generally overhauled non-wrapping mode of BTextView, as it was considerably broken:

* switching from wrapping to non-wrapping mode triggers a recomputation of
  the text rect
* non-wrapping mode now triggers updating of the data rect for the horizontal 
  scrollbar as needed, fixing #4705
* corrected a couple of width computations that confused bounds and text
  rect width, leading to drawing artefacts at the end of a line
* unified computation of text rect width to always take all lines into
  account (not just the first one)
* some cleanup


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@33703 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/interface/TextView.h

@@ -292,6 +292,7 @@ private:
 									const rgb_color* initialColor);
 
 			void				_ValidateLayoutData();
+			void				_ResetTextRect();
 
 			void				_HandleBackspace();
 			void				_HandleArrowKey(uint32 inArrowKey);
@@ -301,12 +302,12 @@ private:
 									int32 numBytes);
 
 			void				_Refresh(int32 fromOffset, int32 toOffset,
-									bool erase, bool scroll);
+									bool scroll);
 			void				_RecalculateLineBreaks(int32* startLine,
 									int32* endLine);
 			int32				_FindLineBreak(int32 fromOffset,
 									float* outAscent, float* outDescent,
-									float* ioWidth);
+									float* inOutWidth);
 
 			float				_StyledWidth(int32 fromOffset, int32 length,
 									float* outAscent = NULL,
@@ -333,8 +334,7 @@ private:
 									int32 startOffset = -1,
 									bool erase = false);
 			void				_RequestDrawLines(int32 startLine,
-									int32 endLine, int32 startOffset = -1,
-									bool erase = false);
+									int32 endLine);
 
 			void				_DrawCaret(int32 offset);
 			void				_ShowCaret();