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===Darwin Documentation===
===Darwin Documentation===
There is plenty of documentation available about Darwin, a good start is [http://developer.apple.com/documentation/Darwin/Kernel-date.html Kernel Programming], which gives a nice overview about the design of the kernel.
There is plenty of documentation available about Darwin, a good start is [http://developer.apple.com/documentation/Darwin/Kernel-date.html Kernel Programming], which gives a nice overview about the design of the kernel.
* [http://www.kernelthread.com/software/fslogger/ Filechange notification] in Mac OSX "Tiger".


==Technologies to study==
==Technologies to study==

Revision as of 14:42, 19 November 2005

Discussion

This document is already some kind of discussion, you can add your comments in here as well. For real discussion please consult the mailinglist voyager-dev@netlabs.org, or use the gmane.org web/news interface to it.

Documentation

IBM Redbooks

  • SG24-4630-00 OS/2 Warp (PowerPC Edition) A First Look
  • SG24-4639-00 OS/2 Warp (PowerPC Edition) Graphical Subsystem

We do have the first one digitaly, but not the second one. In case anyone finds that, let us know.

Darwin Documentation

There is plenty of documentation available about Darwin, a good start is Kernel Programming, which gives a nice overview about the design of the kernel.

Technologies to study

Design Decisions

Creating a binary compatible OS/2 clone may be tempting but is not strictly necessary. Important is the user experience. Which toolkit should be used for primary development?

Graphics Drivers

These graphics engines can be emulated vice-versa: You can run X11, OpenGL, and DirectFB programs on the same graphics driver. We should have a look at HW support when chosing the driver system. For example I've read OpenGL drivers are not that common (often they're not HW accelerated). A viable idea may be to just use OpenGL as the core API on top of something else. There're quite a lot OpenGL implementations running on different low level drivers or even Mesa.

2D API

  • Cairo. Cairo has a PDF-like engine which seems to be inspired by Quartz of MacOS X.
  • Cairo runs on almost everything, including OS/2 and X but also directly on OpenGL hardware with Glitz. So one could use it as a complete GPI replacement without the need of X one day.
  • To make things easier 24Bit screens should be the primary target. Hell it's 2005 today...

It seems there are many possiblities here!

We will have to use more than one. KDE programs use Arthur, GTK+ ones use Cairo, and so on ... These libraries are (mostly) used for display and printing. So we won't have a consistent graphical subsystem with this multitude.

All these libraries have several backends, e.g. X11, DirectFB, OpenGL, OS/2, ...

Even if we do have to use more than one we should focus on a library that is widly supported, at the moment my impression is that Cairo will win the race. Mozilla is using it for new versions, OOo will use it and GTK+ is migrating into it as well. Also projects like Glitz will dramatically speedup the rendering in the Cairo engine. See some comments of one of the GTK+ developers.

Layer between 2D API and window manager (please enter name suggestions)

Between the 2D API and the window manager one layer is missing

  • that cares for user input by mouse, keyboard, ...
  • that knows the basics about windows and controls their behaviour (A window manager only modifies this behaviour!)
  • a Session manager that manages the processes which want do to screen output
  • a message architecture that connects everything and enables inter-client communication

Questions:

  • Should we choose X for that? Quasi-standard, but old
  • modify existing(?) systems
  • port Presentation Manager -> access to source code needed
  • code that ourselves?

Window Manager

To manage the windows we need some sort of window manager. So far most implementations are done for X, we need to abstract that directly on Cairo.

Ideas for a new Window Manager

What features should a new windows manager have?

Cinc: Obviously these ideas are inspired by stuff usually found on X. The WM needed for this project isn't the kind of WM X uses. I think WM is the wrong word for it anyway. What's needed is primarily a compositing engine which is in charge of allocating surfaces, giving them to the app, the app draws into them and the compositor puts it on the screen. Input support is probably needed for this layer, too, so the compositor may move and stack windows correctly. The final appearance of the graphics drawn on the surfacces is up to the applications not the compositor. It must be that way IMHO because no compositor coder can imagine what app developer will finally do with a given infrastructure. E.g. creating close, maximize etc. widgets in the compositor/WM effectively prevents the application developer from adding his own widgets or removing the given one. OTOH if there's a documented way to tinker with (per window) then it's ok.

The compositor/WM should be inspired by the Presentation manager (PM) found in OS/2. Granted it's old technology it's unbelievable flexible. It's possible for the coder to alter the handling of every window/widget by subclassing the window procedures provided by the system. For example the information area found in WPS-wizard uses this feature. PM is directed to order all the window areas differently (titlebar, close/maximize, client area) to give room for the information area. The coders of PM never thought about the possibility to add such informations to windows back when they did PM. It's not a hack and there's no need to change any WM code to get this to work.

Lexip: What about the common look and feel of all the headers of the client windows? I'd like to have a common theme for example, and all apps should have a header (with a little icon, and the close/minimize/... buttons) that paints according to that theme file.

Cinc: ACK. What I mean is the WM should not restrict the developer from adding/removing widgets, from modifying the way how things are done for a particular window (e.g. positioning of widgets). This also applies on how things are painted. If the developer decides to remove all widgets and use an ugly custom theme (which is bad) he should be free to do so.


Main Features
  • Built i18n (internationoalization)
  • .prestartup and .poststartup files
  • Multiscreen support (with possibility of virtual desktops 1 being on physical screen 1, while having virtual desktop 4 on screen 2)
  • Anti aliasing
  • Virtual desktops (different layouts and number of desktops - 4x2, 3x3, ...)
  • Storing sessions. Cinc: not sure the WM should do that
  • 100% ewmh complient. Cinc: ???? if this is some X thingie it's probably not needed -> Lexip: yeah, it's X stuff, but if we want to support starting Xapps, and we should do that, then we gotta be ewmh complient with our WM/compositor
  • Large desktops (scrolling and paging)
  • Themes with possibility of associating a background image or pattern (i.e. blackbox)
Client Window Features
  • Client window header can be top/bottom/right/left (with vertical text if necessary).
  • Window manager keeps track of stacking order of all client windows
  • Sticky windows - Possibility to show clients on all or few or just one virtual desktop
  • Virtual desktops with resolutions different from the physical screen resolution.
  • Ability to display multiple virtual desktops on one physical screen.
  • Maximization:
    • Maximize to given area
    • Maximize to actual screen
    • Maximize to more than one screen
    • Maximize vertically only
    • Maximize horizontally only
  • Clients can influence their states:
    • Maximized
    • Stacking order
    • Shading
    • Stickiness
    • Desktop(s)
  • Window in Window handling for MDI applications
  • Edge snapping while move- resizing a client window
  • Client window shading
  • Store client window properties per application (size, position, etc)
  • Client window can drop shadow
  • Application icons in client window headers
  • Different focus models (click to focus, focus follows mouse, ...)
Docking Area Features
  • Allow having multiple docking areas
  • Docking areas can be hid (approaching mouse makes them appeare)
  • Transparency
  • Drop shadow

Cinc: The WM should not be in charge of this. The Dock (or whatever) is just an application and should be treated as one.

Lexip: question again about the theme. If the WM/compositor is not in charge of the docker, how can we set a common theme to it?

Cinc: The WM/OS should provide the default bitmaps for it (or better any app) which can be queried by the app. Changing the theme will automatically change these BMPs. For buttons and alike the OS should provide a default drawing function which will ensure every app which uses the default automatically has a similar look and feel.

Menu Features
  • Dynamically filled menus (piped menus). Cinc: That's mostly up to the application IMHO with the exception of system menus.
  • Menu configuration can be separated over several files, i.e. one file for each submenu section
  • All the submenues can be called separatly (by key combination for example)
  • Dockable menues (like blackbox)
  • Transparency
  • Drop shadow
  • Icons for entries

Cinc: I think the WM/compositor should only provide the infrastructure to show menus. The final appearance/usability is up to the app.

Lexip: Here I'm talking about the system menu. The menu where you can start all you apps, or anything that you'd like to have in a menu. System menu is startable by right clicking on an empty spot on the background, or by keying-in some keyboard combination.

Cinc: IMHO such a system menu also should be a dedicated app (so it is replacable without tinkering with the WM). This app monitors the input queue and reacts when the configured message arrives (keyboard/mouse/whatever).

Configuration Features
  • Configuration changes take effect withou restarting the wm
  • Every single command is configurable to hava a certain keyboard or mouse click shortcut.
  • Shortcuts are simple keyboard shortcuts (i.e. Ctrl+F1), or so called keychains known from Emacs editor (i.e. Alt+e+x)
  • The wm allows mouse gestures, and keyboard mouse combined input (i.e. ctrl+mouse1 click, etc.)
  • Single, double, or even tripple clicks call different actions (attention with patent from M$ in USA)
  • Clicking the client window header is a different action than clicking the clients body for example. Cinc: can easily be done by treating those two as two coupled windows.
Extensibility
  • Programming interface (every single command can be called from outside).
  • Allow writing modules and applications that interact with the wm. Cinc: ah ok, addresses some of my concerns from above
Other
  • Ability to play (opengl) games in fullscreen on virtual desktops instead of physical screens. (Today, if a game goes fullscreen, it'll either spread over all physical screens or the other screens are switched off... which is not nice if you would like to have the server stats/a map/whatever on the secondary screen).

Lexip: that sounds as a nice idea to me. we gotta do that

CMD

  • full capabilities of current CMD.EXE concerning
    • usage of system messages and error codes
    • nested io redirection
    • grouping commands with round brackets
    • &, && |, and || operators
    • correct wildcard matching for files with multiple extensions
    • PROMPT command
    • keep UPPERCASE environment variable names only ! (unlike 32-bit Command Interpreter from Jonathan de Boyne Pollard)
  • proper implementation of EXTPROC command (fix errors with exptproc scripts not residing in current

directory)

  • new general features
    • support extended command set of Win NT CMD.EXE
      • at least include string functions with extended SET command
    • extend IF clause with new conditions
      • os version match
      • free space on a drive
      • is drive removeable
      • is drive USB mass storage
      • more ?
      • easy syncing/unmounting for usb mass storage devices
    • support PATHEXT variable
      • start files with their associated program
    • automatic environment vars
      • DATE, DATE_SORTED, TIME, TIME_SORTED, WEEKDAY, DAY, MONTH, YEAR, YEARDAY
      • CMDLINE, ERRORLEVEL
      • OS, OSVER
      • BOOTDRIVE
    • support filename completion
  • new internal or extended commands
    • INITVIOCMD determines a command being executed when initialized as a VIO session
    • INITPMCMD determines a command being executed when initialized as a PM session
    • SET allows to include equal signs in value of environment var
    • SET /P retrieves value of environment var from keyboard
    • SHIFT xx shifts parameter by positive number
    • ECHO /N does not append CRLF to output
    • CDD command changes directory and drive
    • TIMER command starts, stops or displays the value of a timer
    • SLEEP n waits for n secs
    • PAUSE n waits for n secs
    • implement START command with all features of DosStartSession, among others implement
      • /WAIT (synchronous start)
      • /NC (NoAutoClose)
      • /DOS[:settings.dat] (if DOS-Box still available)
      • /POS:x,y,x1,y1 (initial window position)
      • /ICON:icon.ico (system menu icon)
    • MOVE files with implicit copy/delete across partitions
    • exlicit UNLOCK command
    • implicit unlock with COPY, DEL, REN, MOVE (very usefull, but also dangerous ?)
    • macro support with ALIAS command
  • new batch handling or batch commands
    • %* specifies all parameters (like %1, %2 etc)
    • in for loops support %%a%f, %%a%p, %%a%d and more for specifying filename, path and driveletter of matching file
    • GOSUB - executes a subroutine
    • RETURN [xx] - exits a batchfile or subroutine [with errorlevel]
    • CANCEL (ends batch processing, but does not close window as EXIT does)
  • Integration of any REXX replacement like with current CMD.EXE
    • call of REXX Scripts with CMD
    • usage of exit handlers
    • manipulation of environment vars within REXX (changes remain after end of script, unless setlocal/endlocal() is called), including BEGINLIBPATH and ENDLIBPATH
    • readonly access to the LIBPATH value as an environment variable

MM

  • The concept of IO procedures should be retained at least for file IO and format converting.

Toolkits

  • GTK+
  • GnuStep (look at Apples programs to see what's possible. Yes I know Apple uses Cocoa not Gnustep)
  • other?

SOM

Dropping SOM for something better? Creating a poor mans SOM kernel isn't too difficult (Cinc: there's already a working prototype for the basic functionality).

If SOM is dropped, no binary compatibility for old WPS enhancements is given. This may break a considerable amount of OS/2 apps. This may not be an issue if applications have to be recompiled anyway for a new plattform. Cinc: I don't see many OS/2-apps which are worth to be supported no matter how much work it needs. Binary compatibility is out of sight IMHO. Nobody really needs it (anyone really using OD nowadays?).

WPS

  • The WPS should be designed with REXX scriptability in mind (like WPS-wizard addon)

REXX

  • REXX should be implemented like AppleScript so controlling of applications from other apps is possible (commands not tied to one process).
  • Regina may be used as an interpreter.
  • any REXX replacement should implement the following
    • true CMD integration like under OS/2
      • access to environment vars of the calling interpreter. Cinc: ???
    • support of the full REXX C API or an equivalent concept (macro space control, app handlers, WPS object access API etc). Most of this is supported by Regina AFAIK.
    • complete reimplementation of REXXUTIL ! I seem to remember having seen such a project for Windows and Unix.
  • It should be possible to write GUI based apps with REXX, a bit Dr.Dialog like

Backward Compatibility

The question about backward compatibility is indeed a good one, it's risky to break with the current OS/2 API for religious reasons but one should have a look at that more from a technical point of view. The OS/2 API is not really modern anymore, programming directly on PM is much more work than using a modern toolkit like GTK+.

At the moment it's unfortunately unlikely that PM and WPS source get released by IBM.

Options:

  • implement parts of PM and GPI on top of the new 2D API and try to integrate it with the toolkit choosen (same look & feel, clipboard support, D&D, etc. That's a lot of work, the question is if this is really necessary. We would have to do the same for supporting other toolkits like qt (which is a requirement).
  • Implement only some crucial parts to ease source code migration. For example message queues, concept of object windows (often used to comunicate with background threads).
  • Map often used PM-functions to counterparts of the chosen toolkit.
  • Use a VM and run OS/2 or eCS inside the VM. There are very promising opensource VMs like

XEN seems to be the most promising one at the moment because it will support dual core CPUs in the future so one can run the guest OS on a separate CPU core. So far one had to alter the guest OS in sourcecode but that changes at the moment because they integrate parts of QEMU sourcecode inside XEN to emulate those parts (memory allocation and such stuff).

Stuff

  • With the advance of virtualization technologies like XEN, Vanderpool and multicore cpus it becomes more and more common to have a second, virtual computer running in a VM. It should be possible to map the virtual screen of the VM to a physically existing display. (The idea is to give the user the feeling that he actually has two different computers (with a shared set of input devices). It might even be possible to add another set of input devices, so that two users could work on one computer. (one or maybe even both using an emulated computer...)
  • What's bad about Unix. Nice reading
  • Plan 9. The system the author of the reading above advocates to some degree. Not compatible enough, but interesting concepts.

Questions

  • the Xegl diagram mentioned above only shows the path of the graphics; the path of e.g. mouse and keyboard input is missing; that's not as trivial as it sounds (it has been missing in Xegl, when that was stopped); will we use OS/2-like driver model or wait for x.org 7.0 (currently RC1!) and take out the input system from there? Other sources (hotplug, ...)?
  • one good thing about OS/2 are the fast interactions when you click somewhere, like opening a folder or getting the focus on a window. Why is that like this? We should try to keep that stuff fast.
    • I think the problem of current user interfaces is that they have a lot data dependencies. This increases the response time as they often have to wait for the data to become available before they can start to draw. Data dependencies mostly stem from an overdose of flexibility (I'm talking windows xp now).
      • XP's start menu: it is based on the directory structure in the startmenu folder. So in order to draw the menu it has to read from the hard disk several times as it needs to find out the structure and load the icons of the programs (they are mostly cached after the first time).
      • Drive windows, where the window needs to gather/update the drive information before it can be drawn the first time.
      • Explorer windows that display extended file info (eg id3 tags of mp3s) need to parse the files first. (in xp a corrupt media file can block the explorer, before you even get the chance to touch it)

Short: 

 Eyecandy and advanced/unnecessary features (even when switched off) waste cpu time.
  • do we want the traditional window manager<->application scheme? With the Gnome/KDE interfaces? Then we are deep in X again ...
    • the question is if we can incooperate the WM functionality in GTK somehow. As far as I remember Fresco implemented GTK API as well so one might have a look at that.
    • IMO GTK runs on top of a WM. The WM just gives GTK a surface to work with but manages where on screen this surface will be painted. Even OS/2 has something like a WM managing the windows for us.

Implementation

You will find links to pages with some beef here later on.

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