Tone: Add 'valueChanged' signal

src/etc.cpp

@@ -180,30 +180,39 @@ void Tone::set(double red, double green, double blue, double gray)
 	this->gray  = gray;
 
 	updateInternal();
+	valueChanged();
 }
 
 void Tone::setRed(double value)
 {
 	red = value;
 	norm.x = (float) clamp<double>(value, -255, 255) / 255;
+
+	valueChanged();
 }
 
 void Tone::setGreen(double value)
 {
 	green = value;
 	norm.y = (float) clamp<double>(value, -255, 255) / 255;
+
+	valueChanged();
 }
 
 void Tone::setBlue(double value)
 {
 	blue = value;
 	norm.z = (float) clamp<double>(value, -255, 255) / 255;
+
+	valueChanged();
 }
 
 void Tone::setGray(double value)
 {
 	gray = value;
 	norm.w = (float) clamp<double>(value, 0, 255) / 255;
+
+	valueChanged();
 }
 
 /* Serializable */

src/etc.h

@@ -134,6 +134,8 @@ struct Tone : public Serializable
 
 	/* Normalized (-1.0 ~ 1.0) */
 	Vec4 norm;
+
+	sigc::signal<void> valueChanged;
 };
 
 struct Rect : public Serializable