Transformation Matrix for Element Editor

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https://qelectrotech.org/forum/viewtopic.php?id=1725

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https://github.com/qelectrotech/qelectrotech-source-mirror/blob/master/sources/editor/qetelementeditor.h
https://gitlab.com/inkscape/inkscape/-/blob/master/src/ui/dialog/transformation.h
https://doc.qt.io/qt-5/qtransform.html

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https://doc.qt.io/qt-5/qdial.html

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Translation is the simplest transformation. Setting dx and dy will move the coordinate system dx units along the X axis and dy units along the Y axis. Scaling can be done by setting m11 and m22. For example, setting m11 to 2 and m22 to 1.5 will double the height and increase the width by 50%. The identity matrix has m11, m22, and m33 set to 1 (all others are set to 0) mapping a point to itself. Shearing is controlled by m12 and m21. Setting these elements to values different from zero will twist the coordinate system. Rotation is achieved by setting both the shearing factors and the scaling factors. Perspective transformation is achieved by setting both the projection factors and the scaling factors.

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A first attempt at location and layout

https://qelectrotech.org/forum/viewtopic.php?pid=12796#p12796

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https://gerrysweeney.com/horizontal-and-vertical-flip-transformations-of-a-qgraphicsitem-in-qt-qgraphicsview/
https://doc.qt.io/qt-5/qgraphicsitem.html#setTransform
https://doc.qt.io/qt-5/qquaternion.html