Mono Bitmap

			    January '90

			     Ed Mills


    This application loads a monochrome bitmap from its resource and displays
it on the screen. That sounds pretty unremarkable until you learn about all
the inversion problems invloved in placing bitmaps on both the CGA and EGA
displays. In addition to handling the relative inversion from the CGA to EGA,
MONOBMAP detects the monchrome displays that have fixed the inversion problem
and handles them as well.
    The idea is to load a monochrome bitmap, blit it to a bitmap compatible
with the screen, and check for any inversion.
    To understand why the CGA and EGA are inverted relative to one another
please refer to the KnowledgeBase article "Color Verses Monochrome Bitmap
Conversions", Q51230. The key points are that when blitting a monochrome
bitmap to the CGA, it becomes a mono to mono blit which maps one bits to
white, whereas blitting to the EGA is a mono to color blit which maps one
bits to the forground color.
    Note that some monochrome devices model after the EGA in that they map
one bits to the forground color. This is why we need to check for inversions.
We can't tell by querying the device.
    In testing this technique, be sure to try reversing the window background
and text colors to switch the default image bundle colors. The sample prints
these out so you can see when they are inverted.
    SenseBMapInversion must be called whenever there is a WM_SYSCOLORCHANGE
message or whenever the bitmap is used. This is because monochrome devices
can change their inversion sense when the colors change.