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8.3. Common Range Methods

The Range widget class is fairly complicated internally, but, like all the "base class" widgets, most of its complexity is only interesting if you want to hack on it. Also, almost all of the methods and signals it defines are only really used in writing derived widgets. There are, however, a few useful methods that will work on all range widgets.

8.3.1. Setting the Update Policy

The "update policy" of a range widget defines at what points during user interaction it will change the value field of its Adjustment and emit the "value_changed" signal on this Adjustment. The update policies are:

UPDATE_CONTINUOUS - This is the default. The "value_changed" signal is emitted continuously, i.e., whenever the slider is moved by even the tiniest amount.

UPDATE_DISCONTINUOUS - The "value_changed" signal is only emitted once the slider has stopped moving and the user has released the mouse button.

UPDATE_DELAYED - The "value_changed" signal is emitted when the user releases the mouse button, or if the slider stops moving for a short period of time.

The update policy of a range widget can be set by passing it to this method:

range.set_update_policy(policy)

8.3.2. Getting and Setting Adjustments

Getting and setting the adjustment for a range widget "on the fly" is done, predictably, with:

adjustment = range.get_adjustment()

range.set_adjustment(adjustment)

The get_adjustment() method returns a reference to the adjustment to which range is connected.

The set_adjustment() method does absolutely nothing if you pass it the adjustment that range is already using, regardless of whether you changed any of its fields or not. If you pass it a new Adjustment, it will unreference the old one if it exists (possibly destroying it), connect the appropriate signals to the new one, and will recalculate the size and/or position of the slider and redraw if necessary. As mentioned in the section on adjustments, if you wish to reuse the same Adjustment, when you modify its values directly, you should emit the "changed" signal on it, like this:

adjustment.emit("changed")

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