Browser: Implement zoom :^)

Largely based on the Ladybird implementation in 0cc151b.

Userland/Applications/Browser/BrowserWindow.cpp

@@ -180,6 +180,25 @@ void BrowserWindow::build_menus()
     view_menu.add_action(WindowActions::the().show_bookmarks_bar_action());
     view_menu.add_action(WindowActions::the().vertical_tabs_action());
     view_menu.add_separator();
+    view_menu.add_action(GUI::CommonActions::make_zoom_in_action(
+        [this](auto&) {
+            auto& tab = active_tab();
+            tab.view().zoom_in();
+        },
+        this));
+    view_menu.add_action(GUI::CommonActions::make_zoom_out_action(
+        [this](auto&) {
+            auto& tab = active_tab();
+            tab.view().zoom_out();
+        },
+        this));
+    view_menu.add_action(GUI::CommonActions::make_reset_zoom_action(
+        [this](auto&) {
+            auto& tab = active_tab();
+            tab.view().reset_zoom();
+        },
+        this));
+    view_menu.add_separator();
     view_menu.add_action(GUI::CommonActions::make_fullscreen_action(
         [this](auto&) {
             auto& tab = active_tab();

Userland/Libraries/LibWebView/OutOfProcessWebView.cpp

@@ -159,6 +159,35 @@ void OutOfProcessWebView::handle_resize()
     request_repaint();
 }
 
+void OutOfProcessWebView::zoom_in()
+{
+    if (m_zoom_level >= ZOOM_MAX_LEVEL)
+        return;
+    m_zoom_level += ZOOM_STEP;
+    update_zoom();
+}
+
+void OutOfProcessWebView::zoom_out()
+{
+    if (m_zoom_level <= ZOOM_MIN_LEVEL)
+        return;
+    m_zoom_level -= ZOOM_STEP;
+    update_zoom();
+}
+
+void OutOfProcessWebView::reset_zoom()
+{
+    m_zoom_level = 1.0f;
+    update_zoom();
+}
+
+void OutOfProcessWebView::update_zoom()
+{
+    client().async_set_device_pixels_per_css_pixel(m_device_pixel_ratio * m_zoom_level);
+    // FIXME: Refactor this into separate update_viewport_rect() + request_repaint() like in Ladybird
+    handle_resize();
+}
+
 void OutOfProcessWebView::keydown_event(GUI::KeyEvent& event)
 {
     enqueue_input_event(event);

Userland/Libraries/LibWebView/OutOfProcessWebView.h

@@ -77,6 +77,10 @@ public:
 
     void set_system_visibility_state(bool visible);
 
+    void zoom_in();
+    void zoom_out();
+    void reset_zoom();
+
     Gfx::ShareableBitmap take_screenshot() const;
     Gfx::ShareableBitmap take_document_screenshot();
 
@@ -121,6 +125,10 @@ public:
     Function<void()> on_forward_button;
 
 private:
+    static constexpr auto ZOOM_MIN_LEVEL = 0.3f;
+    static constexpr auto ZOOM_MAX_LEVEL = 5.0f;
+    static constexpr auto ZOOM_STEP = 0.1f;
+
     OutOfProcessWebView();
 
     // ^Widget
@@ -197,6 +205,7 @@ private:
 
     void request_repaint();
     void handle_resize();
+    void update_zoom();
 
     void create_client();
     WebContentClient& client();
@@ -231,6 +240,9 @@ private:
     Queue<InputEvent> m_pending_input_events;
 
     bool m_content_scales_to_viewport { false };
+
+    float m_zoom_level { 1.0 };
+    float m_device_pixel_ratio { 1.0 };
 };
 
 }