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In article <10574@decwrl.DEC.COM> harrow@exodus.dec.com (Jeff Harrow, NCSE BXB1-2/E02 DTN=293-5128) writes:
>In response  to  a  recent comment from Larry Rosenstein, I would 
>like to suggest  that  20K  or so of patches to continue to allow 
>*ALL* programs written for  *ANY*  Macintosh  (specifically  full 
>color programs written for the  Mac  II  to  be  runable   on any 
>Classic  Mac  with  appropriate translation to  B&W)  is  a  VERY 
>reasonable tradeoff.

I apologize for the confusion.  The 25K figure was picked out of a hat.
(That is the size of the current patches for the Mac Plus).   For all I
know, it could require 50K or 100K to implement the necessary code.  (After
thinking about it a bit longer, I think the 100K figure might be more
accurate.)

I don't have any concrete information on the work that went into
implementing Color Quickdraw.  My intuitive feel is that it was
considerable.  Consider what would be required.

You would have to provide support for all the new data structures (colored
grafPorts, patterns, cursors, windows, controls, menus; PixMaps; graphics
devices; color palettes).  The patches would have to understand these
structures and map the colors to black or white (whichever is closer).

There are probably 100+ new calls that would have to be implemented.  It is
not a matter of making these calls NOOPs.  You need to get the same results
as on a Mac II running a 1-bit deep screen, so these call have to do some
amount of work.  Also, some of the Color Quickdraw algorithms were written
assuming a 68020.  If any of these needed to be ported to the Mac Plus,
they would have to be rewritten.  (In this case, it is not clear that you
could achieve an adequate level of performance.)

On top of this, consider color printing.  One would naturally want to have
the same color output as on a Mac II.  I think this would require most of
Color Quickdraw to be ported to the Mac Plus.

>One of the cornerstones of the Mac  line  has been this fantastic 
>compatibility,  and  it should indeed be carried forward.    Will 
>every program written to make use of full color  look  decent (or 
>even work well) in B&W?  No, of course not, but that also applies 
>to  a  Mac II running with a B&W  monitor  -  it  is  up  to  the 
>developer to make  sure  that  the result is reasonable (the gray 
>scales could be automatically  translated to standard replacement 
>patterns by the patches).

On a Mac II, every machine is capable of 16 levels of gray.  On a Mac Plus,
there is only black and white.  The gray levels makes a big difference.  I
don't think you can simulate 16 levels of gray adequately on a Mac Plus.

As far as compatibility goes, I think there are 3 kinds of color
applications:

(1) Applications that use the old color model.  These are limited to 8 fixed
colors, but this model is supported on all machines.  This is a way to get
limited color with no compatibility issues.

(2) Applications that use the new color model, but only in a simple way.  In
this case, it is easy to check for the existence of a Mac II, and make
different calls if color is available.   The MacApp DrawShapes example does
this, and I expect most commerical program will also work this way. 

(3) Applications that use color in a sophisticated way.  Examples would be a
color painting program, color animation program, a program that uses color
table animation, etc.  In these cases, it would be difficult to make tests
at all the necessary places to support color and B&W machines.  

On the other hand, since they are advanced users of color, the programs
would not be very useable on a B&W screen.  (Consider a color painting
program on a B&W screen; you would have a difficult time distinguishing
colors..)

>As a developer AND a user, I don't want to see the Macintosh line 
>in the position  of  so  many  of  its  competitors,  where  some 
>programs require THIS configuration,  and  some  require THAT.  I 

As far as color goes, the situation is not (and hopefully will never be) as
bad as the MS-DOS world.  The Mac II has a definite color architecture,
which is extensible.  

I expect commercial developer to write application that fit into categories
(2) or (3).  In other words, either the application will either be
compatible on all machines (but color machines will have extra color
features), or the application will run only on color machines because it is
more sophisticated.

Sorry for the confusion caused by my earlier message.

-- 
Larry Rosenstein

Object Specialist
Apple Computer

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