Syntax highlighting with a gradient background

Tmalfrere

Hi,

I've created a syntax highlighter that should display lines with "error" with a red gradient background and all lines with "warning" with a yellow gradient background.

I feed the document from a QPlainTextEdit to my highlighter and everything works except that half the time the gradients are not gradient but solid colors.

Am I doing something wrong or do I have a bug?

here's my highlighter class I derived from QSyntaxHighlighter()

@

class QLseSyntaxHighlighter : public QSyntaxHighlighter
{
Q_OBJECT
public:
explicit QLseSyntaxHighlighter(QObject *parent = 0);
explicit QLseSyntaxHighlighter(QTextDocument *parent = 0);
void highlightBlock(const QString &text);

signals:

public slots:

private:
QTextCharFormat m_FormatWarning;
QTextCharFormat m_FormatError;

QRegExp         m_ExpressionForWarning;
QRegExp         m_ExpressionForError;

};

QLseSyntaxHighlighter::QLseSyntaxHighlighter(QTextDocument *parent) :
QSyntaxHighlighter(parent)
{
QString ErrorPattern(QLatin1String("^.error.$"));
m_ExpressionForError = QRegExp(ErrorPattern,Qt::CaseInsensitive);

QString WarningPattern(QLatin1String("^.*warning.*$"));
m_ExpressionForWarning = QRegExp(WarningPattern, Qt::CaseInsensitive);

m_FormatError = QTextCharFormat();
m_FormatError.setFontWeight(QFont::Bold);
QFont   ErrorFont(m_FormatError.font());
QFontMetrics Errorfm(ErrorFont);
QLinearGradient GradientError(0,Errorfm.height(),0,0);
GradientError.setColorAt(1, QColor(255, 224, 224, 255));
GradientError.setColorAt(0, QColor(255, 32, 32, 255));
QBrush  BrushError(GradientError);
m_FormatError.setBackground(BrushError);

m_FormatWarning = QTextCharFormat();
m_FormatWarning.setFontWeight(QFont::Bold);
QFont   WarningFont(m_FormatWarning.font());
QFontMetrics fm(WarningFont);
QLinearGradient GradientWarning(0,fm.height(),0,0);
GradientWarning.setColorAt(1, QColor(255, 253, 239, 255));
GradientWarning.setColorAt(0, QColor(255, 224, 0, 255));
QBrush  BrushWarning(GradientWarning);
m_FormatWarning.setBackground(BrushWarning);

}

void QLseSyntaxHighlighter::highlightBlock(const QString &text)
{
int index;

//WriteLog("highlightBlock\n");
//WriteLog(text);
//WriteLog("\n");

index = text.indexOf(m_ExpressionForError);
while (index >= 0)
{
    int length = m_ExpressionForError.matchedLength();
    setFormat(index, length, m_FormatError);
    index = text.indexOf(m_ExpressionForError, index + length);
}

index = text.indexOf(m_ExpressionForWarning);
while (index >= 0)
{
    int length = m_ExpressionForWarning.matchedLength();
    setFormat(index, length, m_FormatWarning);
    index = text.indexOf(m_ExpressionForWarning, index + length);
}

}
@

tucnak

Hey there!

Most probably, Qt just doesn't support this sort of behavior. I don't have an opportunity to check it now, but I am hardly sure that documentation says somewhere something like "you can't use gradient-based brushes for text format backgrounds".

Still not sure, lemme see.

SGaist

Hi,

You might have discovered something. What version of Qt are you using ? On what OS ?

Here it look's like only the first line of the QTextDocument gets the proper gradient.

Tmalfrere

@tuknak: well, it does work 30% of the time...

@SGalst: I'm using Qt 5.2.1

I do have created a small test application that clearly demonstrates the problem, but I don't no where to post it...

SGaist

"The bug report system":http://bugreports.qt-project.org

Don't forget to check it's something already known