[Interest] How long is QMatrix obsolete?

Gunnar Sletta gunnar.sletta at jolla.com
Sat Aug 9 10:16:22 CEST 2014

All uses of QMatrix have an equivalent version which uses QTransform. If you want a proper matrix, use QMatrix3x3 or QMatrix4x4.


On 09 Aug 2014, at 09:55, Guido Seifert <wargand at gmx.de> wrote:

> Yes, and even QTransform has a constructor, which uses the old QMatrix.
> Naturally all this QMatrix dependencies cannot be removed without breaking thousands of programs,
> but it makes one wonder what sense it makes to mark QMatrix as obsolete. It can never be removed.
> And if in the unlikely event that a bug is discovered in QMatrix, it has to be fixed. For the same
> reason that it cannot be removed: Far too much code depends on it. I doubt that even for a Qt 6 
> version this kind of breakage will be accepted.
> Guido
> On Sat, 9 Aug 2014 11:30:35 +0400
> Иван Комиссаров <abbapoh at gmail.com> wrote:
>> See QImage QImage::transformed(const QTransform & matrix, Qt::TransformationMode mode = Qt::FastTransformation) const
>> QTransform differs from QMatrix(obsolete) in that it is a true 3x3 matrix, allowing perspective transformations. QTransform's toAffine() method allows casting QTransform to QMatrix(obsolete). If a perspective transformation has been specified on the matrix, then the conversion will cause loss of data.
>> QTransform is the recommended transformation class in Qt.
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