mesa: Expose function to calculate whether a shader image unit is valid.

A future commit will remove all texture object-dependent derived state
from the image unit struct to make validation unnecessary on texture
state changes.  Instead of checking gl_image_unit::_Valid drivers will
be required to call this function when needed to find out whether an
image unit is in a valid state and whether access from the shader is
allowed.

Tested-by: Ye Tian <[email protected]>
CC: "11.0" <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/mesa/main/shaderimage.h b/src/mesa/main/shaderimage.h
index bbe088a2459..14a544fca8a 100644
--- a/src/mesa/main/shaderimage.h
+++ b/src/mesa/main/shaderimage.h
@@ -55,6 +55,17 @@ void
 _mesa_init_image_units(struct gl_context *ctx);
 
 /**
+ * Return GL_TRUE if the state of the image unit passed as argument is valid
+ * and access from the shader is allowed.  Otherwise loads from this unit
+ * should return zero and stores should have no effect.
+ *
+ * The result depends on context state other than the passed image unit, part
+ * of the _NEW_TEXTURE set.
+ */
+GLboolean
+_mesa_is_image_unit_valid(struct gl_context *ctx, struct gl_image_unit *u);
+
+/**
  * Recalculate the \c _Valid flag of a context's shader image units.
  *
  * To be called when the state of any texture bound to an image unit