The Qt graphics platform's scrollbar behavior for setting the visible amount is unlike that seen from motif, windows, and gtk. In Qt, there is no direct api to set the visible amount. The visible amount and it's associated behavior is linked with the QScrollbar.setPageStep() call in Qt. This QScrollbar.setPageStep() call is used in Qt to directly set the block increment value, and, the visible amount is automatically changed to match this value. Therefore, there is a direct coupling of the setVisibleAmount and setBlockIncrement behavior on Qt. They cannot be separated, which is suggested in the Scrollbar spec.

There has been much talk of this between Denis Mikhalkin (AWT spec lead), the TCK team (represented by Stan Avzan), and the J2ME Personal Profile team (Brandon Passanisi and Chihiro Saito). It was requested to file this spec bug and list the conclusion that came about from all parties. The conclusion is listed below:

1) Setting blockSize shouldn't affect the visible amount, and vice versa. Those two should be independent, not connected.
2) VisibleAmount should be treated as a hint rather than a requirement for the native to change the thumbnail size. So getVisibleAmount() should return the value set by setVisibleAmount(), but this value is not required to be connected to native.


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