focusing.txt

操作系统文件管理

							1999-05-13
							Emil Brink

		Keyboard focusing in gentoo

1. INTRODUCTION
This little scratch document introduces the support for keyboard-
controlled focusing introduced with gentoo 0.11.6.


2. WHAT?
The #1 request I've received from users of gentoo during the time
it has been publicly available (around 8 months or so, I think),
has been to add support for keyboard navigation. I have always
responded with that this is difficult under current versions of
the GTK+ toolkit.
	It still is, but I hacked around that.
	Basically, gentoo now supports the notion of "focus",
which works a bit like a cursor would in a text-editing program.
At any one time, zero or one row is currently focused. There is
a command which does the equivalent of a double-click on the
currently focused row, thus allowing you to e.g. enter directories,
view text files, and so on. It's pretty neat.
	The focused row is rendered in what is hopefully a clear
manner, allowing you to distinguish between it and other, non-
focused rows. The focusing is also visible regardless of whether
the focused row is currently selected or not.
	It is at this point not possible to customize the colors
used for focusing. I expect this to become possible in a later
release.


3. HOW?
The focusing is controlled by the addition of a single new built-
in command, DpFocus. Various internal routines have also been
extended and modified to be focus-aware.
	The DpFocus command works with command arguments, and is
therefore documented in "docs/scratch/command_args.txt".
	Since the documentation there is perhaps a bit terse,
I might as well repeat it here using 1,000 words (but no pictures).

3.1 The DpFocus Command Syntax
The general syntax of the command is:

	DpFocus [center=<bool>] [select=<bool>] <what>

The parts within brackets are optional. When left out, they both
default to FALSE (see below for what this really means). The word
<what> controls what should be focused, or what should be done with
the already focused row.
	<what> must be one of:
none	Hides the focus. It will not reappear until you execute a
	DpFocus command with <what> equal to one of {next,prev,
	last,first}.
same	Keeps the same row focused. Handy for creating a command
	that just toggles the selection of the currently focused
	row, without moving the focus (the command would then be
	"DpFocus select=true same"). This is the default value
	for the <what> part of the command, but I generally think
	it should be included anyway, for clarity.
next	These two simply move the focus one row up ("prev") or down
prev	("next"). If the wanted row is outside of the pane, the
	focus will wrap around. The pane will scroll to keep up.
last	These two move the focus to the lower ("last") or upper
first	("first") extreme of the pane.

Finally, if <what> is "activate", gentoo will simulate a double-
click on the currently focused row.

If "center" is TRUE, the pane will scroll to make the focused
row appear close to the vertical center. A handy command to bind
to e.g. Ctrl-L is "DpFocus center=true same".

If "select" is TRUE, the row that was focused BEFORE the rest
of the DpFocus command changes the selection (assuming it does)
has its selection status toggled. This means that if you're on
row 0, and execute "DpFocus select=true next", row 0 will have
its selection toggled, and then row 1 will be in focus.

(Darn, that's only 571 words)