NEW! I’ve extended MetaSprite’s API to manipulate File MetaData in the sprite file’s Extension Area as well as the existing Sprite MetaData functionality.

Note that despite !Paint being the de facto RISC OS Sprite editor, it dates to RISC OS 2.0 and hence predates some of the APIs that MetaSprite modifies – !Paint is therefore very bad at coping with modified Sprites, and ought to be updated to use the APIs provided by RISC OS 3.0. I don’t think that would be rushing things, under the circumstances. Pleasingly, !Draw seems to manage perfectly.

• MetaSprite provides the new SpriteOp,39 to deal with Sprite MetaData.

• NEW  for v0.20 is SpriteOp,23 for dealing with File MetaData in the Extension Area, instead of inside a Sprite.

• The module increases the number of Palette types that can be created by SpriteOp,37.

• It augments SpriteOp,36 “Set Pointer” with the ability to embed the coordinates of the pointer hot-spot in a MetaData chunk that automatically overrides the provided coordinates when present.

• MetaSprite provides support for Truncated Palettes, which make “optimal” and converted Sprites much more memory efficient, especially when 8bpp.

• And finally it fixes a number of bugs in ColourTrans regarding 8bpp Sprites.

NoSpriteImage formalises and enables a Sprite construction containing no Image pixels, for those Sprites intended to be plotted as a Mask only.

Again, there is a technical document, and a couple of example files.

This is an experiment. I’m not sure how I feel about the results.

Uses MetaSprite to enable Sprites to have long names. There’s no limit on the length, but as they’re not subject to a 12-byte maximum, they must be space or ctrl terminated.

Currently adds three SpriteOps to deal with longnames:

SpriteOp,&x8D  Return long name or find sprite index

 => R0 = &x8D (+&100 if R1=Area; +&200 if R2=ptr - only useful for R4=-1)

    R1 = Area (if R0>&100)

    R2 = if R4=-1 and R0=&28D:  Sprite Ptr

         if R4=-1 and R3<>0:    Sprite name,termi (ctrl or space)

         if R4=-1 and R3=0:     Sprite name,termi (max 12 bytes) 

         if R4>0:               Buffer for sprite name,0 (or 0 to read length)

    R3 = if R4=-1:  0 to treat R2 as an old 12-byte name, else longname,termi

         if R4>0:   length of buffer in R2 in which to return the name

    R4 = >0 to return name of nth sprite

         -1 to return index of sprite with given name (or SpritePtr)

 <= R3 = if R4 was >0: length of name (even if it didn't fit)

    R4 = if R4 was -1: index

SpriteOp,&x98  Find sprite address by long name

 => R0 = &x98 (+&100 if R1=Area; +&200 obviously makes no sense)

    R1 = Area (if R0>&100)

    R2 = Name,termi (space or control)

 <= R2 = SpritePtr

SpriteOp,&x9A  Rename long sprite name

 => R0 = &x9A (+&100 if R1=Area; +&200 if R2=ptr)

    R1 = Area (if R0>&100)

    R2 = old name,termi (if R0<&200) or SpritePtr (if R0=&29A)

    R3 = new name,termi (spc or ctrl)

I had considered using R0b7 to enable longnames for all SpriteOps, but that seemed a bit greedy. Also, shortnames are 12-bytes long for performance reasons, so it’s better to use longnames to find a Sprite (SOP,&98) and then pass that address to ColourTrans and SpriteOp.

OS_SpriteOp,37 (Create/find/remove palette) will correctly locate the Palette even if it's in another Sprite (or the Extension Area). However, you MUST pass R1=Area EVEN WHEN R2=SpritePtr (you should ALWAYS provide the SpriteArea to both SpriteOp and ColourTrans to allow for future expansion).

OS_SpriteOp,39 (Create/find/remove metadata) should be used to attach a PalN palette name to the sprite instead of having its own palette. This contains a null-terminated name which is either the name of a Sprite in the same Area, or of a Palette in an NPal chunk in the Extension Area. Note that sprite names are MUCH safer as they survive sprite merging - nothing merges Extension Areas at all, sadly.