🚀 go-pugleaf

In a recent article Robert George Johnston, Jr. writes:
>
>	Putting two different monitors side by side with different dimensions and 
>color abilities is perfectly alright. The Monitors cdev will allow you to set 
>the orientation of the two monitors to each other and they will act as an 
>extension of each other. If you are displaying a color picture on the color 
>monitor and drag half of it over to the B&W monitor, the B&W will usually show 
>mostly black pixels. For single color text or pictures, there really isn't a 
>problem.

It's no problem for the system software, true.  But I have been running
a SuperMac Spectrum and an Apple Monochrome (both 8-bit, although variously
set to different bit depths) side by side for about 4 months.  Very little
thrid-party software that does Mac II specific stuff (like greyscale) works
properly with two monitors (virtually all software that is written for 128K
ROMs works fine on either (or straddling) screen).

Image Studio (a greyscale Paint program) lets you move the window to the
non-menu-bar screen but then doesn't work right until you move it back.
PixelPaint works better but the tools stop working.  All pop-up menus
(like the .h files in LSC) always appear on the screen with the menu bar,
as close as possible to the postition they should be in (i.e., pinned
against the edge of the screen nearest the screen they should have popped
up in).  Programs (like Screensavers) that compare mouse position to 
screenBits.bounds don't get the real corners of the screen, making it 
difficult to put the mouse in the lower left corner when there's no left
edge on that screen (DragWindow and other system calls have less of a
problem through "judicious comparison of the rectangle passed").  The
default ZoomBox code (TrackZoomBox or something like that) starts seeming
a little dumb when clicking in the zoombox of a window on the SuperMac
screen makes it fill the Apple Monochrome screen [I propose that it should
cycle through the bounds of all attached screens and finally recycle to
the non-zoomed size].

Note that with the advent of multiple screens, coordinates for windows
can be negative.  The upper left of the menu bar is always at Global
Coordinate (0,0), but not always at the leftmost of the logical screen.

It is possible to write code that does greyscale on the Mac II with
arbitrary screens correctly, but it is damned difficult and my own
code doesn't do it quite right yet.

For most uses, the multiple screen implementation is the cleanest I have
ever seen (especially considering it's compatible with software that
had no idea this was coming) and extremely convenient.  Currently, many
Mac-II specific programs work correctly only on the screen with the menu
bar (called the "Main GDevice"), but this will doubtless change as we
all become smarter about programming the Mac II.

-Eric
	    "We're writing tomorrow's software yesterday."
Eric K. Olson     olson@endor.harvard.edu     harvard!endor!olson     D0760
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