[Development] Property bindings in Qt 6

Uwe Rathmann Uwe.Rathmann at tigertal.de
Wed Oct 2 17:06:53 CEST 2019

On 10/2/19 4:36 PM, Jason H wrote:

> There is fontSizeMode: Text.Fit, .HorizontalFit and .VerticalFit. 
> Horizontal fit is what you want in that situation. But the whole 
> implementation is lacking because you can't actually ask the Text 
> what size it used to render so that other text items on the screen 
> can be the same size.

Typical layout classes have 2 things to do:

a) calculating the geometry of the children
b) offering layout information to the parent calculated from the 
information provided by the children.

With Widgets, GraphicsView or my framework the system depends on the
min/preferred/max hints being evaluated by a size policy. F.e
QSizePolicy::hasHeightForWidth() tells the layout classes, what to do.

QQuickItem has the implicitSize ( = implicit preferred size ) only - no
other explicit/implicit size hints and no policy.

And b) has become something you have to implement manually on 
application side. With anchoring things are even worse: there is not 
even a container who is in control of the scenario, that could do the job.

Ironically GridLayout/RowLayout/ColumnLayout are using the same layout
engine as the layout classes of the QGraphicsView framework. It
offers all the whistles and bells, but QQuickItem does not have the 
parameters to feed it.


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