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BCB 1.0 & 3.0 TRichEdit bugs

Obvious VCL Bugs

As best I recall, the specific Windows messages that were problems were:

BCB 1.0 has a number of bugs.  New Windows API messages were added to take advantage of the large amount of text that a Rich Edit control can handle.  The BCB 1.0 TRichEdit used the older messages and, therefore, could not handle large documents properly.

Message BCB 1.0 used

Message that should have been used









These messages work fine for small documents but, if you want to use BCB 1.0 TRichEdit controls with large text files, you will need to write your own code to set or get the current selection, set the maximum amount of text the control can hold, get the line number from an offset position in the text, and find text in the control.

Most of these appear to be fixed in BCB 3.0.  However, both BCB 1.0 and 3.0 use the EM_FINDTEXT message instead of the EM_FINDTEXTEX message to implement the FindText() method.  I am somewhat unclear on whether this is a problem.  If it is, you will need to write your own routine to use EM_FINDTEXTEX.

Another Type Of Bug

So much for VCL code that clearly has bugs.  There is another type of bug that falls into the "unexpected behavior" or "unnecessary limitation" or "might be a feature" category.

The first of these has to do with the undocumented fact that the VCL occasionally deletes and re-creates the TRichEdit control's underlying Windows Rich Edit.  See the paper titled " Window handles vs. TRichEdit (and other VCL) controls" available on this site for more information.  If you have not read this paper, please do -- otherwise, you are almost guaranteed to spend many hours chasing this one down.

A second might-be-a-feature-but-is-a-bug-to-me has to do with the non-granularity of text styles.  Ok, that phrasing is more than a little obscure.  What I mean is this:  If you change a text style say, to italics, any other styles in the selected text are lost.  For example, assume that you have selected text that looks like this:

this is normal text, this is bold text, this is underlined text

To add the italics style to the text, you might try to use code something like this:

RichEdit1->SelAttributes->Style = RichEdit1->SelAttributes << fsItalic;

The resulting text would look like this:

this is normal text, this is bold text, this is underlined text

instead of like this:

this is normal text, this is bold text, this is underlined text

Ok....  What happened?  Well, the style returned by RichEdit1->SelAttributes was the style of the first character in the selected range (in this case, normal text, no bold or underlined attributes).  The code then added the fsItalic attribute to the returned value and then applies this combination of attributes to the selected text.

I would prefer -- actually, I expected -- the bold and underlined text remain bold and underlined with the italics added.  Obviously not.  Had the VCL treated each style as a separate property, this would work as I would want and expected it to work.

Unfortunately, since the VCL treats all of the styles as a single property, this is not what you get.  The Rich Edit 2.0 sample code on this site demonstrates how to get around this unnecessary limitation.  Although written for BCB 3.0+, the relevant code should easily back-port to BCB 1.0.

Finally -- True Rich Edit Bugs

Rich Edit controls definitely have a bug or two.  Some of these are difficult to classify as true Microsoft Rich Edit control bugs, mainly because the Borland VCL does some strange things and I do not have the time to trace through all of the code.  On the other hand, much of the code that I have written to handle Rich Edit controls bypasses the VCL for exactly that reason.  These are bugs that I am all but certain are true Rich Edit bugs.

The only case that I will cite here (because of the uncertainty factor) is this:  If you have text that is "normal" and underlined to the left of italicized text that is not underlined, the text is drawn to the screen with extra space after the italicized text.  For example, text that should be formatted as:

this text contains the word "synchronicity" which is drawn oddly

is drawn as:

this text contains the word "synch ronicity" which is drawn oddly

Note the extra underlined space in the middle of the word "synchronicity."  This bug appears both when the text is displayed in the control (although it seems to occur only after formatting the text for a preview with the EM_FORMATRANGE message) and when the text is drawn on the screen for a preview (which implies that you have already formatted the text with the EM_FORMATRANGE message).  Oddly, the text prints exactly as it should. I do not yet have a work-around for this one.

If you spend much time with Rich Edit controls, you will almost certainly find other VCL and true Rich Edit bugs.  If you find more, please send me sample code that clearly demonstrates the bug so that we can save others a little time.  If you have workarounds, please share them, too.

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