Ladybird: Implement zoom :^)

Author: https://github.com/linusg
Commit: 0cc151bc1c
Pull-request: https://github.com/SerenityOS/serenity/pull/16973
Reviewed-by: https://github.com/AtkinsSJ ✅

Ladybird/WebContentView.h

@@ -113,6 +113,10 @@ public:
 
     void set_color_scheme(ColorScheme);
 
+    void zoom_in();
+    void zoom_out();
+    void reset_zoom();
+
     virtual void notify_server_did_layout(Badge<WebContentClient>, Gfx::IntSize content_size) override;
     virtual void notify_server_did_paint(Badge<WebContentClient>, i32 bitmap_id) override;
     virtual void notify_server_did_invalidate_content_rect(Badge<WebContentClient>, Gfx::IntRect const&) override;
@@ -184,9 +188,14 @@ signals:
     Gfx::IntRect fullscreen_window();
 
 private:
+    static constexpr auto ZOOM_MIN_LEVEL = 0.3f;
+    static constexpr auto ZOOM_MAX_LEVEL = 5.0f;
+    static constexpr auto ZOOM_STEP = 0.1f;
+
     void request_repaint();
     void update_viewport_rect();
     void handle_resize();
+    void update_zoom();
 
     void ensure_js_console_widget();
     void ensure_inspector_widget();
@@ -197,6 +206,7 @@ private:
     void close_sub_widgets();
     ErrorOr<Ladybird::DOMNodeProperties> inspect_dom_node(i32 node_id, Optional<Web::CSS::Selector::PseudoElement> pseudo_element);
 
+    float m_zoom_level { 1.0 };
     float m_device_pixel_ratio { 1.0 };
     qreal m_inverse_pixel_scaling_ratio { 1.0 };
     bool m_should_show_line_box_borders { false };