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authorDavid Thompson <dthompson2@worcester.edu>2016-01-08 21:38:32 -0500
committerDavid Thompson <dthompson2@worcester.edu>2016-01-08 21:38:32 -0500
commit33863df70267b72aaeb94e4b1c0165cb1ec94b74 (patch)
tree07e01a9629fdfaa199a04b56a21d5198c7af0302
parent6b2ecade1079c5bef1c066b9f092a8179d78d932 (diff)
video: Add SDL_GL_SetSwapInterval binding.
* sdl2/bindings.scm (sdl-gl-set-swap-interval): New procedure. * sdl2/video.scm (set-gl-swap-interval!): New procedure.
-rw-r--r--sdl2/bindings.scm3
-rw-r--r--sdl2/video.scm22
2 files changed, 24 insertions, 1 deletions
diff --git a/sdl2/bindings.scm b/sdl2/bindings.scm
index 6c638ab..b6f9431 100644
--- a/sdl2/bindings.scm
+++ b/sdl2/bindings.scm
@@ -202,6 +202,9 @@ RETURN-TYPE and accept arguments of ARG-TYPES."
(define-foreign sdl-gl-set-attribute
int "SDL_GL_SetAttribute" (list int int))
+(define-foreign sdl-gl-set-swap-interval
+ int "SDL_GL_SetSwapInterval" (list int))
+
(define-public SDL_RENDERER_SOFTWARE #x00000001)
(define-public SDL_RENDERER_ACCELERATED #x00000002)
(define-public SDL_RENDERER_PRESENTVSYNC #x00000004)
diff --git a/sdl2/video.scm b/sdl2/video.scm
index 7cf14ff..8c65023 100644
--- a/sdl2/video.scm
+++ b/sdl2/video.scm
@@ -56,7 +56,8 @@
delete-gl-context!
call-with-gl-context
swap-gl-window
- set-gl-attribute!))
+ set-gl-attribute!
+ set-gl-swap-interval!))
;;;
@@ -318,3 +319,22 @@ Possible values for ATTR are:
('framebuffer-srgb-capable ffi:SDL_GL_FRAMEBUFFER_SRGB_CAPABLE))))
(unless (zero? (ffi:sdl-gl-set-attribute attr-enum value))
(sdl-error "set-gl-attribute!" "failed to set OpenGL attribute"))))
+
+(define (set-gl-swap-interval! interval)
+ "Set the framebuffer swap interval for the current OpenGL context to
+the type indicated by the symbol INTERVAL. Possible values of INTERVAL are:
+
+- immediate, for immediate updates
+- vsync, for updates synchronized with the screen's vertical retrace
+- late-swap-tear, for late swap tearing
+
+Late swap tearing works the same as vsync, but if the vertical retrace
+has been missed for a given frame, buffers are swapped immediately,
+which might be less jarring for the user during occasional framerate
+drops."
+ (unless (zero? (ffi:sdl-gl-set-swap-interval
+ (match interval
+ ('immediate 0)
+ ('vsync 1)
+ ('late-swap-tear -1))))
+ (sdl-error "set-gl-swap-interval!" "failed to set OpenGL swap interval")))