From 372abd79211d84fa9a9b4e7cd90925109614a730 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Mon, 10 Sep 2018 21:27:25 -0400
Subject: render: texture: Add flip? argument to make-texture.

* chickadee/render/texture.scm (make-texture): Add #:flip? keyword argument.
---
 chickadee/render/texture.scm | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/chickadee/render/texture.scm b/chickadee/render/texture.scm
index 4214c70..e37e4ec 100644
--- a/chickadee/render/texture.scm
+++ b/chickadee/render/texture.scm
@@ -139,6 +139,7 @@
   (gpu-state-set! (vector-ref *texture-states* n) texture))
 
 (define* (make-texture pixels width height #:key
+                       flip?
                        (min-filter 'linear)
                        (mag-filter 'linear)
                        (wrap-s 'repeat)
@@ -146,10 +147,13 @@
                        (format 'rgba))
   "Translate the bytevector PIXELS into an OpenGL texture with
 dimensions WIDTHxHEIGHT where each pixel is in 32-bit RGBA format.
-The generated texture uses MIN-FILTER for downscaling and MAG-FILTER
-for upscaling.  WRAP-S and WRAP-T are symbols that control how texture
-access is handled for texture coordinates outside the [0, 1] range.
-Allowed symbols are: repeat (the default), clamp, clamp-to-border,
+The first pixe lin PIXELS corresponds to the upper-left corner of the
+image.  If this is not the case and the first pixel corresponds to the
+lower-left corner of the image, set FLIP? to #t.  The generated
+texture uses MIN-FILTER for downscaling and MAG-FILTER for upscaling.
+WRAP-S and WRAP-T are symbols that control how texture access is
+handled for texture coordinates outside the [0, 1] range.  Allowed
+symbols are: repeat (the default), clamp, clamp-to-border,
 clamp-to-edge.  FORMAT specifies the pixel format.  Currently only
 32-bit RGBA format is supported."
   (define (gl-wrap mode)
@@ -164,7 +168,9 @@ clamp-to-edge.  FORMAT specifies the pixel format.  Currently only
                                  min-filter mag-filter wrap-s wrap-t
                                  0 0 width height
                                  (make-rect 0.0 0.0 width height)
-                                 (make-rect 0.0 0.0 1.0 1.0)))))
+                                 (if flip?
+                                     (make-rect 1.0 1.0 -1.0 -1.0)
+                                     (make-rect 0.0 0.0 1.0 1.0))))))
     (texture-set! 0 texture)
     (gl-texture-parameter (texture-target texture-2d)
                           (texture-parameter-name texture-min-filter)
-- 
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