LibGUI+LibDraw: Add "Palette" concept for scoped color theming

GApplication now has a palette. This palette contains all the system
theme colors by default, and is inherited by a new top-level GWidget.
New child widgets inherit their parents palette.

It is possible to override the GApplication palette, and the palette
of any GWidget.

The Palette object contains a bunch of colors, each corresponding to
a ColorRole. Each role has a convenience getter as well.

Each GWidget now has a background_role() and foreground_role(), which
are then looked up in their current palette when painting. This means
that you no longer alter the background color of a widget by setting
it directly, rather you alter either its background role, or the
widget's palette.

3 files changed, 8 insertions, 4 deletions

diff --git a/Libraries/LibHTML/HtmlView.cpp b/Libraries/LibHTML/HtmlView.cpp
index cb72d44d61..db6f094317 100644
--- a/Libraries/LibHTML/HtmlView.cpp
+++ b/Libraries/LibHTML/HtmlView.cpp
@@ -118,7 +118,7 @@ void HtmlView::paint_event(GPaintEvent& event)
     painter.add_clip_rect(event.rect());
 
     if (!layout_root()) {
-        painter.fill_rect(event.rect(), background_color());
+        painter.fill_rect(event.rect(), palette().color(background_role()));
         return;
     }
 
@@ -131,7 +131,7 @@ void HtmlView::paint_event(GPaintEvent& event)
     painter.translate(frame_thickness(), frame_thickness());
     painter.translate(-horizontal_scrollbar().value(), -vertical_scrollbar().value());
 
-    RenderingContext context { painter };
+    RenderingContext context(painter, palette());
     context.set_should_show_line_box_borders(m_should_show_line_box_borders);
     context.set_viewport_rect(visible_content_rect());
     layout_root()->render(context);
diff --git a/Libraries/LibHTML/Layout/LayoutImage.cpp b/Libraries/LibHTML/Layout/LayoutImage.cpp
index 2666d2149b..43213bbc44 100644
--- a/Libraries/LibHTML/Layout/LayoutImage.cpp
+++ b/Libraries/LibHTML/Layout/LayoutImage.cpp
@@ -43,7 +43,7 @@ void LayoutImage::render(RenderingContext& context)
 
     if (renders_as_alt_text()) {
         context.painter().set_font(Font::default_font());
-        StylePainter::paint_frame(context.painter(), enclosing_int_rect(rect()), FrameShape::Container, FrameShadow::Sunken, 2);
+        StylePainter::paint_frame(context.painter(), enclosing_int_rect(rect()), context.palette(), FrameShape::Container, FrameShadow::Sunken, 2);
         auto alt = node().alt();
         if (alt.is_empty())
             alt = node().src();
diff --git a/Libraries/LibHTML/RenderingContext.h b/Libraries/LibHTML/RenderingContext.h
index ee048035ab..7994b61cb0 100644
--- a/Libraries/LibHTML/RenderingContext.h
+++ b/Libraries/LibHTML/RenderingContext.h
@@ -1,17 +1,20 @@
 #pragma once
 
+#include <LibDraw/Palette.h>
 #include <LibDraw/Rect.h>
 
 class GPainter;
 
 class RenderingContext {
 public:
-    explicit RenderingContext(GPainter& painter)
+    explicit RenderingContext(GPainter& painter, const Palette& palette)
         : m_painter(painter)
+        , m_palette(palette)
     {
     }
 
     GPainter& painter() const { return m_painter; }
+    const Palette& palette() const { return m_palette; }
 
     bool should_show_line_box_borders() const { return m_should_show_line_box_borders; }
     void set_should_show_line_box_borders(bool value) { m_should_show_line_box_borders = value; }
@@ -21,6 +24,7 @@ public:
 
 private:
     GPainter& m_painter;
+    const Palette& m_palette;
     Rect m_viewport_rect;
     bool m_should_show_line_box_borders { false };
 };