source/blender/blenkernel/BKE_grease_pencil.hh

@@ -196,6 +196,30 @@ class TreeNode : public ::GreasePencilLayerTreeNode {
 
 class Layer : public TreeNode, ::GreasePencilLayer {
  private:
+  /**
+   * This Map maps a scene frame number (key) to an index into GreasePencil->drawings (value). The
+   * frame number indicates the first frame the drawing is shown. The end time is implicitly
+   * defined by the next greater frame number (key) in the map. If the value mapped to (index) is
+   * -1, no drawing is shown at this frame.
+   *
+   *    \example:
+   *
+   *    {0: 0, 5: 1, 10: -1, 12: 2, 16: -1}
+   *
+   *    In this example there are three drawings (drawing #0, drawing #1 and drawing #2). The first
+   *    drawing starts at frame 0 and ends at frame 5 (excusive). The second drawing starts at
+   *    frame 5 and ends at frame 10. Finally, the third drawing starts at frame 12 and ends at
+   *    frame 16.
+   *
+   *           | | | | | | | | | | |1|1|1|1|1|1|1|
+   *    Time:  |0|1|2|3|4|5|6|7|8|9|0|1|2|3|4|5|6|...
+   *    Frame: [#0      ][#1      ]    [#2    ]
+   *
+   * \note If a drawing references another data-block, all of the drawings in that data-block are
+   * mapped sequentially to the frames (frame-by-frame). If another frame starts, the rest of the
+   * referenced drawings are discarded. If the frame is longer than the number of referenced
+   * drawings, then the last referenced drawing is held for the rest of the duration.
+   */
   Map<int, int> frames_;
 
  public:
@@ -224,6 +248,16 @@ class Layer : public TreeNode, ::GreasePencilLayer {
   {
     return this != &other;
   }
+
+  bool insert_frame(int frame_number, int index)
+  {
+    return frames_.add(frame_number, index);
+  }
+
+  bool overwrite_frame(int frame_number, int index)
+  {
+    return frames_.add_overwrite(frame_number, index);
+  }
 };
 
 class LayerGroup : public TreeNode {
@@ -264,14 +298,16 @@ class LayerGroup : public TreeNode {
     children_.append(std::make_unique<LayerGroup>(group));
   }
 
-  void add_layer(Layer &layer)
+  Layer &add_layer(Layer &layer)
   {
-    children_.append(std::make_unique<Layer>(layer));
+    int64_t index = children_.append_and_get_index(std::make_unique<Layer>(layer));
+    return children_[index].get()->as_layer();
   }
 
-  void add_layer(Layer &&layer)
+  Layer &add_layer(Layer &&layer)
   {
-    children_.append(std::make_unique<Layer>(layer));
+    int64_t index = children_.append_and_get_index(std::make_unique<Layer>(layer));
+    return children_[index].get()->as_layer();
   }
 
   int num_children()
@@ -286,24 +322,30 @@ class LayerGroup : public TreeNode {
   }
 };
 
-class LayerTree {
- private:
-  LayerGroup root_;
-};
-
 namespace convert {
 
-CurvesGeometry legacy_gpencil_frame_to_curves_geometry(bGPDframe &gpf);
+void legacy_gpencil_frame_to_curves_geometry(GreasePencilDrawing &drawing, bGPDframe &gpf);
 
-void legacy_gpencil_to_grease_pencil(bGPdata &gpd, GreasePencil &grease_pencil);
+void legacy_gpencil_to_grease_pencil(GreasePencil &grease_pencil, bGPdata &gpd);
 
 }  // namespace convert
 
 }  // namespace gpencil
 
+using namespace blender::bke::gpencil;
 class GreasePencilRuntime {
  private:
-  gpencil::LayerTree layer_tree_;
+  LayerGroup root_group_;
+
+ public:
+  GreasePencilRuntime()
+  {
+  }
+
+  LayerGroup &root_group()
+  {
+    return root_group_;
+  }
 };
 
 }  // namespace blender::bke

source/blender/blenkernel/intern/grease_pencil_convert_legacy.cc

@@ -16,7 +16,7 @@
 
 namespace blender::bke::gpencil::convert {
 
-CurvesGeometry legacy_gpencil_frame_to_curves_geometry(bGPDframe &gpf)
+void legacy_gpencil_frame_to_curves_geometry(GreasePencilDrawing &drawing, bGPDframe &gpf)
 {
   /* Get the number of points, number of strokes and the offsets for each stroke. */
   Vector<int> offsets;
@@ -88,11 +88,13 @@ CurvesGeometry legacy_gpencil_frame_to_curves_geometry(bGPDframe &gpf)
 
   curves.tag_topology_changed();
 
-  return curves;
+  drawing.geometry.wrap() = std::move(curves);
 }
 
-void legacy_gpencil_to_grease_pencil(bGPdata &gpd, GreasePencil &grease_pencil)
+void legacy_gpencil_to_grease_pencil(GreasePencil &grease_pencil, bGPdata &gpd)
 {
+  using namespace blender::bke::gpencil;
+
   int num_layers = 0;
   int num_drawings = 0;
   LISTBASE_FOREACH (bGPDlayer *, gpl, &gpd.layers) {
@@ -102,21 +104,22 @@ void legacy_gpencil_to_grease_pencil(bGPdata &gpd, GreasePencil &grease_pencil)
 
   grease_pencil.drawing_array_size = num_drawings;
   grease_pencil.drawing_array = reinterpret_cast<GreasePencilDrawingOrReference **>(
-      MEM_cnew_array<GreasePencilDrawing>(num_drawings, __func__));
+      MEM_cnew_array<GreasePencilDrawing *>(num_drawings, __func__));
 
   int i = 0;
   LISTBASE_FOREACH (bGPDlayer *, gpl, &gpd.layers) {
-    /* TODO: create a new layer here. */
+    Layer &new_layer = grease_pencil.runtime->root_group().add_layer(Layer(gpl->info));
     LISTBASE_FOREACH (bGPDframe *, gpf, &gpl->frames) {
+      grease_pencil.drawing_array[i] = reinterpret_cast<GreasePencilDrawingOrReference *>(
+          MEM_new<GreasePencilDrawing>(__func__));
       GreasePencilDrawing &drawing = *reinterpret_cast<GreasePencilDrawing *>(
           grease_pencil.drawing_array[i]);
       drawing.base.type = GREASE_PENCIL_DRAWING;
       /* TODO: copy flag. */
 
       /* Convert the frame to a drawing. */
-      drawing.geometry = legacy_gpencil_frame_to_curves_geometry(*gpf);
-
-      /* TODO: add drawing to layer. Using the gpf->framenum. */
+      legacy_gpencil_frame_to_curves_geometry(drawing, *gpf);
+      new_layer.insert_frame(gpf->framenum, i);
       i++;
     }
   }

source/blender/editors/object/object_add.cc

@@ -2767,8 +2767,8 @@ static const EnumPropertyItem convert_target_items[] = {
     {OB_GPENCIL_LEGACY,
      "GPENCIL",
      ICON_OUTLINER_OB_GREASEPENCIL,
-     "Grease Pencil",
-     "Grease Pencil from Curve or Mesh objects"},
+     "Grease Pencil (legacy)",
+     "Grease Pencil (legacy) from Curve or Mesh objects"},
 #ifdef WITH_POINT_CLOUD
     {OB_POINTCLOUD,
      "POINTCLOUD",
@@ -2777,6 +2777,11 @@ static const EnumPropertyItem convert_target_items[] = {
      "Point Cloud from Mesh objects"},
 #endif
     {OB_CURVES, "CURVES", ICON_OUTLINER_OB_CURVES, "Curves", "Curves from evaluated curve data"},
+    {OB_GREASE_PENCIL,
+     "GREASEPENCIL",
+     ICON_OUTLINER_OB_GREASEPENCIL,
+     "Grease Pencil",
+     "Grease Pencil from Grease Pencil (legacy)"},
     {0, nullptr, 0, nullptr, nullptr},
 };
 
@@ -3063,37 +3068,10 @@ static int object_convert_exec(bContext *C, wmOperator *op)
       }
       ob_gpencil->actcol = actcol;
     }
-    else if (ob->type == OB_GPENCIL_LEGACY && target == OB_CURVES) {
-      ob->flag |= OB_DONE;
-
-      bGPdata *gpd = static_cast<bGPdata *>(ob->data);
-      bGPDlayer *gpl = BKE_gpencil_layer_active_get(gpd);
-      bGPDframe &gpf = *BKE_gpencil_layer_frame_find(gpl, scene->r.cfra);
-
-      if (keep_original) {
-        BLI_assert_unreachable();
-      }
-      else {
-        newob = ob;
-      }
-
-      Curves *new_curves = static_cast<Curves *>(BKE_id_new(bmain, ID_CV, newob->id.name + 2));
-
-      newob->data = new_curves;
-      newob->type = OB_CURVES;
-
-      new_curves->geometry.wrap() = std::move(
-          bke::gpencil::convert::legacy_gpencil_frame_to_curves_geometry(gpf));
-
-      BKE_object_free_derived_caches(newob);
-      BKE_object_free_modifiers(newob, 0);
-    }
     else if (ob->type == OB_GPENCIL_LEGACY && target == OB_GREASE_PENCIL) {
       ob->flag |= OB_DONE;
 
       bGPdata *gpd = static_cast<bGPdata *>(ob->data);
-      bGPDlayer *gpl = BKE_gpencil_layer_active_get(gpd);
-      bGPDframe &gpf = *BKE_gpencil_layer_frame_find(gpl, scene->r.cfra);
 
       if (keep_original) {
         BLI_assert_unreachable();
@@ -3102,13 +3080,12 @@ static int object_convert_exec(bContext *C, wmOperator *op)
         newob = ob;
       }
 
-      Curves *new_curves = static_cast<Curves *>(BKE_id_new(bmain, ID_CV, newob->id.name + 2));
+      GreasePencil *new_grease_pencil = static_cast<GreasePencil *>(
+          BKE_id_new(bmain, ID_GP, newob->id.name + 2));
+      newob->data = new_grease_pencil;
+      newob->type = OB_GREASE_PENCIL;
 
-      newob->data = new_curves;
-      newob->type = OB_CURVES;
-
-      new_curves->geometry.wrap() = std::move(
-          bke::gpencil::convert::legacy_gpencil_frame_to_curves_geometry(gpf));
+      bke::gpencil::convert::legacy_gpencil_to_grease_pencil(*new_grease_pencil, *gpd);
 
       BKE_object_free_derived_caches(newob);
       BKE_object_free_modifiers(newob, 0);

source/blender/makesdna/DNA_grease_pencil_types.h

@@ -68,28 +68,8 @@ typedef struct GreasePencilDrawingReference {
 } GreasePencilDrawingReference;
 
 /**
- * This Map maps a scene frame number (key) to an index into GreasePencil->drawings (value). The
- * frame number indicates the first frame the drawing is shown. The end time is implicitly
- * defined by the next greater frame number (key) in the map. If the value mapped to (index) is
- * -1, no drawing is shown at this frame.
- *
- *    \example:
- *
- *    {0: 0, 5: 1, 10: -1, 12: 2, 16: -1}
- *
- *    In this example there are three drawings (drawing #0, drawing #1 and drawing #2). The first
- *    drawing starts at frame 0 and ends at frame 5 (excusive). The second drawing starts at
- *    frame 5 and ends at frame 10. Finally, the third drawing starts at frame 12 and ends at
- *    frame 16.
- *
- *           | | | | | | | | | | |1|1|1|1|1|1|1|
- *    Time:  |0|1|2|3|4|5|6|7|8|9|0|1|2|3|4|5|6|...
- *    Frame: [#0      ][#1      ]    [#2    ]
- *
- * \note If a drawing references another data-block, all of the drawings in that data-block are
- * mapped sequentially to the frames (frame-by-frame). If another frame starts, the rest of the
- * referenced drawings are discarded. If the frame is longer than the number of referenced
- * drawings, then the last referenced drawing is held for the rest of the duration.
+ * Storage for the Map in `blender::bke::gpencil::Layer`.
+ * See the description there for more detail.
  */
 typedef struct GreasePencilLayerFramesMapStorage {
   /* Array of `frames` keys (sorted in ascending order). */
@@ -173,12 +153,7 @@ typedef struct GreasePencil {
   int drawing_array_size;
   char _pad[4];
 
-#ifdef __cplusplus
-  /**
-   * The layer tree.
-   */
-  // const bke::gpencil::LayerTree &layer_tree() const;
-#endif
+  /* Only used for storage in the .blend file. */
   GreasePencilLayerTreeStorage layer_tree_storage;
 
   /**