[Qt-qml] Advanced layout support

[Adriano Rezende]

Hi,

I'm moving a layout discussion to this mailing list.

I've pushed an initial version of a linear layout element in the
following branch:

http://qt.gitorious.org/~arezende/qt-components/arezende-desktop/commits/layouts

It basically provides more powerful layout management than Row/Column
elements, since it handles item stretching, individual item spacing,
minimum/preferred/maximum size policies.

These are mandatory features in most of the desktop applications and I
think they should be addressed in a proper manner. Currently, we end
up simulating such features using a lot of anchors and property binds
that increases the code size and impacts in performance.

The current implementation provides a RowLayout and a ColumnLayout element.

Follows an example:

RowLayout {
    spacing: 10

    Item {
        Layout.spacing: 6
        Layout.minimumWidth: 100
    }
    Item {
        Layout.maximumWidth: 300
        Layout.stretchFactor: 2.0
    }
}

There are some features in the TODO list, like accepting different
size policies and some improvements in the layout behavior.

I would like to get a feedback about this API, suggestions or any
extra feature that would make sense to add.

Regarding QtQuick2, I would like to bring to discussion if such
support should be added for the Row, Column and Grid elements. That
would provide a better integration with QtCreator.

As a suggestion, we could handle more complex use cases like the following:

Row {
    spacing: 10

    Item {
        Row.spacing: 5
        Row.sizePolicy: Row.Fixed
    }
    Item {
        Row.maximumWidth: 300
        Row.stretchFactor: 2.0
        Row.sizePolicy: Row.Expanding
    }
}

If one wants to use the default Row/Column features, no attached
properties would be needed. The same would be applied for Grid, like
span support.


Cheers,
Adriano