TX Tops Top 10, Syntax Highlighting Revisited

The new version of TX Text Control with support for Microsoft Visual C++ has been out for several weeks now. There is the announcement article.

We would love to know how you are coming on with the new VCC+ support offered by TX Text Control. How do you find the documentation?

We would really love to hear your comments. If you have got a few moments, why not hit the REPLY button and let us know your thoughts - it'll only take you a few moments.

TX Tops Top 10 at Component Source

In this week's best-seller list published by Component Source, TX Text Control is at place number 8. See for yourself.

This makes it by far the best-selling text component resold by Component Source.

Confusion About Service Pack #3 Clarified

On reviewing the support questions from last week, it became apparent that there are certain misconceptions about Service Pack #3. Please allow me to clear a few issues.

Top TX Tip: Syntax Highlighting Revisited

Back in Syntax article we started a discussion on syntax highlighting and how you can use TX Text Control to construct a simple programming editor which highlights the keywords of your chosen language (be it VB, HTML or C++). If you missed this article, you can read everything you need to know in the Newsletter Archive

However, version one of our little program only allowed the keywords to be highlighted in one go, once the text had been entered. Naturally, this sucks. So, enter version two. This time we are going to change the color of all entered word on-the-fly and so fast that the user only notices the change of color and nothing else.

To keep our little program running as fast as possible, we are only going to check the last and the second to last word.

This is necessary as the user could split a keyword with a space. For example: it is quite possible that a user splits the keyword <html> into to two, thus <ht ml>.

In this case, both the '<ht' and the 'ml>' must be returned to their neutral color. In other words, the highlighting which was applied to the keyword '<html>' must be again removed.

"Sounds good, but exactly how do I go about coding this?" is probably what is running through your mind right now.

' When a key is pressed in the TX window, this function determines
' the last and the next word and checks if these are keywords.
' If so, they are colored accordingly...
'
Public Function CheckEditedText()

    Dim nOldSelStart As Integer, nOldSelLength As Integer
    Dim nPos As Integer, nLen As Integer
    Dim szTmp As String
    Dim index As Integer

    With Form1.TXTextControl1

        ' Turn off the wait cursor
        SendMessage .hwnd, TX_SETMODEEX, TF_NOWAITCURSOR, 0

        ' Lock TX window update
        LockWindowUpdate .hwnd

        ' Store current selection
        nOldSelStart = .SelStart
        nOldSelLength = .SelLength

        szTmp = .Text

        ' First find the last word from the current position
        nPos = LastDelimiter(szTmp, nOldSelStart - 1)
        nLen = NextDelimiter(szTmp, nOldSelStart - 1) - nPos

        If (nLen > 0) Then

            index = IsKeyWord(Mid(szTmp, nPos + 1, nLen))

            If index <> -1 Then
                .SelStart = nPos
                .SelLength = nLen
                .ForeColor = Colors(index)
            Else
                .SelStart = nPos
                .SelLength = nLen
                .ForeColor = vbBlack
            End If
        End If

        ' Now find the next word from the current position
        nPos = LastDelimiter(szTmp, nOldSelStart)
        nLen = NextDelimiter(szTmp, nOldSelStart) - nPos

        If (nLen > 0) Then

            index = IsKeyWord(Mid(szTmp, nPos + 1, nLen))

            If index <> -1 Then
                .SelStart = nPos
                .SelLength = nLen
                .ForeColor = Colors(index)
            Else
                .SelStart = nPos
                .SelLength = nLen
                .ForeColor = vbBlack
            End If
        End If

        ' Set back the stored values
        .SelStart = nOldSelStart
        .SelLength = nOldSelLength
        .ForeColor = RGB(0, 0, 0)

        LockWindowUpdate 0

        ' Turn on wait cursor
        SendMessage .hwnd, TX_SETMODEEX, TF_WAITCURSOR, 0

    End With

End Function

The only difference is that we look for the last word before the current Cursorposition and check whether it is a keyword or not. Should it be a keyword, then we color it appropriately, otherwise we simply set the color to its default. We then move on to the next word and repeat the procedure again. However, when is this function actually called? Theoretically, whenever something is changed in the document.

But should the call to CheckEditedText be directly in the TXTextControl1_Change() event handler we would be in a situation of a never-ending look, as the document is changed in the Change handler. Not good.

Because of this we have inserted a Drity-Flag which is set to true as soon as the document is changed. This flag is looked up in the KeyUp handler. Should it be set, the function CheckEditedText is called.

Solving the dilemma in this way, we do not have to check which key is currently pressed. Should the user then press the cursor keys to scroll through the document, no Change notification will be called. And thus nothing happens in the Key handler.

As you have probably noticed, copy and paste operations have not been added to this example. We shall leave that to you, as it should not be too difficult. Naturally, you should take care to check the pasted text and highlight the inserted keywords accordingly.

how are you coming on with the TX Text Control Class Library?

TX Tops Top 10 at Component Source

Confusion About Service Pack #3 Clarified

Top TX Tip: Syntax Highlighting Revisited