Ladybird+LibWebView: Move backing store management code to LibWebView

This lets us share this code on all platforms, and makes resizing the
window much faster on SerenityOS as well. :^)

Userland/Libraries/LibWebView/OutOfProcessWebView.cpp

@@ -105,44 +105,13 @@ void OutOfProcessWebView::paint_event(GUI::PaintEvent& event)
 void OutOfProcessWebView::resize_event(GUI::ResizeEvent& event)
 {
     Super::resize_event(event);
+    client().async_set_viewport_rect(Gfx::IntRect({ horizontal_scrollbar().value(), vertical_scrollbar().value() }, available_size()));
     handle_resize();
 }
 
-void OutOfProcessWebView::handle_resize()
+Gfx::IntRect OutOfProcessWebView::viewport_rect() const
 {
-    client().async_set_viewport_rect(Gfx::IntRect({ horizontal_scrollbar().value(), vertical_scrollbar().value() }, available_size()));
-
-    if (m_client_state.has_usable_bitmap) {
-        // NOTE: We keep the outgoing front bitmap as a backup so we have something to paint until we get a new one.
-        m_backup_bitmap = m_client_state.front_bitmap.bitmap;
-    }
-
-    if (m_client_state.front_bitmap.bitmap)
-        client().async_remove_backing_store(m_client_state.front_bitmap.id);
-
-    if (m_client_state.back_bitmap.bitmap)
-        client().async_remove_backing_store(m_client_state.back_bitmap.id);
-
-    m_client_state.front_bitmap = {};
-    m_client_state.back_bitmap = {};
-    m_client_state.has_usable_bitmap = false;
-
-    if (available_size().is_empty())
-        return;
-
-    if (auto new_bitmap_or_error = Gfx::Bitmap::create_shareable(Gfx::BitmapFormat::BGRx8888, available_size()); !new_bitmap_or_error.is_error()) {
-        m_client_state.front_bitmap.bitmap = new_bitmap_or_error.release_value();
-        m_client_state.front_bitmap.id = m_client_state.next_bitmap_id++;
-        client().async_add_backing_store(m_client_state.front_bitmap.id, m_client_state.front_bitmap.bitmap->to_shareable_bitmap());
-    }
-
-    if (auto new_bitmap_or_error = Gfx::Bitmap::create_shareable(Gfx::BitmapFormat::BGRx8888, available_size()); !new_bitmap_or_error.is_error()) {
-        m_client_state.back_bitmap.bitmap = new_bitmap_or_error.release_value();
-        m_client_state.back_bitmap.id = m_client_state.next_bitmap_id++;
-        client().async_add_backing_store(m_client_state.back_bitmap.id, m_client_state.back_bitmap.bitmap->to_shareable_bitmap());
-    }
-
-    request_repaint();
+    return visible_content_rect();
 }
 
 void OutOfProcessWebView::update_zoom()
@@ -556,21 +525,6 @@ void OutOfProcessWebView::did_scroll()
     request_repaint();
 }
 
-void OutOfProcessWebView::request_repaint()
-{
-    // If this widget was instantiated but not yet added to a window,
-    // it won't have a back bitmap yet, so we can just skip repaint requests.
-    if (!m_client_state.back_bitmap.bitmap)
-        return;
-    // Don't request a repaint until pending paint requests have finished.
-    if (m_client_state.back_bitmap.pending_paints) {
-        m_client_state.got_repaint_requests_while_painting = true;
-        return;
-    }
-    m_client_state.back_bitmap.pending_paints++;
-    client().async_paint(m_client_state.back_bitmap.bitmap->rect().translated(horizontal_scrollbar().value(), vertical_scrollbar().value()), m_client_state.back_bitmap.id);
-}
-
 void OutOfProcessWebView::js_console_input(DeprecatedString const& js_source)
 {
     client().async_js_console_input(js_source);

Userland/Libraries/LibWebView/OutOfProcessWebView.h

@@ -179,8 +179,7 @@ private:
     virtual void notify_server_did_request_file(Badge<WebContentClient>, DeprecatedString const& path, i32) override;
     virtual void notify_server_did_finish_handling_input_event(bool event_was_accepted) override;
 
-    void request_repaint();
-    void handle_resize();
+    virtual Gfx::IntRect viewport_rect() const override;
 
     void handle_web_content_process_crash();
 
@@ -188,7 +187,6 @@ private:
     void enqueue_input_event(InputEvent const&);
     void process_next_input_event();
 
-    RefPtr<Gfx::Bitmap> m_backup_bitmap;
     RefPtr<GUI::Dialog> m_dialog;
 
     bool m_is_awaiting_response_for_input_event { false };

Userland/Libraries/LibWebView/ViewImplementation.cpp

@@ -10,6 +10,13 @@
 
 namespace WebView {
 
+ViewImplementation::ViewImplementation()
+{
+    m_backing_store_shrink_timer = Core::Timer::create_single_shot(3000, [this] {
+        resize_backing_stores_if_needed(WindowResizeInProgress::No);
+    }).release_value_but_fixme_should_propagate_errors();
+}
+
 WebContentClient& ViewImplementation::client()
 {
     VERIFY(m_client_state.client);
@@ -124,6 +131,12 @@ void ViewImplementation::run_javascript(StringView js_source)
     client().async_run_javascript(js_source);
 }
 
+void ViewImplementation::handle_resize()
+{
+    resize_backing_stores_if_needed(WindowResizeInProgress::Yes);
+    m_backing_store_shrink_timer->restart();
+}
+
 #if !defined(AK_OS_SERENITY)
 
 ErrorOr<NonnullRefPtr<WebView::WebContentClient>> ViewImplementation::launch_web_content_process(ReadonlySpan<String> candidate_web_content_paths, EnableCallgrindProfiling enable_callgrind_profiling, IsLayoutTestMode is_layout_test_mode)
@@ -196,4 +209,66 @@ ErrorOr<NonnullRefPtr<WebView::WebContentClient>> ViewImplementation::launch_web
 
 #endif
 
+void ViewImplementation::resize_backing_stores_if_needed(WindowResizeInProgress window_resize_in_progress)
+{
+    if (m_client_state.has_usable_bitmap) {
+        // NOTE: We keep the outgoing front bitmap as a backup so we have something to paint until we get a new one.
+        m_backup_bitmap = m_client_state.front_bitmap.bitmap;
+        m_backup_bitmap_size = m_client_state.front_bitmap.last_painted_size;
+    }
+
+    m_client_state.has_usable_bitmap = false;
+
+    auto viewport_rect = this->viewport_rect();
+    if (viewport_rect.is_empty())
+        return;
+
+    Gfx::IntSize minimum_needed_size;
+
+    if (window_resize_in_progress == WindowResizeInProgress::Yes) {
+        // Pad the minimum needed size so that we don't have to keep reallocating backing stores while the window is being resized.
+        minimum_needed_size = { viewport_rect.width() + 256, viewport_rect.height() + 256 };
+    } else {
+        // If we're not in the middle of a resize, we can shrink the backing store size to match the viewport size.
+        minimum_needed_size = viewport_rect.size();
+        m_client_state.front_bitmap = {};
+        m_client_state.back_bitmap = {};
+    }
+
+    auto reallocate_backing_store_if_needed = [&](SharedBitmap& backing_store) {
+        if (!backing_store.bitmap || !backing_store.bitmap->size().contains(minimum_needed_size)) {
+            if (auto new_bitmap_or_error = Gfx::Bitmap::create_shareable(Gfx::BitmapFormat::BGRx8888, minimum_needed_size); !new_bitmap_or_error.is_error()) {
+                if (backing_store.bitmap)
+                    client().async_remove_backing_store(backing_store.id);
+
+                backing_store.pending_paints = 0;
+                backing_store.bitmap = new_bitmap_or_error.release_value();
+                backing_store.id = m_client_state.next_bitmap_id++;
+                client().async_add_backing_store(backing_store.id, backing_store.bitmap->to_shareable_bitmap());
+            }
+            backing_store.last_painted_size = viewport_rect.size();
+        }
+    };
+
+    reallocate_backing_store_if_needed(m_client_state.front_bitmap);
+    reallocate_backing_store_if_needed(m_client_state.back_bitmap);
+
+    request_repaint();
+}
+
+void ViewImplementation::request_repaint()
+{
+    // If this widget was instantiated but not yet added to a window,
+    // it won't have a back bitmap yet, so we can just skip repaint requests.
+    if (!m_client_state.back_bitmap.bitmap)
+        return;
+    // Don't request a repaint until pending paint requests have finished.
+    if (m_client_state.back_bitmap.pending_paints) {
+        m_client_state.got_repaint_requests_while_painting = true;
+        return;
+    }
+    m_client_state.back_bitmap.pending_paints++;
+    client().async_paint(viewport_rect(), m_client_state.back_bitmap.id);
+}
+
 }

Userland/Libraries/LibWebView/ViewImplementation.h

@@ -124,15 +124,28 @@ public:
     virtual void notify_server_did_request_file(Badge<WebContentClient>, DeprecatedString const& path, i32) = 0;
     virtual void notify_server_did_finish_handling_input_event(bool event_was_accepted) = 0;
 
+    virtual Gfx::IntRect viewport_rect() const = 0;
+
 protected:
     static constexpr auto ZOOM_MIN_LEVEL = 0.3f;
     static constexpr auto ZOOM_MAX_LEVEL = 5.0f;
     static constexpr auto ZOOM_STEP = 0.1f;
 
+    ViewImplementation();
+
     WebContentClient& client();
     WebContentClient const& client() const;
     virtual void update_zoom() = 0;
 
+    enum class WindowResizeInProgress {
+        No,
+        Yes,
+    };
+    void resize_backing_stores_if_needed(WindowResizeInProgress);
+
+    void request_repaint();
+    void handle_resize();
+
     virtual void create_client(EnableCallgrindProfiling = EnableCallgrindProfiling::No) {};
 
 #if !defined(AK_OS_SERENITY)
@@ -160,6 +173,11 @@ protected:
 
     float m_zoom_level { 1.0 };
     float m_device_pixel_ratio { 1.0 };
+
+    RefPtr<Core::Timer> m_backing_store_shrink_timer;
+
+    RefPtr<Gfx::Bitmap> m_backup_bitmap;
+    Gfx::IntSize m_backup_bitmap_size;
 };
 
 }