GPencil: Support camera "Frame Selected" and object previews

Using the "Camera Fit Frame to Selected" operator didn't work for Grease Pencil
objects. The same issue caused grease pencil preview thumbnails to be useless
(e.g. when using "Mark Asset" on a Grease Pencil object).
Reason was that there was no logic to handle grease pencil data and its strokes
for the object display-point iterators used for the "Frame Selected" logic.

Addresses T89656.

Reviewed by: Antonio Vazquez, Campbell Barton

Differential Revision: https://developer.blender.org/D11833

1 files changed, 31 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 2a37aebd8f0..37c3d9017cd 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -4143,6 +4143,30 @@ bool BKE_object_minmax_dupli(Depsgraph *depsgraph,
   return ok;
 }
 
+struct GPencilStrokePointIterData {
+  const float (*obmat)[4];
+
+  void (*point_func_cb)(const float co[3], void *user_data);
+  void *user_data;
+};
+
+static void foreach_display_point_gpencil_stroke_fn(bGPDlayer *UNUSED(layer),
+                                                    bGPDframe *UNUSED(frame),
+                                                    bGPDstroke *stroke,
+                                                    void *thunk)
+{
+  struct GPencilStrokePointIterData *iter_data = thunk;
+  {
+    bGPDspoint *pt;
+    int i;
+    for (i = 0, pt = stroke->points; i < stroke->totpoints; i++, pt++) {
+      float co[3];
+      mul_v3_m4v3(co, iter_data->obmat, &pt->x);
+      iter_data->point_func_cb(co, iter_data->user_data);
+    }
+  }
+}
+
 void BKE_object_foreach_display_point(Object *ob,
                                       const float obmat[4][4],
                                       void (*func_cb)(const float[3], void *),
@@ -4160,6 +4184,13 @@ void BKE_object_foreach_display_point(Object *ob,
       func_cb(co, user_data);
     }
   }
+  else if (ob->type == OB_GPENCIL) {
+    struct GPencilStrokePointIterData iter_data = {
+        .obmat = obmat, .point_func_cb = func_cb, .user_data = user_data};
+
+    BKE_gpencil_visible_stroke_iter(
+        ob->data, NULL, foreach_display_point_gpencil_stroke_fn, &iter_data);
+  }
   else if (ob->runtime.curve_cache && ob->runtime.curve_cache->disp.first) {
     DispList *dl;