X-Git-Url: http://git.itanic.dy.fi/?p=mandelbrot;a=blobdiff_plain;f=mandelbrot.c;h=9ca242101ae1bad4a2f98aa5e89387dee82f36f0;hp=06e0a743b54d265223766a01131cf614e17b387e;hb=HEAD;hpb=024dd9cad678c07057f58d43024b0d4bd5b3c7af

diff --git a/mandelbrot.c b/mandelbrot.c
index 06e0a74..9ca2421 100644
--- a/mandelbrot.c
+++ b/mandelbrot.c
@@ -7,7 +7,8 @@
 struct context {
 	struct SDL_Surface *screen;
 	long double origo_x, origo_y;
-	int motion_x, motion_y;
+	int motion_x, motion_y;		/* mouse motion */
+	int mx, my;			/* mouse position */
 	long double zoom;
 	int scroll_enabled;
 	int zooms;
@@ -77,6 +78,8 @@ int draw_mandelbrot(struct SDL_Surface *screen, long double x1, long double x2,
 	return 0;
 }
 
+#define ZOOM_FACTOR	1.5
+
 static int read_events(struct context *ctx)
 {
 	SDL_Event event;
@@ -111,11 +114,9 @@ static int read_events(struct context *ctx)
 			break;
 		case SDL_MOUSEBUTTONDOWN:
 			if (event.button.button == 4) {
-				ctx->zoom *= 1.5;
 				ctx->zooms++;
 				delayed_exit++;
 			} else if (event.button.button == 5) {
-				ctx->zoom /= 1.5;
 				ctx->zooms--;
 				delayed_exit++;
 			} else {
@@ -124,9 +125,11 @@ static int read_events(struct context *ctx)
 			break;
 		case SDL_MOUSEBUTTONUP:
 			ctx->scroll_enabled = 0;
-			exit++;
+			delayed_exit++;
 			break;
 		case SDL_MOUSEMOTION:
+			ctx->mx = event.motion.x;
+			ctx->my = event.motion.y;
 			if (!ctx->scroll_enabled)
 				break;
 
@@ -157,19 +160,45 @@ static void loop(struct context *ctx)
 {
 	long double aspect_ratio;
 	long double x1, x2, y1, y2;
+	int last_zoom;
 
 	do {
-		aspect_ratio = ctx->screen->w / ctx->screen->h;
+		aspect_ratio = ctx->screen->w / (long double)ctx->screen->h;
 		ctx->origo_x += ctx->motion_x / ctx->zoom / ctx->screen->w;
 		ctx->origo_y += ctx->motion_y / ctx->zoom / ctx->screen->h;
 		ctx->motion_x = ctx->motion_y = 0;
 
+		if (ctx->zooms != last_zoom) {
+			int dx, dy;
+
+			dx = ctx->mx - ctx->screen->w / 2;
+			dy = ctx->my - ctx->screen->h / 2;
+
+			if (ctx->zooms > last_zoom) {
+				ctx->zoom *= ZOOM_FACTOR;
+				ctx->origo_x += dx / ctx->zoom /
+					(long double) ctx->screen->w;
+				ctx->origo_y += dy / ctx->zoom /
+					(long double) ctx->screen->h;
+			} else {
+				ctx->origo_x -= dx / ctx->zoom /
+					(long double) ctx->screen->w;
+				ctx->origo_y -= dy / ctx->zoom /
+					(long double) ctx->screen->h;
+				ctx->zoom /= ZOOM_FACTOR;
+			}
+
+			last_zoom = ctx->zooms;
+		}
+
 		x1 = ctx->origo_x - aspect_ratio / ctx->zoom;
 		x2 = ctx->origo_x + aspect_ratio / ctx->zoom;
 		y1 = ctx->origo_y - 1 / ctx->zoom;
 		y2 = ctx->origo_y + 1 / ctx->zoom;
+
 		printf("Drawing area (%LF, %LF)(%LF, %LF), zoom %d\n",
 			x1, y1, x2, y2, ctx->zooms);
+
 		draw_mandelbrot(ctx->screen, x1, x2, y1, y2);
 	} while (!read_events(ctx));
 }