+/**
+ * Figure out which stage of the pipeline is the source of transform feedback
+ * data given the current context state, and return its gl_shader_program.
+ *
+ * If no active program can generate transform feedback data (i.e. no vertex
+ * shader is active), returns NULL.
+ */
+static struct gl_shader_program *
+get_xfb_source(struct gl_context *ctx)
+{
+ int i;
+ for (i = MESA_SHADER_GEOMETRY; i >= MESA_SHADER_VERTEX; i--) {
+ if (ctx->Shader.CurrentProgram[i] != NULL)
+ return ctx->Shader.CurrentProgram[i];
+ }
+ return NULL;
+}
+
+