UI: Allow a custom why-disabled message on views and setting items

View::SetDisabledReason, and SettingItem::DisabledReason for settings
pages. When set, it's shown instead of the message worked out from the
enabled pointer, and it also works for items with enabled callbacks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Common/UI/View.h

@@ -478,6 +478,10 @@ public:
 		*meansDisabled = enabledMeansDisabled_;
 		return enabledPtr_;
 	}
+	// Shown when the user tries to activate the view while it's disabled, instead of the
+	// message worked out from the enabled pointer (see SetDisabledActivationCallback).
+	void SetDisabledReason(std::string_view reason) { disabledReason_ = reason; }
+	const std::string &GetDisabledReason() const { return disabledReason_; }
 
 	virtual void SetVisibility(Visibility visibility) { visibility_ = visibility; }
 	Visibility GetVisibility() const { return visibility_; }
@@ -544,6 +548,7 @@ private:
 	bool enabled_ = true;
 	bool enabledMeansDisabled_ = false;
 	bool alwaysVisibleInSearch_ = false;
+	std::string disabledReason_;
 
 	DISALLOW_COPY_AND_ASSIGN(View);
 };

UI/SettingsPage.cpp

@@ -71,6 +71,10 @@ static SettingText LabelText(const ConfigSettingInfo &info) {
 }
 
 void ShowWhyViewDisabled(UI::View *view) {
+	if (!view->GetDisabledReason().empty()) {
+		g_OSD.Show(OSDType::MESSAGE_INFO, view->GetDisabledReason(), 0.0f, "disabledsetting");
+		return;
+	}
 	bool meansDisabled = false;
 	const bool *ptr = view->GetEnabledPtr(&meansDisabled);
 	if (!ptr) {
@@ -413,6 +417,9 @@ static UI::View *CreateSettingView(const SettingItem &item, I18NCat pageCat, UI:
 	} else if (item.disabledPtr) {
 		view->SetDisabledPtr(item.disabledPtr);
 	}
+	if (!item.disabledReason.empty()) {
+		view->SetDisabledReason(item.disabledReason.Translate(pageCat));
+	}
 	if (item.opensScreen) {
 		if (UI::Choice *choice = dynamic_cast<UI::Choice *>(view)) {
 			choice->SetIconRight(ImageID("I_CHEVRON_RIGHT"));

UI/SettingsPage.h

@@ -153,6 +153,7 @@ struct SettingItem {
 	bool *enabledPtr = nullptr;
 	bool *disabledPtr = nullptr;
 	std::function<bool()> enabledFunc;
+	SettingText disabledReason;
 	// Called on click (Bool, Choice), choice (choices) or change (sliders).
 	std::function<void(UI::EventParams &)> onChange;
 	// From the config, for settings described there. Called before onChange.
@@ -167,6 +168,8 @@ struct SettingItem {
 	SettingItem &Enabled(bool *ptr) { enabledPtr = ptr; return *this; }
 	SettingItem &Disabled(bool *ptr) { disabledPtr = ptr; return *this; }
 	SettingItem &EnabledFunc(std::function<bool()> func) { enabledFunc = std::move(func); return *this; }
+	// Shown when the user tries to use the item while it's disabled (see ShowWhyViewDisabled).
+	SettingItem &DisabledReason(SettingText text) { disabledReason = text; return *this; }
 	SettingItem &OnChange(std::function<void(UI::EventParams &)> func) { onChange = std::move(func); return *this; }
 	SettingItem &OnClick(std::function<void(UI::EventParams &)> func) { onChange = std::move(func); return *this; }
 	SettingItem &Setup(std::function<void(UI::View *)> func) { setup = std::move(func); return *this; }
@@ -223,8 +226,9 @@ private:
 };
 
 // If views is set, it gets the view created for each item (or null), in the same order.
-// Explains in an OSD message which setting has to be on or off for a disabled view to be usable,
-// if it's disabled by one (SetEnabledPtr or SetDisabledPtr on a config setting).
+// Explains in an OSD message why a disabled view can't be used: its SetDisabledReason text if it
+// has one, otherwise which setting has to be on or off, if it's disabled by one (SetEnabledPtr or
+// SetDisabledPtr on a config setting).
 void ShowWhyViewDisabled(UI::View *view);
 
 void CreateSettingViews(const SettingsPage &page, UI::ViewGroup *parent, ScreenManager *screenManager, std::vector<UI::View *> *views = nullptr);