Cache title controls layout value

So it's not requested on every window width change and etc...

ui/platform/linux/ui_utility_linux.cpp

@@ -548,6 +548,8 @@ void ShowWindowMenu(not_null<QWidget*> widget, const QPoint &point) {
 	}
 }
 
+namespace internal {
+
 TitleControls::Layout TitleControlsLayout() {
 	[[maybe_unused]] static const auto Inited = [] {
 #ifndef DESKTOP_APP_DISABLE_X11_INTEGRATION
@@ -634,5 +636,6 @@ TitleControls::Layout TitleControlsLayout() {
 	};
 }
 
+} // namespace internal
 } // namespace Platform
 } // namespace Ui

ui/platform/mac/ui_utility_mac.mm

@@ -147,6 +147,8 @@ std::optional<bool> IsOverlapped(
 	return false;
 }
 
+namespace internal {
+
 TitleControls::Layout TitleControlsLayout() {
 	return TitleControls::Layout{
 		.left = {
@@ -157,5 +159,6 @@ TitleControls::Layout TitleControlsLayout() {
 	};
 }
 
+} // namespace internal
 } // namespace Platform
 } // namespace Ui

ui/platform/ui_platform_utility.cpp

@@ -8,26 +8,33 @@
 
 namespace Ui {
 namespace Platform {
+namespace internal {
 namespace {
 
-rpl::event_stream<TitleControls::Layout> TitleControlsLayoutChanges;
+auto &CachedTitleControlsLayout() {
+	using Layout = TitleControls::Layout;
+	static rpl::variable<Layout> Result = TitleControlsLayout();
+	return Result;
+};
 
 } // namespace
 
+void NotifyTitleControlsLayoutChanged() {
+	CachedTitleControlsLayout() = TitleControlsLayout();
+}
+
+} // namespace internal
+
+TitleControls::Layout TitleControlsLayout() {
+	return internal::CachedTitleControlsLayout().current();
+}
+
 rpl::producer<TitleControls::Layout> TitleControlsLayoutValue() {
-	return rpl::single(
-		TitleControlsLayout()
-	) | rpl::then(
-		TitleControlsLayoutChanged()
-	);
+	return internal::CachedTitleControlsLayout().value();
 }
 
 rpl::producer<TitleControls::Layout> TitleControlsLayoutChanged() {
-	return TitleControlsLayoutChanges.events();
-}
-
-void NotifyTitleControlsLayoutChanged() {
-	TitleControlsLayoutChanges.fire_copy(TitleControlsLayout());
+	return internal::CachedTitleControlsLayout().changes();
 }
 
 } // namespace Platform

ui/platform/ui_platform_utility.h

@@ -17,6 +17,13 @@ class PopupMenu;
 } // namespace Ui
 
 namespace Ui::Platform {
+namespace internal {
+
+// Actual requestor, cached by the public interface
+[[nodiscard]] TitleControls::Layout TitleControlsLayout();
+void NotifyTitleControlsLayoutChanged();
+
+} // namespace internal
 
 [[nodiscard]] bool IsApplicationActive();
 
@@ -48,7 +55,6 @@ void ShowWindowMenu(not_null<QWidget*> widget, const QPoint &point);
 [[nodiscard]] TitleControls::Layout TitleControlsLayout();
 [[nodiscard]] rpl::producer<TitleControls::Layout> TitleControlsLayoutValue();
 [[nodiscard]] rpl::producer<TitleControls::Layout> TitleControlsLayoutChanged();
-void NotifyTitleControlsLayoutChanged();
 
 void FixPopupMenuNativeEmojiPopup(not_null<PopupMenu*> menu);
 

ui/platform/win/ui_utility_win.cpp

@@ -134,6 +134,8 @@ void ShowWindowMenu(not_null<QWidget*> widget, const QPoint &point) {
 		MAKELPARAM(p.x, p.y));
 }
 
+namespace internal {
+
 TitleControls::Layout TitleControlsLayout() {
 	return TitleControls::Layout{
 		.right = {
@@ -144,6 +146,8 @@ TitleControls::Layout TitleControlsLayout() {
 	};
 }
 
+} // namespace internal
+
 void FixPopupMenuNativeEmojiPopup(not_null<PopupMenu*> menu) {
 	// Windows native emoji selector, that can be called by Win+. shortcut,
 	// is behaving strangely within an input field in a popup menu.