* Change to the working of the left mouse select preference

Previously, the implementation of this was quite awkward, with
the preference swapping mouse buttons globally, rather than just 
selection, as is advertised on the pref. This had the effect of 
changing the painting in sculpt/texture paint/weight paint/etc to 
the left mouse button. This was totally silly, since when using a 
tablet, left mouse select is the sane way to go, but it meant 
that every time you wanted to sculpt or paint, you had to switch 
the mouse buttons around so you could actually use the tablet as 
normal.

This commit fixes that, and makes the preference do just what it 
says, use left mouse for selection (i.e. in object/edit mode) and 
only that.

source/blender/src/sculptmode.c

@@ -1700,8 +1700,7 @@ void sculpt(void)
 	mvalo[0]= mouse[0];
 	mvalo[1]= mouse[1];
 
-	if (U.flag & USER_LMOUSESELECT) mousebut = R_MOUSE;
+	mousebut = L_MOUSE;
-	else mousebut = L_MOUSE;
 
 	/* If modifier_calculations is true, then extra time must be spent
 	   updating the mesh. This takes a *lot* longer, so it's worth

source/blender/src/space.c

@@ -1131,7 +1131,7 @@ static void winqreadview3dspace(ScrArea *sa, void *spacedata, BWinEvent *evt)
 	Object *ob= OBACT;	/* do not change! */
 	float *curs;
 	int doredraw= 0, pupval;
-	unsigned short event= evt->event, origevent= evt->event;
+	unsigned short event= evt->event;
 	short val= evt->val;
 	char ascii= evt->ascii;
 	
@@ -1148,9 +1148,16 @@ static void winqreadview3dspace(ScrArea *sa, void *spacedata, BWinEvent *evt)
 		
 		/* swap mouse buttons based on user preference */
 		if (U.flag & USER_LMOUSESELECT) {
+			/* only swap mouse button for selection, in modes where it is relevant.
+			 * painting/sculpting stays on LEFTMOUSE */
+			if (   !((G.f & G_SCULPTMODE) || (G.f & G_WEIGHTPAINT) ||
+				(G.f & G_VERTEXPAINT) || (G.f & G_TEXTUREPAINT)) ||
+				(G.obedit) )
+			{			
 				if (event==LEFTMOUSE) event = RIGHTMOUSE;
 				else if (event==RIGHTMOUSE) event = LEFTMOUSE;
 			}
+		}
 
 		if(!mouse_in_header(sa)) {
 			if(!G.obedit && (G.f & G_SCULPTMODE)) {
@@ -1538,7 +1545,7 @@ static void winqreadview3dspace(ScrArea *sa, void *spacedata, BWinEvent *evt)
 					vertex_paint();
 				}
 				else if (G.f & G_TEXTUREPAINT) {
-					imagepaint_paint(origevent==LEFTMOUSE? L_MOUSE: R_MOUSE, 1);
+					imagepaint_paint(L_MOUSE, 1);
 				}
 				break;
 			case MIDDLEMOUSE:
@@ -4739,7 +4746,7 @@ static void changeimagepace(ScrArea *sa, void *spacedata)
 static void winqreadimagespace(ScrArea *sa, void *spacedata, BWinEvent *evt)
 {
 	SpaceImage *sima= spacedata;
-	unsigned short event= evt->event, origevent= evt->event;
+	unsigned short event= evt->event;
 	short val= evt->val;
 	
 	if(val==0) return;
@@ -4761,10 +4768,10 @@ static void winqreadimagespace(ScrArea *sa, void *spacedata, BWinEvent *evt)
 				scrarea_queue_winredraw(sa);
 				break;
 			case LEFTMOUSE:
-				imagepaint_paint(origevent==LEFTMOUSE? L_MOUSE: R_MOUSE, 0);
+				imagepaint_paint(L_MOUSE, 0);
 				break;
 			case RIGHTMOUSE:
-				imagepaint_pick(origevent==LEFTMOUSE? L_MOUSE: R_MOUSE);
+				imagepaint_pick(R_MOUSE);
 				break;
 		}
 	}

source/blender/src/vpaint.c

@@ -1089,7 +1089,7 @@ void weight_paint(void)
 	float vpimat[3][3];
 	int *indexar, index, totindex, alpha, totw;
 	int vgroup_mirror= -1;
-	short mval[2], mvalo[2], firsttime=1, mousebut;
+	short mval[2], mvalo[2], firsttime=1;
 
 	if((G.f & G_WEIGHTPAINT)==0) return;
 	if(G.obedit) return;
@@ -1162,9 +1162,6 @@ void weight_paint(void)
 	mvalo[0]= mval[0];
 	mvalo[1]= mval[1];
 	
-	if (U.flag & USER_LMOUSESELECT) mousebut = R_MOUSE;
-	else mousebut = L_MOUSE;
-	
 	/* if mirror painting, find the other group */
 	if(Gwp.flag & VP_MIRROR_X) {
 		bDeformGroup *defgroup= BLI_findlink(&ob->defbase, ob->actdef-1);
@@ -1190,7 +1187,7 @@ void weight_paint(void)
 		}
 	}
 	
-	while (get_mbut() & mousebut) {
+	while (get_mbut() & L_MOUSE) {
 		getmouseco_areawin(mval);
 		
 		if(firsttime || mval[0]!=mvalo[0] || mval[1]!=mvalo[1]) {
@@ -1362,7 +1359,7 @@ void vertex_paint()
 	float vpimat[3][3];
 	unsigned int paintcol=0, *mcol, *mcolorig, fcol1, fcol2;
 	int *indexar, index, alpha, totindex;
-	short mval[2], mvalo[2], firsttime=1, mousebut;
+	short mval[2], mvalo[2], firsttime=1;
 	
 	if((G.f & G_VERTEXPAINT)==0) return;
 	if(G.obedit) return;
@@ -1405,10 +1402,7 @@ void vertex_paint()
 	mvalo[0]= mval[0];
 	mvalo[1]= mval[1];
 	
-	if (U.flag & USER_LMOUSESELECT) mousebut = R_MOUSE;
+	while (get_mbut() & L_MOUSE) {
-	else mousebut = L_MOUSE;
-	
-	while (get_mbut() & mousebut) {
 		getmouseco_areawin(mval);
 		
 		if(firsttime || mval[0]!=mvalo[0] || mval[1]!=mvalo[1]) {