WebContent: Coalesce paint invalidations to avoid spamming client

Some content cause a lot of paint invalidations (e.g someone drawing to
a <canvas> repeatedly) and we don't need to spam the client about this.
Instead, accumulate a dirty rect, and send it once per event loop step.

2 files changed, 11 insertions, 2 deletions

diff --git a/Userland/Services/WebContent/PageHost.cpp b/Userland/Services/WebContent/PageHost.cpp
index 4dcbabfdf7..0414a88044 100644
--- a/Userland/Services/WebContent/PageHost.cpp
+++ b/Userland/Services/WebContent/PageHost.cpp
@@ -21,6 +21,10 @@ PageHost::PageHost(ClientConnection& client)
     , m_page(make<Web::Page>(*this))
 {
     setup_palette();
+    m_invalidation_coalescing_timer = Core::Timer::create_single_shot(0, [this] {
+        m_client.async_did_invalidate_content_rect(m_invalidation_rect);
+        m_invalidation_rect = {};
+    });
 }
 
 PageHost::~PageHost()
@@ -77,9 +81,11 @@ void PageHost::set_viewport_rect(const Gfx::IntRect& rect)
     page().top_level_browsing_context().set_viewport_rect(rect);
 }
 
-void PageHost::page_did_invalidate(const Gfx::IntRect& content_rect)
+void PageHost::page_did_invalidate(Gfx::IntRect const& content_rect)
 {
-    m_client.async_did_invalidate_content_rect(content_rect);
+    m_invalidation_rect = m_invalidation_rect.united(content_rect);
+    if (!m_invalidation_coalescing_timer->is_active())
+        m_invalidation_coalescing_timer->start();
 }
 
 void PageHost::page_did_change_selection()
diff --git a/Userland/Services/WebContent/PageHost.h b/Userland/Services/WebContent/PageHost.h
index ef4b48208a..1db072ede9 100644
--- a/Userland/Services/WebContent/PageHost.h
+++ b/Userland/Services/WebContent/PageHost.h
@@ -72,6 +72,9 @@ private:
     RefPtr<Gfx::PaletteImpl> m_palette_impl;
     Gfx::IntRect m_screen_rect;
     bool m_should_show_line_box_borders { false };
+
+    RefPtr<Core::Timer> m_invalidation_coalescing_timer;
+    Gfx::IntRect m_invalidation_rect;
 };
 
 }