[Mesa-dev] [PATCH] mesa: Fix computation of default vertex attrib stride for 2_10_10_10 formats.

[Paul Berry]

Previously, if the client program didn't specify a stride when setting
up a vertex attribute, we used _mesa_sizeof_type() to compute the size
of the type, and multiplied it by the number of components.

This didn't work for the 2_10_10_10 formats, since _mesa_sizeof_type()
returns -1 for those types, resulting in all kinds of havoc, since it
was causing the hardware to be programmed with a negative stride
value.

This patch adds a new function _mesa_bytes_per_vertex_attrib(), which
is similar to the existing function _mesa_bytes_per_pixel(), but which
computes the size of a vertex attribute based on the type and the
number of formats.  For packed formats (currently only the 2_10_10_10
formats), it verifies that the number of components is correct and
returns the size of the packed format.  For unpacked formats, it
returns the size of the type times the number of components.

In addition, this patch adds an assertion so that if we ever forget to
update _mesa_bytes_per_vertex_attrib() when adding a new vertex
format, we'll see the problem quickly rather than having to debug a
subtle conformance test failure.

Fixes GLES3 conformance tests
vertex_type_2_10_10_10_rev_{conversion,divisor,stride_pointer}.test.
---
 src/mesa/main/glformats.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 src/mesa/main/glformats.h |  3 +++
 src/mesa/main/varray.c    |  3 ++-
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/src/mesa/main/glformats.c b/src/mesa/main/glformats.c
index fefa9c4..b6b16ca 100644
--- a/src/mesa/main/glformats.c
+++ b/src/mesa/main/glformats.c
@@ -308,6 +308,48 @@ _mesa_bytes_per_pixel(GLenum format, GLenum type)
 
 
 /**
+ * Get the number of bytes for a vertex attrib with the given number of
+ * components ant type.
+ *
+ * \param comps number of components.
+ * \param type data type.
+ *
+ * \return bytes per attribute, or -1 if a bad comps/type combination was given.
+ */
+GLint
+_mesa_bytes_per_vertex_attrib(GLint comps, GLenum type)
+{
+   switch (type) {
+   case GL_BYTE:
+   case GL_UNSIGNED_BYTE:
+      return comps * sizeof(GLubyte);
+   case GL_SHORT:
+   case GL_UNSIGNED_SHORT:
+      return comps * sizeof(GLshort);
+   case GL_INT:
+   case GL_UNSIGNED_INT:
+      return comps * sizeof(GLint);
+   case GL_FLOAT:
+      return comps * sizeof(GLfloat);
+   case GL_HALF_FLOAT_ARB:
+      return comps * sizeof(GLhalfARB);
+   case GL_DOUBLE:
+      return comps * sizeof(GLdouble);
+   case GL_FIXED:
+      return comps * sizeof(GLfixed);
+   case GL_INT_2_10_10_10_REV:
+   case GL_UNSIGNED_INT_2_10_10_10_REV:
+      if (comps == 4)
+         return sizeof(GLuint);
+      else
+         return -1;
+   default:
+      return -1;
+   }
+}
+
+
+/**
  * Test if the given format is an integer (non-normalized) format.
  */
 GLboolean
diff --git a/src/mesa/main/glformats.h b/src/mesa/main/glformats.h
index 5d09951..ccfb5e1 100644
--- a/src/mesa/main/glformats.h
+++ b/src/mesa/main/glformats.h
@@ -49,6 +49,9 @@ _mesa_components_in_format( GLenum format );
 extern GLint
 _mesa_bytes_per_pixel( GLenum format, GLenum type );
 
+extern GLint
+_mesa_bytes_per_vertex_attrib(GLint comps, GLenum type);
+
 extern GLboolean
 _mesa_is_type_integer(GLenum type);
 
diff --git a/src/mesa/main/varray.c b/src/mesa/main/varray.c
index f770143..5e4d6c3 100644
--- a/src/mesa/main/varray.c
+++ b/src/mesa/main/varray.c
@@ -251,7 +251,8 @@ update_array(struct gl_context *ctx,
       return;
    }
 
-   elementSize = _mesa_sizeof_type(type) * size;
+   elementSize = _mesa_bytes_per_vertex_attrib(size, type);
+   assert(elementSize != -1);
 
    array = &ctx->Array.ArrayObj->VertexAttrib[attrib];
    array->Size = size;
-- 
1.8.0.1