49 lines
2.2 KiB
Plaintext
49 lines
2.2 KiB
Plaintext
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; IIgs graphical architecture:
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; PREMISE: All small-scale bitmapped graphics are encoded as code that pushes the graphics onto the stack,
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; which has been aligned to the appropriate place to draw said graphics.
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; Jump tables are stored in the main code segment so that eg. tiles can be easily calculated by index, and
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; so we don't have to explicitly pass longs to a regular function.
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(import-macros {:sss ! : compile} :ssc.macros)
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(local lume (require :lib.lume))
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(local {: countiter} (require :lib.util))
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#(compile $1
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(global word draw-object-saved-stack 0)
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(fn draw-object (screen object)
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(asm (sei) ; disable interrupts
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(lda object) (sta [{:abs #(+ ($1:lookup-addr :draw-object-current-object-jump) 1)}])
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(tsc) (sta draw-object-saved-stack)
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(lda screen) (tcs)
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(lda :0xc068) (ora 0x30) (sta :0xc068) ; set altzp
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draw-object-current-object-jump
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(jmp draw-object)
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draw-object-finished (export draw-object-finished)
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(lda :0xc068) (and 0xffcf) (sta :0xc068) ; clear altzp
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(lda draw-object-saved-stack) (tcs)
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(cli))) ; enable interrupts
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(form drawfn [(fn [ssc name ...]
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(assert (not (ssc:defining?)) "drawfn must be defined at top level")
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(set ssc.locals nil) ; locals cannot be used
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(local asm (ssc:expr-poly (lume.concat [:do ...] [[:asm [:jmp :draw-object-finished]]])))
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(set ssc.locals [])
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(ssc:expr-poly [:form name (fn [ssc] (assert (= ssc.locals nil) (.. name " must be called from a drawfn")) [:jmp name])])
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(ssc:expr-poly [:getter name [:ref name]])
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(ssc.org:append name asm))])
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(drawfn pei-slam-tile
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(asm (tdc) (tax) ; store direct page register in X
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(tsc) (sec) (sbc 255) (tcd)
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[(lume.concat [:block] (icollect [_ (countiter 16)]
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[(! block (pei (:d0xfe)) (pei (:d0xfc)) (pei (:d0xfa)) (pei (:d0xf8))
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(tsc) (sbc 152) (tcs) (sbc 255) (tcd))]))]
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(txa) (tcd))) ; restore direct page register
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(drawfn pei-slam-scanline
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(asm (tdc) (tax) ; store direct page register in X
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(tsc) (sec) (sbc 255) (tcd)
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[(lume.concat [:block] (icollect [offset (countiter 0xfe (- 0x100 160) -2)] [:pei [(.. :d offset)]]))]
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(txa) (tcd))) ; restore direct page register
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)
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