additions to the manual

1 files changed, 18 insertions, 1 deletions

diff --git a/manual.en.html b/manual.en.html
index e54dda0..59bd42b 100755
--- a/manual.en.html
+++ b/manual.en.html
@@ -96,7 +96,8 @@ this.</p></li>
 GNU Make that may not be supported by other clones and forks of Make. If a
 system's native Make doesn't have those features and GNU Make isn't available,
 then it's possible to bypass Make and run first Gnatprep and then Gnatmake or
-GPRbuild manually. It's less convenient to build that way though, and some of
+GPRbuild manually. It's less convenient to build that way though, files that the
+GNAT tools don't handle must then be installed in some other way, and some of
 the features listed here are lost.</p></li>
 </ul>
 
@@ -522,6 +523,22 @@ root of the source tree. Here's an example:</p>
 
 <h3 id="rules">Writing Make Rules</h3>
 
+<h4 id="building_projects">Building GNAT Projects</h4>
+
+<p>The projects that are listed in <var>build_GPRs</var> will be built by
+default. Any other project needs a rule to control when it is built. Such a
+rule shall use the variable <var>build_GPR</var> in its recipe.
+<var>build_GPR</var> contains a command that performs a build controlled by the
+first project file among the rule's prerequisites. The command is affected by
+<a href="#build_tools">program-name and options variables</a>, along with
+<var>builder_arguments</var> and <a href="#options"><var>options</var></a>.
+A library that comes with some demo programs might have a rule like this to
+build the demos only on explicit request (also ensuring that the library has
+been built first):</p>
+
+<pre class="example make">demo_programs: demos.gpr build
+	${build_GPR}</pre>
+
 <h4 id="making_directories">Making Directories</h4>
 
 <p>There is no need to write rules to make directories. Comfignat has a pattern