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From: Ray Mitchell on 22 Mar 2010 20:22
Hello,

I am using a RichTextBox to display many lines of text, where the characters
are of various colors. To keep the text box from getting fuller than I would
like, each time it reaches a specific number of lines I copy its contents out
to a string array, copy only the last "n" lines of that array into another
string array, then reassign that new smaller array into the text box. As a
result the text box then only displays the newer lines. For example:

int linesInBox = richTextBox0.Lines.Length;

if (linesInBox > MAX_LINES_WANTED_IN_BOX)
{
// Get all lines from the rich text box
string[] currentLines = richTextBox0.Lines;

// Copy only newer lines from current text box into a new array (starting
from an offset).
string[] newLines = new string[currentLines.Length - TEXT_BOX_LINE_OFFSET];
for (int ix = 0, ixt = TEXT_BOX_LINE_OFFSET; ixt < linesInBox; ++ix,
++ixt)
newLines[ix] = currentLines[ixt];
richTextBox.Lines = newLines;
}

The problem is that the text copied back into the text box no longer has the
various colors (or any other special attributes). This is obviously because
the attributes are associated with the control itself and not with the text
itself. So, is there an easy way to do what I am trying to do that will also
preserve the attributes of each character? A solution I thought of, but I
hate to resort to actually doing it, is that as I place each original
character into the text box, I also place a copy of it into a secondary array
along with its attributes. Then, when it's time to rewrite the text box, I
simply clear it first then individually append each character from my
secondary array along with the appropriate attributes. There must be an
easier way, however.

Thanks,
Ray

From: Peter Duniho on 22 Mar 2010 22:59
Ray Mitchell wrote:
> [...]
> The problem is that the text copied back into the text box no longer has the
> various colors (or any other special attributes). This is obviously because
> the attributes are associated with the control itself and not with the text
> itself. So, is there an easy way to do what I am trying to do that will also
> preserve the attributes of each character? [...]

You could parse the RTF directly. Retrieve it, remove the lines you
don't want, set the text box RTF text to the new RTF.

Alternatively, you could set the selection to the text you want to
remove, and then set the SelectedText property to "". That should
remove just the selected text, leaving the rest intact.

Pete
From: Ray Mitchell on 23 Mar 2010 04:22


"Peter Duniho" wrote:

> Ray Mitchell wrote:
> > [...]
> > The problem is that the text copied back into the text box no longer has the
> > various colors (or any other special attributes). This is obviously because
> > the attributes are associated with the control itself and not with the text
> > itself. So, is there an easy way to do what I am trying to do that will also
> > preserve the attributes of each character? [...]
>
> You could parse the RTF directly. Retrieve it, remove the lines you
> don't want, set the text box RTF text to the new RTF.
>
> Alternatively, you could set the selection to the text you want to
> remove, and then set the SelectedText property to "". That should
> remove just the selected text, leaving the rest intact.
>
> Pete
> .
>

Thanks Pete,

I tried your second suggestion and it was just what I needed. For some
reason, however, a completely empty string "" has no effect. But a string
with at least one character in it, even if it is just a space, does the trick.

Ray
From: Peter Duniho on 23 Mar 2010 04:45
Ray Mitchell wrote:
> I tried your second suggestion and it was just what I needed. For some
> reason, however, a completely empty string "" has no effect. But a string
> with at least one character in it, even if it is just a space, does the trick.

Empty string works fine here. I suspect some mistake in your
implementation.
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