[Bf-codereview] Fixes for a couple brush icon problems (bug #26590) (issue4356045)

[NicholasBishop at gmail.com]

Reviewers: bf-codereview_blender.org,

Description:
Here's the original report:
http://projects.blender.org/tracker/?func=detail&aid=26590&group_id=9&atid=498

Seems that when a custom brush icon was set, the preview was being
regenerated over and over, which prevented other preview jobs from
running. Fixed by not calling BKE_icon_changed every time when calling
get_brush_icon().

Additionally, changing the brush icon path from a valid image path to
empty, or to an invalid path, would leave the original image there.
Fixed by the memsetting the preview before returning.

Please review this at http://codereview.appspot.com/4356045/

Affected files:
   source/blender/editors/render/render_preview.c


Index: source/blender/editors/render/render_preview.c
===================================================================
--- source/blender/editors/render/render_preview.c	(revision 35974)
+++ source/blender/editors/render/render_preview.c	(working copy)
@@ -135,14 +135,15 @@
  					if (path[0])
  						brush->icon_imbuf= IMB_loadiffname(path, flags);
  				}
+
+				if (brush->icon_imbuf)
+					BKE_icon_changed(BKE_icon_getid(&brush->id));
  			}
  		}
  	}

  	if (!(brush->icon_imbuf))
  		brush->id.icon_id = 0;
-	else
-		BKE_icon_changed(BKE_icon_getid(&(brush->id)));

  	return brush->icon_imbuf;
  }
@@ -1247,10 +1248,11 @@

  		br->icon_imbuf= get_brush_icon(br);

+		memset(sp->pr_rect, 0x888888, sp->sizex*sp->sizey*sizeof(unsigned int));
+
  		if(!(br->icon_imbuf) || !(br->icon_imbuf->rect))
  			return;

-		memset(sp->pr_rect, 0x888888, sp->sizex*sp->sizey*sizeof(unsigned int));
  		icon_copy_rect(br->icon_imbuf, sp->sizex, sp->sizey, sp->pr_rect);

  		*do_update= 1;