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.

Applications/FontEditor/GlyphMapWidget.cpp

@@ -1,4 +1,5 @@
 #include "GlyphMapWidget.h"
+#include <LibDraw/Palette.h>
 #include <LibGUI/GPainter.h>
 
 GlyphMapWidget::GlyphMapWidget(Font& mutable_font, GWidget* parent)
@@ -74,7 +75,7 @@ void GlyphMapWidget::paint_event(GPaintEvent& event)
                 font().max_glyph_width(),
                 font().glyph_height());
             if (glyph == m_selected_glyph) {
-                painter.fill_rect(outer_rect, SystemColor::Selection);
+                painter.fill_rect(outer_rect, palette().selection());
                 painter.draw_glyph(inner_rect.location(), glyph, Color::White);
             } else {
                 painter.draw_glyph(inner_rect.location(), glyph, Color::Black);

Applications/HexEditor/HexEditor.cpp

@@ -1,6 +1,7 @@
 #include "HexEditor.h"
 #include <AK/StringBuilder.h>
 #include <Kernel/KeyCode.h>
+#include <LibDraw/Palette.h>
 #include <LibGUI/GAction.h>
 #include <LibGUI/GClipboard.h>
 #include <LibGUI/GFontDatabase.h>
@@ -492,7 +493,7 @@ void HexEditor::paint_event(GPaintEvent& event)
                 text_color = Color::Red;
             }
 
-            Color highlight_color = SystemColor::Selection;
+            Color highlight_color = palette().selection();
             auto highlight_flag = false;
             if (m_selection_start > -1 && m_selection_end > -1) {
                 if (byte_position >= m_selection_start && byte_position <= m_selection_end) {

Applications/IRCClient/IRCAppWindow.cpp

@@ -156,7 +156,6 @@ void IRCAppWindow::setup_widgets()
     auto widget = GWidget::construct();
     set_main_widget(widget);
     widget->set_fill_with_background_color(true);
-    widget->set_background_color(SystemColor::Window);
     widget->set_layout(make<GBoxLayout>(Orientation::Vertical));
     widget->layout()->set_spacing(0);
 

Applications/PaintBrush/PaletteWidget.cpp

@@ -51,7 +51,6 @@ PaletteWidget::PaletteWidget(PaintableWidget& paintable_widget, GWidget* parent)
     set_frame_shadow(FrameShadow::Raised);
     set_frame_thickness(0);
     set_fill_with_background_color(true);
-    set_background_color(SystemColor::Window);
 
     set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
     set_preferred_size(0, 34);

Applications/PaintBrush/ToolboxWidget.cpp

@@ -35,7 +35,6 @@ private:
 ToolboxWidget::ToolboxWidget(GWidget* parent)
     : GFrame(parent)
 {
-    set_background_color(SystemColor::Window);
     set_fill_with_background_color(true);
 
     set_frame_thickness(1);

Applications/SystemMonitor/NetworkStatisticsWidget.cpp

@@ -11,7 +11,6 @@ NetworkStatisticsWidget::NetworkStatisticsWidget(GWidget* parent)
         set_layout(make<GBoxLayout>(Orientation::Vertical));
         layout()->set_margins({ 4, 4, 4, 4 });
         set_fill_with_background_color(true);
-        set_background_color(SystemColor::Window);
 
         auto adapters_group_box = GGroupBox::construct("Adapters", this);
         adapters_group_box->set_layout(make<GBoxLayout>(Orientation::Vertical));

Applications/SystemMonitor/main.cpp

@@ -53,7 +53,6 @@ int main(int argc, char** argv)
     auto keeper = GWidget::construct();
     keeper->set_layout(make<GBoxLayout>(Orientation::Vertical));
     keeper->set_fill_with_background_color(true);
-    keeper->set_background_color(SystemColor::Window);
     keeper->layout()->set_margins({ 4, 4, 4, 4 });
 
     auto tabwidget = GTabWidget::construct(keeper);
@@ -192,7 +191,7 @@ class ProgressBarPaintingDelegate final : public GTableCellPaintingDelegate {
 public:
     virtual ~ProgressBarPaintingDelegate() override {}
 
-    virtual void paint(GPainter& painter, const Rect& a_rect, const GModel& model, const GModelIndex& index) override
+    virtual void paint(GPainter& painter, const Rect& a_rect, const Palette& palette, const GModel& model, const GModelIndex& index) override
     {
         auto rect = a_rect.shrunken(2, 2);
         auto percentage = model.data(index, GModel::Role::Custom).to_int();
@@ -201,7 +200,7 @@ public:
         String text;
         if (data.is_string())
             text = data.as_string();
-        StylePainter::paint_progress_bar(painter, rect, 0, 100, percentage, text);
+        StylePainter::paint_progress_bar(painter, rect, palette, 0, 100, percentage, text);
         painter.draw_rect(rect, Color::Black);
     }
 };
@@ -355,7 +354,7 @@ NonnullRefPtr<GWidget> build_graphs_tab()
 
     graphs_container->on_first_show = [](auto& self) {
         self.set_fill_with_background_color(true);
-        self.set_background_color(SystemColor::Window);
+        self.set_background_role(ColorRole::Button);
         self.set_layout(make<GBoxLayout>(Orientation::Vertical));
         self.layout()->set_margins({ 4, 4, 4, 4 });
 

Applications/Terminal/main.cpp

@@ -98,13 +98,13 @@ RefPtr<GWindow> create_settings_window(TerminalWidget& terminal, RefPtr<CConfigF
     auto settings = GWidget::construct();
     window->set_main_widget(settings);
     settings->set_fill_with_background_color(true);
+    settings->set_background_role(ColorRole::Button);
     settings->set_layout(make<GBoxLayout>(Orientation::Vertical));
     settings->layout()->set_margins({ 4, 4, 4, 4 });
 
     auto radio_container = GGroupBox::construct("Bell Mode", settings);
     radio_container->set_layout(make<GBoxLayout>(Orientation::Vertical));
     radio_container->layout()->set_margins({ 6, 16, 6, 6 });
-    radio_container->set_fill_with_background_color(true);
     radio_container->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
     radio_container->set_preferred_size(100, 70);
 
@@ -119,12 +119,9 @@ RefPtr<GWindow> create_settings_window(TerminalWidget& terminal, RefPtr<CConfigF
     auto slider_container = GGroupBox::construct("Background Opacity", settings);
     slider_container->set_layout(make<GBoxLayout>(Orientation::Vertical));
     slider_container->layout()->set_margins({ 6, 16, 6, 6 });
-    slider_container->set_fill_with_background_color(true);
     slider_container->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
     slider_container->set_preferred_size(100, 50);
     auto slider = GSlider::construct(Orientation::Horizontal, slider_container);
-    slider->set_fill_with_background_color(true);
-    slider->set_background_color(SystemColor::Window);
 
     slider->on_value_changed = [&terminal, &config](int value) {
         terminal.set_opacity(value);

Applications/Welcome/TextWidget.cpp

@@ -1,10 +1,10 @@
+#include "TextWidget.h"
 #include <AK/String.h>
 #include <AK/StringBuilder.h>
 #include <AK/Vector.h>
+#include <LibDraw/Palette.h>
 #include <LibGUI/GPainter.h>
 
-#include "TextWidget.h"
-
 TextWidget::TextWidget(GWidget* parent)
     : GFrame(parent)
 {
@@ -49,7 +49,7 @@ void TextWidget::paint_event(GPaintEvent& event)
             text_rect.set_width(text_rect.width() - indent * 2);
 
         if (is_enabled()) {
-            painter.draw_text(text_rect, line, m_text_alignment, foreground_color(), TextElision::None);
+            painter.draw_text(text_rect, line, m_text_alignment, palette().color(foreground_role()), TextElision::None);
         } else {
             painter.draw_text(text_rect.translated(1, 1), line, font(), text_alignment(), Color::White, TextElision::Right);
             painter.draw_text(text_rect, line, font(), text_alignment(), Color::from_rgb(0x808080), TextElision::Right);