WindowServer: Implement simple window shadows

This implements simple window shadows around most windows, including
tooltips. Because this method uses a bitmap for the shadow bits,
it is limited to rectangular window frames. For non-rectangular
window frames we'll need to implement a more sophisticated algorithm.

Userland/Libraries/LibGfx/ClassicWindowTheme.h

@@ -47,6 +47,7 @@ public:
     virtual IntRect frame_rect_for_window(WindowType, const IntRect& window_rect, const Palette&) const override;
 
     virtual Vector<IntRect> layout_buttons(WindowType, const IntRect& window_rect, const Palette&, size_t buttons) const override;
+    virtual bool is_simple_rect_frame() const override { return true; }
 
 private:
     struct FrameColors {

Userland/Libraries/LibGfx/Painter.cpp

@@ -735,13 +735,13 @@ void Painter::blit_with_alpha(const IntPoint& position, const Gfx::Bitmap& sourc
     }
 }
 
-void Painter::blit(const IntPoint& position, const Gfx::Bitmap& source, const IntRect& a_src_rect, float opacity)
+void Painter::blit(const IntPoint& position, const Gfx::Bitmap& source, const IntRect& a_src_rect, float opacity, bool apply_alpha)
 {
     ASSERT(scale() >= source.scale() && "painter doesn't support downsampling scale factors");
 
     if (opacity < 1.0f)
         return blit_with_opacity(position, source, a_src_rect, opacity);
-    if (source.has_alpha_channel())
+    if (source.has_alpha_channel() && apply_alpha)
         return blit_with_alpha(position, source, a_src_rect);
 
     auto safe_src_rect = a_src_rect.intersected(source.rect());

Userland/Libraries/LibGfx/Painter.h

@@ -70,7 +70,7 @@ public:
     void draw_line(const IntPoint&, const IntPoint&, Color, int thickness = 1, LineStyle style = LineStyle::Solid);
     void draw_quadratic_bezier_curve(const IntPoint& control_point, const IntPoint&, const IntPoint&, Color, int thickness = 1, LineStyle style = LineStyle::Solid);
     void draw_elliptical_arc(const IntPoint& p1, const IntPoint& p2, const IntPoint& center, const FloatPoint& radii, float x_axis_rotation, float theta_1, float theta_delta, Color, int thickness = 1, LineStyle style = LineStyle::Solid);
-    void blit(const IntPoint&, const Gfx::Bitmap&, const IntRect& src_rect, float opacity = 1.0f);
+    void blit(const IntPoint&, const Gfx::Bitmap&, const IntRect& src_rect, float opacity = 1.0f, bool apply_alpha = true);
     void blit_dimmed(const IntPoint&, const Gfx::Bitmap&, const IntRect& src_rect);
     void blit_brightened(const IntPoint&, const Gfx::Bitmap&, const IntRect& src_rect);
     void blit_filtered(const IntPoint&, const Gfx::Bitmap&, const IntRect& src_rect, Function<Color(Color)>);

Userland/Libraries/LibGfx/Palette.h

@@ -140,6 +140,7 @@ public:
     int window_title_button_height() const { return metric(MetricRole::TitleButtonHeight); }
 
     String title_button_icons_path() const { return path(PathRole::TitleButtonIcons); }
+    String window_shadow_path() const { return path(PathRole::WindowShadow); }
 
     Color color(ColorRole role) const { return m_impl->color(role); }
     int metric(MetricRole role) const { return m_impl->metric(role); }

Userland/Libraries/LibGfx/SystemTheme.cpp

@@ -119,6 +119,7 @@ Core::AnonymousBuffer load_system_theme(const String& path)
     } while (0)
 
     DO_PATH(TitleButtonIcons);
+    DO_PATH(WindowShadow);
 
     return buffer;
 }

Userland/Libraries/LibGfx/SystemTheme.h

@@ -144,6 +144,7 @@ enum class MetricRole {
 enum class PathRole {
     NoRole,
     TitleButtonIcons,
+    WindowShadow,
     __Count,
 };
 

Userland/Libraries/LibGfx/WindowTheme.h

@@ -61,6 +61,7 @@ public:
     virtual IntRect frame_rect_for_window(WindowType, const IntRect& window_rect, const Palette&) const = 0;
 
     virtual Vector<IntRect> layout_buttons(WindowType, const IntRect& window_rect, const Palette&, size_t buttons) const = 0;
+    virtual bool is_simple_rect_frame() const = 0;
 
 protected:
     WindowTheme() { }