Itemviews - ScrollPerItem, ScrollPerPixel

Rafael Fernández López ereslibre at
Thu Jun 5 01:33:39 BST 2008

Hi there,

Those who are used to itemviews know that we have to set some flags to them 
for they working "properly". We have been discussing on IRC whether itemviews 
should have a ScrollPerItem or ScrollPerPixel scrolling mode.

The default in Qt is ScrollPerItem, but somehow this looks like a bit 90's, 
and doesn't let the user easily "track the movements".

This is specially critical, since the usage of itemviews have been extended to 
the maximum, as for example, what a combobox shows when being opened, is an 
item view.

For example, I was asked to add smooth scrolling to the config dialog of 
plasma (backgrounds and themes), and had to do something like:


what is pretty crazy all over the system.

And there seems to be users that prefer ScrollPerItem to ScrollPerPixel.

Given this situation, I propose the next (4.2, of course):

1) Create a new entry on KGlobalSettings. Something like:
	static QAbstractItemView::ScrollMode itemViewsScrollMode();

2) We have 3 different approaches at this point:

	2.a) Do let the developer read this value. Bad stuff: We only gain the
             possibility of configuration, but we can't assure total
             integration in the system, we would have to trust the developer,
             and he could miss this value, what could be very understandable.

	2.b) Create KAbstractItemView, KListView, KTreeView, KTableView. All of those
	     will read on their constructor this value, and automatically set the 	  
             value. We should always use K's classes on this case. We already
             have this rule. Problem: crazyness, probably impossible changes  
             because of BIC.

	2.c) Add on kstyle.cpp, on the polish() method, the call to this method
             reading the value of the setting. Problem: would only work with
             KStyles, not with QStyles.

From my POV the best solution would be 2.c).

We could add another check box, for example like "Smooth scrolling on 
itemviews" below the style selection. If the style is a QStyle the checkbox 
becomes disabled, while if the style is a KStyle it becomes enabled.

Apart from special places, like for instance, Dolphin itemviews, after having 
a solution, we should remove those calls where we force one or the other.

Rafael Fernández López.
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