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;;; Sly
;;; Copyright (C) 2014, 2015 David Thompson <davet@gnu.org>
;;;
;;; Sly is free software: you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation, either version 3 of the License, or
;;; (at your option) any later version.
;;;
;;; Sly 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 General Public License
;;; along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; Viewports.
;;
;;; Code:
(define-module (sly render viewport)
#:use-module (ice-9 match)
#:use-module (srfi srfi-9)
#:use-module (gl)
#:use-module (gl low-level)
#:use-module (sly wrappers gl)
#:use-module (sly math rect)
#:use-module (sly utils)
#:use-module (sly render color)
#:export (make-viewport
viewport?
viewport-area
viewport-clear-color
viewport-clear-flags
null-viewport
%standard-clear-flags
apply-viewport
clear-viewport))
;;;
;;; Viewport
;;;
(define-record-type <viewport>
(%make-viewport area clear-color clear-flags)
viewport?
(area viewport-area)
(clear-color viewport-clear-color)
(clear-flags viewport-clear-flags))
(define %standard-clear-flags '(color-buffer depth-buffer))
(define* (make-viewport area #:optional #:key (clear-color black)
(clear-flags %standard-clear-flags))
"Create a viewport that covers the rectangle AREA of the window.
Fill the viewport with CLEAR-COLOR when clearing the screen. Clear
the buffers denoted by the list of symbols in CLEAR-FLAGS. Possible
values for CLEAR-FLAGS are 'color-buffer', 'depth-buffer',
'accum-buffer', and 'stencil-buffer'."
(%make-viewport area clear-color clear-flags))
(define null-viewport (make-viewport (make-rect 0 0 0 0)))
(define clear-buffer-mask
(memoize
(lambda (flags)
(apply logior
;; Map symbols to OpenGL constants.
(map (match-lambda
('depth-buffer 256)
('accum-buffer 512)
('stencil-buffer 1024)
('color-buffer 16384))
flags)))))
(define (apply-viewport viewport)
"Set the OpenGL state for VIEWPORT. Clip rendering to the viewport
area, set the clear color, and clear necessary buffers."
(gl-enable (enable-cap scissor-test))
(match (viewport-area viewport)
(($ <rect> x y width height)
(gl-viewport x y width height)
(gl-scissor x y width height)))
(match (viewport-clear-color viewport)
(($ <color> r g b a)
(gl-clear-color r g b a))))
(define (clear-viewport viewport)
"Clear the relevant OpenGL buffers VIEWPORT."
(gl-clear (clear-buffer-mask (viewport-clear-flags viewport))))
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