+
+ /* Convert floating point values in [0,1] to device Z coordinates in
+ * [0, DepthMax].
+ * ex: If the Z buffer has 24 bits, DepthMax = 0xffffff.
+ *
+ * XXX this all falls apart if we have 31 or more bits of Z because
+ * the triangle rasterization code produces unsigned Z values. Negative
+ * vertex Z values come out as large fragment Z uints.
+ */
+ min = (GLint) (min_f * fb->_DepthMaxF);
+ max = (GLint) (max_f * fb->_DepthMaxF);
+ if (max < 0)
+ max = 0x7fffffff; /* catch over flow for 30-bit z */
+
+ /* Note that we do the comparisons here using signed integers.
+ */