Mandelbrot: mouse wheel zooming.

Fixes #9533.

src/apps/mandelbrot/tsb.cpp

@@ -26,15 +26,10 @@
 
 /*------------------------------------------------------------*/
 
-TShowBit	*tsbb;
+static TShowBit	*tsbb;
+static long		niter = 256;
+static uchar	palette[256];
 
-/*------------------------------------------------------------*/
-long	niter = 256; 
-/*------------------------------------------------------------*/
-
-uchar	palette[256];
-
-/*------------------------------------------------------------*/
 
 void	TShowBit::MouseDown(BPoint where)
 {
@@ -54,7 +49,41 @@ void	TShowBit::MouseDown(BPoint where)
 	redraw_mand();
 }
 
-/*------------------------------------------------------------*/
+
+void
+TShowBit::MessageReceived(BMessage* message)
+{
+	switch(message->what) {
+		case B_MOUSE_WHEEL_CHANGED:
+		{
+			//float factor = 1;
+			float change = message->FindFloat("be:wheel_delta_y");
+			BPoint where;
+			GetMouse(&where, 0, 0);
+
+			selection = Bounds();
+
+			if (change < 0) {
+				// zoom in
+				selection.top = (where.y + selection.top) / 2;
+				selection.bottom = (where.y + selection.bottom) / 2;
+				selection.left = (where.x + selection.left) / 2;
+				selection.right = (where.x + selection.right) / 2;
+			} else {
+				// zoom out
+				selection.top = - where.y + selection.top * 2;
+				selection.bottom = - where.y + selection.bottom * 2;
+				selection.left = - where.x + selection.left * 2;
+				selection.right = - where.x + selection.right * 2;
+			}
+			redraw_mand();
+			break;
+		}
+		default:
+			BView::MessageReceived(message);
+	}
+}
+
 
 void	TShowBit::redraw_mand()
 {
@@ -66,8 +95,7 @@ void	TShowBit::redraw_mand()
 		px -= (scale / 2.0);
 		py -= (scale / 2.0);
 		scale *= 2.0;
-	}
-	else {
+	} else {
 		px0 = px + (scale * (selection.left / (1.0*size_x)));
 		py0 = py + (scale * (selection.top / (1.0*size_x)));
 		scale0 = scale * ((selection.bottom-selection.top) / (1.0*size_x));

src/apps/mandelbrot/tsb.h

@@ -37,6 +37,7 @@ public:
 virtual					~TShowBit();
 virtual		void		Draw(BRect);
 virtual		void		MouseDown(BPoint where);
+			void		MessageReceived(BMessage* message);
 virtual		void		Pulse();
 			void		mand(double vx, double vy, double sx, double sy);
 			long		limit_v(long v);