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perf: avoid full string scans in StrEllipsis #2557

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Merged
ansgarbecker merged 1 commit into from
Jul 20, 2026
+14 −4
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perf: avoid full string scans in StrEllipsis #2557

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18 changes: 14 additions & 4 deletions source/apphelpers.pas
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Original file line number Diff line number Diff line change
Expand Up @@ -535,18 +535,28 @@ function Explode(Separator, Text: String): TStringList;
@return string
}
function StrEllipsis(const S: String; MaxLen: Integer; FromLeft: Boolean=True): String;
var
CutPos: PtrInt;
begin
// Truncate on UTF-8 codepoint boundaries, not raw bytes. A byte-wise cut (SetLength/Copy)
// can split a multi-byte character and produce invalid UTF-8. On the Cocoa widgetset such a
// string converts to a nil NSString, which crashes -[NSMenuItem initWithTitle:] when the
// result is used as a menu caption (e.g. quick filter items).
Result := S;
if UTF8Length(Result) <= MaxLen then
// A string with <= MaxLen bytes cannot contain more than MaxLen codepoints
if Length(Result) <= MaxLen then
Exit;
if FromLeft then
Result := UTF8Copy(Result, 1, MaxLen) + '…'
else
if FromLeft then begin
CutPos := UTF8CodepointToByteIndex(PChar(Result), Length(Result), MaxLen);
if (CutPos < 0) or (CutPos >= Length(Result)) then
Exit;
SetLength(Result, CutPos);
Result := Result + '…';
end else begin
if UTF8Length(Result) <= MaxLen then
Exit;
Result := '…' + UTF8Copy(Result, UTF8Length(Result) - MaxLen + 1, MaxLen);
end;
end;


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