讲述如何开发一个控件,很有价值(二)

would be divided up into:

procedure	tsKeyWord
	tsSpace
TForm1	tsIdentifier
.	tsSymbol
FormCreate	tsIdentifier
(	tsSymbol
Sender	tsIdentifier
:	tsSymbol
TObject	tsIdentifier
);	tsSymbol
	tsSpace
{Create Form}	tsComment
<CR><LF>	tsCRLF

How is it Done?

The RichEdit control normally loads preformatted text from .RTF files by way of by of the RichEdit.Lines.LoadFromFile() function. YourPasEdit uses the RichEdit.Lines.LoadFromStream() function to load the file from a TPasConversion - a custom TMemoryStream descendant. This stream takes the plaint text Pascal source file, loads it into its internal memory buffe, and then converts it from plain text to a text impregnated with RTF codes. This way when it is loaded into the RichEdit control via RichEdit.Lines.LoadFromStream the Pascal source file appears in the control color-syntax highlighted.

To the main Editor, this process is transparent - the code looks something like this:

begin

NewRichEdit := TRichEdit.Create;

    PasCon.Clear;                    // Prepare the TPasConversion
    PasCon.LoadFromFile(FName);      // Load the File into the Memory Stream
    PasCon.ConvertReadStream;        // Convert the stream to RTF format

    NewRichEdit.Lines.BeginUpdate;
    NewRichEdit.Lines.LoadFromStream(PasCon);   // Read from the TPasConversion
    NewRichEdit.Lines.EndUpdate

NewRichEdit.Show;

Result := NewRichEdit;

end

EXAMPLE - snippet of code from the NewRichEditCreate(Fname) routine

As I said, it is the TMemoryStream derived TPasConversion which does all the hard work:

<SOURCE PASCAL FILE>
|
V
Plain source loaded into memory
(TPasConversion.LoadFromFile)
|
V
Converted internally by parsing the source file
(ConvertReadStream)
|
V
Result made available
(SetMemoryPointer)
|
V
RichEdit.LoadFromStream

Most of the work in TPasConversion is done by the ConvertReadStream procedure. Its purpose is to split up each line of source code into tokens (as showed previously) and then depending on its TokenType, load it into the outbuffer preceded by RTF codes to make it a particular Color, Bold, Italics etc. Here what it looks like:

// prepare the Outbuf to a certain default size

FOutBuffSize:= size+3;
ReAllocMem(FOutBuff, FOutBuffSize);

// Initialise the parser to its begining state

FTokenState := tsUnknown;
FComment     := csNo;
FBuffPos     := 0;
FReadBuff    := Memory;

// Write leading RTF Header

WriteToBuffer({tf1ansideff0deftab720{fonttbl{f0fswiss MS SansSerif;}
{f1fromanfcharset2 Symbol;}{f2fmodern Courier New;}}+#13+#10);
WriteToBuffer({colortbled0green0lue0;}+#13+#10);
WriteToBuffer(deflang1033pardplainf2fs20 );

// Create the INSTREAM (FReadBuff) and tokenize it

Result:= Read(FReadBuff^, Size);
FReadBuff[Result] := #0;

if Result > 0 then
begin

Run:= FReadBuff;
TokenPtr:= Run;

while Run^ <> #0 do
begin

Case Run^ of

          #13:                        // Deal with CRLFs
          begin
             FComment:= csNo;
             HandleCRLF;