LibGUI: Add a GProgressBar widget.

LibGUI/GProgressBar.cpp

@@ -0,0 +1,65 @@
+#include <LibGUI/GProgressBar.h>
+#include <SharedGraphics/Painter.h>
+
+GProgressBar::GProgressBar(GWidget* parent)
+    : GWidget(parent)
+{
+    start_timer(10);
+}
+
+GProgressBar::~GProgressBar()
+{
+}
+
+void GProgressBar::set_value(int value)
+{
+    if (m_value == value)
+        return;
+    m_value = value;
+    update();
+}
+
+void GProgressBar::set_range(int min, int max)
+{
+    ASSERT(min < max);
+    m_min = min;
+    m_max = max;
+    if (m_value > m_max)
+        m_value = m_max;
+    if (m_value < m_min)
+        m_value = m_min;
+}
+
+void GProgressBar::paint_event(GPaintEvent& event)
+{
+    Painter painter(*this);
+    painter.set_clip_rect(event.rect());
+
+    // First we fill the entire widget with the gradient. This incurs a bit of
+    // overdraw but ensures a consistent look throughout the progression.
+    Color start_color(110, 34, 9);
+    Color end_color(244, 202, 158);
+    painter.fill_rect_with_gradient(rect(), start_color, end_color);
+
+    float range_size = m_max - m_min;
+    float progress = (m_value - m_min) / range_size;
+
+    // Then we draw the progress text over the gradient.
+    // We draw it twice, once offset (1, 1) for a drop shadow look.
+    auto progress_text = String::format("%d%%", (int)(progress * 100));
+    painter.draw_text(rect().translated(1, 1), progress_text, TextAlignment::Center, Color::Black);
+    painter.draw_text(rect(), progress_text, TextAlignment::Center, Color::White);
+
+    // Then we carve out a hole in the remaining part of the widget.
+    // We draw the text a third time, clipped and inverse, for sharp contrast.
+    painter.save();
+    float progress_width = progress * width();
+    Rect hole_rect { (int)progress_width, 0, (int)(width() - progress_width), height() };
+    painter.set_clip_rect(hole_rect);
+    painter.fill_rect(hole_rect, Color::White);
+    painter.draw_text(rect().translated(0, 0), progress_text, TextAlignment::Center, Color::Black);
+    painter.restore();
+
+    // Finally, draw a frame around the widget.
+    painter.draw_rect(rect(), Color::Black);
+}