GPencil: Improve drawing feeling in big files

When drawing in big files, the first points of the stroke were not smooth because the system was doing a copy of the depsgraph datablock.

Now, the depsgraph is not updated at the beginning and the feeling is far better, especially for big files.

To avoid the copy, the original datablock is used while drawing, because it's faster the lookup of the original data, than a full datablock copy.

Also some cleanup of the code.

2 files changed, 24 insertions, 16 deletions

diff --git a/source/blender/draw/engines/gpencil/gpencil_engine.c b/source/blender/draw/engines/gpencil/gpencil_engine.c
index 1cc493dd8f5..3a74e44836d 100644
--- a/source/blender/draw/engines/gpencil/gpencil_engine.c
+++ b/source/blender/draw/engines/gpencil/gpencil_engine.c
@@ -617,9 +617,20 @@ void GPENCIL_cache_populate(void *vedata, Object *ob)
 		}
 
 		/* draw current painting strokes
-		 * (only if region is equal to originated paint region) */
+		 * (only if region is equal to originated paint region)
+		 *
+		 * Need to use original data because to use the copy of data, the paint
+		 * operator must update depsgraph and this makes that first events of the
+		 * mouse are missed if the datablock is very big due the time required to
+		 * copy the datablock. The search of the original data is faster than a
+		 * full datablock copy.
+		 * Using the original data doesn't require a copy and the feel when drawing
+		 * is far better.
+		 */
+
+		bGPdata *gpd_orig = (bGPdata *)DEG_get_original_id(&gpd->id);
 		if ((draw_ctx->obact == ob) &&
-		    ((gpd->runtime.ar == NULL) || (gpd->runtime.ar == draw_ctx->ar)))
+			((gpd_orig->runtime.ar == NULL) || (gpd_orig->runtime.ar == draw_ctx->ar)))
 		{
 			DRW_gpencil_populate_buffer_strokes(&e_data, vedata, ts, ob);
 		}
diff --git a/source/blender/editors/gpencil/gpencil_paint.c b/source/blender/editors/gpencil/gpencil_paint.c
index b66956b090d..d544bd8f9b6 100644
--- a/source/blender/editors/gpencil/gpencil_paint.c
+++ b/source/blender/editors/gpencil/gpencil_paint.c
@@ -1708,6 +1708,9 @@ static void gp_session_validatebuffer(tGPsdata *p)
 	/* reset flags */
 	gpd->runtime.sbuffer_sflag = 0;
 
+	/* reset region */
+	gpd->runtime.ar = NULL;
+
 	/* reset inittime */
 	p->inittime = 0.0;
 
@@ -1784,11 +1787,12 @@ static void gp_init_drawing_brush(bContext *C, tGPsdata *p)
 	ToolSettings *ts = CTX_data_tool_settings(C);
 
 	Paint *paint = &ts->gp_paint->paint;
-
+	bool changed = false;
 	/* if not exist, create a new one */
 	if (paint->brush == NULL) {
 		/* create new brushes */
 		BKE_brush_gpencil_presets(C);
+		changed = true;
 	}
 	/* be sure curves are initializated */
 	curvemapping_initialize(paint->brush->gpencil_settings->curve_sensitivity);
@@ -1813,7 +1817,9 @@ static void gp_init_drawing_brush(bContext *C, tGPsdata *p)
 	 * Maybe this update can be removed when the new tool system
 	 * will be in place, but while, we need this to keep drawing working.
 	 */
-	DEG_id_tag_update(&scene->id, ID_RECALC_COPY_ON_WRITE);
+	if (changed) {
+		DEG_id_tag_update(&scene->id, ID_RECALC_COPY_ON_WRITE);
+	}
 }
 
 
@@ -1946,13 +1952,6 @@ static bool gp_session_initdata(bContext *C, wmOperator *op, tGPsdata *p)
 		p->gpd = *gpd_ptr;
 	}
 
-	if (ED_gpencil_session_active() == 0) {
-		/* initialize undo stack,
-		 * also, existing undo stack would make buffer drawn
-		 */
-		gpencil_undo_init(p->gpd);
-	}
-
 	/* clear out buffer (stored in gp-data), in case something contaminated it */
 	gp_session_validatebuffer(p);
 
@@ -1961,6 +1960,9 @@ static bool gp_session_initdata(bContext *C, wmOperator *op, tGPsdata *p)
 
 	/* setup active color */
 	if (curarea->spacetype == SPACE_VIEW3D) {
+		/* region where paint was originated */
+		p->gpd->runtime.ar = CTX_wm_region(C);
+
 		/* NOTE: This is only done for 3D view, as Materials aren't used for
 		 *       annotations in 2D editors
 		 */
@@ -1984,9 +1986,6 @@ static bool gp_session_initdata(bContext *C, wmOperator *op, tGPsdata *p)
 		p->lock_axis = 0;
 	}
 
-	/* region where paint was originated */
-	p->gpd->runtime.ar = CTX_wm_region(C);
-
 	return 1;
 }
 
@@ -2134,8 +2133,6 @@ static void gp_paint_initstroke(tGPsdata *p, eGPencil_PaintModes paintmode, Deps
 			add_frame_mode = GP_GETFRAME_ADD_NEW;
 
 		p->gpf = BKE_gpencil_layer_getframe(p->gpl, cfra_eval, add_frame_mode);
-		/* set as dirty draw manager cache */
-		gp_update_cache(p->gpd);
 
 		if (p->gpf == NULL) {
 			p->status = GP_STATUS_ERROR;