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-rw-r--r--sdl2/surface.scm46
1 files changed, 45 insertions, 1 deletions
diff --git a/sdl2/surface.scm b/sdl2/surface.scm
index dee9781..1537c58 100644
--- a/sdl2/surface.scm
+++ b/sdl2/surface.scm
@@ -26,13 +26,18 @@
(define-module (sdl2 surface)
#:use-module (ice-9 format)
#:use-module (ice-9 match)
+ #:use-module (rnrs bytevectors)
#:use-module (system foreign)
#:use-module ((sdl2 bindings) #:prefix ffi:)
#:use-module (sdl2)
#:export (surface?
delete-surface!
call-with-surface
- load-bmp))
+ load-bmp
+ surface-width
+ surface-height
+ surface-pitch
+ surface-pixels))
(define-wrapped-pointer-type <surface>
surface?
@@ -64,3 +69,42 @@ PROC."
(if (null-pointer? ptr)
(sdl-error "load-bmp" "failed to load bitmap")
(wrap-surface ptr))))
+
+(define %int-size (sizeof int))
+(define %pointer-size (sizeof '*))
+
+(define (pointer-int-ref pointer offset)
+ (bytevector-sint-ref (pointer->bytevector pointer %int-size offset)
+ 0 (native-endianness) %int-size))
+
+;; The offsets below correspond to the SDL_Surface struct elements
+;; that come before the element in question.
+(define %width-offset (sizeof (list uint32 '*)))
+(define %height-offset (sizeof (list uint32 '* int)))
+(define %pitch-offset (sizeof (list uint32 '* int int)))
+(define %pixels-offset 32)
+
+(define (surface-width surface)
+ "Return the width of SURFACE in pixels."
+ (pointer-int-ref (unwrap-surface surface) %width-offset))
+
+(define (surface-height surface)
+ "Return the height of SURFACE in pixels."
+ (pointer-int-ref (unwrap-surface surface) %height-offset))
+
+(define (surface-pitch surface)
+ "Return the length of a row of pixels in SURFACE in bytes."
+ (pointer-int-ref (unwrap-surface surface) %pitch-offset))
+
+(define (surface-pixels surface)
+ "Return a bytevector containing the raw pixel data in SURFACE."
+ (let* ((ptr (unwrap-surface surface))
+ (height (pointer-int-ref ptr %height-offset))
+ (pitch (pointer-int-ref ptr %pitch-offset))
+ (pixels-ptr (pointer->bytevector ptr %pointer-size %pixels-offset))
+ (pixels (make-pointer
+ (bytevector-uint-ref pixels-ptr
+ 0
+ (native-endianness)
+ %pointer-size))))
+ (pointer->bytevector pixels (* height pitch))))