LibGUI: Add GUI::AbstractSlider and move generic parts of Slider there

This will allow us to share some code between Slider and ScrollBar.

Libraries/LibGUI/AbstractSlider.cpp

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Assertions.h>
+#include <AK/StdLibExtras.h>
+#include <LibGUI/Painter.h>
+#include <LibGUI/Slider.h>
+#include <LibGfx/Palette.h>
+#include <LibGfx/StylePainter.h>
+
+namespace GUI {
+
+AbstractSlider::AbstractSlider(Orientation orientation)
+    : m_orientation(orientation)
+{
+    REGISTER_INT_PROPERTY("min", min, set_min);
+    REGISTER_INT_PROPERTY("max", max, set_max);
+    REGISTER_INT_PROPERTY("step", step, set_step);
+    REGISTER_ENUM_PROPERTY("orientation", this->orientation, set_orientation, Orientation,
+        { Orientation::Horizontal, "Horizontal" },
+        { Orientation::Vertical, "Vertical" });
+}
+
+AbstractSlider::~AbstractSlider()
+{
+}
+
+void AbstractSlider::set_orientation(Orientation value)
+{
+    if (m_orientation == value)
+        return;
+    m_orientation = value;
+    update();
+}
+
+void AbstractSlider::set_range(int min, int max)
+{
+    ASSERT(min <= max);
+    if (m_min == min && m_max == max)
+        return;
+    m_min = min;
+    m_max = max;
+    m_value = clamp(m_value, m_min, m_max);
+    update();
+}
+
+void AbstractSlider::set_value(int value)
+{
+    value = clamp(value, m_min, m_max);
+    if (m_value == value)
+        return;
+    m_value = value;
+    update();
+
+    if (on_value_changed)
+        on_value_changed(m_value);
+}
+
+}