zgv.texi

一个利用SDL语言来实现svgalib函数的示例程序

Online help (of a sort) is available in both the file selector and
viewer:

@table @kbd
@kindex ?
@item ?
Gives online help. This lists some of the most commonly-used keypresses
in the current context.
@end table

In the viewer, you can also get a list of which key combinations select
which video modes. @xref{Selecting a Video Mode}.


@node  The File Selector, The Viewer, Online help, Top
@comment  node-name,  next,  previous,  up
@chapter The File Selector

@c XXX could do with synonyms for `selector' here...
@cindex file selector
@cindex the file selector
@cindex selector

Usually, on starting up zgv, you will enter the file selector, which
lets you pick files to view (among other things). This lists the
subdirectories and picture files in the current directory, along with
small `thumbnail' versions of the pictures if they exist.

@menu
* Exiting zgv::                 Why would you want to? :-)
* Thumbnails::                  How to create thumbnails, and how they
                                  work.
* Screen Layout::               The file selector lists dirs/files.
* Moving Around The List::      How to move the cursor.
* Viewing a File::              How to view a single file.
* Dialog Boxes::                How zgv reports errors and asks you things.
* Tagging::                     You can tag (mark) multiple files, then
                                  view/copy/move/delete them.
* Renaming a File::             Renaming a single file or directory.
* Changing Directory::          As well as the normal dir-by-dir way,
                                  you can jump directly to a directory.
* Changing the Sorting Order::  Files can be sorted by name,
                                  `extension', size, and date/time.
* File Selector Toggles::       Some options can be changed while zgv is
                                  running.
* Other File Sel Commands::     Miscellaneous operations.
* Showing More Files::          You can use different video modes for the
                                  file selector, showing more files at
                                  once.
* 16-colour File Selector::     If 640x480 256-colour mode is absent
                                  thumbnails don't look as good, but you
                                  can choose between monochrome and
                                  colour approximations.
@end menu


@node  Exiting zgv, Thumbnails, The File Selector, The File Selector
@comment  node-name,  next,  previous,  up
@section Exiting zgv

@cindex exiting zgv
@cindex quitting zgv
@cindex leaving zgv

Exiting zgv can be achieved two ways:

@table @kbd
@kindex Esc (Selector)
@item Esc
@kindex x (Selector)
@itemx x
Quit zgv normally.

@kindex ^C
@item ^C
Quit zgv in a rather immediate and nasty way, by sending @samp{SIGINT}.
(This is actually dealt with by svgalib.) You should only use ^C to quit
if zgv appears to lock up or takes an unbearably long time to do
something.

(Technically it may not be @kbd{^C} which sends @samp{SIGINT}, but you
would have to have a strange setup for this to be the case.)
@end table


@node  Thumbnails, Screen Layout, Exiting zgv, The File Selector
@comment  node-name,  next,  previous,  up
@section Thumbnails

@cindex thumbnails
@cindex picture thumbnails
@cindex file thumbnails
@cindex xv-compatible thumbnails

(This section is deliberately early on in the manual, as thumbnails are
probably the most important feature of the file selector, so it's best
that you know how to create/update them sooner rather than later.)

Thumbnails are small versions of the pictures they represent, and are
displayed by the file selector if they exist. zgv uses xv-compatible
thumbnails --- if you create thumbnails with xv they will work with zgv,
and vice versa. zgv's thumbnails are also compatible with the Gimp, and
xzgv.

If no thumbnail exists for a file or directory, a small `document' or
`folder' graphic appears instead.

@menu
* Updating Thumbnails::         How to create or update thumbnails.
* Thumbnail Storage::           Where thumbnails are stored.
* Thumbnail Issues::            Thumbnails need all 256 colours.
@end menu

@node  Updating Thumbnails, Thumbnail Storage, Thumbnails, Thumbnails
@comment  node-name,  next,  previous,  up
@subsection Updating Thumbnails

@cindex updating thumbnails
@cindex creating thumbnails
@cindex making thumbnails
@cindex thumbnails, creating
@cindex thumbnails, updating
@cindex directory, updating thumbnails in a
@cindex recursively, updating thumbnails
@cindex tree, updating all thumbnails in a directory

While thumbnails can be made relatively quickly, it's by no means an
instant process. For this reason, thumbnails have to be created in
advance, and are stored as files in their own right in (usually) a
subdirectory @file{.xvpics}.

zgv never creates/updates thumbnails without you telling it to. So, if
you enter a directory where the picture files don't have any thumbnails,
or where the thumbnails seem to be out of date, you should press
@kbd{u}.

Alternatively, you can create/update thumbnails for the current
directory and all subdirectories by using @kbd{Alt-u}. But be warned
that a recursive update can take some time!

@table @kbd
@kindex u (Selector)
@item u
Create thumbnails for any files which don't have them, and update
thumbnails which are older than than the corresponding file. While this
is going on, the text @samp{updating index of} prefixes the usual
display of the current directory's name.

You can press @kbd{Esc} while the update is in progress to abort it; zgv
will stop once it has finished the thumbnail it is currently working on
(if any).

If you switch consoles while the update is in progress, it will continue
to run `in the background'. When you switch back, if the update is still
in progress, it may look as though zgv is doing nothing (or the screen
may look a bit confusing) for some time. The reason is that the screen
is not updated unless zgv is running on the currently displayed console
(this is unfortunately necessary). The screen is redrawn when the
current thumbnail has been dealt with.

@kindex Alt-u (Selector)
@item Alt-u
Create/update thumbnails for all files in the current directory and all
subdirectories --- in other words, do a recursive update. This can take
some time, so you are prompted to confirm that you really want to do
this (@pxref{Dialog Boxes}). As above, it will continue running `in the
background' if you switch consoles, and you can press @kbd{Esc} to
abort.

@kindex d (Selector)
@item d
Create thumbnails for subdirectories. Don't confuse this with the
recursive update; this generates thumbnails for the directories
@emph{themselves}, not the files within them. (Most people probably
won't want to bother with these, as they're not as helpful as you might
think.) These consist of the first four files in the subdir, squeezed
together into a single thumbnail. There is (currently) no `update'
mechanism for subdir thumbnails --- all of them are newly created each
time you press @kbd{d}.
@end table


@node Thumbnail Storage, Thumbnail Issues, Updating Thumbnails, Thumbnails
@comment  node-name,  next,  previous,  up
@subsection Thumbnail Storage

@cindex thumbnails, storage
@cindex thumbnails, location
@cindex storage of thumbnails
@cindex location of thumbnails

Normally, thumbnails are stored in the subdirectory @file{.xvpics}
(creating the dir first if needed), with the same name as the filename
they represent. However, there are times when using @file{.xvpics} isn't
possible --- for example, the filesystem may be read-only (such as on a
CD), or may not support the @file{.xvpics} name (such as on an
@samp{msdos} filesystem), or you may not have permission to write to the
directory.

In these situations, zgv stores the thumbnails elsewhere. They go in
directories under the @file{.xvpics} dir in your home directory. The
name for the directory they go in there is the directory name they were
found in, but with slashes (@code{/}) converted to underscores
(@code{_}).

An example should make things clearer. Say zgv needs to create a
thumbnail for @file{wibble.jpg}, in the directory @file{/foo/bar/baz},
but can't use @file{.xvpics}. It will put the thumbnail in
@file{$HOME/.xvpics/_foo_bar_baz/wibble.jpg}, creating directories as
necessary.

Where a thumbnail is stored makes virtually no difference to how zgv
works; the main difference is that the latter, more indirect way of
storing thumbnails means that thumbnails will take slighter longer to
display.


@node  Thumbnail Issues,  , Thumbnail Storage, Thumbnails
@comment  node-name,  next,  previous,  up
@subsection Thumbnail Issues

@c XXX could do with one here which doesn't start "thumbnails" :-)
@cindex thumbnails, issues relating to
@cindex thumbnails, problems with displaying

The thumbnails used in zgv require 256 colours to display.
Unfortunately, the rest of zgv's file selector needs an additional five
colours. Normally this is dealt with by finding the `closest' thumbnail
colours, and (this is the important part) changing them to the file
selector colours. The disturbance to the thumbnails should be barely
noticeable.

(All the same, you can disable this using the config file setting
@samp{fs-perfect-cols} (@pxref{Configuring zgv}). But bear in mind
that the selector will then look rather strange!)

In 16-colour mode (@pxref{16-colour File Selector}), the way it works
means fewer colours are needed, and the file selector's five colours can
be (and are) separate from the thumbnail colours.


@node  Screen Layout, Moving Around The List, Thumbnails, The File Selector
@comment  node-name,  next,  previous,  up
@section Screen Layout

@cindex screen layout
@cindex layout, screen
@cindex file selector, layout of

@c I avoid saying "dirs are shown in brackets" here because that might
@c be gratuitously confusing for American English speakers, especially
@c since [square brackets] (the US meaning of brackets, IIRC) *are*
@c used for showing dirs in some other programs.
@c
@c Yes, I know I could instead say they're in parentheses. Shut up. :-)

The file selector is simply a list of subdirectories and filenames,
along with any thumbnails that exist for them. The list is in
asciibetical order (but you can change this; @pxref{Changing the Sorting
Order}). Names of directories are shown (like this), and they are shown
in order at the beginning of the list, before all the picture files.
Long filenames are truncated to fit; three dots indicate where this has
happened. (@xref{Other File Sel Commands}, for how to display the full
filename.)

The list is often larger than can fit on the screen at once. If this is
the case, only part is shown at a time, but you can move around the list
with the cursor keys and the like.

The colours used for the file selector can be changed, if you dislike
the defaults (@pxref{Configuring zgv}).


@node  Moving Around The List, Viewing a File, Screen Layout, The File Selector
@comment  node-name,  next,  previous,  up
@section Moving Around The List

@cindex moving around the file list
@cindex file selector, moving around
@cindex file selector, cursor movement in
@cindex cursor
@cindex choosing a file
@cindex selecting a file
@cindex picture, selecting

The cursor in zgv is (normally) shown as a `raised' entry in the list.
The cursor has two main functions:

@itemize @minus
@item
It selects a file for `view', `tag' etc. commands to operate on.

@item
It determines which part of the list is shown, as the part of the list
shown onscreen always contains the cursor.
@end itemize

There are many commands for moving the cursor. In summary, most
`special' keys like the cursors do what you'd imagine they do --- also,
a few Emacs-like keys, a few vi-like keys, and the Sinclair
Spectrum-style (!) QAOP keys are supported.

@c This para should really go at the root file-sel node, but it
@c just doesn't fit there. It's probably tolerable to have it here I
@c guess; it's a good bet that people would read this before reading any
@c later stuff, and/or that they'd guess the "Using a Mouse" section
@c might be relevant. ;-)

Using a mouse in the file selector is not covered here. @xref{Mouse
Funcs in the File Selector}, for details of what you can do with a
mouse. (Experienced users may wish to consult the @cite{Tom & Jerry} and
@cite{Pinky and the Brain} cartoons for further enlightenment on this
subject.)

@table @kbd
@kindex Cursor Up (Selector)
@item Cursor Up
@kindex ^P (Selector)
@itemx ^P
@kindex k (Selector)
@itemx k
@kindex q (Selector)
@itemx q
Move up. Moving up from a topmost entry moves to the bottom of the
previous column.

@kindex Cursor Down (Selector)
@item Cursor Down
@kindex ^N (Selector)
@itemx ^N
@kindex j (Selector)
@itemx j
@kindex a (Selector)
@itemx a
Move down. Moving down from a bottommost entry moves to the top of the
next column.

@kindex Cursor Left (Selector)
@item Cursor Left
@kindex ^B (Selector)
@itemx ^B
@kindex h (Selector)
@itemx h
@kindex o (Selector)
@itemx o
Move left one column.

@kindex Cursor Right (Selector)
@item Cursor Right
@kindex ^F (Selector)
@itemx ^F
@kindex l (Selector)
@itemx l
@kindex p (Selector)
@itemx p
Move right one column.

@kindex Page Up (Selector)
@item Page Up
@kindex ^U (Selector)
@itemx ^U
Move the cursor back (nearly) a page.

@kindex Page Down (Selector)
@item Page Down
@kindex ^V (Selector)
@itemx ^V
Move the cursor forward (nearly) a page.