Speed up a little drawing of UVs in the Image Editor

In my tests the previous loop was running in 200 ms. With this change it now runs in 17 ms.

The difference in the end is still not great because the `draw_uvs_lineloop_bmface` function is called for each face and has an ImmBegin and ImmEnd in the function itself

1 files changed, 45 insertions, 42 deletions

diff --git a/source/blender/editors/uvedit/uvedit_draw.c b/source/blender/editors/uvedit/uvedit_draw.c
index db6f2c27623..ff803b9f1ba 100644
--- a/source/blender/editors/uvedit/uvedit_draw.c
+++ b/source/blender/editors/uvedit/uvedit_draw.c
@@ -622,7 +622,7 @@ static void draw_uvs(SpaceImage *sima, Scene *scene, ViewLayer *view_layer, Obje
 
 	const int cd_loop_uv_offset  = CustomData_get_offset(&bm->ldata, CD_MLOOPUV);
 
-	unsigned int pos;
+	unsigned int pos, color;
 
 	efa_act = EDBM_uv_active_face_get(em, false, false); /* will be set to NULL if hidden */
 	ts = scene->toolsettings;
@@ -671,58 +671,61 @@ static void draw_uvs(SpaceImage *sima, Scene *scene, ViewLayer *view_layer, Obje
 	if (sima->flag & SI_DRAW_STRETCH) {
 		draw_uvs_stretch(sima, scene, em, efa_act);
 	}
-	else if (!(sima->flag & SI_NO_DRAWFACES)) {
-		/* draw transparent faces */
-		UI_GetThemeColor4ubv(TH_FACE, col1);
-		UI_GetThemeColor4ubv(TH_FACE_SELECT, col2);
-		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-		glEnable(GL_BLEND);
-		
-		pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
-
-		immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
-
-		for (unsigned int i = 0; i < em->tottri; i++) {
-			efa = em->looptris[i][0]->f;
+	else {
+		unsigned int tri_count = 0;
+		BM_ITER_MESH(efa, &iter, bm, BM_FACES_OF_MESH) {
 			if (uvedit_face_visible_test(scene, ima, efa)) {
-				const bool is_select = uvedit_face_select_test(scene, efa, cd_loop_uv_offset);
 				BM_elem_flag_enable(efa, BM_ELEM_TAG);
-
-				if (efa == efa_act) {
-					/* only once */
-					immUniformThemeColor(TH_EDITMESH_ACTIVE);
-				}
-				else {
-					immUniformColor4ubv(is_select ? col2 : col1);
-				}
-
-				immBegin(GWN_PRIM_TRIS, (em->looptris[i][0]->f->len - 2) * 3);
-				draw_uvs_looptri(em, &i, cd_loop_uv_offset, pos);
-				immEnd();
+				tri_count += efa->len - 2;
 			}
 			else {
 				BM_elem_flag_disable(efa, BM_ELEM_TAG);
 			}
 		}
 
-		immUnbindProgram();
+		if (!(sima->flag & SI_NO_DRAWFACES)) {
+			/* draw transparent faces */
+			UI_GetThemeColor4ubv(TH_FACE, col1);
+			UI_GetThemeColor4ubv(TH_FACE_SELECT, col2);
+			glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+			glEnable(GL_BLEND);
 
-		glDisable(GL_BLEND);
-	}
-	else {
-		/* would be nice to do this within a draw loop but most below are optional, so it would involve too many checks */
-		
-		BM_ITER_MESH (efa, &iter, bm, BM_FACES_OF_MESH) {
-			if (uvedit_face_visible_test(scene, ima, efa)) {
-				BM_elem_flag_enable(efa, BM_ELEM_TAG);
+			Gwn_VertFormat *format = immVertexFormat();
+			pos = GWN_vertformat_attr_add(format, "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
+			color = GWN_vertformat_attr_add(format, "color", GWN_COMP_U8, 4, GWN_FETCH_INT_TO_FLOAT_UNIT);
+
+			immBindBuiltinProgram(GPU_SHADER_2D_FLAT_COLOR);
+
+			immBegin(GWN_PRIM_TRIS, tri_count * 3);
+			for (unsigned int i = 0; i < em->tottri; i++) {
+				efa = em->looptris[i][0]->f;
+				if (BM_elem_flag_test(efa, BM_ELEM_TAG)) {
+					const bool is_select = uvedit_face_select_test(scene, efa, cd_loop_uv_offset);
+
+					if (efa == efa_act) {
+						/* only once */
+						unsigned char tmp_col[4];
+						UI_GetThemeColor4ubv(TH_EDITMESH_ACTIVE, tmp_col);
+						immAttrib4ubv(color, tmp_col);
+					}
+					else {
+						immAttrib4ubv(color, is_select ? col2 : col1);
+					}
+
+					draw_uvs_looptri(em, &i, cd_loop_uv_offset, pos);
+				}
 			}
-			else {
-				if (efa == efa_act)
-					efa_act = NULL;
-				BM_elem_flag_disable(efa, BM_ELEM_TAG);
+			immEnd();
+
+			immUnbindProgram();
+
+			glDisable(GL_BLEND);
+		}
+		else {
+			if (efa_act && !uvedit_face_visible_test(scene, ima, efa_act)) {
+				efa_act = NULL;
 			}
 		}
-		
 	}
 
 	/* 3. draw active face stippled */
@@ -813,7 +816,7 @@ static void draw_uvs(SpaceImage *sima, Scene *scene, ViewLayer *view_layer, Obje
 
 				Gwn_VertFormat *format = immVertexFormat();
 				pos = GWN_vertformat_attr_add(format, "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
-				unsigned int color = GWN_vertformat_attr_add(format, "color", GWN_COMP_U8, 4, GWN_FETCH_INT_TO_FLOAT_UNIT);
+				color = GWN_vertformat_attr_add(format, "color", GWN_COMP_U8, 4, GWN_FETCH_INT_TO_FLOAT_UNIT);
 
 				if (interpedges) {
 					immBindBuiltinProgram(GPU_SHADER_2D_SMOOTH_COLOR);