From fa2c00ae91f04fad82da7a0593978031e3ec94cb Mon Sep 17 00:00:00 2001
From: Germano Cavalcante <germano.costa@ig.com.br>
Date: Sat, 17 Apr 2021 13:51:33 -0300
Subject: Fix wrong logic used in 'ED_view3d_depth_read_cached'

It is important to limit the pixels read on `BLI_array_iter_spiral_square`.

Fortunately `ED_view3d_depth_read_cached` was not being called with a
`margin` parameter.

Wrong logic introduced in rB44c76e4ce310.
---
 source/blender/editors/space_view3d/view3d_utils.c | 30 ++++++++++++++++++----
 1 file changed, 25 insertions(+), 5 deletions(-)

(limited to 'source/blender/editors/space_view3d')

diff --git a/source/blender/editors/space_view3d/view3d_utils.c b/source/blender/editors/space_view3d/view3d_utils.c
index fde98c18803..f96c17d7cff 100644
--- a/source/blender/editors/space_view3d/view3d_utils.c
+++ b/source/blender/editors/space_view3d/view3d_utils.c
@@ -1630,12 +1630,23 @@ bool ED_view3d_camera_to_view_selected(struct Main *bmain,
 /** \name Depth Buffer Utilities
  * \{ */
 
+struct ReadData {
+  int count;
+  int count_max;
+  float r_depth;
+};
+
 static bool depth_read_test_fn(const void *value, void *userdata)
 {
-  float *r_depth = userdata;
+  struct ReadData *data = userdata;
   float depth = *(float *)value;
-  if (depth < *r_depth) {
-    *r_depth = depth;
+  if (depth < data->r_depth) {
+    data->r_depth = depth;
+  }
+
+  if ((++data->count) >= data->count_max) {
+    /* Outside the margin. */
+    return true;
   }
   return false;
 }
@@ -1657,9 +1668,18 @@ bool ED_view3d_depth_read_cached(const ViewDepths *vd,
 
   float depth = 1.0f;
   if (margin) {
-    /* TODO: No need to go spiral. */
     int shape[2] = {vd->w, vd->h};
-    BLI_array_iter_spiral_square(vd->depths, shape, mval, depth_read_test_fn, &depth);
+    int pixel_count = (min_ii(x + margin + 1, shape[1]) - max_ii(x - margin, 0)) *
+                      (min_ii(y + margin + 1, shape[0]) - max_ii(y - margin, 0));
+
+    struct ReadData data;
+    data.count = 0;
+    data.count_max = pixel_count;
+    data.r_depth = 1.0f;
+
+    /* TODO: No need to go spiral. */
+    BLI_array_iter_spiral_square(vd->depths, shape, mval, depth_read_test_fn, &data);
+    depth = data.r_depth;
   }
   else {
     depth = vd->depths[y * vd->w + x];
-- 
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