On Wed, 7 Feb 2001, Christoph Egger wrote:
> > struct Overlay {
> > enum Overlaytype type;
> > union {
> > struct Sprite sprite;
> > struct VidOvl vidovl;
> > struct OvlWin window;
> > }
> > }
>
> Should "struct Sprite", "struct VidOvl" and "struct
> OvlWin" contain a pointer to a directbuffer?
This has been one of those "up in the air" questions.
Not all sprites have db access, but we decided it was
impractical to have a full renderer/visual attached
to the object to get data in, because it would waste
a lot of space if there were a lot of sprites.
I would suggest this:
1) A pointer to a "sprite family" db struct; that is, the db
struct would be able to be shared between more than one
sprite. Since it is shared, the "read" and "write" members
of the db struct itself would be invalid, so you need:
2) Pointers to the buffer data for read and write access,
to be used instead of (overloading) the read and write members
of the sprite family db struct. If the sprite data can be
accessed directly, then these point to the VRAM address.
If they cannot, they point to some RAM allocated from system
memory.
3) Pointer to set/get functions. These functions will
transfer the contents of a system RAM buffer to/from the
sprite. If you are writing to VRAM directly, the function
will do nothing, unsuccessfully, returning something like
-E(INFO_DOESNOTHING). Simple apps would ignore the
error. Sophisticated apps would check the error and stop
making the calls to that function to save CPU cycles.
Below are some other snippets I have on files from when
this was discussed. Consider merging them, and what Andy has
in his libs, and if you don't get what something is doing there,
feel free to ask.
This first is part of a proposal for something even more low-level
than libbse, to handle all "features".
#define GGI_FT_SUBTYPE_MASK 0x00000fff /* defined by extension */
#define GGI_FT_TYPE_MASK 0x000ff000
#define GGI_FT_NONE 0x00000000 /* used with ZBUFFER/ALPHA
when not accompanying
another type of buffer. */
#define GGI_FT_FRAME 0x00001000 /* frame of main framebuffer */
#define GGI_FT_SWATCH 0x00002000 /* generic drawing area in same
format as the main fb */
#define GGI_FT_STEREO 0x00003000 /* Right/left eye data */
#define GGI_FT_3DTEXTURE 0x00004000 /* texture usable by 3d engine */
#define GGI_FT_2DTEXTURE 0x00005000 /* texture usable by BLT */
#define GGI_FT_CHARCELL 0x00006000 /* Character font cell */
#define GGI_FT_SPRITE 0x00007000 /* Sprite/hw cursors */
#define GGI_FT_PASSTHRU 0x00008000 /* e.g. feature connector */
#define GGI_FT_OVERLAY_MASK 0x0ff00000 /* # of hardware "layers" */
#define GGI_FT_ZBUFFER 0x10000000 /* with a Z-buffer */
#define GGI_FT_ALPHA 0x20000000 /* with separate alpha buffer */
#define GGI_FT_MEMVIS 0x80000000 /* emulate/cache offboard */
...and then the "BSE" specific stuff:
/* Subtypes for sprite features */
#define GGI_FT_SPRITE_DONTCARE 0x00000000
#define GGI_FT_SPRITE_POINTER 0x00000001 /* Hardware pointer cursor */
#define GGI_FT_SPRITE_CURSOR 0x00000002 /* Hardware text cursor */
#define GGI_FT_SPRITE_SPRITE 0x00000003 /* True sprite (a-la C-64) */
/* Attributes common to sprites, BLTs, and video overlays. */
struct ggi_sprite_attrib {
int active; /* if in active slot, is it on or off. */
ggi_coord res_mul; /* pixel scaling numerator ( < 0 is flipped) */
ggi_coord res_div; /* pixel scaling denominator ( < 0 is flipped) */
ggi_coord pos; /* position on screen (units 1/res_div pixels) */
ggi_coord pos_offset; /* hot spot offset (units 1/res_div pixels) */
ggi_coord pos_snap; /* grid for position (units 1/res_div pixels) */
ggi_coord size_snap; /* grid for sizing (units 1/res_div pixels) */
uint priority; /* priority (depth) relative to other sprites */
} ggi_sprite_attrib;
/* Attributes common to sprites/BLTs */
struct ggi_rops_attrib {
uint rops; /* Mask of available raster ops. */
ggi_visual_t palown; /* If non-null, non-inverse/transparent
pallette entries are shared with this visual */
ggi_pixel rop_cmp; /* Value for ROP compare */
ggi_pixel rop_mask; /* Dontcare bitmask for ROP */
ggi_pixel trans_cmp; /* Value for transparency */
ggi_pixel trans_mask; /* Dontcare bitmask for transparency */
}
--
Brian
