main.c: add zooming on mousewheel events

Signed-off-by: Dave Reisner <d@falconindy.com>

main.c

@@ -31,10 +31,12 @@
 
 void on_keypress(XEvent*);
 void on_configurenotify(XEvent*);
+void on_buttonpress(XEvent*);
 
 void update_title();
 
 static void (*handler[LASTEvent])(XEvent*) = {
+	[ButtonPress] = on_buttonpress,
 	[KeyPress] = on_keypress,
 	[ConfigureNotify] = on_configurenotify
 };
@@ -126,6 +128,31 @@ void cleanup() {
 	}
 }
 
+void on_buttonpress(XEvent *ev) {
+	int changed;
+	XButtonEvent *buttonevent;
+
+	changed = 0;
+	buttonevent = &ev->xbutton;
+
+	switch (buttonevent->button) {
+		case Button4:
+			changed = img_zoom_in(&img);
+			break;
+		case Button5:
+			changed = img_zoom_out(&img);
+			break;
+		default:
+			return;
+	}
+
+	if (changed) {
+		img_render(&img, &win);
+		update_title();
+		timeout = 0;
+	}
+}
+
 void on_keypress(XEvent *ev) {
 	char key;
 	KeySym keysym;