logic analyzer: fix annotation empty string causing infinite loop

- Handle the edge case where an empty string passed to the shortenAnnotationText
function causes an infinite loop.
This fix ensures that the function returns the extension ("...") when
the text is empty or the maxWidth is too small to fit the extension.

Signed-off-by: Adrian Stanea <[email protected]>

src/logicanalyzer/annotationcurve.cpp

@@ -700,16 +700,27 @@ uint64_t AnnotationCurve::getMaxAnnotationCount(int index)
 
 QString AnnotationCurve::shortenAnnotationText(const QString text, const double maxWidth, QPainter *painter) const
 {
-    const int padding = 12;
-    const QString extension = "...";
-    int count = 0;
+	const int PADDING = 12;
+	const QString EXTENSION = "...";
+	int count = 0;
 
-    // find maximum number of characters that fit
-    while(QSizeF(QwtText(text.left(count) + extension).textSize(painter->font())).width() <= maxWidth - padding) {
-	count++;
-    }
+	bool isWithinTextLength = true;
+	bool isWithinMaxWidth = true;
+
+	// Empty text or maxWidth is too small to even fit the extension
+	if(text.isEmpty() || maxWidth <= PADDING + painter->fontMetrics().horizontalAdvance(EXTENSION)) {
+		return EXTENSION;
+	}
+
+	// find maximum number of characters that fit
+	while(isWithinTextLength && isWithinMaxWidth) {
+		count++;
+		isWithinTextLength = count < text.length();
+		isWithinMaxWidth = QSizeF(QwtText(text.left(count) + EXTENSION).textSize(painter->font())).width() <=
+			maxWidth - PADDING;
+	}
 
-    return count ? text.left(count) + extension : "";
+	return isWithinTextLength ? text.left(count) + EXTENSION : "";
 }