* unified application of style into a separate method _ApplyStyleRange()

in order to maintain the null-style appropriately, if required
* finally fix #3040 for real (a single style is now maintained at all times
  for non-stylable textviews)
* the caret is now being drawn with the correct size, even if it is on
  the empty line at the end of the buffer and a specific font size has been
  requested


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@30532 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/interface/TextView.h

@@ -362,6 +362,13 @@ private:
 			void				_SetRunArray(int32 startOffset, int32 endOffset,
 									const text_run_array* inRuns);
 
+			void				_ApplyStyleRange(int32 fromOffset,
+									int32 toOffset,
+									uint32 inMode = B_FONT_ALL,
+									const BFont *inFont = NULL,
+									const rgb_color *inColor = NULL,
+									bool syncNullStyle = true);
+
 			uint32				_CharClassification(int32 offset) const;
 			int32				_NextInitialByte(int32 offset) const;
 			int32				_PreviousInitialByte(int32 offset) const;
@@ -385,6 +392,8 @@ private:
 			int32				_LineAt(const BPoint& point) const;
 			bool				_IsOnEmptyLastLine(int32 offset) const;
 
+			float				_NullStyleHeight() const;
+
 			BPrivate::TextGapBuffer*	fText;
 			LineBuffer*			fLines;
 			StyleBuffer*		fStyles;