nanogui: Re: Screen Driver ans Subdriver
Subject:
Re: Screen Driver ans Subdriver
From:
"Greg Haerr" ####@####.####
Date:
12 Jun 2001 18:00:36 -0000
Message-Id: <05e901c0f369$420df320$3aba46a6@xmission.com>
: Could you tell me why we have screen driver and subdriver structure
: at the same time ?? It seems that subdriver is, well, a subset of screen
: driver so why not remove all those funtion pointers in screen driver
: and replaced by a pointer to subdriver ?? i.e.
:
: struct subdriver {
: xxx();
: yyy();
: zzz();
: };
:
: struct screendriver {
: struct subdriver * subdriver;
: };
The subdriver structure is there so that the
SCREENDRIVER replaced entry points can be called in
the portrait modes without incurring an extra procedure call
or jump instruction, for fastest speed. The subdriver
only holds the replaced screendriver entry points
required for portrait mode.
:
: Also it seems in the current framebuffer drivers you are intermixing
: Sytem memory with Video memory, is it true ?? Do you drawing in
: system memory then copy to video memory ?? Or you are drawing
: directly to video memory ?? Our 2D engine can only BitBlit between
: Video memory (ON/OFF screen).
The PSD structure allows drawing into video memory
(used for actual windows) as well as offscreen system
memory (used for pixmaps). Then, the blit routine is
called when it is desired to copy screen<->offscreen
memory. The idea was to keep the PSD structure identical
whether talking to video or system memory. A flag,
PSF_MEMORY is used to differentiate the memory used,
which you can query for hardware accelleration purposes.
Regards,
Greg
:
: Thanks.
:
: Ollie
