render: mesh: Add null-mesh.

* sly/render/mesh.scm (null-mesh): New variable.
* sly/render/context.scm (render-context-reset!): Reset to null-mesh.

2 files changed, 3 insertions, 1 deletions

diff --git a/sly/render/context.scm b/sly/render/context.scm
index 49547dc..0e96e26 100644
--- a/sly/render/context.scm
+++ b/sly/render/context.scm
@@ -79,7 +79,7 @@
   (glUseProgram 0)
   (%set-render-context-shader! context #f)
   (glBindVertexArray 0)
-  (%set-render-context-mesh! context #f))
+  (%set-render-context-mesh! context null-mesh))
 
 (define-syntax-rule (with-render-context context body ...)
   (begin (render-context-reset! context)
diff --git a/sly/render/mesh.scm b/sly/render/mesh.scm
index 9eea8ed..5f577ca 100644
--- a/sly/render/mesh.scm
+++ b/sly/render/mesh.scm
@@ -206,6 +206,8 @@
                                (vertex-buffer-id vbo)))
                              buffers))))))
 
+(define null-mesh (%make-mesh 0 0 '()))
+
 (define (generate-vertex-array)
   (let ((bv (u32vector 1)))
     (glGenVertexArrays 1 (bytevector->pointer bv))