BLI: New 'BLI_array_iter_spiral_square'

No functional changes.

This function replaces some of the logic in
`DRW_select_buffer_find_nearest_to_point` that traverses a buffer in a
spiral way to search for a closer pixel (not the closest).

Differential Revision: https://developer.blender.org/D10548

1 files changed, 33 insertions, 59 deletions

diff --git a/source/blender/draw/intern/draw_select_buffer.c b/source/blender/draw/intern/draw_select_buffer.c
index b5151293c1b..d7438b7e0f0 100644
--- a/source/blender/draw/intern/draw_select_buffer.c
+++ b/source/blender/draw/intern/draw_select_buffer.c
@@ -24,6 +24,7 @@
 
 #include "MEM_guardedalloc.h"
 
+#include "BLI_array_utils.h"
 #include "BLI_bitmap.h"
 #include "BLI_bitmap_draw_2d.h"
 #include "BLI_rect.h"
@@ -336,6 +337,26 @@ uint DRW_select_buffer_sample_point(struct Depsgraph *depsgraph,
   return ret;
 }
 
+struct SelectReadData {
+  const void *val_ptr;
+  uint id_min;
+  uint id_max;
+  uint r_index;
+};
+
+static bool select_buffer_test_fn(const void *__restrict value, void *__restrict userdata)
+{
+  struct SelectReadData *data = userdata;
+  uint hit_id = *(uint *)value;
+  if (hit_id && hit_id >= data->id_min && hit_id < data->id_max) {
+    /* Start at 1 to confirm. */
+    data->val_ptr = value;
+    data->r_index = (hit_id - data->id_min) + 1;
+    return true;
+  }
+  return false;
+}
+
 /**
  * Find the selection id closest to \a center.
  * \param dist: Use to initialize the distance,
@@ -349,13 +370,8 @@ uint DRW_select_buffer_find_nearest_to_point(struct Depsgraph *depsgraph,
                                              const uint id_max,
                                              uint *dist)
 {
-  /* Smart function to sample a rect spiraling outside, nice for selection ID. */
-
   /* Create region around center (typically the mouse cursor).
-   * This must be square and have an odd width,
-   * the spiraling algorithm does not work with arbitrary rectangles. */
-
-  uint index = 0;
+   * This must be square and have an odd width. */
 
   rcti rect;
   BLI_rcti_init_pt_radius(&rect, center, *dist);
@@ -364,7 +380,6 @@ uint DRW_select_buffer_find_nearest_to_point(struct Depsgraph *depsgraph,
 
   int width = BLI_rcti_size_x(&rect);
   int height = width;
-  BLI_assert(width == height);
 
   /* Read from selection framebuffer. */
 
@@ -372,64 +387,23 @@ uint DRW_select_buffer_find_nearest_to_point(struct Depsgraph *depsgraph,
   const uint *buf = DRW_select_buffer_read(depsgraph, region, v3d, &rect, &buf_len);
 
   if (buf == NULL) {
-    return index;
+    return 0;
   }
 
-  BLI_assert(width * height == buf_len);
-
-  /* Spiral, starting from center of buffer. */
-  int spiral_offset = height * (int)(width / 2) + (height / 2);
-  int spiral_direction = 0;
-
-  for (int nr = 1; nr <= height; nr++) {
-    for (int a = 0; a < 2; a++) {
-      for (int b = 0; b < nr; b++) {
-        /* Find hit within the specified range. */
-        uint hit_id = buf[spiral_offset];
-
-        if (hit_id && hit_id >= id_min && hit_id < id_max) {
-          /* Get x/y from spiral offset. */
-          int hit_x = spiral_offset % width;
-          int hit_y = spiral_offset / width;
-
-          int center_x = width / 2;
-          int center_y = height / 2;
+  const int shape[2] = {height, width};
+  const int center_yx[2] = {(height - 1) / 2, (width - 1) / 2};
+  struct SelectReadData data = {NULL, id_min, id_max, 0};
+  BLI_array_iter_spiral_square(buf, shape, center_yx, select_buffer_test_fn, &data);
 
-          /* Manhattan distance in keeping with other screen-based selection. */
-          *dist = (uint)(abs(hit_x - center_x) + abs(hit_y - center_y));
-
-          /* Indices start at 1 here. */
-          index = (hit_id - id_min) + 1;
-          goto exit;
-        }
-
-        /* Next spiral step. */
-        if (spiral_direction == 0) {
-          spiral_offset += 1; /* right */
-        }
-        else if (spiral_direction == 1) {
-          spiral_offset -= width; /* down */
-        }
-        else if (spiral_direction == 2) {
-          spiral_offset -= 1; /* left */
-        }
-        else {
-          spiral_offset += width; /* up */
-        }
-
-        /* Stop if we are outside the buffer. */
-        if (spiral_offset < 0 || spiral_offset >= buf_len) {
-          goto exit;
-        }
-      }
-
-      spiral_direction = (spiral_direction + 1) % 4;
-    }
+  if (data.val_ptr) {
+    size_t offset = ((size_t)data.val_ptr - (size_t)buf) / sizeof(*buf);
+    int hit_x = offset % width;
+    int hit_y = offset / width;
+    *dist = (uint)(abs(hit_y - center_yx[0]) + abs(hit_x - center_yx[1]));
   }
 
-exit:
   MEM_freeN((void *)buf);
-  return index;
+  return data.r_index;
 }
 
 /** \} */