Fix scaling overflow

1 files changed, 26 insertions, 7 deletions

diff --git a/examples/julia_set.c b/examples/julia_set.c
index 6ae8e6f..e819ca5 100644
--- a/examples/julia_set.c
+++ b/examples/julia_set.c
@@ -1,5 +1,7 @@
 #include "../graphics.c"
 
+#define SCALE_LIMIT (0.9)
+
 f64 view_x = 0.;
 f64 view_y = 0.;
 f64 view_s = 1.;
@@ -9,6 +11,28 @@ f64 radius = 2.;
 i64 limit  = 1024;
 i64 time_0;
 
+void apply_scale(f64 delta) {
+  while (delta > SCALE_LIMIT) {
+    apply_scale(SCALE_LIMIT);
+    delta -= SCALE_LIMIT;
+  }
+  while (delta < -SCALE_LIMIT) {
+    apply_scale(-SCALE_LIMIT);
+    delta += SCALE_LIMIT;
+  }
+
+  f64 ds = view_s * delta * .1;
+  if (view_s + ds < EPSILON)
+    return;
+  f64 dx  = (g_platform.cursor_x * 1. - g_platform.real_width  * .5);
+  f64 dy  = (g_platform.cursor_y * 1. - g_platform.real_height * .5);
+  view_x -= view_s * dx;
+  view_y -= view_s * dy;
+  view_s += ds;
+  view_x += view_s * dx;
+  view_y += view_s * dy;
+}
+
 void update_and_render_frame(void) {
   i32 num_events = p_handle_events();
 
@@ -44,13 +68,8 @@ void update_and_render_frame(void) {
   }
 
   if (g_platform.wheel_dy != 0.) {
-    f64 dx  = (g_platform.cursor_x * 1. - g_platform.real_width  * .5);
-    f64 dy  = (g_platform.cursor_y * 1. - g_platform.real_height * .5);
-    view_x -= view_s * dx;
-    view_y -= view_s * dy;
-    view_s += view_s * g_platform.wheel_dy * .1;
-    view_x += view_s * dx;
-    view_y += view_s * dy;
+    apply_scale(g_platform.wheel_dy / 2.0);
+    apply_scale(g_platform.wheel_dy / 2.0);
   }
 
   for (i32 j = 0; j < g_platform.frame_height; ++j)