From ec6e55cfc630bbd089875b0e3fd6536013789399 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 22 Mar 2020 01:07:07 +0100
Subject: [PATCH] LibGUI: Don't spam WindowServer with SetWindowOverrideCursor
 messages

Remember the override cursor in GUI::Window and avoid sending a message
to WindowServer when possible.

This removes a lot of synchronous IPC between Browser and WindowServer,
which noticeably improves DOM event responsiveness. :^)
---
 Libraries/LibGUI/Window.cpp | 5 +++++
 Libraries/LibGUI/Window.h   | 1 +
 2 files changed, 6 insertions(+)

diff --git a/Libraries/LibGUI/Window.cpp b/Libraries/LibGUI/Window.cpp
index 9cb37b02c5..7257ecdd32 100644
--- a/Libraries/LibGUI/Window.cpp
+++ b/Libraries/LibGUI/Window.cpp
@@ -89,6 +89,7 @@ void Window::show()
 {
     if (is_visible())
         return;
+    m_override_cursor = StandardCursor::None;
     auto response = WindowServerConnection::the().send_sync<Messages::WindowServer::CreateWindow>(
         m_rect_when_windowless,
         m_has_alpha_channel,
@@ -123,6 +124,7 @@ void Window::hide()
     m_pending_paint_event_rects.clear();
     m_back_bitmap = nullptr;
     m_front_bitmap = nullptr;
+    m_override_cursor = StandardCursor::None;
 
     bool app_has_visible_windows = false;
     for (auto& window : *all_windows) {
@@ -183,7 +185,10 @@ void Window::set_override_cursor(StandardCursor cursor)
 {
     if (!is_visible())
         return;
+    if (m_override_cursor == cursor)
+        return;
     WindowServerConnection::the().send_sync<Messages::WindowServer::SetWindowOverrideCursor>(m_window_id, (u32)cursor);
+    m_override_cursor = cursor;
 }
 
 void Window::event(Core::Event& event)
diff --git a/Libraries/LibGUI/Window.h b/Libraries/LibGUI/Window.h
index 10527fed6d..f8fe54652d 100644
--- a/Libraries/LibGUI/Window.h
+++ b/Libraries/LibGUI/Window.h
@@ -212,6 +212,7 @@ private:
     Gfx::Size m_base_size;
     Color m_background_color { Color::WarmGray };
     WindowType m_window_type { WindowType::Normal };
+    StandardCursor m_override_cursor { StandardCursor::None };
     bool m_is_active { false };
     bool m_has_alpha_channel { false };
     bool m_double_buffering_enabled { true };