customkeyfocus.C's
x::w::create_nonrecursive_visibility_focusframe_impl()
and
x::w::create_always_visible_focusframe_impl()
assemble the implementation object for a standard input focus
frame container. They implement two ways of handling the visibility
of the focus frame container's contents.
A widget's show() or
hide() makes the widget visible or
invisible.
A container's show_all() and
hide_all() recursively updates the visibility
of the container itself and everything inside it. This is equivalent
to show() or hide()
not just for the container itself, but for everything inside it,
recursively.
This matters because a given widget is visible not only
when it's show()n, but only if all of its
parent containers are also show()n.
hide()ing a container makes the entire
container disappear, even if some widgets in the container
are show()n. Each widget maintains
its own visibility state, and the final visibility of a given
widget requires all of its parent containers to be visible.
x::w::nonrecursive_visibilityObj template mixin
x::w::create_nonrecursive_visibility_focusframe_impl()
uses x::w::nonrecursive_visibilityObj
to create the
focus frame container's implementation object class.
x::w::nonrecursive_visibilityObj is a
template mixin that overrides show_all()
and hide_all() for the resulting widget. They become equivalent to
show() and
hide().
This makes the resulting container behave similar to a monolithic
widget. Otherwise, a
hide_all() followed by
show() results
in the container being visible, but none of the container's
elements being visible. This is because
hide_all() hid everything, but
show() made only the container visible.
For a simple widget, and not a container,
show() and
hide() are the same as
show_all() and
hide_all().
Only containers have
other widgets that
show_all() and
hide_all() affects.
This template mixin makes containers look like simple widgets
in that respect.
The
x::w::nonrecursive_visibilityObj
template mixin results in a container that behaves as a monolithic
widget, for visibility purposes.
hide_all() followed by
show() makes the container's contents appear,
as if the container is just a single widget, because
hide_all() ignored the container's elements
in the first place.
New widgets are not visible upon creation, by default.
This remains the case. Each widget that gets added to this
container should still be
show()n (or
show_all()ed, perhaps),
in order for this to work
correctly.
This is why
customkeyfocus.C
still needs to show() the custom
widget after it gets added to a non-recursive visibility
input focus frame.
x::w::always_visibleObj template mixin
x::w::create_always_visible_focusframe_impl()
uses the x::w::always_visibleObj to create the
focus frame container's implementation object class.
x::w::always_visibilityObj is a
template mixin that overrides show_all()
and hide_all() for the resulting widget.
x::w::always_visibleObj disables
show_all() and
hide_all() for its container,
but only for the container itself.
show_all() and
hide_all() still apply to
all widgets in the container.
Additionally, x::w::always_visibleObj
automatically show()s the container after
it gets created.
Only show_all() and
hide_all() get disabled.
show() and
hide() still have the usual effect
on the container.
x::w::container_visibleObj template mixin
x::w::create_nonrecursive_visibility_focusframe_impl()
and
x::w::create_always_visible_focusframe_impl()
use the x::w::container_visible_elementObj
template mixin.
LibCXXW automatically provides
scroll-bars
for the application's window if it's too big to fit on the screen.
When that happens,
widgets that receive keyboard focus get automatically
scrolled into view if they are not fully visible.
This template mixin adjusts the scrolling so that its entire container gets scrolled into view instead of just some widget in the container. The standard input focus frame is a container, and using this template mixin scrolls the entire input focus frame into view, instead of the focusable widget in the container, leaving one edge of the input focus frame scrolled out of view.