GPencil: "Add Blank Frame" operator (D+B)

This operator adds a new frame with nothing in it on the current frame.
If there is already a frame there, all existing frames are shifted one frame later.

Quite often when animating, you may want a quick way to get a blank frame,
ready to start drawing something new. Or maybe you just need a quick way to
add a "placeholder" frame so that a suddenly-appearing element does not show
up before its time.

release/scripts/startup/bl_ui/properties_grease_pencil_common.py

@@ -115,6 +115,12 @@ class GreasePencilDrawingToolsPanel:
         row.operator("gpencil.draw", icon='LINE_DATA', text="Line").mode = 'DRAW_STRAIGHT'
         row.operator("gpencil.draw", icon='MESH_DATA', text="Poly").mode = 'DRAW_POLY'
 
+        col.separator()
+
+        sub = col.column(align=True)
+        sub.operator("gpencil.blank_frame_add", icon='NEW')
+        sub.operator("gpencil.active_frames_delete_all", icon='X', text="Delete Frame(s)")
+
         sub = col.column(align=True)
         sub.prop(context.tool_settings, "use_gpencil_additive_drawing", text="Additive Drawing")
         sub.prop(context.tool_settings, "use_gpencil_continuous_drawing", text="Continuous Drawing")

source/blender/editors/gpencil/gpencil_edit.c

@@ -682,6 +682,80 @@ void GPENCIL_OT_move_to_layer(wmOperatorType *ot)
 	RNA_def_enum_funcs(ot->prop, ED_gpencil_layers_with_new_enum_itemf);
 }
 
+/* ********************* Add Blank Frame *************************** */
+
+/* Basically the same as the drawing op */
+static int gp_blank_frame_add_poll(bContext *C)
+{
+	if (ED_operator_regionactive(C)) {
+		/* check if current context can support GPencil data */
+		if (ED_gpencil_data_get_pointers(C, NULL) != NULL) {
+			return 1;
+		}
+		else {
+			CTX_wm_operator_poll_msg_set(C, "Failed to find Grease Pencil data to draw into");
+		}
+	}
+	else {
+		CTX_wm_operator_poll_msg_set(C, "Active region not set");
+	}
+	
+	return 0;
+}
+
+static int gp_blank_frame_add_exec(bContext *C, wmOperator *UNUSED(op))
+{
+	Scene *scene = CTX_data_scene(C);
+	bGPdata *gpd = ED_gpencil_data_get_active(C);
+	bGPDlayer *gpl = BKE_gpencil_layer_getactive(gpd);
+	
+	/* Initialise datablock and an active layer if nothing exists yet */
+	if (ELEM(NULL, gpd, gpl)) {
+		/* let's just be lazy, and call the "Add New Layer" operator, which sets everything up as required */
+		WM_operator_name_call(C, "GPENCIL_OT_layer_add", WM_OP_EXEC_DEFAULT, NULL);
+	}
+	
+	/* Go through each layer, adding a frame after the active one 
+	 * and/or shunting all the others out of the way
+	 */
+	CTX_DATA_BEGIN(C, bGPDlayer *, gpl, editable_gpencil_layers)
+	{
+		/* 1) Check for an existing frame on the current frame */
+		bGPDframe *gpf = BKE_gpencil_layer_find_frame(gpl, CFRA);
+		if (gpf) {
+			/* Shunt all frames after (and including) the existing one later by 1-frame */
+			for (; gpf; gpf = gpf->next) {
+				gpf->framenum += 1;
+			}
+		}
+		
+		/* 2) Now add a new frame, with nothing in it */
+		gpl->actframe = BKE_gpencil_layer_getframe(gpl, CFRA, GP_GETFRAME_ADD_NEW);
+	}
+	CTX_DATA_END;
+	
+	/* notifiers */
+	WM_event_add_notifier(C, NC_GPENCIL | ND_DATA | NA_EDITED, NULL);
+	
+	return OPERATOR_FINISHED;
+}
+
+void GPENCIL_OT_blank_frame_add(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Add Blank Frame";
+	ot->idname = "GPENCIL_OT_blank_frame_add";
+	ot->description = "Add a new frame with nothing in it on the current frame. "
+	                  "If there is already a frame, all existing frames are shifted one frame later";
+	
+	/* callbacks */
+	ot->exec = gp_blank_frame_add_exec;
+	ot->poll = gp_add_poll;
+	
+	/* properties */
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+}
+
 /* ******************* Delete Active Frame ************************ */
 
 static int gp_actframe_delete_poll(bContext *C)

source/blender/editors/gpencil/gpencil_intern.h

@@ -287,6 +287,8 @@ void GPENCIL_OT_unlock_all(struct wmOperatorType *ot);
 void GPENCIL_OT_layer_isolate(struct wmOperatorType *ot);
 void GPENCIL_OT_layer_merge(struct wmOperatorType *ot);
 
+void GPENCIL_OT_blank_frame_add(struct wmOperatorType *ot);
+
 void GPENCIL_OT_active_frame_delete(struct wmOperatorType *ot);
 void GPENCIL_OT_active_frames_delete_all(struct wmOperatorType *ot);
 

source/blender/editors/gpencil/gpencil_ops.c

@@ -102,6 +102,10 @@ static void ed_keymap_gpencil_general(wmKeyConfig *keyconf)
 	WM_keymap_add_menu_pie(keymap, "GPENCIL_PIE_tool_palette", QKEY, KM_PRESS, 0, DKEY);
 	WM_keymap_add_menu_pie(keymap, "GPENCIL_PIE_settings_palette", WKEY, KM_PRESS, 0, DKEY);
 	
+	/* Add Blank Frame */
+	/* XXX: BKEY or NKEY? BKEY is easier to reach from DKEY, so we'll use that for now */
+	WM_keymap_add_item(keymap, "GPENCIL_OT_blank_frame_add", BKEY, KM_PRESS, 0, DKEY);
+	
 	/* Delete Active Frame - For easier video tutorials/review sessions */
 	/* NOTE: This works even when not in EditMode */
 	WM_keymap_add_item(keymap, "GPENCIL_OT_active_frames_delete_all", XKEY, KM_PRESS, 0, DKEY);
@@ -401,6 +405,8 @@ void ED_operatortypes_gpencil(void)
 	WM_operatortype_append(GPENCIL_OT_layer_isolate);
 	WM_operatortype_append(GPENCIL_OT_layer_merge);
 
+	WM_operatortype_append(GPENCIL_OT_blank_frame_add);
+	
 	WM_operatortype_append(GPENCIL_OT_active_frame_delete);
 	WM_operatortype_append(GPENCIL_OT_active_frames_delete_all);