zgv.1

一个利用SDL语言来实现svgalib函数的示例程序

.RS
Enable mouse support in zgv. \fI/dev/mouse\fR must be (usually a
symlink to) the mouse device. The actual configuration of the mouse
should be done via svgalib's config file \fIlibvga.config\fR; see the
man page for that for details.
.PP
.RE
`\fB--mouse-scale \fIscale\fR\fR'
.RS
Set the ratio of `mouse pixels' to onscreen pixels. The larger the
number, the slower the mouse moves, and vice versa. (However, the number
must be greater than zero.) If the mouse pointer moves at the wrong
speed for your tastes, play about with this setting and you should be
able to fix it.
.PP
.RE
`\fB--pcd-res \fIresnum\fR\fR'
.RS
Selects the resolution used for Photo-CD files; 1=192x128, 2=384x256,
3=768x512 (default), 4=1536x1024, 5=3072x2048. (This setting only has an
effect if Photo-CD support was enabled at compile-time.)
.PP
.RE
`\fB-g\fR'
.RS
.RE
`\fB--pgm-truecol\fR'
.RS
This one needs some background to fully explain --- greyscale files are
normally displayed in 8-bit modes, which due to VGA's limited palette
means that only 64 greyscales can be shown (zgv normally fakes extra
ones, though; see \fBIncreased Greyscales\fR). But for people who work
with greyscale files and have 24/32-bit video modes available this can
be frustrating, as 24/32-bit modes display 256 greyscales. For this
reason, using the `\fB--pgm-truecol\fR' option enables a special-case
hack to read (only) PGM files as if they were 24-bit. Using a 24/32-bit
mode then gives you 256 greyscales. (Be careful to avoid 15/16-bit modes
as these will only give 32! See \fBDrawbacks of 15/16-bit Modes\fR.)
.PP
.RE
`\fB-r \fIseconds\fR\fR'
.RS
.RE
`\fB--reload-delay \fIseconds\fR\fR'
.RS
If \fIseconds\fR is positive, then any picture displayed is re-read
and redisplayed (without clearing the screen first) every
\fIseconds\fR seconds. If it's `\fB0\fR' (zero), or negative, the
picture is only read once --- the default. Unless this option has
suddenly inspired you to write an interesting little shell script,
you're unlikely ever to have a use for it. :-)
.PP
.RE
`\fB--reverse-bc-order\fR'
.RS
Normally, any brightness modification is applied after applying any
contrast. Enabling this reverses the order.
.PP
.RE
`\fB--revert-orient\fR'
.RS
(Normally enabled, use `\fB--revert-orient=off\fR' to disable.) If
disabled, orientation (flip/mirror/rotate) state is retained between
pictures.
.PP
.RE
`\fB--revert-scale\fR'
.RS
(Normally enabled, use `\fB--revert-scale=off\fR' to disable.) If
disabled, scaling is retained between pictures.
.PP
.RE
`\fB--scrollbar\fR'
.RS
(Normally enabled, use `\fB--scrollbar=off\fR' to disable.) If disabled,
don't show a scrollbar below the selector.
.PP
.RE
`\fB-s\fR'
.RS
.RE
`\fB--show-dimensions\fR'
.RS
Cause zgv to output the x and y offsets, and width and height of the
section of the image being displayed when you exit zgv. Can be useful
for things like `\fBpnmcut `zgv -s input.ppm` input.ppm > output.ppm\fR'.
.PP
.RE
`\fB-T\fR'
.RS
.RE
`\fB--show-tagged\fR'
.RS
Print names of tagged files on exit. This can be useful in constructions
something like `\fBmv `zgv -T` /tmp\fR', which moves to \fI/tmp\fR only
the files you select.
.PP
.RE
`\fB--show-xvpics-dir\fR'
.RS
Show any \fI.xvpics\fR directories so that the thumbnails can be viewed
even if the files they referred to no longer exist. (However, it's
usually easier to simply start zgv in the \fI.xvpics\fR dir.)
.PP
.RE
`\fB-S \fIdelay\fR\fR'
.RS
.RE
`\fB--slideshow-delay \fIdelay\fR\fR'
.RS
Set time to wait in seconds before loading the next picture in a
slideshow. The default is 4.
.PP
.RE
`\fB-l\fR'
.RS
.RE
`\fB--slideshow-loop\fR'
.RS
Loop in slideshows `forever' (or rather, until you exit).
.PP
.RE
`\fB-R\fR'
.RS
.RE
`\fB--slideshow-randomise\fR'
.RS
.RE
`\fB--slideshow-randomize\fR'
.RS
Randomise picture order in slideshows. Due to the shuffling approach
taken, there will be no repeats or omissions.
.PP
.RE
`\fB--viewer-16col-colour\fR'
.RS
.RE
`\fB--viewer-16col-color\fR'
.RS
Give a dithered colour image in 640x480x4 mode when in the viewer
(see \fBThe Viewer 640x480x4 Mode\fR), rather than greyscale.
.PP
.RE
`\fB-m \fImodespec\fR\fR'
.RS
.RE
`\fB--viewer-start-mode \fImodespec\fR\fR'
.RS
Specify the video mode zgv should start off using for the viewer. The
default is generally 640x480x8, but it's actually a bit more complicated
than that (see \fBDefault Video Mode\fR). The `modespec' should be the
width, height, and depth in quotes, e.g. `\fB"640 480 8"\fR'. See \fBVideo
Modes\fR, for details of precisely what this means.
.PP
.RE
`\fB--visual\fR'
.RS
(Normally enabled, use `\fB--visual=off\fR' to disable.) If disabled, no
thumbnails are shown.
.PP
.RE
`\fB-k\fR'
.RS
.RE
`\fB--vkludge\fR'
.RS
enables vkludge, which smoothes slightly when `zooming' a big picture
down to screen size, and also when in 320x400 and 360x480 modes.
.PP
.RE
`\fB--version\fR'
.RS
Show version number.
.PP
.RE
`\fB-w\fR'
.RS
.RE
`\fB--write-ppm\fR'
.RS
Write the file as a PPM to stdout rather than viewing it. (This only
works if you run zgv on a single file, specified on the command-line.)
You're usually better off using a dedicated image-converting program,
though.
.PP
.RE
`\fB--xzgv-keys\fR'
.RS
Makes zgv acts a bit more like xzgv, at least in terms of the keypresses
it supports (see \fBxzgv Compatibility\fR).
.PP
.RE
`\fB-z\fR'
.RS
.RE
`\fB--zoom\fR'
.RS
Enable zoom mode, which resizes the picture to fit the screen.
See \fBZoom Mode\fR.
.PP
.RE
`\fB--zoom-reduce-only\fR'
.RS
When in zoom mode, only \fIreduce\fR pictures to fit; i.e. make big
pictures viewable all-at-once while leaving small picures intact.
.RE
.PP
If zgv is started with `\fBzgv \fIfile\fR\fR', zgv auto-loads the file
(bypassing the file selector), and exits when you exit from viewing the
picture. (By the way, this also makes it possible to view single files
without the usual extensions such as \fI.gif\fR, etc. See \fBFile Type
Identification\fR.)
.PP
If started with `\fBzgv \fIfile file2 ...\fR\fR' --- i.e. with more than
one filename --- zgv works in a similar way, except the multiple files
are shown as a slideshow, one after the other. You may want to specify
`\fB-l\fR' so that zgv will loop around these pictures until `\fBEsc\fR' is
pressed, and the `\fB-R\fR' option to shuffle (randomise) the picture
order may also be of interest.
.PP
If started with `\fBzgv \fIstart-dir\fR\fR', zgv starts up with the usual
file selector, but with the current directory being the one specified.
.PP
Settings which are either on or off (boolean) are, as you might expect,
enabled by using e.g. `\fB-z\fR' or `\fB--zoom\fR'. However, there's an
alternative long-option form for setting these, resembling how they're
set in config files --- the syntax is `\fB--option=\fIstate\fR\fR', where
\fIstate\fR is `\fBon\fR'/`\fBy\fR'/`\fByes\fR'/`\fB1\fR' to enable the
option, or `\fBoff\fR'/`\fBn\fR'/`\fBno\fR'/`\fB0\fR' to disable it. The
most useful thing about this is that it allows you to disable options
which were previously enabled, by using e.g. `\fB--zoom=off\fR'.
.PP
(Readers used to the way GNU-style long options work should note that,
since this `\fBon\fR'/`\fBoff\fR'/etc. arg is optional, you can't use the
`\fB--option arg\fR' form in this case; it must be `\fB--option=arg\fR'
for it to work.)
.PP
.SH "ONLINE HELP"
Online help (of a sort) is available in both the file selector and
viewer:
.PP
`\fB?\fR'
.RS
Gives online help. This lists some of the most commonly-used keypresses
in the current context.
.RE
.PP
In the viewer, you can also get a list of which key combinations select
which video modes. See \fBSelecting a Video Mode\fR.
.PP
.SH "THE FILE 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.
.PP
.SH "EXITING ZGV"
Exiting zgv can be achieved two ways:
.PP
`\fBEsc\fR'
.RS
.RE
`\fBx\fR'
.RS
Quit zgv normally.
.PP
.RE
`\fB^C\fR'
.RS
Quit zgv in a rather immediate and nasty way, by sending \fISIGINT\fR.
(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.
.PP
(Technically it may not be `\fB^C\fR' which sends \fISIGINT\fR, but you
would have to have a strange setup for this to be the case.)
.RE
.PP
.SH "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.)
.PP
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.
.PP
If no thumbnail exists for a file or directory, a small `document' or
`folder' graphic appears instead.
.PP
.SS "Updating Thumbnails"
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 \fI.xvpics\fR.
.PP
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
`\fBu\fR'.
.PP
Alternatively, you can create/update thumbnails for the current
directory and all subdirectories by using `\fBAlt-u\fR'. But be warned
that a recursive update can take some time!
.PP
`\fBu\fR'
.RS
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 \fIupdating index of\fR prefixes the usual
display of the current directory's name.
.PP
You can press `\fBEsc\fR' 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).
.PP
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.
.PP
.RE
`\fBAlt-u\fR'
.RS
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 (see \fBDialog Boxes\fR). As above, it will continue running `in the
background' if you switch consoles, and you can press `\fBEsc\fR' to
abort.
.PP
.RE
`\fBd\fR'
.RS
Create thumbnails for subdirectories. Don't confuse this with the
recursive update; this generates thumbnails for the directories
\fIthemselves\fR, 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 `\fBd\fR'.
.RE
.PP
.SS "Thumbnail Storage"
Normally, thumbnails are stored in the subdirectory \fI.xvpics\fR
(creating the dir first if needed), with the same name as the filename
they represent. However, there are times when using \fI.xvpics\fR isn't
possible --- for example, the filesystem may be read-only (such as on a
CD), or may not support the \fI.xvpics\fR name (such as on an
\fImsdos\fR filesystem), or you may not have permission to write to the
directory.
.PP
In these situations, zgv stores the thumbnails elsewhere. They go in
directories under the \fI.xvpics\fR 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 (`\fB/\fR') converted to underscores
(`\fB_\fR').
.PP
An example should make things clearer. Say zgv needs to create a
thumbnail for \fIwibble.jpg\fR, in the directory \fI/foo/bar/baz\fR,
but can't use \fI.xvpics\fR. It will put the thumbnail in
\fI$HOME/.xvpics/_foo_bar_baz/wibble.jpg\fR, creating directories as
necessary.
.PP
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.
.PP
.SS "Thumbnail Issues"
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.
.PP
(All the same, you can disable this using the config file setting
\fIfs-perfect-cols\fR (see \fBConfiguring zgv\fR). But bear in mind
that the selector will then look rather strange!)
.PP
In 16-colour mode (see \fB16-colour File Selector\fR), 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.
.PP
.SH "SCREEN LAYOUT"
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; see \fBChanging the Sorting
Order\fR). 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. (See \fBOther File Sel Commands\fR, for how to display the full
filename.)
.PP
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.
.PP
The colours used for the file selector can be changed, if you dislike
the defaults (see \fBConfiguring zgv\fR).
.PP
.SH "MOVING AROUND THE LIST"
The cursor in zgv is (normally) shown as a `raised' entry in the list.
The cursor has two main functions:
.PP
\fB-\fR 
It selects a file for `view', `tag' etc. commands to operate on.
.PP
\fB-\fR 
It determines which part of the list is shown, as the part of the list
shown onscreen always contains the cursor.