GPencil: Fill tool refactor and Multiframe in Draw mode

This commit is a refactor of the fill tool to solve several problems we had since the first version of the tool.

Changes:

* The filling speed has been improved for each step of the process with the optimization of each algorithm/function.
* New `AutoFit` option to fill areas outside of the viewport. When enable, the total size of the frame is calculated to fit the filling area.
* New support multiframe filling. Now it is possible to fill multiple similar frames in one go.
* New `Stroke Extension` option to create temporary closing strokes. These strokes can be displayed and adjusted dynamically using wheel mouse or PageUp/Down keys.
* Parameter `Resolution` now is named `Precision` and has been moved to topbar.
* `Resolution` now has decimals and can be lower than 1 to allow quick filling in storyboarding workflows. Maximum value has been set as 5.
* Parameter `Simplify` has been moved to Advanced panel.
* Improved fill outline detection. In some cases, the outline penetrated the area to be filled with unexpected results.
* Fixes some corner case bugs with infinite loops.

As a result of this refactor, also these new functionalities has been added.

* New support for multiframe in `Draw` mode. Any drawing in active frame is duplicated to all selected frame.
* New multiframe display mode. Keyframes before or after of the active frame are displayed using onion colors. This can be disable using Onion overlay options.

1 files changed, 32 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/gpencil.c b/source/blender/blenkernel/intern/gpencil.c
index 0c813c170ad..3d0152a6c7d 100644
--- a/source/blender/blenkernel/intern/gpencil.c
+++ b/source/blender/blenkernel/intern/gpencil.c
@@ -851,6 +851,7 @@ bGPDstroke *BKE_gpencil_stroke_new(int mat_idx, int totpoints, short thickness)
 
   gps->mat_nr = mat_idx;
 
+  gps->dvert = NULL;
   gps->editcurve = NULL;
 
   return gps;
@@ -2606,6 +2607,15 @@ void BKE_gpencil_visible_stroke_iter(ViewLayer *view_layer,
       LISTBASE_FOREACH (bGPDframe *, gpf, &gpl->frames) {
         if (gpf == act_gpf || (gpf->flag & GP_FRAME_SELECT)) {
           gpf->runtime.onion_id = 0;
+          if (do_onion) {
+            if (gpf->framenum < act_gpf->framenum) {
+              gpf->runtime.onion_id = -1;
+            }
+            else {
+              gpf->runtime.onion_id = 1;
+            }
+          }
+
           if (sta_gpf == NULL) {
             sta_gpf = gpf;
           }
@@ -2939,4 +2949,26 @@ int BKE_gpencil_material_find_index_by_name_prefix(Object *ob, const char *name_
   return -1;
 }
 
+/* Create a hash with the list of selected frame number. */
+void BKE_gpencil_frame_selected_hash(bGPdata *gpd, struct GHash *r_list)
+{
+  const bool is_multiedit = (bool)GPENCIL_MULTIEDIT_SESSIONS_ON(gpd);
+  bGPDlayer *gpl = BKE_gpencil_layer_active_get(gpd);
+
+  LISTBASE_FOREACH (bGPDlayer *, gpl_iter, &gpd->layers) {
+    if ((gpl != NULL) && (!is_multiedit) && (gpl != gpl_iter)) {
+      continue;
+    }
+
+    LISTBASE_FOREACH (bGPDframe *, gpf, &gpl_iter->frames) {
+      if (((gpf == gpl->actframe) && (!is_multiedit)) ||
+          ((gpf->flag & GP_FRAME_SELECT) && (is_multiedit))) {
+        if (!BLI_ghash_lookup(r_list, POINTER_FROM_INT(gpf->framenum))) {
+          BLI_ghash_insert(r_list, POINTER_FROM_INT(gpf->framenum), gpf);
+        }
+      }
+    }
+  }
+}
+
 /** \} */