Modifications to the view3d.select() operator:

1. Two new boolean options have been added to the operator: "deselect"
   and "toggle".
2. The previous behavior of "extend" (toggling the selection) has
   been moved to the "toggle" option.
3. "extend" now only extends the selection, it never deselects.
4. "deselect" is pretty self-explanatory: it deselects (i.e. opposite
   of extend).
5. The built-in keymap has been changed to use "toggle" where
   "extend" was used before for this operator, to maintain the
   previous behavior in the default keymap.

In short, this works towards making "extend" and "deselect" fully
consistent across all selection tools (adding to and removing from
selection, respectively), but still preserves the old behavior
as well.

(Patch reviewed by Brecht.)

2 files changed, 66 insertions, 13 deletions

diff --git a/source/blender/editors/mesh/editface.c b/source/blender/editors/mesh/editface.c
index 3da2b4711f3..b592449fff5 100644
--- a/source/blender/editors/mesh/editface.c
+++ b/source/blender/editors/mesh/editface.c
@@ -509,7 +509,7 @@ void seam_mark_clear_tface(Scene *scene, short mode)
 }
 #endif
 
-int paintface_mouse_select(struct bContext *C, Object *ob, const int mval[2], int extend)
+int paintface_mouse_select(struct bContext *C, Object *ob, const int mval[2], int extend, int deselect, int toggle)
 {
 	Mesh *me;
 	MPoly *mpoly, *mpoly_sel;
@@ -530,7 +530,7 @@ int paintface_mouse_select(struct bContext *C, Object *ob, const int mval[2], in
 	/* clear flags */
 	mpoly = me->mpoly;
 	a = me->totpoly;
-	if (!extend) {
+	if (!extend && !deselect && !toggle) {
 		while (a--) {
 			mpoly->flag &= ~ME_FACE_SEL;
 			mpoly++;
@@ -540,6 +540,12 @@ int paintface_mouse_select(struct bContext *C, Object *ob, const int mval[2], in
 	me->act_face = (int)index;
 
 	if (extend) {
+		mpoly_sel->flag |= ME_FACE_SEL;
+	}
+	else if (deselect) {
+		mpoly_sel->flag &= ~ME_FACE_SEL;
+	}
+	else if (toggle) {
 		if (mpoly_sel->flag & ME_FACE_SEL)
 			mpoly_sel->flag &= ~ME_FACE_SEL;
 		else
diff --git a/source/blender/editors/mesh/editmesh_select.c b/source/blender/editors/mesh/editmesh_select.c
index 55f575bbdea..0a8fe142aaf 100644
--- a/source/blender/editors/mesh/editmesh_select.c
+++ b/source/blender/editors/mesh/editmesh_select.c
@@ -1454,7 +1454,7 @@ void MESH_OT_select_shortest_path(wmOperatorType *ot)
 /* ************************************************** */
 /* here actual select happens */
 /* gets called via generic mouse select operator */
-int mouse_mesh(bContext *C, const int mval[2], short extend)
+int mouse_mesh(bContext *C, const int mval[2], short extend, short deselect, short toggle)
 {
 	ViewContext vc;
 	BMVert *eve = NULL;
@@ -1468,40 +1468,87 @@ int mouse_mesh(bContext *C, const int mval[2], short extend)
 	
 	if (unified_findnearest(&vc, &eve, &eed, &efa)) {
 		
-		if (extend == 0) EDBM_flag_disable_all(vc.em, BM_ELEM_SELECT);
+		// Deselect everything
+		if (extend == 0 && deselect == 0 && toggle == 0)
+			EDBM_flag_disable_all(vc.em, BM_ELEM_SELECT);
 		
 		if (efa) {
-			/* set the last selected face */
-			BM_active_face_set(vc.em->bm, efa);
-			
-			if (!BM_elem_flag_test(efa, BM_ELEM_SELECT)) {
+			if (extend) {
+				// set the last selected face
+				BM_active_face_set(vc.em->bm, efa);
+				
+				// Work-around: deselect first, so we can guarantee it will
+				// be active even if it was already selected
+				BM_select_history_remove(vc.em->bm, efa);
+				BM_face_select_set(vc.em->bm, efa, FALSE);
 				BM_select_history_store(vc.em->bm, efa);
 				BM_face_select_set(vc.em->bm, efa, TRUE);
 			}
-			else if (extend) {
+			else if (deselect) {
 				BM_select_history_remove(vc.em->bm, efa);
 				BM_face_select_set(vc.em->bm, efa, FALSE);
 			}
+			else {
+				// set the last selected face
+				BM_active_face_set(vc.em->bm, efa);
+			
+				if (!BM_elem_flag_test(efa, BM_ELEM_SELECT)) {
+					BM_select_history_store(vc.em->bm, efa);
+					BM_face_select_set(vc.em->bm, efa, TRUE);
+				}
+				else if (toggle) {
+					BM_select_history_remove(vc.em->bm, efa);
+					BM_face_select_set(vc.em->bm, efa, FALSE);
+				}
+			}
 		}
 		else if (eed) {
-			if (!BM_elem_flag_test(eed, BM_ELEM_SELECT)) {
+			if (extend) {
+				// Work-around: deselect first, so we can guarantee it will
+				// be active even if it was already selected
+				BM_select_history_remove(vc.em->bm, eed);
+				BM_edge_select_set(vc.em->bm, eed, FALSE);
 				BM_select_history_store(vc.em->bm, eed);
 				BM_edge_select_set(vc.em->bm, eed, TRUE);
 			}
-			else if (extend) {
+			else if (deselect) {
 				BM_select_history_remove(vc.em->bm, eed);
 				BM_edge_select_set(vc.em->bm, eed, FALSE);
 			}
+			else {
+				if (!BM_elem_flag_test(eed, BM_ELEM_SELECT)) {
+					BM_select_history_store(vc.em->bm, eed);
+					BM_edge_select_set(vc.em->bm, eed, TRUE);
+				}
+				else if (toggle) {
+					BM_select_history_remove(vc.em->bm, eed);
+					BM_edge_select_set(vc.em->bm, eed, FALSE);
+				}
+			}
 		}
 		else if (eve) {
-			if (!BM_elem_flag_test(eve, BM_ELEM_SELECT)) {
+			if (extend) {
+				// Work-around: deselect first, so we can guarantee it will
+				// be active even if it was already selected
+				BM_select_history_remove(vc.em->bm, eve);
+				BM_vert_select_set(vc.em->bm, eve, FALSE);
 				BM_select_history_store(vc.em->bm, eve);
 				BM_vert_select_set(vc.em->bm, eve, TRUE);
 			}
-			else if (extend) {
+			else if (deselect) {
 				BM_select_history_remove(vc.em->bm, eve);
 				BM_vert_select_set(vc.em->bm, eve, FALSE);
 			}
+			else {
+				if (!BM_elem_flag_test(eve, BM_ELEM_SELECT)) {
+					BM_select_history_store(vc.em->bm, eve);
+					BM_vert_select_set(vc.em->bm, eve, TRUE);
+				}
+				else if (toggle) {
+					BM_select_history_remove(vc.em->bm, eve);
+					BM_vert_select_set(vc.em->bm, eve, FALSE);
+				}
+			}
 		}
 		
 		EDBM_selectmode_flush(vc.em);