Hi,
currently Qml makes is very easy to use rectangles, but misses the other basic
geometric shapes. As I understand, the main reason for not including them were
possible performance issues, in particular during animation. A separate plugin
though could easily come with the disclaimer that speed isn't guaranteed in
all cases - so I started prototyping one that exposes the QPainter API to Qml.
Allowing imperative painting in a declarative world sounds counter-intuitive
at first, but I feel easy access to ellipses, lines, polygons and other basic
drawing functions can be very handy for prototyping. At the moment, you'd be
required to dip back to C++ to do these things.
Example uses:
// logo impostor, should be fast since 'paint' is only evaluated once
// and cached in a pixmap
PaintArea {
width: 100
height: 100
paint: {
var p = beginRepaint();
p.setPen({ color: "red" });
p.drawEllipse(50, 50, 45, 45);
p.drawText(10, 30, 100, 100, 0, "Impostor logo");
return p;
}
}
// basis for an Ellipse item, possibly slow since it repaints
// whenever width, height or penWidth change
PaintArea {
property real penWidth: 3
paint: {
var p = beginRepaint();
p.setPen({ width: penWidth });
p.drawEllipse(width/2, height/2, (width-penWidth)/2, (height-
penWidth)/2);
return p;
}
}
The code for this prototype is available at
http://gitorious.org/qml-painterplugin . It's functional, but incomplete and
mainly intended to illustrate the idea.
Could something like this eventually become part of Qt's standard Qml plugins?
(Qt.labs.painter?)
Cheers,
Christian
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