Clear the screen even when nothing is being drawn.

1 files changed, 10 insertions, 5 deletions

diff --git a/chickadee.scm b/chickadee.scm
index 8250e19..0a9b0b3 100644
--- a/chickadee.scm
+++ b/chickadee.scm
@@ -31,6 +31,8 @@
   #:use-module (chickadee render gpu)
   #:use-module (chickadee render viewport)
   #:use-module (chickadee utils)
+  #:use-module (gl)
+  #:use-module (gl enums)
   #:use-module (ice-9 match)
   #:use-module (sdl2)
   #:use-module (sdl2 events)
@@ -237,7 +239,11 @@ border is disabled, otherwise it is enabled.")
          (default-viewport (make-viewport 0 0 window-width window-height))
          (default-projection (orthographic-projection 0 window-width
                                                       window-height 0
-                                                      0 1)))
+                                                      0 1))
+         (clear-mask (logior (attrib-mask color-buffer)
+                             (attrib-mask depth-buffer)
+                             (attrib-mask stencil-buffer)
+                             (attrib-mask accum-buffer))))
     (define (invert-y y)
       ;; SDL's origin is the top-left, but our origin is the bottom
       ;; left so we need to invert Y coordinates that SDL gives us.
@@ -308,10 +314,9 @@ border is disabled, otherwise it is enabled.")
       ;; Free any GPU resources that have been GC'd.
       (gpu-reap!))
     (define (render-sdl-opengl alpha)
-      ;; Switch to the null viewport to ensure that
-      ;; the default viewport will be re-applied and
-      ;; clear the screen.
-      (set-gpu-viewport! gpu null-viewport)
+      ;; Switch to the default viewport so we can clear the whole screen.
+      (set-gpu-viewport! gpu default-viewport)
+      (gl-clear clear-mask)
       (with-viewport default-viewport
         (with-projection default-projection
           (draw alpha)))