Friday, March 09, 2007


In the spirit of my never ending "pimp your Qt application" series comes another example. This time, "how to make iTunes-like album selector". It's funny how much attention this widget got. I looked at it yesterday on one of the Macs at the office and just implemented it. I probably should make it a view for a list model but for now it's just a simple widget. It runs at perfectly smooth 60 frames per second while utilizing ~7% cpu on my 3GHz Pentium4 with NVIDIA GeForce 6600, so by no means a monster of a machine. Oh, and of course this is all done with pure Qt. Reflections are actually a vector effect, so they would work equally well for any vector based graphics (by using the same code as this example, you can reflect your svg's or even whole widgets with no problem). Mandatory screenshot:
And as with every animated example a movie (again, framerate of the screencapture does not come close to the real world performance) is available here . Finally the code is available here.

Wednesday, March 07, 2007

Gradient bounds

The most unfriendly thing about rendering gradients with Qt has been the fact that you had to specify gradients in coordinates of the shape they were to be rendered on. It wasn't ideal especially for all applications which included any kind of animations or were rendering large number of items because it meant that the gradient had to be individually created for each and every one of items/frames. I've fixed that two days ago by adding a coordinate-mode property to QGradient, which now accepts ObjectBoundingMode. Object bounding mode, just like in SVG, means that the gradient coordinates are percentages of bounding box of the shape that the gradient is about to fill. So all the coordinates are between 0 and 1 and Qt automatically adjusts the bounds for gradient when it's being rendered. This makes it possible to easily use QGradient's with QPalette. An example where I'm drawing a bunch of rectangles and animate them along while the gradient is set only once with (0,0, 1, 1) coordinate box (meaning starting at the topleft and ending at the bottom right corner of each rectangle).
And since it's an animation (including a widget show/hide effect) here's a movie showing it in action.