mesa/main: Check for 0 size draws after validation.

When validating draw parameters move check for 0 draw count last
(drawing with count 0 is not an error), so that other parameters (e.g.: the
primitive type) are validated and the correct errors (if applicable) are
generated.

>From the OpenGL 3.3 spec page 33 (page 48 of the PDF):
"[Regarding DrawArraysOneInstance, in terms of which other draw operations
are defined:]
If count is negative, an INVALID_VALUE error is generated."

This patch also changes the bahavior of MultiDrawElements to perform the draw
operation if some primitive's index counts are zero.

Signed-off-by: Fabian Bieler <[email protected]>
Reviewed-by: Brian Paul <[email protected]>
Reviewed-by: Paul Berry <[email protected]>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/mesa/vbo/vbo_exec_array.c b/src/mesa/vbo/vbo_exec_array.c
index bd05cd0c369..1670409d48b 100644
--- a/src/mesa/vbo/vbo_exec_array.c
+++ b/src/mesa/vbo/vbo_exec_array.c
@@ -1334,6 +1334,16 @@ vbo_validated_multidrawelements(struct gl_context *ctx, GLenum mode,
       }
    }
 
+   /* Draw primitives individually if one count is zero, so we can easily skip
+    * that primitive.
+    */
+   for (i = 0; i < primcount; i++) {
+      if (count[i] == 0) {
+         fallback = GL_TRUE;
+         break;
+      }
+   }
+
    /* If the index buffer isn't in a VBO, then treating the application's
     * subranges of the index buffer as one large index buffer may lead to
     * us reading unmapped memory.
@@ -1370,6 +1380,8 @@ vbo_validated_multidrawelements(struct gl_context *ctx, GLenum mode,
    } else {
       /* render one prim at a time */
       for (i = 0; i < primcount; i++) {
+	 if (count[i] == 0)
+	    continue;
 	 ib.count = count[i];
 	 ib.type = type;
 	 ib.obj = ctx->Array.ArrayObj->ElementArrayBufferObj;