Joseph Ferano
25f56c24a8
vendor/raylib/modes.flan: five macros over the five pairs the package binds -- with-drawing, with-mode-2d, with-mode-3d, with-texture-mode, with-scissor-mode. A second file with no declare-c in it, split out on vector.flan's reasoning: raylib.flan is the package's statement about C and nothing here names C, so nothing here can be made wrong by raylib changing. Each expands to (do (begin-... args) body... (end-...)) -- the calls the author used to type, in the order they typed them. No let, no gensym: nothing binds a name, so there is nothing for a caller's name to collide with. What it removes is the End* that is missing, wrong, or no longer beside its Begin*. What it cannot remove is a body leaving through the unwind path: a return or an invoke-restart skips the rest of the do and the End* with it. defer is the obvious fix and is refused inside a loop body, which is where a pair always lives -- checked, not assumed. So sand.flan's discipline stays: keep the restart boundary outside the pair. 35 call sites converted across examples/ and sand.flan. The one left is core-scissor-test.flan, whose Begin and End sit in two separate `when`s with the drawing between them -- a conditional pair is a shape a bracketing macro cannot express. test/programs/rl-with.flan covers with-scissor-mode, which no example can, with a frame function unreachable from main so it needs no libraylib; rl-with-reject.flan is the arity half.
111 lines
5.1 KiB
Plaintext
111 lines
5.1 KiB
Plaintext
;;;; raylib [shapes] example - following eyes
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;;;;
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;;;; examples/shapes/shapes_following_eyes.c. Ported for the thing it needs
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;;;; that raylib does not supply: the whole update is vector arithmetic —
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;;;; subtract two points, take the angle, walk back out along it — and every
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;;;; one of those steps is raymath. raymath is `static inline` in
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;;;; raymath.h, so Vector2Subtract and Vector2Angle have no symbol in
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;;;; libraylib at all and there is nothing for declare-c to bind. NEXT.md
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;;;; names this as one of the three open gaps.
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;;;;
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;;;; What that costs here is nothing, because the C does not use raymath
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;;;; either — it writes the four subtractions out and calls atan2f, cosf and
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;;;; sinf from libm, and Flan's prelude already declares all three as
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;;;; atan2-f32, cos-f32 and sin-f32. So this file is the *measurement* of the
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;;;; gap rather than a workaround for it: an example whose every line is
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;;;; vector maths, written without a vector library, in the same shape the C
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;;;; has. It reads fine. A Vector2Add would have saved two lines in the whole
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;;;; file.
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;;;;
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;;;; That measurement is what decided the answer, and the answer landed:
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;;;; vendor/raylib/vector.flan is raymath written in Flan, since a C shim
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;;;; re-exporting the inlines would have bought identical arithmetic at the
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;;;; price of a compilation unit and a second place raylib's semantics live.
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;;;; The measurement is left standing rather than rewritten away — one
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;;;; subtraction below is `rl/v2-sub` and the rest of the file is unchanged,
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;;;; including the atan2/cos/sin path, which is deliberate: it needs no guard
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;;;; for a zero-length vector where a normalise would. One line saved, in a
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;;;; file that is nothing but vector maths, is the honest size of the gap.
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;;;;
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;;;; The raylib call it does exercise is collision-point-circle?, which no
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;;;; ported example had called, on a frame path, with the point coming
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;;;; straight out of get-mouse-position — one struct out of raylib and back
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;;;; into it untouched.
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;;;;
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;;;; The eye geometry, since the C hides it in a subtraction: the iris is
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;;;; pinned inside a circle of (sclera - iris) radius about the sclera's
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;;;; centre, so the iris disc is tangent to the sclera's edge at the extreme
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;;;; rather than hanging over it.
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(import rl "vendor:raylib")
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(defconst screen-width 800)
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(defconst screen-height 450)
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(defconst sclera-radius f32 80.0)
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(defconst iris-radius f32 24.0)
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(defvar sclera-left rl/Vector2)
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(defvar sclera-right rl/Vector2)
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(defvar iris-left rl/Vector2)
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(defvar iris-right rl/Vector2)
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;; One eye's pupil, given where the mouse is and where the eye is. Answers the
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;; mouse position unchanged while it is inside the eye, and the point on the
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;; limit circle in that direction when it is outside.
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;;
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;; The C repeats this block twice with different variables; it is one function
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;; here because the two copies are identical and a difference between them
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;; would be invisible.
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(defn track [mouse rl/Vector2 centre rl/Vector2] rl/Vector2
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(let [limit (- sclera-radius iris-radius)]
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(if (rl/collision-point-circle? mouse centre limit)
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mouse
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;; Outside: the direction from the eye to the mouse, and then `limit`
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;; units back out along it. atan2 then cos/sin rather than a normalise,
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;; because that is what the C does and because it needs no guard for a
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;; zero-length vector — atan2(0,0) is 0 and the pupil sits at the right
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;; of the eye, which is unreachable anyway since (0,0) is inside.
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(let [d (rl/v2-sub mouse centre)
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angle (atan2-f32 (.y d) (.x d))]
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(rl/Vector2 {.x (+ (.x centre) (* limit (cos-f32 angle)))
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.y (+ (.y centre) (* limit (sin-f32 angle)))})))))
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(defn main [] ()
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(rl/init-window screen-width screen-height
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"raylib [shapes] example - following eyes")
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(defer (rl/close-window))
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;; The C reads these off get-screen-width/get-screen-height after the window
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;; is open rather than off the constants, and so does this: on a high-DPI
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;; display the two can differ.
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(set sclera-left (rl/Vector2 {.x (- (/ (f32 (rl/get-screen-width)) 2.0) 100.0)
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.y (/ (f32 (rl/get-screen-height)) 2.0)}))
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(set sclera-right (rl/Vector2 {.x (+ (/ (f32 (rl/get-screen-width)) 2.0) 100.0)
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.y (/ (f32 (rl/get-screen-height)) 2.0)}))
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(set iris-left sclera-left)
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(set iris-right sclera-right)
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(rl/set-target-fps 60)
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(until (rl/window-should-close?)
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;; Update
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(let [mouse (rl/get-mouse-position)]
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(set iris-left (track mouse sclera-left))
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(set iris-right (track mouse sclera-right)))
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;; Draw
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(rl/with-drawing
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(rl/clear-background rl/raywhite)
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;; White of the eye, iris, pupil — in that order, each over the last.
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(rl/draw-circle-v sclera-left sclera-radius rl/lightgray)
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(rl/draw-circle-v iris-left iris-radius rl/brown)
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(rl/draw-circle-v iris-left 10.0 rl/black)
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(rl/draw-circle-v sclera-right sclera-radius rl/lightgray)
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(rl/draw-circle-v iris-right iris-radius rl/darkgreen)
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(rl/draw-circle-v iris-right 10.0 rl/black)
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(rl/draw-fps 10 10))))
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