two-pass doc

[Nicolas Sceaux]

Hi,

Here is a documentation for the two-pass spacing technique.
Would an English speaking person review it before I commit it?

nicolas

Index: page.itely
===================================================================
RCS file: /cvsroot/lilypond/lilypond/Documentation/user/page.itely,v
retrieving revision 1.11
diff -u -r1.11 page.itely
--- page.itely  22 Sep 2006 08:12:22 -0000      1.11
+++ page.itely  1 Oct 2006 13:05:51 -0000
@@ -460,6 +460,7 @@
 * Vertical spacing of piano staves::  
 * Vertical spacing between systems::  
 * Controlling spacing of individual systems::  
+* Two-pass vertical spacing::
 @end menu
 
 
@@ -610,6 +611,56 @@
 negative.
 
 
address@hidden Two-pass vertical spacing
address@hidden Two-pass vertical spacing
+
+In order to automatically stretch systems so that they should fill the
+space left on a page, a two-pass technique can be used:
+
address@hidden
address@hidden in the first pass, the amount of vertical space used to increase 
each 
+system height in computed, and dumped to a file;
address@hidden in the second run, this page layout file is read to actually 
+stretch the systems when they are drawn.
address@hidden enumerate
+
+To allow this behaviour, a @code{tweak-key} variable has to be set in
+each score @code{\layout} block, and the tweaks included in each score
+music, using the @code{\scoreTweak} music function.
+
address@hidden
address@hidden
+%% include the generated page layout file:
+\includePageLayoutFile
+
+\score {
+  \new StaffGroup <<
+    \new Staff <<
+      %% Include this score tweaks:
+      \scoreTweak "scoreA"
+      { \clef french c''1 \break c''1 } 
+    >>
+    \new Staff { \clef soprano g'1 g'1 }
+    \new Staff { \clef mezzosoprano e'1 e'1 }
+    \new Staff { \clef alto g1 g1 }
+    \new Staff { \clef bass c1 c1 }
+  >>
+  \header {
+    piece = "Score with tweaks"
+  }
+  %% Define how to name the tweaks for this score:
+  \layout { #(define tweak-key "scoreA") }
+}
address@hidden verbatim
address@hidden quotation
+
+For the first pass, the @code{dump-tweaks} option should be set to
+generate the page layout file.
+
address@hidden
+lilypond -b null -d dump-tweaks <file>.ly
+lilypond <file>.ly
address@hidden example
 
 @node Horizontal spacing
 @section Horizontal Spacing