
@@ -875,10 +865,12 @@ of the modifiers *must* be valid XKB key names, and the button name
 *must* be a valid libinput name. You can find the button names using
 *libinput debug-events*.
 
-Note that the modifiers set in *mouse.selection-override-modifiers*
-(by default, *Shift*) cannot be used as modifiers in mouse bindings
-since they are used to enable selection when the client application is
-grabbing the mouse.
+The modifiers set in *[mouse-bindings].selection-override-modifiers*
+(by default, *Shift*) cannot be used as modifiers in mouse bindings,
+and are instead used to enable selecting text with the mouse
+irrespective of whether a client application currently has the mouse
+grabbed. Because the order of bindings is significant, it's best to
+set this prior to any other mouse bindings that might use *Shift*.
 
 The trailing *COUNT* is optional and specifies the click count
 required to trigger the binding. The default if *COUNT* is omitted is

foot.ini

@@ -63,7 +63,6 @@
 [mouse]
 # hide-when-typing=no
 # alternate-scroll-mode=yes
-# selection-override-modifiers=Shift
 
 [colors]
 # alpha=1.0
@@ -170,6 +169,7 @@
 # toggle-url-visible=t
 
 [mouse-bindings]
+# selection-override-modifiers=Shift
 # primary-paste=BTN_MIDDLE
 # select-begin=BTN_LEFT
 # select-begin-block=Control+BTN_LEFT