LibGUI: Add option to disable on_change call for sliders set_value()

This makes it possible to avoid messy situations where a slider
controlled value can be changed from multiple sources.

Userland/Libraries/LibGUI/AbstractSlider.cpp

@@ -53,7 +53,7 @@ void AbstractSlider::set_range(int min, int max)
     update();
 }
 
-void AbstractSlider::set_value(int value)
+void AbstractSlider::set_value(int value, CallOnChange call_on_change)
 {
     value = clamp(value, m_min, m_max);
     if (m_value == value)
@@ -61,7 +61,7 @@ void AbstractSlider::set_value(int value)
     m_value = value;
     update();
 
-    if (on_change)
+    if (on_change && call_on_change == CallOnChange::Yes)
         on_change(m_value);
 }
 

Userland/Libraries/LibGUI/AbstractSlider.h

@@ -30,7 +30,7 @@ public:
     bool is_max() const { return m_value == m_max; }
 
     void set_range(int min, int max);
-    virtual void set_value(int);
+    virtual void set_value(int, CallOnChange call_on_change = CallOnChange::Yes);
 
     void set_min(int min) { set_range(min, max()); }
     void set_max(int max) { set_range(min(), max); }

Userland/Libraries/LibGUI/ValueSlider.cpp

@@ -141,9 +141,9 @@ int ValueSlider::value_at(const Gfx::IntPoint& position) const
     return (int)(relative_offset * (float)max());
 }
 
-void ValueSlider::set_value(int value)
+void ValueSlider::set_value(int value, CallOnChange call_on_change)
 {
-    AbstractSlider::set_value(value);
+    AbstractSlider::set_value(value, call_on_change);
     m_textbox->set_text(formatted_value());
 }
 

Userland/Libraries/LibGUI/ValueSlider.h

@@ -24,7 +24,7 @@ public:
     void set_suffix(String suffix) { m_suffix = move(suffix); }
     void set_knob_style(KnobStyle knobstyle) { m_knob_style = knobstyle; }
 
-    virtual void set_value(int value) override;
+    virtual void set_value(int value, CallOnChange call_on_change = CallOnChange::Yes) override;
 
 protected:
     virtual void paint_event(PaintEvent&) override;

Userland/Libraries/LibGUI/Widget.h

@@ -39,6 +39,7 @@ enum class HorizontalDirection {
     Left,
     Right
 };
+
 enum class VerticalDirection {
     Up,
     Down
@@ -53,6 +54,11 @@ enum class FocusPolicy {
 
 AK_ENUM_BITWISE_OPERATORS(FocusPolicy)
 
+enum class CallOnChange {
+    No,
+    Yes
+};
+
 class Widget : public Core::Object {
     C_OBJECT(Widget)
 public: