1 files changed, 59 insertions, 31 deletions

diff --git a/tex/context/base/page-spr.mkiv b/tex/context/base/page-spr.mkiv
index f4768d4e9..dc1e013d5 100644
--- a/tex/context/base/page-spr.mkiv
+++ b/tex/context/base/page-spr.mkiv
@@ -17,10 +17,9 @@
 
 \unprotect
 
-\newbox\spreadbox
-\newif \ifinspread
-
-\setnewconstant\showspreadmode\plusone
+\newbox        \b_page_spread_content
+\newconditional\c_page_spread_busy
+\newconditional\c_page_spread_once     % when true only one flush (writes etc)
 
 % beware, ugly overload, to be redone
 
@@ -35,52 +34,81 @@
          \noindent             % content can be < \hsize
          \page_otr_command_package_contents#2#3}}%
    \dp#1\zeropoint
-   \setbox#1\hbox to \makeupwidth
-     {\ifinspread
-        \ifvoid\spreadbox
-          \global\setbox\spreadbox\box#1%
-          \copy\spreadbox\hss % left page
+   \ifconditional\c_page_spread_busy
+      \normalsettextpagecontent_spread{#1}%
+   \else
+      \normalsettextpagecontent_normal{#1}%
+   \fi}
+
+\def\normalsettextpagecontent_normal#1%
+  {\setbox#1\hbox to \makeupwidth
+     {\hss\box#1\hss}} % never change the \hss's
+
+\def\normalsettextpagecontent_spread#1%
+  {\setbox#1\hbox to \makeupwidth
+     {\ifvoid\b_page_spread_content
+        \ifconditional\c_page_spread_once
+          \box#1%
         \else
-          % prevent duplicate writes in normal run
-          \ifarrangingpages \else \ifcase\showspreadmode
-            \global\setbox\spreadbox\emptyhbox
-            \wd\spreadbox\makeupwidth
-            \ht\spreadbox\textheight
-          \fi \fi
-          \hss\box\spreadbox % right page
+          \global\setbox\b_page_spread_content\box#1%
+          \copy\b_page_spread_content
         \fi
+        \hss % left page
       \else
-        \hss\box#1\hss % never change the \hss's
+        \hss % right page
+        \ifarrangingpages
+          % writes don't matter anyway
+        \else\ifconditional\c_page_spread_once
+          \global\setbox\b_page_spread_content\emptyhbox
+          \wd\b_page_spread_content\makeupwidth
+          \ht\b_page_spread_content\textheight
+        \else
+          % writes can interfere (todo: write stripper, but how about hyperlinks)
+        \fi \fi
+        \box\b_page_spread_content
       \fi}}
 
-\def\doflushspread
-  {\ifinspread \ifvoid\spreadbox\else
+\unexpanded\def\page_spread_flush
+  {\ifconditional\c_page_spread_busy \ifvoid\b_page_spread_content\else
      % this page will be discarded later
      \emptyhbox \page
    \fi \fi }
 
 \unexpanded\def\startspread
-  {\bgroup
-   \ifdoublesided
-     \page[\v!left]%
-    %\setsystemmode{spread}%
-     \inspreadtrue
-     \expanded{\setuplayout[\c!textwidth=\the\dimexpr2\textwidth+2\backspace\relax]}%
-     \unexpanded\def\startspread{\bgroup\let\stopspread\egroup}%
-     \let\stopspread\dostopspread
+  {\ifdoublesided
+     \ifconditional\c_page_spread_busy
+       \doubleexpandafter\page_spread_start_nop
+     \else
+       \doubleexpandafter\page_spread_start_yes
+     \fi
    \else
-     \let\stopspread\egroup
+     \expandafter\page_spread_start_nop
    \fi}
 
 \let\stopspread\relax
 
-\def\dostopspread
-  {\kern\zeropoint\page
-   \inspreadfalse
+\unexpanded\def\page_spread_start_yes
+  {\bgroup
+   \page[\v!left]%
+  %\setsystemmode{spread}%
+   \settrue\c_page_spread_busy
+   \expanded{\setuplayout[\c!textwidth=\the\dimexpr2\textwidth+2\backspace\relax]}%
+   \let\stopspread\page_spread_stop_yes}
+
+\unexpanded\def\page_spread_stop_yes
+  {\kern\zeropoint
+   \page
    \setuplayout[\c!textwidth=\textwidth]
    \page[\v!left]
    \egroup}
 
+\unexpanded\def\page_spread_start_nop
+  {\bgroup
+   \let\stopspread\page_spread_stop_nop}
+
+\unexpanded\def\page_spread_stop_nop
+  {\egroup}
+
 \protect \endinput
 
 % texexec --arr --pdf test