EGS.svdriver

  © 1994 by Andreas R. Kleinert.

  FREEWARE. All rights reserved.

  Version      : 1.3
  Release Date : 18.04.1994
  OS Version   : OS V2.04+ (V37) and the specific EGS-Libraries


  Description
  ~~~~~~~~~~~
  EGS.svdriver is an external Library-Module for the superview.library V3+.

  It supplies functions for V2+ SVObjects to allow object-orientated
  displaying of graphics on EGS Screens (Enhanced-Graphic-System Screens).
  All corresponding EGS-Libraries are needed.

  The internal graphics interchange format is the same as supported by
  superview.library V3+ in connection with V2+ SVObjects, which can be
  used by external custom programs.

  This Driver supports the following :

  Emulation   Dimensions      max. Depth    Type

  EGS-Card    [EGS-Card]      8/24	    ONEPLANE
  ECS/AGA     [ECS/AGA]       8 	    ONEPLANE


  Currently only ONEPLANE graphics are supported, which means, that
  they either have to consist on 8 Bit-ChunkyPixel Data (with max.
  256 Colors) or 24 Bit-RGB (16 Bit R5:G5:B5:1 not supported yet).
  So you will e.g. be able to display 8-Bit PCX, GIF, or TIFF and
  24 Bit TIFF, but for example not IFF-ILBM, because these are
  BITPLANE Data.


  EGS-Cards
  ---------
  When using an EGS Card, all supported ColorDepths should be displayed
  correctly in TrueColor.

  Amiga ECS/AGA emulation
  -----------------------
  When using the ECS/AGA emulation, you should set the max. possible
  ColorDepth in the ScreenMode preferences program.

  AGA :
  With AGA any Graphics with less than 256 Colors should be displayed
  100% correctly. Only 256 Colors graphics will usually have some Colors
  wrong, because those are obtained by the EGS-System for the Display itself
  (Window-Borders, etc.), so that they usually can't be used for the graphics.
  24 Bit graphics will be dithered to 256 Colors under AGA (usually
  GreyScaled).

  ECS:
  Using the ECS emulation will perhaps nearly always result in very
  ugly Colors, if you're displaying more than, let's say, 8 Colors.
  This results out of the maximum ColorDepth of 16 Colors in Hires,
  of which some - see AGA notes - are already reserved.
  Of course 24 Bit graphics may also be dithered to 16 Colors/GreyScales,
  but better don't try it out ...

  Closing of the current EGS Display is possible by freeing the handle's
  resources or delocating the handle, but no screen or window addresses
  (for IDCMP checking) are returned by the related library functions,
  because EGS is (as far as I know) binary incompatible to Intuition.
  To fix this a little bit, every time when displaying a graphic on the EGS-
  Screen a Workbench Window is opened which allows usual IDCMP access.
  Window IDCMP and Window Flags (except backdrop/borderless) are recognized
  and used.


  Author
  ~~~~~~
  Andreas R. Kleinert
  Grube Hohe Grethe 23
  D-57074 Siegen
  Germany


  History
  ~~~~~~~
  V1.3 (18.04.1994) :

   - MAJOR REVISION
   - changed way of setting/handling Colors : now using ObtainColor()
     and ReleaseColor().
     Colors are released immediately after writing the graphics into
     the BitMap, to allow any later displayed graphics to obtain their
     own colors : otherwise no more colors would be free and they would
     be displayed with the wrong colors.
   - improved handling of 8 Bit graphics :

      - ECS/AGA emulation :
	256 Color graphics usually will be displayed with some wrong colors,
	which are actually obtained for the EGS-Display itself (Window
	Borders, etc.) and cannot be changed by the application.
	ChunkyPixel-Graphics with less than 256 Colors will be displayed
	100% perfect as long as only unused Color-Registers are already
	obtained by any applications.
      - EGS Cards :
	Due to the fact, that we are working with 24 Bit, all graphics
	should be displayed with their 100% correct Colors.

   - added support for 24 Bit graphics :

      - ECS/AGA emulation :
	24 Bit graphics are dithered to 256 Colors and should be displayed
	in GreyScales usually (see notes concerning 256 Color graphics)
      - EGS Cards :
	24 Bit graphics are displayed in TrueColor


  V1.2 (29.03.1994) :

   - small improvements :

      - now using SMART_REFRESH Window
      - no longer Backdrop-Window
      - fixed handling of Control-Window

   - with newer versions of the EGS-Libraries it should no longer crash
     (tested with Version 15-Mar-1993, found on AmigaMagazin PD 4/93-4a/b)


  V1.1 (17.03.1994) :

   - first version with the beginnings of rudimentary EGS-Support


  Copyrights
  ~~~~~~~~~~
  Some of the mentioned names or products above may be copyrighted by
  companies or trademarks of companies.