The adjustable widgets can be roughly divided into those which use and
require specific units for these values and those which treat them as
arbitrary numbers. The group which treats the values as arbitrary
numbers includes the range widgets (scrollbars and scales, the
progress bar widget, and the spin button widget). These widgets are
all the widgets which are typically "adjusted" directly by the user
with the mouse or keyboard. They will treat the lower and
upper values of an adjustment as a range within which the user
can manipulate the adjustment's value. By default, they will only
modify the value of an adjustment.
The other group includes the text widget, the viewport widget, the
compound list widget, and the scrolled window widget. All of these
widgets use pixel values for their adjustments. These are also all
widgets which are typically "adjusted" indirectly using scrollbars.
While all widgets which use adjustments can either create their own
adjustments or use ones you supply, you'll generally want to let this
particular category of widgets create its own adjustments. Usually,
they will eventually override all the values except the value
itself in whatever adjustments you give them, but the results are, in
general, undefined (meaning, you'll have to read the source code to
find out, and it may be different from widget to widget).
Now, you're probably thinking, since text widgets and viewports insist
on setting everything except the value of their adjustments,
while scrollbars will only touch the adjustment's value, if
you share an adjustment object between a scrollbar and a text
widget, manipulating the scrollbar will automagically adjust the text
widget? Of course it will! Just like this:
/* creates its own adjustments */
text = gtk_text_new (NULL, NULL);
/* uses the newly-created adjustment for the scrollbar as well */
vscrollbar = gtk_vscrollbar_new (GTK_TEXT(text)->vadj); |
