Drawing Qt controls in paintEvent with respecting style sheets properties

Question

Is there a class or method in Qt to get properties like "border-color", "border-style", ...

This may be usefull to create and paint own (derived) controls based on currently selected style sheets.

Example:

QPushButton {
    border: 3px solid red;
    background: blue;
    margin: 5px;
    padding: 10px;
}

The code:

class QPushButtonCircle : public QPushButton {
};

QPushButtonCircle would be a button that is circular. Even the border is circular. The border should 3 pixels width, solid and colored red. The background should be colored blue.

I din't find any way expect drawing entierly in paintEvent and ignoring any style sheets. But there must be a better way.

The best would be something like:

QCssStyle cssStyle = widget->...->getCssStyle();

QPen border = cssStyle->border(QCssStyle::Top);
QBrush background = cssStyle->background();
QMargins margins = cssStyle->margins();
QMargins padding = cssStyle->padding();
...

This would allow us to draw our own controls like in:

QStylePainter p(this);

QRect r = rect();
r.adjust(cssStyle->margins().left(), ...);

p.setPen(cssStyle->border());
p.setBrush(cssStyle->brush());
p.drawEllipse(r);

r.adjust(cssStyle->padding().left(), ...);
p.drawText(r, ...);

A better solution would be a method to draw things like with QStyle::drawControl, QStyle::drawPrimitive... but with respecting a QPainterPath (or simpler primitives) instead of assuming rectangular controls.

What is the best way to create owner drawn controls in Qt with derived colors from style sheets?

Whoa, that would be a really great thing to have, but there is no. Probably you can implement it as a wrapper over QString css property by parsing it with some parser. But without touching the Qt internals it is difficult to handle this: widget's stylesheet property is not the complete computed style: parents and qApp also influence. Probably a reason for feature request to Qt devs... — NIA

UmNyobe UmNyobe · Accepted Answer · 2013-01-30T16:53:55

I din't find any way expect drawing entierly in paintEvent and ignoring any style sheets. But there must be a better way.

Widgets in Qt are rectangles, and cannot have any other shape. Take a look at the box model. So any other way will be as tricky as the one you are trying to use.

There is a suggestion using QGraphicView.

EDIT:

I have never tried myself, but you can try to set a mask on top of the button with the shape you want, either using a QBitmap or a QRegion. The other css elements (color, etc..)can be set up by updating the stylesheet. This is a much less pain in the you know what solution if you can make it work, because you don't need to deal with custom paint events.

Drawing Qt controls in paintEvent with respecting style sheets properties

1 Answers