diff options
| -rw-r--r-- | sly/game.scm | 54 |
1 files changed, 47 insertions, 7 deletions
diff --git a/sly/game.scm b/sly/game.scm index 1b0e0a0..888d10d 100644 --- a/sly/game.scm +++ b/sly/game.scm @@ -23,6 +23,7 @@ (define-module (sly game) #:use-module (srfi srfi-9) + #:use-module (srfi srfi-11) #:use-module ((sdl sdl) #:prefix SDL:) #:use-module (gl) #:use-module (sly agenda) @@ -31,6 +32,7 @@ #:use-module (sly signal) #:use-module (sly window) #:export (draw-hook + after-game-loop-error-hook start-game-loop stop-game-loop)) @@ -39,10 +41,22 @@ ;;; (define draw-hook (make-hook 2)) +(define after-game-loop-error-hook (make-hook)) (define (interval rate) (floor (/ 1000 rate))) +(define (display-game-loop-error stack key . args) + "Display a backtrace and error message using the current error port +for the given STACK and error KEY with additional arguments ARGS." + (let ((cep (current-error-port))) + (display "Sly game loop error!\n\n" cep) + (display "Backtrace:\n" cep) + (display-backtrace stack cep) + (newline cep) + (apply display-error (stack-ref stack 0) cep args) + (newline cep))) + (define* (start-game-loop #:optional #:key (frame-rate 60) (tick-rate 60) @@ -90,16 +104,42 @@ leftover frame time LAG." (SDL:get-ticks)))) (usleep (max 0 (* t 1000))))) + (define (process-frame previous-time lag) + "Render and/or update the game as needed, integrating from the +PREVIOUS-TIME to the current time, and updating using a game tick +accumulator initialized to LAG. Returns a timestamp to be used as the +starting point of the next delta time calculation and the leftover +time in the game tick accumulator." + (let* ((current-time (SDL:get-ticks)) + (dt (- current-time previous-time))) + (catch #t + (lambda () + (process-events) + (let ((lag (update (+ lag dt)))) + (draw dt (alpha lag)) + (frame-sleep current-time) + (values current-time lag))) + (lambda (key . args) + (if (hook-empty? after-game-loop-error-hook) + ;; Rethrow error if there's nothing to handle it. + (apply throw key args) + (begin + (run-hook after-game-loop-error-hook) + ;; An unknown amount of time has passed since running the + ;; hook, so let's start with a fresh timer. + (values (SDL:get-ticks) 0)))) + (lambda (key . args) + ;; Strip out 3 stack frames to get to the frame where the + ;; error happened. The stripped frames include the throw + ;; call, and the make-stack call. + (apply display-game-loop-error (make-stack #t 3) key args))))) + (define (game-loop previous-time lag) "Update game state, and render. PREVIOUS-TIME is the time in milliseconds of the last iteration of the game loop." - (let* ((current-time (SDL:get-ticks)) - (dt (- current-time previous-time))) - (process-events) - (let ((lag (update (+ lag dt)))) - (draw dt (alpha lag)) - (frame-sleep current-time) - (game-loop current-time lag)))) + (let-values (((time lag) + (process-frame previous-time lag))) + (game-loop time lag))) (call-with-prompt 'game-loop-prompt |