From 95d31ad231800026e7b0a44ddda42c584dad5671 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson@member.fsf.org>
Date: Mon, 26 Aug 2013 22:09:45 -0400
Subject: Make the origin the top-left corner of the window again.

---
 2d/font.scm          | 17 ++++++++++++++---
 2d/texture.scm       |  2 ++
 2d/window.scm        |  2 +-
 2d/wrappers/ftgl.scm | 16 +++++++++++++++-
 4 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/2d/font.scm b/2d/font.scm
index 70b0904..8bf66a3 100644
--- a/2d/font.scm
+++ b/2d/font.scm
@@ -47,11 +47,21 @@
     (ftgl-set-font-face-size ftgl-font size 72)
     (make-font ftgl-font size)))
 
+(define (flip-text font)
+  "Flips current GL matrix about the x-axis and translates by the
+negative font ascender value. This is necessary before rendering text
+because guile-2d flips the y-axis so that the origin is in the
+upper-left corner rather than the bottom-left."
+  (gl-scale 1 -1 1)
+  (gl-translate 0 (- (ftgl-get-font-ascender (font-ftgl-font font))) 0))
+
 (define (draw-font font text)
   "Renders the string text using the given font."
-  (ftgl-render-font (font-ftgl-font font)
-                    text
-                    (ftgl-render-mode all)))
+  (with-gl-push-matrix
+    (flip-text font)
+    (ftgl-render-font (font-ftgl-font font)
+                      text
+                      (ftgl-render-mode all))))
 
 (export <font>
         make-font
@@ -88,6 +98,7 @@
   (let ((pos (textbox-position textbox)))
     (with-gl-push-matrix
       (gl-translate (vx pos) (vy pos) 0)
+      (flip-text (textbox-font textbox))
       (apply-color (textbox-color textbox))
       (ftgl-render-layout (textbox-layout textbox)
                           (textbox-text textbox)
diff --git a/2d/texture.scm b/2d/texture.scm
index 19c26c8..8df5e51 100644
--- a/2d/texture.scm
+++ b/2d/texture.scm
@@ -141,6 +141,8 @@
          (bitmap (freeimage-load image-type filename))
          (32bit-bitmap (freeimage-convert-to-32-bits bitmap)))
     (freeimage-unload bitmap)
+    ;; Need to flip because y-axis is reversed.
+    (freeimage-flip-vertical 32bit-bitmap)
     32bit-bitmap))
 
 (define (load-texture filename)
diff --git a/2d/window.scm b/2d/window.scm
index de824d8..9c863f6 100644
--- a/2d/window.scm
+++ b/2d/window.scm
@@ -45,7 +45,7 @@ initializes OpenGL state."
     (gl-viewport 0 0 width height)
     (set-gl-matrix-mode (matrix-mode projection))
     (gl-load-identity)
-    (gl-ortho 0 width 0 height -1 1)
+    (gl-ortho 0 width height 0 -1 1)
     (set-gl-matrix-mode (matrix-mode modelview))
     (gl-load-identity)
     ;; Enable texturing and alpha blending
diff --git a/2d/wrappers/ftgl.scm b/2d/wrappers/ftgl.scm
index 1d18fad..537655c 100644
--- a/2d/wrappers/ftgl.scm
+++ b/2d/wrappers/ftgl.scm
@@ -73,6 +73,12 @@
 (define-foreign %ftgl-render-font
   void "ftglRenderFont" (list '* '* unsigned-int))
 
+(define-foreign %ftgl-get-font-descender
+  float "ftglGetFontDescender" '(*))
+
+(define-foreign %ftgl-get-font-ascender
+  float "ftglGetFontAscender" '(*))
+
 (define (ftgl-create-texture-font filename)
   (wrap-ftgl-font
    (%ftgl-create-texture-font (string->pointer filename))))
@@ -85,9 +91,17 @@
                      (string->pointer text)
                      render-mode))
 
+(define (ftgl-get-font-descender font)
+  (%ftgl-get-font-descender (unwrap-ftgl-font font)))
+
+(define (ftgl-get-font-ascender font)
+  (%ftgl-get-font-ascender (unwrap-ftgl-font font)))
+
 (export ftgl-create-texture-font
         ftgl-set-font-face-size
-        ftgl-render-font)
+        ftgl-render-font
+        ftgl-get-font-descender
+        ftgl-get-font-ascender)
 
 ;;;
 ;;; SimpleLayout
-- 
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