I have been avoiding QSlider for sometime now. Sliding the QSlider would have been straightforward if the code was correct :). You need this teeny weeny patch against 4.3 (If you are using a week old 4.3 snapshot, you are good). Comments inline.
border: 1px solid #999999;
height: 8px; /* the groove expands to the size of the slider by default. by giving it a height, it has a fixed size */
background: qlineargradient(x1:0, y1:0, x2:0, y2:1, stop:0 #B1B1B1, stop:1 #c4c4c4);
background: qlineargradient(x1:0, y1:0, x2:1, y2:1, stop:0 #b4b4b4, stop:1 #8f8f8f);
border: 1px solid #5c5c5c;
margin: -2px 0; /* handle is placed by default on the contents rect of the groove. Expand outside the groove */
If you require more control, play around with something like this (note that this is a vertical slider):
position: absolute; /* absolutely position 4px from the left and right of the widget. setting margins on the widget should work too... */
left: 4px; right: 4px;
margin: 0 -4px; /* expand outside the groove */
I thought I will have a go at something that looks like the header view in this plasmoid and show some advanced usage of the new pseudo states but I gotta run (and this posts been sitting as a draft for way too long).
background-color: qlineargradient(x1:0, y1:0, x2:0, y2:1, stop:0 #616161, stop: 0.5 #505050, stop: 0.6 #434343, stop:1 #656565);
border: 1px solid #6c6c6c;