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1993-08-09
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From: tb@liszt.thorn-emi-crl.co.uk (Tim Browse)
Date: 23 Feb 93 14:06:26 GMT
Proposed Glass File Format
==========================
This file/message concerns the proposal of a new Template file format.
Objectives
~~~~~~~~~
* An alternative to the current Template file.
* Facility to hold information about entities other than windows and icons
e.g. menus, icon names, meta-icons etc.
* Make it simple to use, namely:
+ Provide a template editor that can create Glass files and convert
Glass <-> Template files.
+ Provide support code to use any special features (e.g. meta-icons,
position independent menus etc)
+ Provide a program to create Template files from Glass files so Risc OS
Lib will work ok, and generally ease the transition.
* Reasonably efficient format, within reason - e.g. 32-bit words will be
used for number storage as opposed to bytes - I think we can handle an
overhead of a few hundred bytes in our files (at worst). Unless lots of
numbers are stored.
* Make it an extensible tagged file format. Divide information into chunks,
and have keys + file offsets to find them. Then if you don't understand a
certain chunk, it's ignored. Also, a chunk must only contain relative
file offsets *within* itself so that chunks may just be copied verbatim
from one file to another. This means someone could write a simple filter
to map the font chunk entries to different fonts and still preserve the
rest of the Glass data. i.e. it should be possible to divide up the chunks
of a Glass format file, and write them back in any order and the file
would still be a legal Glass file, as long as the header entries point to
the correct data.
* As you may have noticed, the above is very similar to Acorn's chunk file
format, and hence I propose to use the Chunk file format. The format of
the chunks themselves will of course be defined by myself and others.
The reason I intend to use the chunk file format is that everything it
does is needed by Glass files, and I see no reason to re-invent wheels.
A filetype is still needed so I and all the other lazy people can just
double click on the file to edit it :-)
A considerable amount of file structure will be present in the chunks
themselves, and it may seem unncessary to bother with chunk files with
this first standard, but bear in mind that this format is meant to be
extended.
Remember that if this standard is adopted, you're stuck with it - so it
had better be able to handle what you might want to do in the future.
* Make people *want* to use it by providing features they want(!)
* Where necessary, a chunk will be timestamped to indicate when it was
last edited.
* Don't use icon validation strings - there's already too much crap in them.
* Structure the file so that it's reasonably quick to load. i.e. don't
make it necessary to have to guess memory requirements (can you say
Wimp_LoadTemplate?) or to do excessive disc thrashing.
I have, in a number of places, made various trade-offs between
efficiency and convenience.
To establish a standard
~~~~~~~~~~~~~~~~~~~~~~
For the first standard, the objective is simple. The format will allow
storage of Templates as in a normal Template file, and also a system for
naming Icons, so that names rather than icon numbers can be used to identify
icons in programs. Most programmers use #defines (or their equivalent)
instead of numbers at the moment, but this will automate the process, by
generating one or more header files containing the #defines/equates
necessary.
The programmer would use a template editor to associate names with icons.
The reasoning behind this is:
* People are more likely to adopt a standard if it is initially simple and
provides some feature they like (e.g. like saving them the trouble of
checking icon numbers). I certainly need it - some windows I use have in
excess of 100 icons.
* People are more likely to *comment* on a standard if the basic framework
is put in place and then extensions are added as and when required.
People are, I think, less likely to wade through a 35-page document that
comes at them from nowhere, like some electronic custard pie. And if
people don't comment on it, some important feature may be missed,
causing the standard to fall from favour, and hence from use.
* If a simple standard is put forward, it will be agreed on reasonably
quickly (I hope!) and it can start to be used. If some huge standard is
introduced it will be argued over for ages and will probably die. I don't
want this - I want something I can use, without having to keep on
re-inventing wheels. This concept may pass over the heads of ARM
assembler programmers ;-)
* I don't have time at present to think in depth about all the features
required and produce a *complete* standard. And if I can't think about
it in depth, I'll probably get it wrong, and I don't want to do that.
* The important thing is to have an extensible standard! Chunk files
make this possible.
The Proposed Standard
=====================
Basic Format
~~~~~~~~~~~
As mentioned, the file will be a chunk file as specified in the Acorn C (and,
I assume, Objasm) manuals. For Desktop C, it's on pp226-228 of the "Acorn
Desktop Development Environment" manual. If anyone doesn't have access to it
I'm sure myself or someone else could outline the format if necessary.
In this explanation, the chunk file offset for Glass files is assumed to
be "GLS_".
Chunks in Glass files
~~~~~~~~~~~~~~~~~~~~
Name Use
~~~ ~~~
GLS_INFO Miscellaneous info about this file and the Glass version it
conforms to.
GLS_FONT Maps fonthandles used in Glass file to Risc OS font names.
GLS_WIND Window and icon definitions (much the same as Templates)
GLS_NAME Names used to refer to icons and icon groups.
Chunk formats
~~~~~~~~~~~~
Bear in mind throughout these descriptions that we know the total size
of each chunk from the chunk file header.
Also, please bear in mind that although some structures may seem slightly
wasteful of memory, this is the format of a disc file, and these wastages
may not necessarily translate into memory wastages (e.g. indexes will only
be used while loading the file, and then wholly or partially discarded).
GLS_INFO
========
Chunk Field Field Name &
Offset: Size: Meaning:
0 4 Info_HeaderSize
Size of this header in bytes.
4 4 Info_GlassVersion
This is the version of the Glass Format that this
file conforms to. An unsigned word, at present
assigned as follows:
MSB LSB
AAAABBCC
where:
AA = reserved
BB = Major version number
CC = Minor version number
So version 2.12 would be encoded as &0000020C.
8 4 Info_CreatorName
Chunk offset of a null-terminated string indicating
the program that created this Glass file.
e.g. "TemplEd" or "Glazier"
Comments
~~~~~~~
Good so far, innit?
GLS_FONT
========
Chunk Field Field Name &
Offset: Size: Meaning:
Header:
0 4 Font_HeaderSize - size of header in bytes
4 5 Font_TimeStamp - time stamp of this chunk
9 3 Reserved - must be 0
12 4 Font_Num (0 => no fonts used in Glass file)
Number of font handles defined in this chunk.
Font handles always numbered 0 to Font_Num-1.
Font handle index:
i+0 4 Font_Offset 0
Chunk offset to font data for handle 0.
i+4 4 Font_Offset 1
Chunk offset to font data for handle 1.
...
i+(n-1*4) 4 Font_Offset n-1
Chunk offset to font data for handle n-1.
Font data entries: (pointed to by index entries)
d+0 4 Font_XSize
x point size * 16
d+4 4 Font_YSize
y point size * 16
d+8 ? Font_Name
A null-terminated string.
(e.g. "Trinity.Medium.Italic\0")
Comments
~~~~~~~
If no GLS_FONT chunk, it is assumed the file uses no anti-aliased fonts.
The font data entries must be word aligned.
GLS_WIND
========
Chunk Field Field
Offset: Size: Meaning:
Header:
0 4 Wind_HeaderSize - size of this header in bytes
4 5 Wind_TimeStamp - time stamp of this chunk
9 1 Wind_Flags - flag field for this window chunk.
At present the following flags are defined:
bit 0: Wind_AntiAliased
0 => This window chunk primarily uses the System
font.
1 => This window chunk primarily uses anti-aliased
fonts
bit 1: Window_ThreeD
0 => This window chunk primarily uses 'standard'
Risc OS icons
1 => This window chunk primarily uses 3D 'bordered'
icons to achieve a 3D look and feel.
All other bits in this word should be 0.
10 2 Reserved - must be 0
12 4 Wind_NumWindows - number of windows defined in
this chunk.
16 4 Wind_WindDefnSize
Size of the Wind_WindDefn Fields in window data
blocks (see below).
At present 88, but may change.
20 4 Wind_IconDefnSize
Size of the IconDefn fields in window data
blocks (see below).
At present 32, but may change.
24 4 Wind_IndexSize - size of index entries
At present it is 36.
28 4 Wind_MessageFile
Chunk offset of 0-terminated filename of the
message file to use to expand message tags.
0 if the default message file (whatever that
means to the programmer's library) is to be used,
or if no message tags are used.
Index:
i+0 12 Wind_Id
A null-terminated string identifying the window.
e.g. "ProgInfo".
i+12 4 Wind_Offset
Chunk offset for data for this window entry.
i+16 4 Wind_Size
Size of data for this window entry.
i+20 4 Wind_IndDataOffset
Chunk offset of indirected data for this window.
i+24 4 Wind_IndDataSize
Size of indirected data for this entry.
i+28 4 Wind_NumGroups
Number of icon groups for this window.
i+32 4 Wind_GroupOffset
Chunk offset of group definitions for this entry.
i+Wind_IndexSize Start of next index entry (i.e. Wind_Id).
Window Data blocks:
d+0 88 Wind_WindDefn
A window definition block as passed to the SWI
Wimp_CreateWindow, with the exceptions noted below.
The number of icons is explicitly obtained from this
block from the usual field (d+84).
d+88 32 Wind_IconDefn 0
Icon definition for first icon of this
window (if any). Block is as passed to the SWI
Wimp_CreateIcon, with the exceptions noted below.
d+120 32 Wind_IconDefn 1
etc...
Indirected Data blocks (pointed to by Wind_IndDataOffset):
Free-form entries, of byte resolution, but each entry *must*
be terminated by a 0. Entries for icons such as writable icons
which may have a large buffer but only a short string initially
should be padded to full length with 0s. This is to ensure that the
indirected data size returned by the Glass SWI is correct.
Icon Group Blocks (pointed to by Wind_GroupOffset):
g+0 12 Group_Name
Null-terminated string describing group.
Unique within the icon group block.
Used in conjunction with the GLS_NAME chunk.
g+12 4 Group_Type for icon group 0.
0 => Positional group.
No other group types allocated.
g+16 4 Group_NumIcons
Number of icons in this group.
g+20 4 Handle of first icon of this group
g+24 4 Handle of second icon of this group.
...
4 Handle of last icon in this group.
Followed by the rest of the icon group definitions.
Comments
~~~~~~~
Window chunk flags
~~~~~~~~~~~~~~~~~
These flags are, at present, mainly used for customising which set of
templates an application loads. The Glass file may contain only one type
of templates - the Glass loader routine will attempt a 'best-fit' approach
to choosing which set to load.
The caller will supply the flags to match when loading template sets.
There must *not* be more than one window chunk with the same flags.
In practice, at run-time, only one GLS_WIND chunk will be loaded.
Window data blocks
~~~~~~~~~~~~~~~~~
Offsets in these blocks should not be taken to be valid forever - use
Wind_WindDefnSize and Wind_IconDefnSize to ensure any embarrassments are
avoided.
Window data blocks need not be in the order they appear in the index, so
long as the chunk offsets are correct. They need not be contiguous in the
chunk either.
The exceptions in window/icon definition blocks are as follows:
Sprite area control block pointers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In Glass files, sprite areas are interpreted as follows:
0 => Default application sprite area
1 => Wimp sprite area
Option for indirected sprite-only icons only:
2 => Use this window's sprite area pointer.
Option for window sprite areas only:
Any other value => Offset into indirected data area which specifies filename
of sprite file to be used for this window.
This string may be a message tag - see below.
Indirected data
~~~~~~~~~~~~~~
When indirected icons (including the window title bar) occur, the datum for
a sprite name, text buffer or a validation string is actually divided into
two fields, flags and offset:
MSB LSB
FFOOOOOO
The 8-bit FF field is a flag field. These flags will be allocated for
various purposes as and when they become necessary. At present, only the
most significant bit of the flags is allocated - it is the 'message tag
bit' - if clear, the indirected data is the actual data to use in the icon,
if not, it is the message tag to use to look up the actual data.
The message tag format is undefined - i.e. msgstrans or DeskLib format tags
or anything else is legal.
The OOOOOO field is a 24-bit offset value. This allows for indirected data
blocks of up to 16Mb in size - this should be sufficient for most occasions.
I am open to the suggestion that this field be defined as 16 bits of flag
and 16 bits of offset.
Font handles
~~~~~~~~~~~
These are, of course, the internal font handles used throughout the
Glass file, and not font handles as understood by the Risc OS FontManager
module. The GLS_FONT chunk can be used to convert them to real font
handles - this will usually be done by the library routines that support
Glass files.
Groups
~~~~~
So far, only positional groups have been allocated a group type (0).
Positional groups are groups of icons that are treated as a unit in a
Glass editor - they are moved in one operation etc, like a group in !Draw.
GLS_NAME
========
Chunk Field Field
Offset: Size: Meaning:
Header:
0 4 Name_HeaderSize
Size in bytes of this header
4 5 Name_TimeStamp
Standard 5-byte Risc OS Time stamp.
See Risc OS 2 PRMs, p550, "Real time".
9 1 Name_Flags - the flag field for this name chunk.
At present the following flags are defined:
bit 0: Name_AntiAliased
0 => This name chunk refers to the GLS_WIND chunk
that primarily uses the System font.
1 => This name chunk refers to the GLS_WIND chunk
that primarily uses anti-aliased fonts
bit 1: Name_ThreeD
0 => This name chunk refers to the GLS_WIND chunk
that primarily uses 'standard' Risc OS icons
1 => This name chunk refers to the GLS_WIND chunk
that primarily uses 3D 'bordered' icons to
achieve a 3D look and feel.
All other bits in this word should be 0.
10 2 Reserved - must be 0
12 4 Name_IconPrefix
Chunk offset of null-terminated string specifying
the global prefix for icon names.
0 => no prefix.
16 4 Name_IconSuffix
Chunk offset of null-terminated string specifying
the global suffix for icon names.
0 => no suffix.
20 4 Name_GroupPrefix
Chunk offset of null-terminated string specifying
the global prefix for group names.
0 => no prefix.
24 4 Name_GroupSuffix
Chunk offset of null-terminated string specifying
the global suffix for group names.
0 => no suffix.
28 4 Name_IndexSize
Size in bytes of name index entries.
Window name index entries:
i+0 12 Name_WindowId
Window ID of the window this naming block refers
to. (see GLS_WIND chunk details).
i+12 4 Name_WindowPrefix
Chunk offset of null-terminated string specifying
the prefix for names of icons in this window.
0 => no prefix.
i+16 4 Name_WindowSuffix
Chunk offset of null-terminated string specifying
the suffix for names of icons in this window.
0 => no suffix.
i+20 4 Name_IconOffset
Chunk offset of icon name block for this window.
i+Name_IndexSize Next index entry
Icon name block:
i+0 4 Name_IconName 0
Chunk offset of null-terminated string specifying
the name of icon 0 of this window
0 => anonymous icon
i+4 4 Name_IconName 1
Chunk offset of null-terminated string specifying
the name of icon 1 of this window
0 => anonymous icon
...
i+4*n 4 Name_IconName n-1
Chunk offset of null-terminated string specifying
the name of icon (n-1) of this window
0 => anonymous icon
i+4+4*n ? Data for icon names...
Comments
~~~~~~~
There is a window name index entry + icon name block for each window that
contains icons referenced by name. Hence a window with no icons referenced
by name (eg a window with no icons such as Edit's main window) would not
have a window name index entry or icon name block.
As with the GLS_WIND chunk, although there may be multiple GLS_NAME chunks
in the file, only one is loaded at run-time, according to flags passed to
the Glass loader by the client application.
Icon/Group names have 5 components, all but one of which, the actual icon or
group name, may be null. These may be combined in one of two orders:
(Icon is used here but these orders also apply to groups)
Name_IconPrefix +
Name_WindowPrefix +
Name_IconName +
Name_WindowSuffix +
Name_IconSuffix
OR
~~
Name_WindowPrefix +
Name_IconPrefix +
Name_IconName +
Name_IconSuffix +
Name_WindowSuffix
This allows for (almost) any naming scheme the user can think of.
The actual ordering used is not specified in the file - it is specified
to the Glass support module when decoding names.
There may not be two windows with the same name, two icon groups with the
same name, or two icons with the same name. 'name' here means the full name,
i.e. after all the prefixes/suffixes have been added.
End Of Proposed Standard
------ oOo ------
Glass Relocatable Module
========================
There will be support for the Glass file format in the form of a relocatable
module (RM), which will provide SWIs to access and use Glass files. A
number of these will be analogues of Wimp SWIs for handling template.
I have a volunteer to write the first version of this module, and I hope to
be able to thrash out the details of the SWIs with him soon. Below are some
tentative ideas about what should be provided. Contact me if you think
anything's been missed.
It seems to me that without careful thought, SWI number allocations can be
'wasted' by not bothering with reason codes and just having a different SWI
for everything, and then realising a new chunk is needed - for this reason
only two SWIs are defined so far.
Obviously this requires an official SWI chunk from Acorn, so I am writing to
request one (as well as an official chunk file prefix).
SWIs:
Glass_FileOp
============
Operations on Glass files.
Reason codes:
Glass_FileOp 0 : Open Glass File
Glass_FileOp 1 : Close Glass File
Glass_FileOp 2 : Load Window Template
Glass_FileOp 3 : Load Name Information
Glass_FileOp 4 : Get File Version Information
Glass_NameOp
============
Services to decode icon/group names.
Reason codes:
Glass_NameOp 0 : Decode icon name
Glass_NameOp 1 : Decode group name
Registering message tags converters
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It was an interesting exercise collecting all the comments on Glass as I
kept coming up with solutions to problems I thought quite neat, only to
discover that someone else had come up with the same idea a few messages
later :-(. Anyway, one of the main points of interest was the issue of
message tags. It would be nice to 'msgtrans' the whole window template(s)
automatically down to the level of icon text.
This is supported by the format at present, but the client has to convert
the messages 'by hand'. I thought (and so did TMOTA) that the ideal solution
would be to register a message tag converter function which the Glass module
would use to convert the messages automatically when loading a template.
The only problem with this is that as far as I can tell, the main systems
in use are Acorn's msgtrans module, RISCOS_lib's msgs module, and DeskLib's
Msgs module, and these all work in different ways, and have different
calling patterns.
As I see it, there are two solutions:
(1) Define a standard function type/interface to be registered with the Glass
module. Then the client can write a veneer (or use a standard one) for
whatever function they want to use.
(2) Support the main libraries used, and specify what 'type' the function
being registered is - i.e. DeskLib/RISCOS_lib/msgtrans.
Personally I prefer (1), but I would welcome comments on this. Obviously, if
option (2) is supported, then option (1) is too, with no extra work. (i.e.
choose the function type closest to the one you use and write a veneer for
it).
Another connected problem is that it would be nice to specify message tags
in the Glass file but not have to provide a tag. i.e. in a similar way to the
DeskLib automatic help handler, if the indirected data field of an icon has
the message tag bit set, but the chunk offset is 0, then a tag is synthesised
using the window name and icon number, e.g.
proginfo.1
options.3
and so on. The problem is that there are different syntaxes for message
tags around. Some are nicer than others, but ideally all should be
supported. Again, maybe a small set of different syntaxes could be
supported rather like the support for different call patterns of message
tags conversion functions. Comments please!
This facility would make de-nationalising templates very easy as a Glass file
editor could then have an option to save a de-nationalised version and
automatically generate the message tags directly from the icon data.
Scene of the Crime
==================
If anyone wants to contact me, I read comp.sys.acorn{,.tech}, and
occasionally post to it. I am omni-present on Arcade BBS's message areas.
Arcade is a UK ANSI board: 081-654-2212/081-655-4412, most speeds.
Prefix with international code if outside UK, and probably lose the 0 from
the front of 081 too, I shouldn't wonder.
Failing that you might be able to get me on internet:
tbrowse@thorn-emi-crl.co.uk <---- N.B. This is a new address.
(And it may even work!)
Failing that, Snailmail:
1, Arkle House,
6, Chiltern View Road,
Uxbridge,
Middlesex.
UB8 2PA
United Kingdom.
I think that's it - I await your comments. I'll pursue the module SWI
interface and post it when it's half decent.
Cheers,
Tim Browse
