2.5: Texture buttons preview now has an option to display the

texture, the material, or both side by side.

source/blender/editors/interface/interface_widgets.c

@@ -2052,11 +2052,11 @@ static void widget_draw_extra_mask(const bContext *C, uiBut *but, uiWidgetType *
 	
 	if(but->block->drawextra) {
 		/* note: drawextra can change rect +1 or -1, to match round errors of existing previews */
-		but->block->drawextra(C, but->poin, rect);
+		but->block->drawextra(C, but->poin, but->block->drawextra_arg, rect);
 		
 		/* make mask to draw over image */
 		UI_GetThemeColor3ubv(TH_BACK, col);
-		glColor3ubv(col);
+		glColor3ubv((unsigned char*)col);
 		
 		round_box__edges(&wtb, 15, rect, 0.0f, 4.0);
 		widgetbase_outline(&wtb);