render: sprite: Fix bug in rendering texture regions.

The texture-rect procedure contains the pixel location of the texture
region, so if you use that rect to render a sprite the result is a
sprite offset by its location in the greater texture, which is very
very very wrong.

* chickadee/render/sprite.scm (draw-sprite): Dynamically configure
rendering rect based on the texture region's width and height.

1 files changed, 9 insertions, 3 deletions

diff --git a/chickadee/render/sprite.scm b/chickadee/render/sprite.scm
index c284ff4..78a2ce5 100644
--- a/chickadee/render/sprite.scm
+++ b/chickadee/render/sprite.scm
@@ -341,7 +341,8 @@ void main (void) {
 (define %default-scale (vec2 1.0 1.0))
 
 (define draw-sprite
-  (let ((matrix (make-null-matrix4)))
+  (let ((matrix (make-null-matrix4))
+        (%rect (make-rect 0.0 0.0 0.0 0.0)))
     (lambda* (texture
               position
               #:key
@@ -349,7 +350,12 @@ void main (void) {
               (scale %default-scale)
               (rotation 0.0)
               (blend-mode 'alpha)
-              (rect (texture-rect texture))
+              ;; Default to an area that is the same size of the
+              ;; texture.  99% of the time that's what you want.
+              (rect (let ((r (texture-rect texture)))
+                      (set-rect-width! %rect (rect-width r))
+                      (set-rect-height! %rect (rect-height r))
+                      %rect))
               (shader (force default-shader)))
       "Draw TEXTURE at POSITION.
 
@@ -368,7 +374,7 @@ rendered entirely."
                              #:position position
                              #:rotation rotation
                              #:scale scale)
-      (draw-sprite* texture (texture-rect texture) matrix
+      (draw-sprite* texture rect matrix
                     #:blend-mode blend-mode
                     #:shader shader))))