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;;; guile-sdl2 --- FFI bindings for SDL2
;;; Copyright © 2020 Leo Prikler <leo.prikler@student.tugraz.at>
;;; Copyright © 2020 David Thompson <davet@gnu.org>
;;;
;;; This file is part of guile-sdl2.
;;;
;;; Guile-sdl2 is free software; you can redistribute it and/or modify
;;; it under the terms of the GNU Lesser General Public License as
;;; published by the Free Software Foundation; either version 3 of the
;;; License, or (at your option) any later version.
;;;
;;; Guile-sdl2 is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU Lesser General Public
;;; License along with guile-sdl2. If not, see
;;; <http://www.gnu.org/licenses/>.
(define-module (sdl2 blend-mode)
#:use-module (ice-9 match)
#:use-module (srfi srfi-9)
#:use-module (sdl2)
#:use-module ((sdl2 bindings) #:prefix ffi:)
#:export (make-blend-mode
blend-mode?
blend-mode-src-color-factor
blend-mode-dst-color-factor
blend-mode-color-operation
blend-mode-src-alpha-factor
blend-mode-dst-alpha-factor
blend-mode-alpha-operation
none
blend
add
mod
mul))
(define-record-type <blend-mode>
(%make-blend-mode src-color-factor dst-color-factor color-operation
src-alpha-factor dst-alpha-factor alpha-operation
bitmask)
blend-mode?
(src-color-factor blend-mode-src-color-factor)
(dst-color-factor blend-mode-dst-color-factor)
(color-operation blend-mode-color-operation)
(src-alpha-factor blend-mode-src-alpha-factor)
(dst-alpha-factor blend-mode-dst-alpha-factor)
(alpha-operation blend-mode-alpha-operation)
(bitmask blend-mode-bitmask))
(define none
(%make-blend-mode 'one 'zero 'add 'one 'zero 'add
ffi:SDL_BLENDMODE_NONE))
(define blend
(%make-blend-mode 'src-alpha 'one-minus-src-alpha 'add
'one 'one-minus-src-alpha 'add
ffi:SDL_BLENDMODE_BLEND))
(define add
(%make-blend-mode 'src-alpha 'one 'add
'zero 'one 'add
ffi:SDL_BLENDMODE_ADD))
(define mod
(%make-blend-mode 'zero 'src-color 'add
'zero 'one 'add
ffi:SDL_BLENDMODE_MOD))
(define mul
(%make-blend-mode 'dst-color 'one-minus-src-alpha 'add
'dst-alpha 'one-minus-src-alpha 'add
ffi:SDL_BLENDMODE_MUL))
(define (make-blend-mode src-color-factor dst-color-factor color-operation
src-alpha-factor dst-alpha-factor alpha-operation)
"Return a new custom blend mode for renderers.
SRC-COLOR-FACTOR applies to the red, green, and blue components of the
source pixels.
DST-COLOR-FACTOR applies to the red, green, and blue components of the
destination pixels.
COLOR-OPERATION specifies how to combine the red, green, and blue
components of the source and destination pixels.
SRC-ALPHA-FACTOR applies to the alpha component of the source pixels.
DST-ALPHA-FACTOR applies to the alpha component of the destination
pixels.
ALPHA-OPERATION specifies how to combine the alpha component of the
source and destination pixels.
Possible values for factors are zero, one, src-color,
one-minus-src-color, src-alpha, one-minus-src-alpha, dst-color,
one-minus-dst-color, dst-alpha, and one-minus-dst alpha.
Possible values for operations are add, subtract, rev-subtract,
minimum, and maximum."
(define symbol->blend-operation
(match-lambda
('add ffi:SDL_BLENDOPERATION_ADD)
('subtract ffi:SDL_BLENDOPERATION_SUBTRACT)
('rev-subtract ffi:SDL_BLENDOPERATION_REV_SUBTRACT)
('minimum ffi:SDL_BLENDOPERATION_MINIMUM)
('maximum ffi:SDL_BLENDOPERATION_MAXIMUM)))
(define symbol->blend-factor
(match-lambda
('zero ffi:SDL_BLENDFACTOR_ZERO)
('one ffi:SDL_BLENDFACTOR_ONE)
('src-color ffi:SDL_BLENDFACTOR_SRC_COLOR)
('one-minus-src-color ffi:SDL_BLENDFACTOR_ONE_MINUS_SRC_COLOR)
('src-alpha ffi:SDL_BLENDFACTOR_SRC_ALPHA)
('one-minus-src-alpha ffi:SDL_BLENDFACTOR_ONE_MINUS_SRC_ALPHA)
('dst-color ffi:SDL_BLENDFACTOR_DST_COLOR)
('one-minus-dst-color ffi:SDL_BLENDFACTOR_ONE_MINUS_DST_COLOR)
('dst-alpha ffi:SDL_BLENDFACTOR_DST_ALPHA)
('one-minus-dst-alpha ffi:SDL_BLENDFACTOR_ONE_MINUS_DST_ALPHA)))
(let ((bitmask (ffi:sdl-compose-custom-blend-mode
(symbol->blend-factor src-color-factor)
(symbol->blend-factor dst-color-factor)
(symbol->blend-operation color-operation)
(symbol->blend-factor src-alpha-factor)
(symbol->blend-factor dst-alpha-factor)
(symbol->blend-operation alpha-operation))))
(if (eq? bitmask ffi:SDL_BLENDMODE_INVALID)
(sdl-error "make-blend-mode"
"invalid custom blend mode")
(%make-blend-mode src-color-factor
dst-color-factor
color-operation
src-alpha-factor
dst-alpha-factor
alpha-operation
bitmask))))
|
