Mostra

A Universal IFF Viewer

Copyright © 1990-1994 Sebastiano Vigna

Version 2.0

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1 Introduction

Mostra is an IFF ILBM viewer that can process any IFF ILBM file; this means not only IFF ILBM FORMs, but also nested ILBM, FTXT, FORMs, CATs, LISTs and PROPs. It is well renowned in the Amiga community for both its robustness and its flexibility.

Any design requires tradeoffs: Mostra tries to give you a good balance of program size, speed (optimized assembler decompression routines) and features. It tries to be enough smart to have always reasonable defaults, but also lets you force any aspect of the display, such as resolution and video flags. While it is not possible to foresee every possible race condition, Mostra should be able to cope with any reasonable ILBM file.

Version 2.0 has been completely rewritten with the Release 2 in mind (and with an eye towards 3.0). This means complete AGA support, localization, clipboard reading, display database access, selectable autoscroll, no need for arp.library, and more. The support for SHAM images has been dropped, because the new PCHG chunk supports much better line-by-line palette changes.

2 Installation

Mostra does not need any particular treatment when installed. However, if you are interested in localization, you should take some care.

Localization means that Mostra will try to give its messages in your preferred language. It is a feature available under 2.1 and beyond. For it to work, Mostra has to be able to find out its catalogs. There are two ways of doing this: either you copy the ‘Catalogs’ directory coming with Mostra’s distribution in the same directory where Mostra lives, or you copy the contents of the ‘Catalogs’ directory in your ‘Locale:Catalogs’ directory. The first solution allows for easier maintenance, but with the second one you can move Mostra’s executable anywhere, and you will never have any problems. If you decompress Mostra’s archive, the ‘Catalogs’ directory will be automatically created for you.

3 Syntax

Mostra can be called both from the CLI and from the Workbench. It is also a pure program, i.e., it can be made resident.

3.1 Command Line Usage

To get the command line syntax in AmigaDOS style, type ‘M ?’ followed by <RETURN>; this will produce the input template:

Mostra 2.0 Copyright (C) 1990-1994 Sebastiano Vigna
Files/M,Clip/K/N,A=All/S,R=Repeat/S,Q=Quiet/S,
NoFastDraw/S,C=Center/S,B=BlackBackground/S,
Cycle/S,Secs/K/N,Fade/K/N,NO=NoStartup/S,Batch/K,
LockPic/S,N=NoMouse/S,F=FreeMouse/S,LockKeys/S,
NA=NoActivate/S,DB=DoubleBuffering/S,DM=DisplayMode/K,
DC=DisplayClip/K,CAMG/K/N,W=Width/K/N,H=Height/K/N,
AS=AutoScroll/S,HiRes/S,LoRes/S,SuperHiRes/S,
Lace/S,NoLace/S,HAM/S,HalfBrite/S,FallBack/S,
SMR=ScreenModeReq/S,FR=FileReq/S,PubScreen/K

(If you do not know how to read a template, take a look at the AmigaDOS manuals.)

Mostra’s first argument is a list of patterns (or file names) as long as you want; you will get every picture whose name matches one of the patterns. The second argument specifies instead the number of a clipboard unit to read (this will usually be 0). Note that you can specify both arguments on the same line.

Alternatively, you can type only the ‘M’ character, and Mostra will display the system file requester, allowing you to search for the picture you want to show. Note that under version 2.1 and beyond you can select multiple files using <SHIFT>-click.

For a detalied explanation of the keywords, see Options.

While showing each picture, Mostra displays some information about the file and the screen mode. First all the information IFF chunks (such as ANNO, AUTH, et cetera) are printed, then the picture and the display clip dimensions, followed by the size, depth and type of the screen, are displayed.

3.2 Workbench Usage

When Mostra is called from Workbench without any argument icon, it will pop up the file requester and will allow you to select the pictures to show. Alternatively, you can <SHIFT>-select multiple icons together with Mostra’s one, or you can change the default tool of your pictures. For details about this, see Startup Tool Types. Note that if you select an IFF CAT or LIST you will have an automatic little slideshow.

When Mostra is called from Workbench, it never outputs diagnostic or error messages. If you have problem in displaying a picture, you may want to try from the CLI. This can raise a problem if the ‘Repeat’ option is used, and ‘BlackBackground’ is not specified (see section Options). In this case, if none of the specified files and icons is an IFF picture, since no window will be ever opened Mostra will continue to endlessly scan the argument list, and the only way of stopping it will be by sending a break signal using the status and the break commands from the CLI, or some task handling utility.

All the options available on the command line are available through tool types. See section Options, and Startup Tool Types. You can also peek at the tool types of Mostra’s icon.

3.3 Keyboard Usage

Once you are looking at the picture you selected, you can exit by moving the mouse pointer to the very top of the screen and pressing the right button (you can also press the <RETURN>, <SPACE> or <ESCAPE> keys). You can drag or depth arrange the screen with the left mouse button (the gadget(s) are invisible, but they really are there!). <TAB> will toggle on/off color cycling. <SHIFT>-<TAB> will do the same, but it will also reset the palette to its initial value. To stop pattern matching or IFF scanning use <CTRL>-C at any moment.

If the screen size is less than the size of the picture, you can move around with cursor keys alone (moving by 8 pixels) or in combination with the <SHIFT> (a screenful minus 16 pixels), <ALT> (which brings you to the borders), or <CTRL> (16 pixels) keys. A noteworthy feature of Mostra is that the picture is not decrunched all at one time in a very large chunk of memory; instead, a fast assembler routine decrunches the file in real-time every time you move (the routine could be faster, but it has lots of controls to get rid of damaged IFF BODY chunks; safety always first). This is not as fast as the memory-eating method, but I think it’s much better. Very large pictures (like 800x900) will be shown in a full screen (generated on the fly at Workbench size) in which you can move around. Overscan pictures will retain their size of it’s not greater than the video overscan available for the picture video mode (for instance, 362x283 lo-res pixels in PAL, or 362x241 in NTSC). Small brushes will be shown in a minimum 128x128 pixel screen. Of course, moving vertically with multi-palette pictures involves a high system overhead, since Copper lists are continuously built and deleted.

A weird effect of this method is that you can see pictures that can’t even be loaded into your Amiga. Let’s suppose you have a really crunched picture; the BODY chunk and a 256x256 lo-res screen could take much less space than the decrunched picture, so you could create pictures that only Mostra could let you see in all of their parts. Why you would want to do this, well, that’s another matter.

If you own a large amount of Chip memory, you can also consider using the ‘AutoScroll’ keyword, that will force Mostra to decrunch the whole picture in one gulp, and to use the system screen scrolling features.

3.4 Options

This list describes all the options available in Mostra. The letters between parentheses denote availability of a shortening. Options can be put anywhere on the command line, or in tool types (see section Startup Tool Types).

All (A)

forces a recursive scan of all of the subdirectories during the wildcard search.

Repeat (R)

will endlessly restart from the first picture when it has finished with the last one; this includes repeating the wildcard search, checking for the clipboard, and opening the file requester, if any of these options has been specified. If you used the FileReq line argument, the Cancel gadget will break the loop.

Quiet (Q)

turns off all messages except in case of error.

NoFastDraw

leaves the program at priority 0; by default, Mostra will surround the BODY decrunching operations with a SetTaskPri(1). This will not lock the system, but in a multitasking situation Mostra will perform quickly when needed. If your program has already a priority greater than one, Mostra will leave it untouched.

Center (C)

will force the screen to be centered. Note that the centering is based on your Overscan preferences.

BlackBackground (B)

will create a 1-bitplane black screen that will stay until you saw the last picture. This is for aesthetic purposes only (note that almost no Chip memory will be used).

Cycle

will automatically activate color cycling on every picture. Usually this happens only by request, through <TAB>.

Secs

must be followed by a number between 0 and 1000. Mostra will display each picture for the number of seconds specified, but you can skip using the mouse or the keyboard as usual (see section Keyboard Usage) or stop the show with <CTRL>-C. Cursor keys are disabled.

Fade

lets you specify a speed for pictures to fade in and out. Valid numbers are 1 to 4, with four the slowest. Note that HAM pictures can’t be faded.

NoMouse (N)

will hide the mouse pointer while Mostra is displaying a picture.

FreeMouse (F)

will let you pass from one picture to another by clicking either of the mouse buttons at any position on the screen.

LockKeys

will discard any input from the keyboard during the display. You must use the mouse to pass to the following picture. Note that if FreeMouse is not activated, the only way to go is clicking the right mouse button while the mouse pointer is at the top of the screen.

LockPic

will lock the picture displayed. You won’t be able to scroll around, but the memory in which the file is loaded will be immediately freed after the decompression, thus minimizing the memory usage.

NoActivate (NA)

will inhibit the activation of the picture screens, so you can keep on typing on your current screen.

DoubleBuffering (DB)

sets a double buffering show mode: while a new picture is being loaded you will see the old one, no Workbench pop-up or black screens. It eats lots of memory, too.

DisplayMode (DM)

sets a specific display mode from the graphic database. For instance, you can ask to display your picture in ‘NTCS:Lores’. Note that under 2.1 and beyond the database entries are localized, so that you need to know the name of the display mode in the first language currently selected in the locale preferences. This option is the safest and most precise way of forcing a display mode (but see also the ScreeModeReq option).

DisplayClip (DC)

sets a specific display clip from the graphic database. For instance, you can ask to display the maximum available amount with ‘VIDEO’. Allowed values are ‘TEXT’, ‘GRAPHICS’, ‘MAX’ and ‘VIDEO’. Note that these entries are not localized. Under 3.0, in particular, the ‘VIDEO’ display clip allows you to see 736 pixel width pictures in PAL and NTSC (see also the ScreeModeReq option).

CAMG

sets a specific display ID, expressed as a decimal number. This option is mainly useful for developers. It has the same effect as a CAMG ILBM chunk.

Width (W)

Height (H)

want an argument that specifies a dimension of the viewing screen. However, Mostra is an intelligent program, and will almost always find the correct screen by itself. The minimum allowed dimension is 128; smaller values will be silently increased to this value. Note that if ‘AutoScroll’ was specified, only the display clip dimensions are changed—the screen will retain its full size.

AutoScroll (AS)

sets the automatic scrolling feature. The whole picture has to be decompressed in a big chunk of Chip memory, but then you can scan through it very smoothly by moving the mouse towards the edges of the video (exactly like in a Workbench which is bigger than your screen size). It works also with multipalette pictures (but in rare occasions, some glitches may be visible in certain scroll positions).

HiRes

LoRes

SuperHiRes

Lace

NoLace

HAM

HalfBrite

force all screens to have the respective mode bit set (note that if Mostra finds a six bitplane picture with no CAMG chunk, it won’t set the HAM flag by default). These flags are dumb, that is, they will do exactly what you say, even if it is meaningless. However, if you use both HalfBrite and HAM together, only the former will take place. You should avoid in general the use of these options, and rather ask for a specific display mode with ‘DisplayMode’, ‘DisplayClip’ and ‘ScreenModeReq’.

FallBack

forces Mostra to try to guess the best display mode with which it can display a picture in case its natural (or user specified) display mode is not available.

ScreenModeReq (SMR)

forces Mostra to open the screen mode requester on the public screen specified by the ‘PubScreen’ option, allowing you to specify a display mode, display clip, screen size and optional autoscroll. This option is functional only under 2.1 and beyond. Note that the selections made in the requester will supersede all the related keywords (such as ‘Width’, ‘AutoScroll’ et cetera). However, if the keywords are specified they will be used in order to initialize the requester fields.

FileReq (FR)

tells Mostra to open the system file requester on the public screen specified by the ‘PubScreen’ option. Note that you can specify this option together with file names and clip numbers. Mostra will turn its attention to file names, clips and input from the file requester, in this order.

PubScreen

specifies a public screen to open the file and screen mode requesters on. The screen is moved to front before opening the requester. This option is functional only under 2.1 and beyond.

The NoStartup and Batch options will be discussed later, in Startup Files.

3.5 Examples

And now, some examples:

M MyPics:#? Secs 5 Fade 1 NoMouse BlackBackground Repeat Center All

will generate a slide show of the pictures in the ‘MyPics:’ directory and in all its subdirectories, centered and with no mouse pointer hanging around. In order to stop the slide show, you must press <CTRL>-C.

M df0:#?.image df0:pictures/#?.pic DisplayMode PAL:Hires

will show the files ending with ‘.image’ in the directory ‘df0:’ and the files ending with ‘.pic’ in the directory ‘df0:pictures’. Mostra will be forced to use high resolution screens.

M dh0:hirespic PAL:Lores AutoScroll

will show a hi-res picture in lo-res (zooming in). You can move around with the mouse.

Width and Height can be useful when you have a picture that cannot be displayed because there’s not enough Chip RAM. In such a case, try:

M pic Width 128 Height 128

This will usually allow you to at least get a peek at something.

4 Advanced Features

For maximum flexibility, Mostra allows you to use startup files and startup tool types, with which you can configure the program to suit your tastes.

4.1 Startup Files

There is a standard startup file called ‘S:Startup-Mostra’. Mostra will search for it whenever it is launched. The format of this file is exactly the same as Mostra’s command line format minus the command name. Commands may be spread out over several lines or gathered together onto a single line. Every switch or keyword in the startup file will act as a default, and will be toggled or superseded by any command line arguments. Command line switches will act as toggles (if your startup file has the keyword All and you say M * All, you won’t go into subdirectories), while keywords simply assert the new value (if you have Fade 1 in your startup file and you say Fade 3 in the command line, your pictures will be faded at speed 3).

Two options concern startup files:

NoStartup (NO)

inhibits the search for startup files, useful if you have one and you want to specify your options from scratch.

Batch

wants a complete path/filename that Mostra will use as startup file.

4.2 Startup Tool Types

From the Workbench side, you can write the startup options in the tool types of Mostra’s icon, and Mostra will use them. You have to fill each tool type with an option (previous releases would allow even multiple options on the same line, but this is in contrast with Commodore’s guidelines). Please note that ‘Fade=1’, ‘Width=352’ are valid, but ‘FreeMouse=ON’ is not; use only ‘FreeMouse’.

These options supersede or toggle the options specified in the startup file exactly as command line options. See section Startup Files. If you have no startup file, this does no matter.

You can also add tool types to a picture icon, and they will supersede or toggle again the settings specified by the startup file and by Mostra’s icon tool types.

You can also prepare an icon with no related file, but having a tool type such as ‘Files=PICS:#?’. Double clicking on the icon will show all the pictures in ‘PICS:’.

The previous version of Mostra had a feature called style icons, by which a selected pattern of preferences, contained in the tool types of an icon, was applicable to a series of icons. This is no longer possible (and the need for the ‘STARTUP’ keyword is gone), but under Release 2 you can easily create a hard link to Mostra, and give it a new icon with new tool types, and a ‘Files’ tool type. This will produce the same effect.

4.3 Startup Examples

Now, examples, by means of common problems:

• “I have a hundred pictures on my 360M hard disk, and I’ve organized them in a few groups. How can I make simple slideshows, with each group separate?”

  Simple: create a project icon for each group, and add a tool type like ‘FILES=PICS:Group1/*’, plus all the tool types you would like to apply to the pictures; then set the default tool to C:M (or wherever you put it) and double-click (of course, this must be done with every group icon). Don’t give the icons the same name as a directory, or Mostra will collapse in confusion.

• “I want to always see the black screen when I start from WB.”

  Set a Mostra tool type to ‘BlackBackground’.

• “I have some pictures. Sometimes I want to see a few of them with a full screen and no mouse, sometimes with a 128x128 screen, sometimes centered.”

  Create a series of hard links to Mostra (they behave like copies of the program, but they take almost no space on your disk). You can give icons to the hard links, and put different options in the tool types of each icon. Then, using different icons will start Mostra with different settings.

• “I like to click my pics one at a time, each one with different options. I’d like also to see them in irregular groups, each picture with its options.”

  You need a psycho-analyst, not Mostra.

5 Acknowledgments

I would like to thank the people that encouraged me someway or helped me to find bugs, in particular Warren Block, Tom Rokicki, Steve Tibbett, Christopher A. Wichura, Loren Wilton and all the other beta testers, which are really too many to mention.

The catalog files were provided by Reinhard Spisser, Stefan Becker, Martin Taillefer and Tomi Blinnikka.

Mostra is Copyright © 1990-1994 Sebastiano Vigna and it’s not public domain: it is shareware. You should send me $20 (or more, why not?) if you find it useful. Please don’t send checks drawn on a US bank, they’re almost impossible to cash. I’d prefer currency, postal money orders or checks drawn on an italian bank (in this order). Mostra is freely distributable as long as all of its files are included in their original form without additions, deletions, or modifications of any kind, and only a nominal fee is charged for its distribution. This software is provided “AS IS” without warranty of any kind, either expressed or implied. By using Mostra, you agree to accept the entire risk as to the quality and performance of the program.

Comments, complaints, desiderata are welcome.

6 Author Info

    Sebastiano Vigna
    Via California 22
    I-20144 Milano MI

    BIX: svigna@bix.com
    INTERNET: vigna@dsi.unimi.it

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