From 9c6be9b21e3da727ef41908f0377cf1547dfc9c3 Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Mon, 29 Apr 2019 19:20:34 +0200
Subject: [PATCH] LibGUI: Add a GSlider widget.

---
 LibGUI/GSlider.cpp | 106 +++++++++++++++++++++++++++++++++++++++++++++
 LibGUI/GSlider.h   |  40 +++++++++++++++++
 LibGUI/Makefile    |   1 +
 3 files changed, 147 insertions(+)
 create mode 100644 LibGUI/GSlider.cpp
 create mode 100644 LibGUI/GSlider.h

diff --git a/LibGUI/GSlider.cpp b/LibGUI/GSlider.cpp
new file mode 100644
index 00000000000..7f053ddf2bd
--- /dev/null
+++ b/LibGUI/GSlider.cpp
@@ -0,0 +1,106 @@
+#include <LibGUI/GSlider.h>
+#include <LibGUI/GPainter.h>
+#include <SharedGraphics/StylePainter.h>
+
+GSlider::GSlider(GWidget* parent)
+    : GWidget(parent)
+{
+}
+
+GSlider::~GSlider()
+{
+}
+
+void GSlider::set_range(int min, int max)
+{
+    ASSERT(min <= max);
+    if (m_min == min && m_max == max)
+        return;
+    m_min = min;
+    m_max = max;
+
+    if (m_value > max)
+        m_value = max;
+    if (m_value < min)
+        m_value = min;
+    update();
+}
+
+void GSlider::set_value(int value)
+{
+    if (value > m_max)
+        value = m_max;
+    if (value < m_min)
+        value = m_min;
+    if (m_value == value)
+        return;
+    m_value = value;
+    update();
+
+    if (on_value_changed)
+        on_value_changed(m_value);
+}
+
+void GSlider::paint_event(GPaintEvent& event)
+{
+    GPainter painter(*this);
+    painter.add_clip_rect(event.rect());
+
+    auto inner_rect = this->inner_rect();
+
+    Rect track_rect { inner_rect.x(), 0, inner_rect.width(), track_height() };
+    track_rect.center_vertically_within(inner_rect);
+
+    StylePainter::paint_frame(painter, track_rect, FrameShape::Panel, FrameShadow::Sunken, 1);
+
+    StylePainter::paint_button(painter, knob_rect(), ButtonStyle::Normal, false, false);
+}
+
+Rect GSlider::knob_rect() const
+{
+    auto inner_rect = this->inner_rect();
+    float range_size = m_max - m_min;
+    float adjusted_value = m_value - m_min;
+    float relative_value = adjusted_value / range_size;
+    Rect rect { inner_rect.x() + (int)(relative_value * inner_rect.width()) - knob_width() / 2, 0, knob_width(), knob_height() };
+    rect.center_vertically_within(inner_rect);
+    return rect;
+}
+
+void GSlider::mousedown_event(GMouseEvent& event)
+{
+    if (event.button() == GMouseButton::Left) {
+        if (knob_rect().contains(event.position())) {
+            m_dragging = true;
+            m_drag_origin = event.position();
+            m_drag_origin_value = m_value;
+            return;
+        }
+    }
+
+    return GWidget::mousedown_event(event);
+}
+
+void GSlider::mousemove_event(GMouseEvent& event)
+{
+    if (m_dragging) {
+        float delta = event.position().x() - m_drag_origin.x();
+        float scrubbable_range = inner_rect().width();
+        float value_steps_per_scrubbed_pixel = (m_max - m_min) / scrubbable_range;
+        float new_value = m_drag_origin_value + (value_steps_per_scrubbed_pixel * delta);
+        set_value(new_value);
+        return;
+    }
+
+    return GWidget::mousemove_event(event);
+}
+
+void GSlider::mouseup_event(GMouseEvent& event)
+{
+    if (event.button() == GMouseButton::Left) {
+        m_dragging = false;
+        return;
+    }
+
+    return GWidget::mouseup_event(event);
+}
diff --git a/LibGUI/GSlider.h b/LibGUI/GSlider.h
new file mode 100644
index 00000000000..b90cdb2ed86
--- /dev/null
+++ b/LibGUI/GSlider.h
@@ -0,0 +1,40 @@
+#pragma once
+
+#include <LibGUI/GWidget.h>
+
+class GSlider : public GWidget {
+public:
+    explicit GSlider(GWidget*);
+    virtual ~GSlider() override;
+
+    int value() const { return m_value; }
+    int min() const { return m_min; }
+    int max() const { return m_max; }
+
+    void set_range(int min, int max);
+    void set_value(int);
+
+    int track_height() const { return 4; }
+    int knob_width() const { return 8; }
+    int knob_height() const { return 20; }
+
+    Rect knob_rect() const;
+    Rect inner_rect() const { return rect().shrunken(20, 0); }
+
+    Function<void(int)> on_value_changed;
+
+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:
+    int m_value { 0 };
+    int m_min { 0 };
+    int m_max { 100 };
+
+    bool m_dragging { false };
+    int m_drag_origin_value { 0 };
+    Point m_drag_origin;
+};
diff --git a/LibGUI/Makefile b/LibGUI/Makefile
index 924a5d3f601..0255d055206 100644
--- a/LibGUI/Makefile
+++ b/LibGUI/Makefile
@@ -52,6 +52,7 @@ LIBGUI_OBJS = \
     GSplitter.o \
     GSpinBox.o \
     GGroupBox.o \
+    GSlider.o \
     GWindow.o
 
 OBJS = $(SHAREDGRAPHICS_OBJS) $(LIBGUI_OBJS)