Best place to apply a QMatrix transform to paint() event in an app

[Kryzon]

QTransform is a type of matrix that supports perspective transformations (including affine).
QMatrix only supports affine transformations (translation, rotation, shear and scale).

You can create a QTransform and use QTransform::scale( 1.0, -1.0 ) (to flip the vertical axis) and then assign it to the graphics view using setTransform.

Then consider your graphics scene as in cartesian coordinates: treat all coordinates as in a cartesian space. When displayed through the graphics view, the transform of the graphics view will convert from cartesian to device coordinates.

[Caolan O'Domhnaill]

GREAT! Thank you so very much!

-Caolan.

[Caolan O'Domhnaill]

Aaaaaaaand now everything in my view is upside down... *facepalm*

[Kryzon]

Here's a suggestion: translate that transform to the centre of the viewport. It should look more like a cartesian representation.

QPoint viewportCentre = viewport().rect().center();
QTransform::translate( viewportCentre.x(), viewportCentre.y() );

QPoint viewportCentre = viewport().rect().center();
QTransform::translate( viewportCentre.x(), viewportCentre.y() );

To copy to clipboard, switch view to plain text mode 

Make sure you are specifying coordinates in "cartesian" space: +X is to the right, +Y is up.

[Caolan O'Domhnaill]

Here's a suggestion: translate that transform to the centre of the viewport. It should look more like a cartesian representation.

QPoint viewportCentre = viewport().rect().center();
QTransform::translate( viewportCentre.x(), viewportCentre.y() );

QPoint viewportCentre = viewport().rect().center();
QTransform::translate( viewportCentre.x(), viewportCentre.y() );

To copy to clipboard, switch view to plain text mode 

Make sure you are specifying coordinates in "cartesian" space: +X is to the right, +Y is up.

I got it all to work. Thank you very much!