Introduce "invalid" text controls.

* MarkAsInvalid is used to enable or disable the mark
* The B_INVALID BControlLook flag is used
* invalid BTextControls are drawn with a red border.
* You ar encouraged to let the user know more precisely what's wrong, by
showing an helpful error message next to the control or in a tooltip.

headers/os/interface/ControlLook.h

@@ -84,8 +84,9 @@ public:
 		B_IGNORE_OUTLINE		= 1 << 6,
 		B_PARTIALLY_ACTIVATED	= 1 << 7, // like B_ACTIVATED, but for tri-state
 		B_FLAT					= 1 << 8, // flat look (e.g. button background)
+		B_INVALID				= 1 << 9, // invalid value, use B_FAILURE_COLOR
 
-		B_BLEND_FRAME		= 1 << 16
+		B_BLEND_FRAME			= 1 << 16,
 	};
 
 	virtual BAlignment			DefaultLabelAlignment() const;

headers/os/interface/TextControl.h

@@ -40,6 +40,7 @@ public:
 
 	virtual	void				SetText(const char* text);
 			const char*			Text() const;
+			void				MarkAsInvalid(bool invalid);
 
 	virtual	void				SetValue(int32 value);
 	virtual	status_t			Invoke(BMessage* message = NULL);
@@ -139,8 +140,9 @@ private:
 			float				fDivider;
 
 			LayoutData*			fLayoutData;
+			uint32				fLook;
 
-			uint32				_reserved[9];
+			uint32				_reserved[8];
 };
 
 #endif	// _TEXT_CONTROL_H