;;;; raylib [core] example - scissor test
;;;;
;;;; examples/core/core_scissor_test.c. Needed begin-scissor-mode and
;;;; end-scissor-mode, now hand-written in vendor/raylib/raylib.fln: they are
;;;; a begin/end pair inside a frame, which is the class docs/PORTING.md §1 says
;;;; belongs in the hand-written half and not in the importer's. get-mouse-x
;;;; and get-mouse-y come from the generated half — their Flan face is the C
;;;; one, two plain i32s, and there is nothing for a hand-written line to say
;;;; about them that the header does not already say.
;;;;
;;;; The scissor rectangle is a Rectangle of floats in the C and stays one
;;;; here, even though every use of it casts back to i32, because the one call
;;;; that takes it whole — draw-rectangle-lines-ex — wants a Rectangle. That
;;;; is also why the mouse is read through get-mouse-x/get-mouse-y rather than
;;;; get-mouse-position: the C does the arithmetic in floats from integer
;;;; readings, and doing it the other way round would round differently on the
;;;; odd pixel.
;;;;
;;;; What this example is really a test of, and what no headless case could
;;;; be: raylib's scissor rectangle is in screen pixels with y growing DOWN,
;;;; and the GL call underneath measures from the bottom. raylib flips it. If
;;;; the binding or the flip were wrong the clip would appear mirrored about
;;;; the middle of the window — a perfectly plausible picture, in the wrong
;;;; place — so the only check is the outline drawn around it afterwards
;;;; landing on the revealed patch.

import rl "vendor:raylib"

const screen-width = 800
const screen-height = 450

once scissor: rl/Rectangle
once scissor-mode: bool

fn main() -> ()
  rl/init-window(screen-width, screen-height,
                 "raylib [core] example - scissor test")
  defer rl/close-window()
  scissor = rl/Rectangle{.x 0.0 .y 0.0 .width 300.0 .height 300.0}
  scissor-mode = true
  rl/set-target-fps(60)
  until rl/window-should-close()
    ;; Update
    if rl/is-key-pressed(:key-s)
      scissor-mode = not scissor-mode
    ;; Centre the scissor area on the mouse.
    scissor.x = f32(rl/get-mouse-x()) - scissor.width / 2.0
    scissor.y = f32(rl/get-mouse-y()) - scissor.height / 2.0
    ;; Draw
    rl/with-drawing:
      rl/clear-background(rl/raywhite)
      if scissor-mode
        rl/begin-scissor-mode(i32(scissor.x), i32(scissor.y),
                              i32(scissor.width), i32(scissor.height))
      ;; A full-screen rectangle and a line of text. Only the part inside the
      ;; scissor rectangle reaches the framebuffer, which is the whole example.
      rl/draw-rectangle(0, 0, rl/get-screen-width(), rl/get-screen-height(),
                        rl/red)
      rl/draw-text("Move the mouse around to reveal this text!", 190, 200, 20,
                   rl/lightgray)
      if scissor-mode
        rl/end-scissor-mode()
      rl/draw-rectangle-lines-ex(scissor, 1.0, rl/black)
      rl/draw-text("Press S to toggle scissor test", 10, 10, 20, rl/black)