LibGUI: Add a GRadioButton widget.

Radio buttons are automagically exclusive with other radio button children
of the same parent. :^)

LibGUI/GRadioButton.cpp

@@ -0,0 +1,122 @@
+#include <LibGUI/GRadioButton.h>
+#include <LibGUI/GPainter.h>
+#include <SharedGraphics/GraphicsBitmap.h>
+
+static RetainPtr<GraphicsBitmap> s_unfilled_circle_bitmap;
+static RetainPtr<GraphicsBitmap> s_filled_circle_bitmap;
+static RetainPtr<GraphicsBitmap> s_changing_filled_circle_bitmap;
+static RetainPtr<GraphicsBitmap> s_changing_unfilled_circle_bitmap;
+
+GRadioButton::GRadioButton(const String& label, GWidget* parent)
+    : GWidget(parent)
+    , m_label(label)
+{
+    if (!s_unfilled_circle_bitmap) {
+        s_unfilled_circle_bitmap = GraphicsBitmap::load_from_file("/res/icons/unfilled-radio-circle.png");
+        s_filled_circle_bitmap = GraphicsBitmap::load_from_file("/res/icons/filled-radio-circle.png");
+        s_changing_filled_circle_bitmap = GraphicsBitmap::load_from_file("/res/icons/changing-filled-radio-circle.png");
+        s_changing_unfilled_circle_bitmap = GraphicsBitmap::load_from_file("/res/icons/changing-unfilled-radio-circle.png");
+    }
+}
+
+GRadioButton::~GRadioButton()
+{
+}
+
+Size GRadioButton::circle_size()
+{
+    return s_unfilled_circle_bitmap->size();
+}
+
+static const GraphicsBitmap& circle_bitmap(bool checked, bool changing)
+{
+    if (changing)
+        return checked ? *s_changing_filled_circle_bitmap : *s_changing_unfilled_circle_bitmap;
+    return checked ? *s_filled_circle_bitmap : *s_unfilled_circle_bitmap;
+}
+
+void GRadioButton::paint_event(GPaintEvent& event)
+{
+    GPainter painter(*this);
+    painter.add_clip_rect(event.rect());
+
+    Rect circle_rect { { 2, 0 }, circle_size() };
+    circle_rect.center_vertically_within(rect());
+
+    auto& bitmap = circle_bitmap(m_checked, m_changing);
+    painter.blit(circle_rect.location(), bitmap, bitmap.rect());
+
+    if (!m_label.is_empty()) {
+        Rect text_rect { circle_rect.right() + 4, 0, font().width(m_label), font().glyph_height() };
+        text_rect.center_vertically_within(rect());
+        painter.draw_text(text_rect, m_label, TextAlignment::CenterLeft, foreground_color());
+    }
+}
+
+template<typename Callback>
+void GRadioButton::for_each_in_group(Callback callback)
+{
+    if (!parent())
+        return;
+    for (auto& object : parent()->children()) {
+        if (!object->is_widget())
+            continue;
+        if (!static_cast<GWidget*>(object)->is_radio_button())
+            continue;
+        callback(*static_cast<GRadioButton*>(object));
+    }
+}
+
+void GRadioButton::mousedown_event(GMouseEvent& event)
+{
+    if (event.button() != GMouseButton::Left)
+        return;
+
+    m_changing = rect().contains(event.position());
+    m_tracking = true;
+    update();
+}
+
+void GRadioButton::mousemove_event(GMouseEvent& event)
+{
+    if (m_tracking) {
+        bool old_changing = m_changing;
+        m_changing = rect().contains(event.position());
+        if (old_changing != m_changing)
+            update();
+    }
+}
+
+void GRadioButton::mouseup_event(GMouseEvent& event)
+{
+    if (event.button() != GMouseButton::Left)
+        return;
+
+    if (rect().contains(event.position())) {
+        for_each_in_group([this] (auto& button) {
+            if (&button != this)
+                button.set_checked(false);
+        });
+        set_checked(true);
+    }
+
+    m_changing = false;
+    m_tracking = false;
+    update();
+}
+
+void GRadioButton::set_label(const String& label)
+{
+    if (m_label == label)
+        return;
+    m_label = label;
+    update();
+}
+
+void GRadioButton::set_checked(bool checked)
+{
+    if (m_checked == checked)
+        return;
+    m_checked = checked;
+    update();
+}

LibGUI/GRadioButton.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <LibGUI/GWidget.h>
+
+class GRadioButton : public GWidget {
+public:
+    GRadioButton(const String& label, GWidget* parent);
+    virtual ~GRadioButton() override;
+
+    void set_label(const String&);
+    String label() const { return m_label; }
+
+    bool is_checked() const { return m_checked; }
+    void set_checked(bool);
+
+protected:
+    virtual void paint_event(GPaintEvent&) override;
+    virtual void mousedown_event(GMouseEvent&) override;
+    virtual void mousemove_event(GMouseEvent&) override;
+    virtual void mouseup_event(GMouseEvent&) override;
+
+private:
+    virtual bool is_radio_button() const final { return true; }
+
+    template<typename Callback> void for_each_in_group(Callback);
+    static Size circle_size();
+
+    String m_label;
+    bool m_checked { false };
+    bool m_changing { false };
+    bool m_tracking { false };
+};

LibGUI/GWidget.h

@@ -184,6 +184,8 @@ public:
     void register_local_shortcut_action(Badge<GAction>, GAction&);
     void unregister_local_shortcut_action(Badge<GAction>, GAction&);
 
+    virtual bool is_radio_button() const { return false; }
+
 private:
     virtual bool is_widget() const final { return true; }
 

LibGUI/Makefile

@@ -57,6 +57,7 @@ LIBGUI_OBJS = \
     GSlider.o \
     GResizeCorner.o \
     GTabWidget.o \
+    GRadioButton.o \
     GWindow.o
 
 OBJS = $(SHAREDGRAPHICS_OBJS) $(LIBGUI_OBJS)