Nup: When Nup is in use, force PageUsesTransparency on.

This prevents us suddenly having to flush the nest when
PageUsesTransparency changes. This would otherwuse result
in unexpected changes in the way pages are laid out.

This obviously affects whether we use clist or not in some
cases, but does not (currently at least), I believe, cause
extra work with transparency blending.

1 files changed, 9 insertions, 1 deletions

diff --git a/doc/Use.htm b/doc/Use.htm
index 6bad21026..869575b91 100644
--- a/doc/Use.htm
+++ b/doc/Use.htm
@@ -2776,7 +2776,7 @@ The only option strings are as follows:
     to the leftmost place on the next row until the nest is complete.
     <p>
     A partially filled nest will be output when the <code>-sNupControl=</code> string is changed,
-    or when Ghostscript exits.
+    when Ghostscript exits, or when the page size changes.
     <p>
     Pages are scaled to fit the requested number horizontally and vertically, maintaining the
     aspect ratio. If the scaling selected for fitting the nested pages leaves space horizontally
@@ -2790,6 +2790,14 @@ The only option strings are as follows:
     the partially filled master page will be output.
     </li>
     </ul>
+<p>Printer devices typically reallocate their memory whenever the transparency use
+of a page changes (from one page having transparency, to the next page not having
+transparency, or vice versa). This would cause problems with Nup, possibly leading
+to lost or corrupt pages in the output. To avoid this, the Nup device changes
+the parameters of the page to always set the PageUsesTransparency flag. While this
+should be entirely transparent for the user and not cause extra transparency blending
+operations during the standard rendering processes for most devices, it may cause
+devices to use the clist rather than PageMode.
 </dd>
 </dl>