From e3e6af39bcf733e779c7ea187e99ff7b235f2022 Mon Sep 17 00:00:00 2001
From: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
Date: Mon, 18 Mar 2024 20:11:06 +0100
Subject: [PATCH] LibWeb: Add basic implementation of
 has_a_rendering_opportunity()

Return true only if we are ready to repaint. This fixes the issue where
requestAnimationFrame() was invoked more than once between repaints.
---
 Userland/Libraries/LibWeb/HTML/Navigable.cpp          | 7 +++++--
 Userland/Libraries/LibWeb/Page/Page.h                 | 1 +
 Userland/Libraries/LibWeb/SVG/SVGDecodedImageData.cpp | 1 +
 Userland/Services/WebContent/PageClient.cpp           | 5 +++++
 Userland/Services/WebContent/PageClient.h             | 1 +
 Userland/Services/WebWorker/PageHost.h                | 1 +
 6 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/Userland/Libraries/LibWeb/HTML/Navigable.cpp b/Userland/Libraries/LibWeb/HTML/Navigable.cpp
index 7e442aef09..b70b398c96 100644
--- a/Userland/Libraries/LibWeb/HTML/Navigable.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Navigable.cpp
@@ -2073,8 +2073,11 @@ bool Navigable::has_a_rendering_opportunity() const
     // or whether the document's visibility state is "visible".
     // Rendering opportunities typically occur at regular intervals.
 
-    // FIXME: We should at the very least say `false` here if we're an inactive browser tab.
-    return true;
+    // FIXME: Return `false` here if we're an inactive browser tab.
+    auto browsing_context = const_cast<Navigable*>(this)->active_browsing_context();
+    if (!browsing_context)
+        return false;
+    return browsing_context->page().client().is_ready_to_paint();
 }
 
 // https://html.spec.whatwg.org/multipage/nav-history-apis.html#inform-the-navigation-api-about-aborting-navigation
diff --git a/Userland/Libraries/LibWeb/Page/Page.h b/Userland/Libraries/LibWeb/Page/Page.h
index 89152869d7..16f08888ca 100644
--- a/Userland/Libraries/LibWeb/Page/Page.h
+++ b/Userland/Libraries/LibWeb/Page/Page.h
@@ -307,6 +307,7 @@ public:
     virtual void inspector_did_execute_console_script([[maybe_unused]] String const& script) { }
 
     virtual void schedule_repaint() = 0;
+    virtual bool is_ready_to_paint() const = 0;
 
 protected:
     virtual ~PageClient() = default;
diff --git a/Userland/Libraries/LibWeb/SVG/SVGDecodedImageData.cpp b/Userland/Libraries/LibWeb/SVG/SVGDecodedImageData.cpp
index cfac8accfa..95cb61d34d 100644
--- a/Userland/Libraries/LibWeb/SVG/SVGDecodedImageData.cpp
+++ b/Userland/Libraries/LibWeb/SVG/SVGDecodedImageData.cpp
@@ -49,6 +49,7 @@ public:
     virtual void request_file(FileRequest) override { }
     virtual void paint(DevicePixelRect const&, Gfx::Bitmap&, Web::PaintOptions = {}) override { }
     virtual void schedule_repaint() override { }
+    virtual bool is_ready_to_paint() const override { return true; }
 
 private:
     explicit SVGPageClient(Page& host_page)
diff --git a/Userland/Services/WebContent/PageClient.cpp b/Userland/Services/WebContent/PageClient.cpp
index 5420ac63e4..51a4039d71 100644
--- a/Userland/Services/WebContent/PageClient.cpp
+++ b/Userland/Services/WebContent/PageClient.cpp
@@ -96,6 +96,11 @@ void PageClient::schedule_repaint()
         m_repaint_timer->start();
 }
 
+bool PageClient::is_ready_to_paint() const
+{
+    return m_paint_state == PaintState::Ready;
+}
+
 void PageClient::ready_to_paint()
 {
     auto old_paint_state = exchange(m_paint_state, PaintState::Ready);
diff --git a/Userland/Services/WebContent/PageClient.h b/Userland/Services/WebContent/PageClient.h
index fa30eed1e8..82f36e81d7 100644
--- a/Userland/Services/WebContent/PageClient.h
+++ b/Userland/Services/WebContent/PageClient.h
@@ -30,6 +30,7 @@ public:
     static void set_use_gpu_painter();
 
     virtual void schedule_repaint() override;
+    virtual bool is_ready_to_paint() const override;
 
     virtual Web::Page& page() override { return *m_page; }
     virtual Web::Page const& page() const override { return *m_page; }
diff --git a/Userland/Services/WebWorker/PageHost.h b/Userland/Services/WebWorker/PageHost.h
index 61a2b8ef83..dde2af3bd6 100644
--- a/Userland/Services/WebWorker/PageHost.h
+++ b/Userland/Services/WebWorker/PageHost.h
@@ -31,6 +31,7 @@ public:
     virtual void paint(Web::DevicePixelRect const&, Gfx::Bitmap&, Web::PaintOptions = {}) override;
     virtual void request_file(Web::FileRequest) override;
     virtual void schedule_repaint() override {};
+    virtual bool is_ready_to_paint() const override { return true; }
 
 private:
     explicit PageHost(ConnectionFromClient&);