borderlayoutmanager.C
creates two bordered elements. The one on the right has a title.
A bordered widget with a title requires some additional space, to
make room for the title text, so
borderlayoutmanager.C aligns both elements on their
bottom margins, for an even look.
x::w::new_borderlayoutmanager nblm; nblm.title("Hello world");
x::w::new_borderlayoutmanager's
title is an initially empty
x::w::text_param.
A non-empty title creates a title for the bordered
widget.
borderlayoutmanager.C's
left bordered widget does not have a title, unlike the the right
bordered widget. Besides the title, the two bordered elements have
a slightly different visual apperance. The title-less bordered widget
has a slightly shaded, visually-highlighted background color.
The border layout manager uses a slightly non-standard approach
to background colors when no title gets specified.
Without a title the border layout
manager automatically installs a theme-specified background color for
the widget in the border.
Setting the no_background flag in the
x::w::new_borderlayoutmanager
turn off this default behavior.
This behavior gets automatically turned off when creating a border with a title, which is why the right bordered widget has a plain background color. There's no explicit border drawn under the title, to serve as an explicit edge to the highlighted border. It would not look good, so the highlighted background does not get installed when the new border has a title.
blm->update_title("Lorem Ipsum");
The border layout manager's update_title()
replaces the container's current title. It is recommended that
the title should not be an
empty string, and bordered containers that got created without a title
should not use update_title to specify a
title after their creation. Adding or removing a title
requires resizing the container. This is because the title uses up.
additional vertical real estate; and the border layout manager does
not update the existing widget's background color either.
An untitled border widget's default background color gets set when
the bordered widget gets created by
replace()'d factory.
The border layout manager inherits
from the utility singleton layout manager object, which implements
methods for replacing the widget in the container. The border
layout manager overrides the new widget's background color if there's
no title, and explicitly removes the widget's background color
if there is a non-empty title.
A preferred approach to modifying the contents of a bordered
widget is to use
x::w::new_borderlayoutmanager
creator lambda to create a discrete container, with a
stock grid layout manager, and use the grid layout manager to
control the contents inside the border.
The page,
book, or event
pane layout managers are
other available options.