Add a simple ui::Theme impl

Now ui::Theme is not an abstract class anymore and can be used for
simple tests/benchmarks. Some member functions are empty, but can be
implemented later if needed.

src/app/ui/skin/skin_theme.h

@@ -109,7 +109,7 @@ namespace app {
         if (it != m_styles.end())
           return it->second;
         else
-          return getDefaultStyle();
+          return EmptyStyle();
       }
 
       SkinPartPtr getPartById(const std::string& id) const {

src/ui/grid.cpp

@@ -127,7 +127,7 @@ void Grid::setStyle(Style* style)
 {
   ASSERT(style);
   if (!style)
-    style = Theme::getDefaultStyle();
+    style = Theme::EmptyStyle();
   Widget::setStyle(style);
   setGap(style->gap());
 }

src/ui/theme.cpp

@@ -34,6 +34,10 @@ namespace ui {
 
 namespace {
 
+// Colors for a simple default theme.
+constexpr const gfx::Color kBgColor = gfx::rgba(32, 32, 32, 255);
+constexpr const gfx::Color kFgColor = gfx::rgba(255, 255, 200, 255);
+
 int current_ui_scale = 1;       // Global UI Screen Scaling factor
 int old_ui_scale = 1;           // Add this field in InitThemeEvent
 Theme* current_theme = nullptr; // Global active theme
@@ -145,8 +149,14 @@ Theme::~Theme()
     set_theme(nullptr, guiscale());
 }
 
+text::FontRef Theme::getDefaultFont() const
+{
+  return m_fontMgr->defaultFont(kDefaultFontHeight);
+}
+
 // static
-ui::Style Theme::m_defaultStyle(nullptr);
+ui::Style Theme::m_emptyStyle(nullptr);
+ui::Style Theme::m_simpleStyle(nullptr);
 
 void Theme::regenerateTheme()
 {
@@ -154,6 +164,27 @@ void Theme::regenerateTheme()
   onRegenerateTheme();
 }
 
+void Theme::initWidget(Widget* widget)
+{
+  if (m_simpleStyle.layers().empty()) {
+    Style::Layer bg;
+    Style::Layer br;
+    Style::Layer fg;
+    bg.setType(Style::Layer::Type::kBackground);
+    bg.setColor(kBgColor);
+    br.setType(Style::Layer::Type::kBorder);
+    br.setColor(kFgColor);
+    fg.setType(Style::Layer::Type::kText);
+    fg.setColor(kFgColor);
+    m_simpleStyle.layers().push_back(bg);
+    m_simpleStyle.layers().push_back(br);
+    m_simpleStyle.layers().push_back(fg);
+  }
+
+  widget->setFont(getDefaultFont());
+  widget->setStyle(&m_simpleStyle);
+}
+
 void Theme::setDecorativeWidgetBounds(Widget* widget)
 {
   switch (widget->type()) {
@@ -193,6 +224,18 @@ void Theme::setDecorativeWidgetBounds(Widget* widget)
   }
 }
 
+void Theme::paintListBox(PaintEvent& ev)
+{
+  Graphics* g = ev.graphics();
+  g->fillRect(kBgColor, g->getClipBounds());
+}
+
+void Theme::paintViewViewport(PaintEvent& ev)
+{
+  Graphics* g = ev.graphics();
+  g->fillRect(kBgColor, g->getClipBounds());
+}
+
 void Theme::paintWidgetPart(Graphics* g,
                             const Style* style,
                             const gfx::Rect& bounds,

src/ui/theme.h

@@ -62,28 +62,34 @@ namespace ui {
   class Theme {
     friend void set_theme(Theme* theme, const int uiscale);
   public:
+    static constexpr int kDefaultFontHeight = 16;
+
     Theme();
     virtual ~Theme();
 
     virtual text::FontMgrRef fontMgr() const { return m_fontMgr; }
-    virtual text::FontRef getDefaultFont() const = 0;
-    virtual text::FontRef getWidgetFont(const Widget* widget) const = 0;
+    virtual text::FontRef getDefaultFont() const;
+    virtual text::FontRef getWidgetFont(const Widget* widget) const {
+      return getDefaultFont();
+    }
 
-    virtual ui::Cursor* getStandardCursor(CursorType type) = 0;
-    virtual void initWidget(Widget* widget) = 0;
-    virtual void getWindowMask(Widget* widget, gfx::Region& region) = 0;
+    virtual ui::Cursor* getStandardCursor(CursorType type) { return nullptr; }
+    virtual void initWidget(Widget* widget);
+    virtual void getWindowMask(Widget* widget, gfx::Region& region) { }
     virtual void setDecorativeWidgetBounds(Widget* widget);
-    virtual int getScrollbarSize() = 0;
-    virtual gfx::Size getEntryCaretSize(Widget* widget) = 0;
+    virtual int getScrollbarSize() { return kDefaultFontHeight; }
+    virtual gfx::Size getEntryCaretSize(Widget* widget) {
+      return gfx::Size(kDefaultFontHeight, 1);
+    }
 
-    virtual void paintEntry(PaintEvent& ev) = 0;
-    virtual void paintListBox(PaintEvent& ev) = 0;
-    virtual void paintMenu(PaintEvent& ev) = 0;
-    virtual void paintMenuItem(PaintEvent& ev) = 0;
-    virtual void paintSlider(PaintEvent& ev) = 0;
-    virtual void paintComboBoxEntry(PaintEvent& ev) = 0;
-    virtual void paintTextBox(PaintEvent& ev) = 0;
-    virtual void paintViewViewport(PaintEvent& ev) = 0;
+    virtual void paintEntry(PaintEvent& ev) { }
+    virtual void paintListBox(PaintEvent& ev);
+    virtual void paintMenu(PaintEvent& ev) { }
+    virtual void paintMenuItem(PaintEvent& ev) { }
+    virtual void paintSlider(PaintEvent& ev) { }
+    virtual void paintComboBoxEntry(PaintEvent& ev) { }
+    virtual void paintTextBox(PaintEvent& ev) { }
+    virtual void paintViewViewport(PaintEvent& ev);
 
     virtual void paintWidgetPart(Graphics* g,
                                  const Style* style,
@@ -145,10 +151,10 @@ namespace ui {
     static void drawTextBox(Graphics* g, const Widget* textbox,
                             int* w, int* h, gfx::Color bg, gfx::Color fg);
 
-    static ui::Style* getDefaultStyle() { return &m_defaultStyle; }
+    static ui::Style* EmptyStyle() { return &m_emptyStyle; }
 
   protected:
-    virtual void onRegenerateTheme() = 0;
+    virtual void onRegenerateTheme() { }
 
     text::FontMgrRef m_fontMgr;
 
@@ -175,7 +181,8 @@ namespace ui {
                            gfx::Border& borderHint,
                            gfx::Rect& textHint, int& textAlign);
 
-    static ui::Style m_defaultStyle;
+    static ui::Style m_emptyStyle;
+    static ui::Style m_simpleStyle;
   };
 
 } // namespace ui

src/ui/widget.cpp

@@ -216,7 +216,7 @@ void Widget::setStyle(Style* style)
   assert_ui_thread();
   ASSERT(style);
   if (!style)
-    style = Theme::getDefaultStyle();
+    style = Theme::EmptyStyle();
   m_style = style;
   m_border = m_theme->calcBorder(this, style);
   m_bgColor = m_theme->calcBgColor(this, style);