Cursor support
The NFB interface provides three levels of cursor
mouse movement support.
-
Full software cursor emulation is the default behavior.
This is used when the graphics adapter
does not provide cursor support.
The cursor is rendered with a combination of
DrawMonoImage(D3nfb),
DrawImage(D3nfb),
and
ReadImage(D3nfb).
-
If the adapter has some available off-screen memory and can
transparently blit images from off-screen memory to on-screen,
then an intermediate level of cursor support
can be developed that has slightly better performance
than the previous implementation.
-
If either the graphics chip or the DAC
on the graphics adapter
have full hardware cursor support,
then the NFB driver can take advantage of this.
For certain graphics architectures
(fast system bus, limited off-screen memory),
the graphics chip has no hardware cursor support
and the graphics adapters using this chip could potentially
have several different DACs
that implement their hardware cursor differently.
For these devices,
it is wise to always make the full software cursor
emulation (mentioned first above) available,
for example by setting a flag in the
grafinfo(DSP/4dsp)
file on SVR5 and SCO OpenServer 5.
This will avoid situations where a new graphics adapter
comes out that uses chip A, but doesn't have DAC B,
so the NFB driver that uses only
the hardware cursor defined for DAC B breaks.
© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 6 and UnixWare (SVR5) HDK - June 2005