Added TODO about revising the dirty system

gui/gui.c

@@ -140,6 +140,10 @@ typedef struct GUI_Node {
 	GUI_Size semantic_size[GUI_AXIS2_COUNT];
 	// TODO(Zelaven): This needs a better name.
 	// True iff. it (and its children) should generate draw commands.
+	// TODO(Zelaven): Should I make it a flags field, which encodes dirty-reasons?
+	// The "dirty test" would be "dirty != 0", and each bit in the field would be
+	//  a reason that other code can use to figure out why a node was dirtied.
+	//  Multiple reasons for a decision can all be checked in one go as well.
 	bool dirty;
 
 	// NOTE(Zelaven): Don't make decisions about visual things based on this.