GPv3: Add operator to insert blank frames

This adds a new operator to insert blank keyframes for the new
grease pencil data type.

This uses the newly added `insert_frame` API.

source/blender/blenkernel/BKE_grease_pencil.hh

@@ -221,6 +221,7 @@ class Layer : public ::GreasePencilLayer {
 
   bool is_visible() const;
   bool is_locked() const;
+  bool is_editable() const;
 
   /**
    * Inserts the frame into the layer frames map. Will not overwrite existing frames at \a

source/blender/blenkernel/intern/grease_pencil.cc

@@ -498,6 +498,11 @@ bool Layer::is_locked() const
   return this->parent_group().is_locked() || (this->base.flag & GP_LAYER_TREE_NODE_LOCKED) != 0;
 }
 
+bool Layer::is_editable() const
+{
+  return !this->is_locked() && this->is_visible();
+}
+
 bool Layer::insert_frame(const int frame_number, const GreasePencilFrame &frame)
 {
   BLI_assert(!frame.is_null());
@@ -1168,6 +1173,20 @@ void GreasePencil::add_empty_drawings(const int add_num)
   /* TODO: Update drawing user counts. */
 }
 
+bool GreasePencil::insert_blank_frame(blender::bke::greasepencil::Layer &layer,
+                                      int frame_number,
+                                      int duration,
+                                      eBezTriple_KeyframeType keytype)
+{
+  using namespace blender;
+  GreasePencilFrame frame{static_cast<int>(this->drawings().size()), 0, keytype};
+  if (!layer.insert_frame(frame_number, duration, frame)) {
+    return false;
+  }
+  this->add_empty_drawings(1);
+  return true;
+}
+
 void GreasePencil::remove_drawing(const int index_to_remove)
 {
   using namespace blender::bke::greasepencil;
@@ -1256,7 +1275,7 @@ static void foreach_drawing_ex(
         break;
       }
       case EDITABLE: {
-        if (!layer->is_visible() || layer->is_locked()) {
+        if (!layer->is_editable()) {
           continue;
         }
         break;

source/blender/editors/grease_pencil/CMakeLists.txt

@@ -24,6 +24,7 @@ set(INC_SYS
 set(SRC
   intern/grease_pencil_add.cc
   intern/grease_pencil_edit.cc
+  intern/grease_pencil_frames.cc
   intern/grease_pencil_layers.cc
   intern/grease_pencil_ops.cc
   intern/grease_pencil_select.cc

source/blender/editors/grease_pencil/intern/grease_pencil_frames.cc

@@ -0,0 +1,91 @@
+/* SPDX-FileCopyrightText: 2023 Blender Foundation
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup edgreasepencil
+ */
+
+#include "BKE_context.h"
+#include "BKE_grease_pencil.hh"
+
+#include "DEG_depsgraph.h"
+
+#include "DNA_scene_types.h"
+
+#include "ED_grease_pencil.h"
+
+#include "RNA_access.h"
+#include "RNA_define.h"
+
+#include "WM_api.h"
+
+namespace blender::ed::greasepencil {
+
+static int insert_blank_frame_exec(bContext *C, wmOperator *op)
+{
+  using namespace blender::bke::greasepencil;
+  Scene *scene = CTX_data_scene(C);
+  Object *object = CTX_data_active_object(C);
+  GreasePencil &grease_pencil = *static_cast<GreasePencil *>(object->data);
+  const int current_frame = scene->r.cfra;
+  const bool all_layers = RNA_boolean_get(op->ptr, "all_layers");
+  const int duration = RNA_int_get(op->ptr, "duration");
+
+  bool changed = false;
+  if (all_layers) {
+    for (Layer *layer : grease_pencil.layers_for_write()) {
+      if (!layer->is_editable()) {
+        continue;
+      }
+      changed = grease_pencil.insert_blank_frame(
+          *layer, current_frame, duration, BEZT_KEYTYPE_KEYFRAME);
+    }
+  }
+  else {
+    if (!grease_pencil.has_active_layer()) {
+      return OPERATOR_CANCELLED;
+    }
+    changed = grease_pencil.insert_blank_frame(*grease_pencil.get_active_layer_for_write(),
+                                               current_frame,
+                                               duration,
+                                               BEZT_KEYTYPE_KEYFRAME);
+  }
+
+  if (changed) {
+    DEG_id_tag_update(&grease_pencil.id, ID_RECALC_GEOMETRY);
+    WM_event_add_notifier(C, NC_GEOM | ND_DATA, &grease_pencil);
+  }
+
+  return OPERATOR_FINISHED;
+}
+
+static void GREASE_PENCIL_OT_insert_blank_frame(wmOperatorType *ot)
+{
+  PropertyRNA *prop;
+
+  /* identifiers */
+  ot->name = "Insert Blank Frame";
+  ot->idname = "GREASE_PENCIL_OT_insert_blank_frame";
+  ot->description = "Insert a blank frame on the current scene frame";
+
+  /* callbacks */
+  ot->exec = insert_blank_frame_exec;
+  ot->poll = active_grease_pencil_poll;
+
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+
+  /* properties */
+  prop = RNA_def_boolean(
+      ot->srna, "all_layers", false, "All Layers", "Insert a blank frame in all editable layers");
+  RNA_def_property_flag(prop, PROP_SKIP_SAVE);
+  RNA_def_int(ot->srna, "duration", 1, 1, MAXFRAME, "Duration", "", 1, 100);
+}
+
+}  // namespace blender::ed::greasepencil
+
+void ED_operatortypes_grease_pencil_frames()
+{
+  using namespace blender::ed::greasepencil;
+  WM_operatortype_append(GREASE_PENCIL_OT_insert_blank_frame);
+}

source/blender/editors/grease_pencil/intern/grease_pencil_ops.cc

@@ -11,6 +11,7 @@
 void ED_operatortypes_grease_pencil()
 {
   ED_operatortypes_grease_pencil_draw();
+  ED_operatortypes_grease_pencil_frames();
   ED_operatortypes_grease_pencil_layers();
   ED_operatortypes_grease_pencil_select();
 }

source/blender/editors/include/ED_grease_pencil.h

@@ -32,6 +32,7 @@ enum {
 
 void ED_operatortypes_grease_pencil(void);
 void ED_operatortypes_grease_pencil_draw(void);
+void ED_operatortypes_grease_pencil_frames(void);
 void ED_operatortypes_grease_pencil_layers(void);
 void ED_operatortypes_grease_pencil_select(void);
 void ED_keymap_grease_pencil(struct wmKeyConfig *keyconf);

source/blender/makesdna/DNA_grease_pencil_types.h

@@ -9,6 +9,7 @@
 #pragma once
 
 #include "DNA_ID.h"
+#include "DNA_curve_types.h"
 #include "DNA_curves_types.h"
 #include "DNA_listBase.h"
 
@@ -479,6 +480,11 @@ typedef struct GreasePencil {
   void remove_layer(blender::bke::greasepencil::Layer &layer);
 
   void add_empty_drawings(int add_num);
+  bool insert_blank_frame(blender::bke::greasepencil::Layer &layer,
+                          int frame_number,
+                          int duration,
+                          eBezTriple_KeyframeType keytype);
+
   void remove_drawing(int index);
 
   void foreach_visible_drawing(