Syntax Highlighting

[paule32]

Hello,
I have working on a simple Syntax Highlighter for using by other Developers.
At the current Time, only Pascal Comment's are supported.
Pleas forgive me for the poor implementation - I am not so the good programmer.
It would be nice, if you left a note on the work from me.

For doing Syntax Highlighting, I change the "edtis.cpp" from the magiblot 1 source tree of Turbo Vision.
The "Turbo" thing was me so big, to adapt the code, so I working on my own.
Have fun with it, and stay tuned ...

Here is a simple Example source

void
TEditor::formatLine(
    TScreenCell *DrawBuf,
    uint P,
    int Width,
    TAttrPair
    ) { 
    
    TSpan<TScreenCell> Cells(DrawBuf, Width);
    TStringView chars;
    TColorAttr  Color;
    
    char Ch;
    
    int X = 0;
    Color = 0x1e;

    while (1) {
        chars = bufChars(P);
        Ch = chars[0];
        if (X >= Width) break;
        if (Ch == '(') {
            ::setCell(Cells[X], '(', 0x1e);
            X++;
            P++;
            chars = bufChars(P);
            Ch = chars[0];
            if (X >= Width) break;
            if (Ch == '*') {
                tokenIsComment = true;
                ::setCell(Cells[X-1], '(', 0x03);
                ::setCell(Cells[X  ], '*', 0x03);
                X++;
                P++;
                while (1) {
                    chars = bufChars(P);
                    Ch = chars[0];
                    if (X >= Width) break;
                    if (Ch == '*') {
                        ::setCell(Cells[X], '*', 0x03);
                        X++;
                        P++;
                        chars = bufChars(P);
                        Ch = chars[0];
                        if (Ch == ')') {
                            ::setCell(Cells[X], Ch, 0x03);
                            tokenIsComment = false;
                            Color = 0x1e;
                            X++;
                            P++;
                            break;
                        }   else
                        if (Ch == '\r' || Ch == '\n')
                        {
                            while (X < Width)
                            ::setCell(Cells[X++], ' ', 0x03);
                            P++;
                            break;
                        }   else {
                            ::setCell(Cells[X], Ch, 0x03);
                            X++;
                            P++;
                        }
                    }   else
                    if (Ch == '\r' || Ch == '\n') {
                        while (X < Width)
                        ::setCell(Cells[X++], ' ', 0x03);
                        P++;
                        //break;
                    }   else {
                        ::setCell(Cells[X], Ch, 0x03);
                        X++;
                        P++;
                    }
                }
            }   else {
                ::setCell(Cells[X], Ch, 0x1e);
                X++;
                P++;
            }
        }   else
        if (Ch == '*') {
            if (tokenIsComment) {
                ::setCell(Cells[X], '*', 0x03);
                X++;
                P++;
                chars = bufChars(P);
                Ch = chars[0];
            
                if (Ch == ')') {
                    tokenIsComment = false;
                    Color = 0x1e;
                    ::setCell(Cells[X], ')', 0x03);
                    X++;
                    P++;
                }   else {
                    Color = 0x03;
                    ::setCell(Cells[X], '*', 0x03);
                    X++;
                    P++;
                }
            }   else {
                ::setCell(Cells[X], '*', 0x1e);
                X++;
                P++;
            }
        }   else
        if (Ch == '\r' || Ch == '\n')
        {
            if (tokenIsComment)
            Color = 0x03; else
            Color = 0x1e;
        
            while (X < Width)
            ::setCell(Cells[X++], ' ', Color);
            P++;
            break;
        }   else
        if (Ch == '\t')
        {
            if (tokenIsComment)
            Color = 0x03; else
            Color = 0x1e;
            
            if (X < Width) {
                do {
                    ::setCell(Cells[X++], ' ', Color);
                } while (X%8 != 0 && X < Width);
                ++P;
            }   else break;
        }   else {
            if (tokenIsComment)
            Color = 0x03; else
            Color = 0x1e;
        
            if (!formatCell(Cells, (uint&) X, chars, P, Color))
            break;
        }
    }
}

And there, you can see a Example Application with a Text-Editor in Front of:
https://imgur.com/rdAn5sO

[magiblot]

Hi Jens!

First of all, your code contains memory safety errors. The bufChars method reads character from the editor's buffer, so you must always check that P < bufLen before invoking bufChars. Otherwise, you will be reading the buffer out-of-bounds. Similarly, you must always check that X < Width before accessing Cells[X], or you may experience a buffer overrun. Finally, the code is missing the loop that, when text is over, draws spaces until the end of the line. Without it, the draw buffer remains filled with uninitialized data that will be displayed as garbage.

Here is a possible fix:

@@ -16,16 +16,16 @@ TEditor::formatLine(
     Color = 0x1e;
 
     while (1) {
+        if (P >= bufLen || X >= Width) break;
         chars = bufChars(P);
         Ch = chars[0];
-        if (X >= Width) break;
         if (Ch == '(') {
             ::setCell(Cells[X], '(', 0x1e);
             X++;
             P++;
             chars = bufChars(P);
             Ch = chars[0];
-            if (X >= Width) break;
+            if (P >= bufLen || X >= Width) break;
             if (Ch == '*') {
                 tokenIsComment = true;
                 ::setCell(Cells[X-1], '(', 0x03);
@@ -33,13 +33,14 @@ TEditor::formatLine(
                 X++;
                 P++;
                 while (1) {
+                    if (P >= bufLen || X >= Width) break;
                     chars = bufChars(P);
                     Ch = chars[0];
-                    if (X >= Width) break;
                     if (Ch == '*') {
                         ::setCell(Cells[X], '*', 0x03);
                         X++;
                         P++;
+                        if (P >= bufLen || X >= Width) break;
                         chars = bufChars(P);
                         Ch = chars[0];
                         if (Ch == ')') {
@@ -84,6 +85,7 @@ TEditor::formatLine(
                 ::setCell(Cells[X], '*', 0x03);
                 X++;
                 P++;
+                if (P >= bufLen || X >= Width) break;
                 chars = bufChars(P);
                 Ch = chars[0];
 
@@ -137,4 +139,6 @@ TEditor::formatLine(
             break;
         }
     }
+    while (X < Width)
+        ::setCell(Cells[X++], ' ', Color);
 }

Then, the tokenIsComment variable is not defined in your code snippet. It makes sense that this is not a local variable in the formatLine method because you can't know whether you are in the middle of a comment just by looking at the current line. You may have defined tokenIsComment as a TEditor member or as a global variable. This way, tokenIsComment retains the value from previous invocations of formatLine. However, this doesn't always work.

What if you have scrolled down the document and the comment begin ((*) is out of sight? In this case, formatLine won't have been invoked for the line containing the (* and tokenIsComment will be false. For this reason it is not possible to implement a full-fledged syntax highlighter just inside formatLine.

[paule32]

I have made your modify suggestion's.
And yes, "tokenIsComment" is already a global "bool" variable.
It works not perfect - but like I said, I am a hobby programmer, not a pro.
For me. it is enough, firstly.
I had thinking, that the Code was helping other.

edits.cpp.txt

[magiblot]

Don't worry, it's alright. Thanks for sharing.