興味のある方のために、これが私が最終的に使用したコードです。これをTVirtualStringTreeのOnAfterCellPaintイベントにアタッチすると、目的の結果が得られます。
(*
DrawHTML - Draws text on a canvas using tags based on a simple subset of HTML/CSS
<B> - Bold e.g. <B>This is bold</B>
<I> - Italic e.g. <I>This is italic</I>
<U> - Underline e.g. <U>This is underlined</U>
<font-color=x> Font colour e.g.
<font-color=clRed>Delphi red</font-color>
<font-color=#FFFFFF>Web white</font-color>
<font-color=$000000>Hex black</font-color>
<font-size=x> Font size e.g. <font-size=30>This is some big text</font-size>
<font-family> Font family e.g. <font-family=Arial>This is arial</font-family>
*)
procedure TfrmSNMPMIBBrowser.DrawHTML(const ARect: TRect; const ACanvas: TCanvas; const Text: String);
function CloseTag(const ATag: String): String;
begin
Result := concat('/', ATag);
end;
function GetTagValue(const ATag: String): String;
var
p: Integer;
begin
p := pos('=', ATag);
if p = 0 then
Result := ''
else
Result := copy(ATag, p + 1, MaxInt);
end;
function ColorCodeToColor(const Value: String): TColor;
var
HexValue: String;
begin
Result := 0;
if Value <> '' then
begin
if (length(Value) >= 2) and (copy(Uppercase(Value), 1, 2) = 'CL') then
begin
// Delphi colour
Result := StringToColor(Value);
end else
if Value[1] = '#' then
begin
// Web colour
HexValue := copy(Value, 2, 6);
Result := RGB(StrToInt('$'+Copy(HexValue, 1, 2)),
StrToInt('$'+Copy(HexValue, 3, 2)),
StrToInt('$'+Copy(HexValue, 5, 2)));
end
else
// Hex or decimal colour
Result := StrToIntDef(Value, 0);
end;
end;
const
TagBold = 'B';
TagItalic = 'I';
TagUnderline = 'U';
TagBreak = 'BR';
TagFontSize = 'FONT-SIZE';
TagFontFamily = 'FONT-FAMILY';
TagFontColour = 'FONT-COLOR';
var
x, y, idx, CharWidth, MaxCharHeight: Integer;
CurrChar: Char;
Tag, TagValue: String;
PreviousFontColor: TColor;
PreviousFontFamily: String;
PreviousFontSize: Integer;
begin
// Start - required if used with TVirtualStringTree
ACanvas.Font.Size := Canvas.Font.Size;
ACanvas.Font.Name := Canvas.Font.Name;
ACanvas.Font.Color := Canvas.Font.Color;
ACanvas.Font.Style := Canvas.Font.Style;
// End
PreviousFontColor := ACanvas.Font.Color;
PreviousFontFamily := ACanvas.Font.Name;
PreviousFontSize := ACanvas.Font.Size;
x := ARect.Left;
y := ARect.Top;
idx := 1;
MaxCharHeight := ACanvas.TextHeight('Ag');
While idx <= length(Text) do
begin
CurrChar := Text[idx];
// Is this a tag?
if CurrChar = '<' then
begin
Tag := '';
inc(idx);
// Find the end of then tag
while (Text[idx] <> '>') and (idx <= length(Text)) do
begin
Tag := concat(Tag, UpperCase(Text[idx]));
inc(idx);
end;
///////////////////////////////////////////////////
// Simple tags
///////////////////////////////////////////////////
if Tag = TagBold then
ACanvas.Font.Style := ACanvas.Font.Style + [fsBold] else
if Tag = TagItalic then
ACanvas.Font.Style := ACanvas.Font.Style + [fsItalic] else
if Tag = TagUnderline then
ACanvas.Font.Style := ACanvas.Font.Style + [fsUnderline] else
if Tag = TagBreak then
begin
x := ARect.Left;
inc(y, MaxCharHeight);
end else
///////////////////////////////////////////////////
// Closing tags
///////////////////////////////////////////////////
if Tag = CloseTag(TagBold) then
ACanvas.Font.Style := ACanvas.Font.Style - [fsBold] else
if Tag = CloseTag(TagItalic) then
ACanvas.Font.Style := ACanvas.Font.Style - [fsItalic] else
if Tag = CloseTag(TagUnderline) then
ACanvas.Font.Style := ACanvas.Font.Style - [fsUnderline] else
if Tag = CloseTag(TagFontSize) then
ACanvas.Font.Size := PreviousFontSize else
if Tag = CloseTag(TagFontFamily) then
ACanvas.Font.Name := PreviousFontFamily else
if Tag = CloseTag(TagFontColour) then
ACanvas.Font.Color := PreviousFontColor else
///////////////////////////////////////////////////
// Tags with values
///////////////////////////////////////////////////
begin
// Get the tag value (everything after '=')
TagValue := GetTagValue(Tag);
if TagValue <> '' then
begin
// Remove the value from the tag
Tag := copy(Tag, 1, pos('=', Tag) - 1);
if Tag = TagFontSize then
begin
PreviousFontSize := ACanvas.Font.Size;
ACanvas.Font.Size := StrToIntDef(TagValue, ACanvas.Font.Size);
end else
if Tag = TagFontFamily then
begin
PreviousFontFamily := ACanvas.Font.Name;
ACanvas.Font.Name := TagValue;
end;
if Tag = TagFontColour then
begin
PreviousFontColor := ACanvas.Font.Color;
ACanvas.Font.Color := ColorCodeToColor(TagValue);
end;
end;
end;
end
else
// Draw the character if it's not a ctrl char
if CurrChar >= #32 then
begin
CharWidth := ACanvas.TextWidth(CurrChar);
if x + CharWidth > ARect.Right then
begin
x := ARect.Left;
inc(y, MaxCharHeight);
end;
if y + MaxCharHeight < ARect.Bottom then
begin
ACanvas.Brush.Style := bsClear;
ACanvas.TextOut(x, y, CurrChar);
end;
x := x + CharWidth;
end;
inc(idx);
end;
end;