Joseph Ferano
421e09e0d6
(string b) is the mirror of (bytes s) and costs nothing: emit.ml already
lowers Types.String and Types.Slice _ to the same %slice, 16 bytes at
align 8, so a string and a [u8] are the identical value at run time and
both directions emit as the argument itself. What changes is only what
the checker will let the value be passed to — which was the whole gap.
Two decisions, both written into check.ml's comment.
It does not check UTF-8, because `string` does not claim UTF-8. The
prelude settles it: valid-utf8? is an ordinary function you call when you
care, decode-rune / rune-at / rune-count all take [u8] and not string,
and decode-rune answers {:ok false :width 1} on a malformed byte rather
than assuming well-formed input. The one place the runtime treats a
string differently from a byte slice is flan_escape_bytes, for a string
nested in a printed structure, and that is a byte-wise escape table with
no decoding in it. A check here would be the only enforcement point in
the language, which is a claim the rest of it does not make.
It does not widen the literal-write hole. That hole is the other
direction — (bytes "Hi") hands back a writable-looking slice over
constant data — and this direction only loses the ability to write, so
the result reaches strictly fewer stores than its argument could.
Provenance is still what the other direction needs; nothing here waits
on it.
The one sharp edge is not new but is easier to trip over now, and is
recorded in both the checker and digits.flan: i64->bytes, f64->bytes and
u64->bytes all view the same static buffer in the runtime, overwritten
by the next call, and calling it a string does not copy it. Format, draw,
then format the next one.
examples/digits.flan keeps its three signatures and loses its middle: the
[10 string] table, the per-glyph pen and the digit arithmetic are gone,
and draw-int is one draw-text. What survives is the part (string ...)
does not answer — i64->bytes has no field width, so "%03i" is still
assembled, and f64->bytes is "%g", so fixed decimal places are still a
split into two integers. core-input-multitouch and
core-input-virtual-controls ignored the width they were given, so both
inline the draw and stop importing digits.flan entirely.
test/programs/string-of-bytes.flan at -O2 and -O0: a number round-tripped,
an empty slice, sub-views whose length is not the underlying storage's,
and the result across a declare-c boundary. The last is the one that
could have been wrong — "hello world" cut to five bytes has a space where
C wants a NUL, so a shim that trusted the bytes would print all eleven.
71 lines
3.0 KiB
Plaintext
71 lines
3.0 KiB
Plaintext
;;;; raylib [core] example - input multitouch
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;;;;
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;;;; examples/core/core_input_multitouch.c. No new bindings: the whole touch
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;;;; surface was already there for sand.flan's read-out.
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;;;;
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;;;; The C keeps `Vector2 touchPositions[MAX_TOUCH_POINTS]`, and this is the
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;;;; first example that needs a fixed array whose element type is a STRUCT
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;;;; rather than a number. That works — `[10 rl/Vector2]` is ten Vector2s laid
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;;;; out flat, no headers, and `(at touch-positions i)` is a place that can be
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;;;; assigned a whole struct. Nothing in the repository used one before, so it
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;;;; is worth saying that it does.
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;;;;
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;;;; It is a top-level `defvar` and not a local, which is NOT a stylistic
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;;;; choice. A `let` binding takes no type annotation, so the only way to make
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;;;; a fixed array inside a function is to initialise it from a literal with
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;;;; every element written out — ten `(rl/Vector2 {:x 0.0 :y 0.0})`s here, and
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;;;; thirty-two in the gestures testbed. A zeroed local array of a given type
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;;;; cannot be spelled. Static storage is what the C's `= { 0 }` gets anyway.
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;;;;
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;;;; On a desktop with no touchscreen get-touch-point-count is 0 and this draws
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;;;; nothing at all, which is correct and is also what the C does. The window
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;;;; opening and the help text appearing is the whole of what can be checked
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;;;; without hardware.
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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 max-touch-points 10)
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(defvar touch-positions [max-touch-points rl/Vector2])
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(defn main []
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(rl/init-window screen-width screen-height
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"raylib [core] example - input multitouch")
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(defer (rl/close-window))
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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 [count (min max-touch-points (rl/get-touch-point-count))]
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(dotimes [i count]
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(set (at touch-positions i) (rl/get-touch-position i)))
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;; Draw
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(rl/begin-drawing)
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(rl/clear-background rl/raywhite)
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(dotimes [i count]
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(let [p (at touch-positions i)]
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;; raylib reports (0,0) for a slot that is not being touched, so the
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;; C filters on it and so does this. It means a real touch in the
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;; very top-left corner is dropped; that is raylib's ambiguity, not
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;; something the port introduced.
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(when (and (> (.x p) 0.0) (> (.y p) 0.0))
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(rl/draw-circle-v p 34.0 rl/orange)
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;; The C's TextFormat("%d", i). This used to need examples/digits.flan
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;; and a table of one-character strings; (string b) makes the
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;; number a string with no instructions, so it is one draw-text and
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;; this file imports nothing but raylib.
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(rl/draw-text (string (i64->bytes (i64 i)))
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(- (i32 (.x p)) 10) (- (i32 (.y p)) 70) 40
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rl/black))))
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(rl/draw-text "touch the screen at multiple locations to get multiple balls"
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10 10 20 rl/darkgray)
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(rl/end-drawing))))
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