;;;; 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.flan: 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")

(defconst screen-width  800)
(defconst screen-height 450)

(defvar scissor rl/Rectangle)
(defvar scissor-mode bool)

(defn main [] ()
  (rl/init-window screen-width screen-height
                  "raylib [core] example - scissor test")
  (defer (rl/close-window))

  (set scissor (rl/Rectangle {.x 0.0 .y 0.0 .width 300.0 .height 300.0}))
  (set scissor-mode true)

  (rl/set-target-fps 60)

  (until (rl/window-should-close?)
    ;; Update
    (when (rl/key-pressed? :s) (set scissor-mode (not scissor-mode)))

    ;; Centre the scissor area on the mouse.
    (set (.x scissor) (- (f32 (rl/get-mouse-x)) (/ (.width scissor) 2.0)))
    (set (.y scissor) (- (f32 (rl/get-mouse-y)) (/ (.height scissor) 2.0)))

    ;; Draw
    (rl/with-drawing
      (rl/clear-background rl/raywhite)

      (when scissor-mode
        (rl/begin-scissor-mode (i32 (.x scissor)) (i32 (.y scissor))
                               (i32 (.width scissor)) (i32 (.height scissor))))

      ;; 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)

      (when 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))))