From 4cc0ee5f477b709592c400aefdb7eb3d195647fa Mon Sep 17 00:00:00 2001
From: Andreas Kling <andreas@ladybird.org>
Date: Mon, 1 Jun 2026 10:40:42 +0200
Subject: [PATCH] UI/Qt: Keep macOS chrome out of RHI flushes

Stop forcing RHI for every QWidget on macOS. The web content view is
the only widget that needs Metal, and QRhiWidget already requests that.

Make the web content view a native child before parenting it into the
tab UI so Qt does not propagate its RHI config to the browser window
backing store. This keeps chrome repaints on the normal Cocoa backing
store path instead of copying the full window backing store into a
texture.
---
 UI/Qt/WebContentView.cpp | 19 +++++++++++++++++--
 UI/Qt/main.cpp           |  8 ++++----
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/UI/Qt/WebContentView.cpp b/UI/Qt/WebContentView.cpp
index e00d46fb45..961103c7cd 100644
--- a/UI/Qt/WebContentView.cpp
+++ b/UI/Qt/WebContentView.cpp
@@ -53,10 +53,25 @@ namespace Ladybird {
 
 bool is_using_dark_system_theme(QWidget&);
 
-WebContentView::WebContentView(QWidget* window, RefPtr<WebView::WebContentClient> parent_client, size_t page_index, WebContentViewInitialState initial_state)
-    : WebContentViewBase(window)
+static QWidget* initial_web_content_view_parent([[maybe_unused]] QWidget* window)
 {
 #ifdef AK_OS_MACOS
+    return nullptr;
+#else
+    return window;
+#endif
+}
+
+WebContentView::WebContentView(QWidget* window, RefPtr<WebView::WebContentClient> parent_client, size_t page_index, WebContentViewInitialState initial_state)
+    : WebContentViewBase(initial_web_content_view_parent(window))
+{
+#ifdef AK_OS_MACOS
+    // Keep the QRhiWidget out of the top-level QWidget backing store. If it is
+    // parented before becoming native, Qt propagates its RHI config to the whole
+    // browser window and uploads the full backing store texture on chrome repaints.
+    setAttribute(Qt::WA_DontCreateNativeAncestors);
+    setAttribute(Qt::WA_NativeWindow);
+    setParent(window);
     setApi(QRhiWidget::Api::Metal);
 #endif
 
diff --git a/UI/Qt/main.cpp b/UI/Qt/main.cpp
index 9c3e01d0b4..316009ce9c 100644
--- a/UI/Qt/main.cpp
+++ b/UI/Qt/main.cpp
@@ -13,6 +13,7 @@
 #include <UI/Qt/BrowserWindow.h>
 #include <UI/Qt/Settings.h>
 
+#include <QCoreApplication>
 #include <QtGlobal>
 
 #if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
@@ -46,10 +47,9 @@ ErrorOr<int> ladybird_main(Main::Arguments arguments)
     AK::set_rich_debug_enabled(true);
 
 #ifdef AK_OS_MACOS
-    if (!qEnvironmentVariableIsSet("QT_WIDGETS_RHI"))
-        qputenv("QT_WIDGETS_RHI", "1");
-    if (!qEnvironmentVariableIsSet("QT_WIDGETS_RHI_BACKEND"))
-        qputenv("QT_WIDGETS_RHI_BACKEND", "metal");
+    // The web content view is a native QRhiWidget child. Keep it from forcing
+    // every sibling in the tab UI to become native as well.
+    QCoreApplication::setAttribute(Qt::AA_DontCreateNativeWidgetSiblings);
 #endif
 
     auto app = TRY(Ladybird::Application::create(arguments));