Fix T47204: selection failing directly after disabling multisample in user prefs.

Now store the multisample setting each window was created with.

source/blender/blenloader/intern/readfile.c

@@ -6060,9 +6060,12 @@ static void direct_link_windowmanager(FileData *fd, wmWindowManager *wm)
 		win->drawfail = 0;
 		win->active = 0;
 
-		win->cursor      = 0;
-		win->lastcursor  = 0;
-		win->modalcursor = 0;
+		win->cursor       = 0;
+		win->lastcursor   = 0;
+		win->modalcursor  = 0;
+		win->grabcursor   = 0;
+		win->addmousemove = 0;
+		win->multisamples = 0;
 		win->stereo3d_format = newdataadr(fd, win->stereo3d_format);
 
 		/* multiview always fallback to anaglyph at file opening

source/blender/editors/include/ED_view3d.h

@@ -74,6 +74,7 @@ typedef struct ViewContext {
 	struct Object *obedit;
 	struct ARegion *ar;
 	struct View3D *v3d;
+	struct wmWindow *win;
 	struct RegionView3D *rv3d;
 	struct BMEditMesh *em;
 	int mval[2];

source/blender/editors/space_view3d/view3d_draw.c

@@ -1310,7 +1310,7 @@ static void drawviewborder(Scene *scene, ARegion *ar, View3D *v3d)
 
 /* *********************** backdraw for selection *************** */
 
-static void backdrawview3d(Scene *scene, ARegion *ar, View3D *v3d)
+static void backdrawview3d(Scene *scene, wmWindow *win, ARegion *ar, View3D *v3d)
 {
 	RegionView3D *rv3d = ar->regiondata;
 	struct Base *base = scene->basact;
@@ -1365,7 +1365,7 @@ static void backdrawview3d(Scene *scene, ARegion *ar, View3D *v3d)
 	if (multisample_enabled)
 		glDisable(GL_MULTISAMPLE);
 
-	if (U.ogl_multisamples != USER_MULTISAMPLE_NONE) {
+	if (win->multisamples != USER_MULTISAMPLE_NONE) {
 		/* for multisample we use an offscreen FBO. multisample drawing can fail
 		 * with color coded selection drawing, and reading back depths from such
 		 * a buffer can also cause a few seconds freeze on OS X / NVidia. */
@@ -1456,7 +1456,7 @@ static void view3d_opengl_read_Z_pixels(ARegion *ar, int x, int y, int w, int h,
 void ED_view3d_backbuf_validate(ViewContext *vc)
 {
 	if (vc->v3d->flag & V3D_INVALID_BACKBUF)
-		backdrawview3d(vc->scene, vc->ar, vc->v3d);
+		backdrawview3d(vc->scene, vc->win, vc->ar, vc->v3d);
 }
 
 /**
@@ -3830,6 +3830,7 @@ static void update_lods(Scene *scene, float camera_pos[3])
 static void view3d_main_region_draw_objects(const bContext *C, Scene *scene, View3D *v3d,
                                           ARegion *ar, const char **grid_unit)
 {
+	wmWindow *win = CTX_wm_window(C);
 	RegionView3D *rv3d = ar->regiondata;
 	unsigned int lay_used = v3d->lay_used;
 	
@@ -3883,7 +3884,7 @@ static void view3d_main_region_draw_objects(const bContext *C, Scene *scene, Vie
 	view3d_main_region_clear(scene, v3d, ar);
 
 	/* enables anti-aliasing for 3D view drawing */
-	if (U.ogl_multisamples != USER_MULTISAMPLE_NONE) {
+	if (win->multisamples != USER_MULTISAMPLE_NONE) {
 		glEnable(GL_MULTISAMPLE);
 	}
 
@@ -3896,7 +3897,7 @@ static void view3d_main_region_draw_objects(const bContext *C, Scene *scene, Vie
 	}
 
 	/* Disable back anti-aliasing */
-	if (U.ogl_multisamples != USER_MULTISAMPLE_NONE) {
+	if (win->multisamples != USER_MULTISAMPLE_NONE) {
 		glDisable(GL_MULTISAMPLE);
 	}
 

source/blender/editors/space_view3d/view3d_select.c

@@ -108,6 +108,7 @@ void view3d_set_viewcontext(bContext *C, ViewContext *vc)
 	vc->ar = CTX_wm_region(C);
 	vc->scene = CTX_data_scene(C);
 	vc->v3d = CTX_wm_view3d(C);
+	vc->win = CTX_wm_window(C);
 	vc->rv3d = CTX_wm_region_view3d(C);
 	vc->obact = CTX_data_active_object(C);
 	vc->obedit = CTX_data_edit_object(C);

source/blender/makesdna/DNA_windowmanager_types.h

@@ -190,6 +190,8 @@ typedef struct wmWindow {
 	short modalcursor;  /* the current modal cursor */
 	short grabcursor;           /* cursor grab mode */
 	short addmousemove; /* internal: tag this for extra mousemove event, makes cursors/buttons active on UI switching */
+	short multisamples; /* amount of samples for OpenGL FSA the ghost window was created with, if zero no FSA */
+	short pad[3];
 
 	int winid;                  /* winid also in screens, is for retrieving this window after read */
 

source/blender/windowmanager/intern/wm_files.c

@@ -182,6 +182,7 @@ static void wm_window_match_init(bContext *C, ListBase *wmlist)
 static void wm_window_substitute_old(wmWindowManager *wm, wmWindow *oldwin, wmWindow *win)
 {
 	win->ghostwin = oldwin->ghostwin;
+	win->multisamples = oldwin->multisamples;
 	win->active = oldwin->active;
 	if (win->active)
 		wm->winactive = win;
@@ -190,6 +191,7 @@ static void wm_window_substitute_old(wmWindowManager *wm, wmWindow *oldwin, wmWi
 		GHOST_SetWindowUserData(win->ghostwin, win);    /* pointer back */
 
 	oldwin->ghostwin = NULL;
+	oldwin->multisamples = 0;
 
 	win->eventstate = oldwin->eventstate;
 	oldwin->eventstate = NULL;

source/blender/windowmanager/intern/wm_window.c

@@ -163,6 +163,7 @@ static void wm_ghostwindow_destroy(wmWindow *win)
 	if (win->ghostwin) {
 		GHOST_DisposeWindow(g_system, win->ghostwin);
 		win->ghostwin = NULL;
+		win->multisamples = 0;
 	}
 }
 
@@ -433,6 +434,9 @@ static void wm_window_ghostwindow_add(wmWindowManager *wm, const char *title, wm
 		if (win->eventstate == NULL)
 			win->eventstate = MEM_callocN(sizeof(wmEvent), "window event state");
 
+		/* store multisamples window was created with, in case user prefs change */
+		win->multisamples = multisamples;
+		
 		/* store actual window size in blender window */
 		bounds = GHOST_GetClientBounds(win->ghostwin);
 		win->sizex = GHOST_GetWidthRectangle(bounds);