Delphi SynEdit – HighLigth Parenthesis or Bracket

Bracket Highlighting in Delphi 12.0 Using SynEdit

Delphi 12.0 users have a new tool to improve code readability: a procedure for enabling bracket highlighting in SynEdit. This feature helps developers quickly identify matching parentheses, braces, and other types of brackets within their code, which is essential for navigating complex code structures efficiently.

To implement this feature, developers need to associate a custom procedure with the OnPaintTransient event in SynEdit. This approach was inspired by discussions and solutions shared in a bug report on the SynEdit project page on SourceForge (sourceforge.net/p/synedit/bugs/358/#bc9e), which pointed out the necessity of visually distinguishing matching brackets.

This functionality enhances the coding experience by making it easier to track nested structures, thus reducing errors and improving development speed. For Delphi 12.0 developers looking to enhance their coding environment, integrating bracket highlighting with SynEdit offers a practical solution.

procedure TfrmSQLAnalizer.SynSQLPaintTransient(Sender: TObject; Canvas: TCanvas;
  TransientType: TTransientType);
var
  Editor: TSynEdit;
  OpenChars: array of WideChar;//[0..2] of WideChar=();
  CloseChars: array of WideChar;//[0..2] of WideChar=();
  Attri: TSynHighlighterAttributes;

function IsCharBracket(AChar: WideChar): Boolean;
begin
  case AChar of
    '{',
    '[',
    '(',
    '<',
    '}',
    ']',
    ')',
    '>':
    Result:= True;
  else
    Result:= False;
  end;
end;

function CharToPixels(P: TBufferCoord): TPoint;
begin
  Result:=Editor.RowColumnToPixels(Editor.BufferToDisplayPos(P));
end;

procedure SetCanvasStyle;
begin
  Editor.Canvas.Brush.Style:= bsSolid; //Clear;
  Editor.Canvas.Font.Assign(Editor.Font);
  Editor.Canvas.Font.Style:= Attri.Style;
  if (TransientType = ttAfter) then begin
    Editor.Canvas.Font.Color:=  clRed; // FBracketFG;
    Editor.Canvas.Brush.Color:= cl3DLight;
  end
  else begin
    Editor.Canvas.Font.Color:= Attri.Foreground;
    Editor.Canvas.Brush.Color:= Attri.Background;
  end;

  if (Editor.Canvas.Font.Color = clNone) then
    Editor.Canvas.Font.Color:= Editor.Font.Color;
  if (Editor.Canvas.Brush.Color = clNone) then
    Editor.Canvas.Brush.Color:= Editor.Color;
end;

var
P  : TBufferCoord;
Pix: TPoint;
D  : TDisplayCoord;
S  : String;
I,
 ArrayLength,
 start: Integer;
TmpCharA,
 TmpCharB: WideChar;

begin
  try
    // if Memo1.InReplaceStatus = False then
    // begin
    (*
    if fMain.SyntaxHEnabled = False then exit;
    if Memo1.Highlighter = nil then exit;
    if fMain.BracketMatching = False then exit;
    if TSynEdit(Sender).SelAvail then exit;
    *)
    Editor:= TSynEdit(Sender);
    ArrayLength:= 3;
    (*
    if (Editor.Highlighter = SynHTMLSyn1) or (Editor.Highlighter = SynXMLSyn1) then
    inc(ArrayLength);
    *)
    SetLength(OpenChars,
              ArrayLength);
    SetLength(CloseChars,
              ArrayLength);

    for i:= 0 to ArrayLength - 1 do
      Case i of
        0: begin
             OpenChars[i]:= '(';
             CloseChars[i]:= ')';
           end;
        1: begin
             OpenChars[i]:= '{';
             CloseChars[i]:= '}';
           end;
        2: begin
             OpenChars[i]:= '[';
             CloseChars[i]:= ']';
           end;
        3: begin
             OpenChars[i]:= '<';
             CloseChars[i]:= '>';
           end;
      end;

    P:= Editor.CaretXY;
    D:= Editor.DisplayXY;
    Start:= Editor.SelStart;

    if (Start > 0) and
       (Start <= length(Editor.Text)) then
      TmpCharA:= Editor.Text[Start]
    else
      TmpCharA:= #0;

    if (Start < length(Editor.Text)) then
      TmpCharB:= Editor.Text[Start + 1]
    else
      TmpCharB:= #0;

    if not IsCharBracket(TmpCharA) and
       not IsCharBracket(TmpCharB) then
      Exit;

    S:= TmpCharB;
    if not IsCharBracket(TmpCharB) then begin
      P.Char:= P.Char - 1;
      S:= TmpCharA;
    end;

    Editor.GetHighlighterAttriAtRowCol(P,
                                       S,
                                       Attri);

    if (Editor.Highlighter.SymbolAttribute = Attri) then begin
      for i:= low(OpenChars) to High(OpenChars) do begin
        if (S = OpenChars[i]) or
           (S = CloseChars[i]) then begin
          Pix:= CharToPixels(P);
          SetCanvasStyle;
          Editor.Canvas.TextOut(Pix.X,
                                Pix.Y,
                                S);
          P := Editor.GetMatchingBracketEx(P);

          if (P.Char > 0) and
             (P.Line > 0) then begin
            Pix:= CharToPixels(P);
            if Pix.X > Editor.Gutter.RealGutterWidth then begin
              SetCanvasStyle;
              if S = OpenChars[i] then
                Editor.Canvas.TextOut(Pix.X,
                                      Pix.Y,
                                      CloseChars[i])
              else
                Editor.Canvas.TextOut(Pix.X,
                                      Pix.Y,
                                      OpenChars[i]);
            end; //if Pix.X >
          end; //if (P.Char > 0)
        end; //if (S = OpenChars[i])
      end; //for i:= low(OpenChars)
      Editor.Canvas.Brush.Style := bsSolid;
    end; //if (Editor.Highlighter.SymbolAttribute = Attri)
  except
  // TODO
  end; //try
end;

Delphi SynEdit – HighLigth Parenthesis or Bracket

Delphi SynEdit – HighLigth Parenthesis or Bracket

Bracket Highlighting in Delphi 12.0 Using SynEdit

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