WebContent: Basic scrolling support! :^)

The WebContentView widget now inherits from GUI::ScrollableWidget and
will pass its scroll offset over to the WebContent process as it's
changing. This is not super efficient and can get a bit laggy, but it
will do fine as an initial scrolling implementation.

Just like the single-process Web::PageView widget, WebContentView also
paints scrolled content by translating the Gfx::Painter.

Demos/WebView/WebContentClient.cpp

@@ -74,3 +74,11 @@ void WebContentClient::handle(const Messages::WebContentClient::DidChangeSelecti
 #endif
     m_view.notify_server_did_change_selection({});
 }
+
+void WebContentClient::handle(const Messages::WebContentClient::DidLayout& message)
+{
+#ifdef DEBUG_SPAM
+    dbg() << "handle: WebContentClient::DidLayout! content_size=" << message.content_size();
+#endif
+    m_view.notify_server_did_layout({}, message.content_size());
+}

Demos/WebView/WebContentClient.h

@@ -48,6 +48,7 @@ private:
     virtual void handle(const Messages::WebContentClient::DidFinishLoad&) override;
     virtual void handle(const Messages::WebContentClient::DidInvalidateContentRect&) override;
     virtual void handle(const Messages::WebContentClient::DidChangeSelection&) override;
+    virtual void handle(const Messages::WebContentClient::DidLayout&) override;
 
     WebContentView& m_view;
 };

Demos/WebView/WebContentView.cpp

@@ -28,6 +28,7 @@
 #include "WebContentClient.h"
 #include <AK/SharedBuffer.h>
 #include <LibGUI/Painter.h>
+#include <LibGUI/ScrollBar.h>
 #include <LibGfx/SystemTheme.h>
 
 WebContentView::WebContentView()
@@ -59,8 +60,8 @@ void WebContentView::resize_event(GUI::ResizeEvent& event)
     auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::RGB32, event.size());
     m_bitmap = bitmap->to_bitmap_backed_by_shared_buffer();
     m_bitmap->shared_buffer()->share_with(client().server_pid());
-    client().post_message(Messages::WebContentServer::SetViewportRect(Gfx::IntRect({ 0, 0 }, event.size())));
-    client().post_message(Messages::WebContentServer::Paint(m_bitmap->rect(), m_bitmap->shbuf_id()));
+    client().post_message(Messages::WebContentServer::SetViewportRect(Gfx::IntRect({ horizontal_scrollbar().value(), vertical_scrollbar().value() }, event.size())));
+    request_repaint();
 }
 
 void WebContentView::mousedown_event(GUI::MouseEvent& event)
@@ -97,9 +98,20 @@ void WebContentView::notify_server_did_change_selection(Badge<WebContentClient>)
     request_repaint();
 }
 
+void WebContentView::notify_server_did_layout(Badge<WebContentClient>, const Gfx::IntSize& content_size)
+{
+    set_content_size(content_size);
+}
+
+void WebContentView::did_scroll()
+{
+    client().post_message(Messages::WebContentServer::SetViewportRect(Gfx::IntRect({ horizontal_scrollbar().value(), vertical_scrollbar().value() }, size())));
+    request_repaint();
+}
+
 void WebContentView::request_repaint()
 {
-    client().post_message(Messages::WebContentServer::Paint(m_bitmap->rect(), m_bitmap->shbuf_id()));
+    client().post_message(Messages::WebContentServer::Paint(m_bitmap->rect().translated(horizontal_scrollbar().value(), vertical_scrollbar().value()), m_bitmap->shbuf_id()));
 }
 
 WebContentClient& WebContentView::client()

Demos/WebView/WebContentView.h

@@ -26,11 +26,12 @@
 
 #pragma once
 
+#include <LibGUI/ScrollableWidget.h>
 #include <LibGUI/Widget.h>
 
 class WebContentClient;
 
-class WebContentView final : public GUI::Widget {
+class WebContentView final : public GUI::ScrollableWidget {
     C_OBJECT(WebContentView);
 
 public:
@@ -38,6 +39,7 @@ public:
 
     void load(const URL&);
 
+    void notify_server_did_layout(Badge<WebContentClient>, const Gfx::IntSize& content_size);
     void notify_server_did_paint(Badge<WebContentClient>, i32 shbuf_id);
     void notify_server_did_invalidate_content_rect(Badge<WebContentClient>, const Gfx::IntRect&);
     void notify_server_did_change_selection(Badge<WebContentClient>);
@@ -45,12 +47,16 @@ public:
 private:
     WebContentView();
 
+    // ^Widget
     virtual void paint_event(GUI::PaintEvent&) override;
     virtual void resize_event(GUI::ResizeEvent&) override;
     virtual void mousedown_event(GUI::MouseEvent&) override;
     virtual void mouseup_event(GUI::MouseEvent&) override;
     virtual void mousemove_event(GUI::MouseEvent&) override;
 
+    // ^ScrollableWidget
+    virtual void did_scroll() override;
+
     void request_repaint();
 
     WebContentClient& client();

Services/WebContent/PageHost.cpp

@@ -66,26 +66,33 @@ void PageHost::set_palette_impl(const Gfx::PaletteImpl& impl)
     m_palette_impl = impl;
 }
 
+Web::LayoutDocument* PageHost::layout_root()
+{
+    auto* document = page().main_frame().document();
+    if (!document)
+        return nullptr;
+    return document->layout_node();
+}
+
 void PageHost::paint(const Gfx::IntRect& content_rect, Gfx::Bitmap& target)
 {
     Gfx::Painter painter(target);
+    Gfx::IntRect bitmap_rect { {}, content_rect.size() };
 
-    auto* document = page().main_frame().document();
-    if (!document)
-        return;
-
-    auto* layout_root = document->layout_node();
+    auto* layout_root = this->layout_root();
     if (!layout_root) {
-        painter.fill_rect(content_rect, Color::White);
+        painter.fill_rect(bitmap_rect, Color::White);
         return;
     }
 
-    painter.fill_rect(content_rect, document->background_color(palette()));
+    painter.fill_rect(bitmap_rect, layout_root->document().background_color(palette()));
 
-    if (auto background_bitmap = document->background_image()) {
-        painter.draw_tiled_bitmap(content_rect, *background_bitmap);
+    if (auto background_bitmap = layout_root->document().background_image()) {
+        painter.draw_tiled_bitmap(bitmap_rect, *background_bitmap);
     }
 
+    painter.translate(-content_rect.x(), -content_rect.y());
+
     Web::PaintContext context(painter, palette(), Gfx::IntPoint());
     context.set_viewport_rect(content_rect);
     layout_root->paint_all_phases(context);
@@ -109,4 +116,12 @@ void PageHost::page_did_change_selection()
     m_client.post_message(Messages::WebContentClient::DidChangeSelection());
 }
 
+void PageHost::page_did_layout()
+{
+    auto* layout_root = this->layout_root();
+    ASSERT(layout_root);
+    auto content_size = enclosing_int_rect(layout_root->absolute_rect()).size();
+    m_client.post_message(Messages::WebContentClient::DidLayout(content_size));
+}
+
 }

Services/WebContent/PageHost.h

@@ -53,9 +53,11 @@ private:
     virtual Gfx::Palette palette() const override;
     virtual void page_did_invalidate(const Gfx::IntRect&) override;
     virtual void page_did_change_selection() override;
+    virtual void page_did_layout() override;
 
     explicit PageHost(ClientConnection&);
 
+    Web::LayoutDocument* layout_root();
     void setup_palette();
 
     ClientConnection& m_client;

Services/WebContent/WebContentClient.ipc

@@ -4,4 +4,5 @@ endpoint WebContentClient = 90
     DidPaint(Gfx::IntRect content_rect, i32 shbuf_id) =|
     DidInvalidateContentRect(Gfx::IntRect content_rect) =|
     DidChangeSelection() =|
+    DidLayout(Gfx::IntSize content_size) =|
 }