QDoc: Implement -installdir CLI option for module cross-linking.

QDoc needs to know the final location of the installed documentation to
generate correct relative links between the modules. Normally you can
use QLibraryInfo::DocumentationPath for this, but since QDoc gets compiled
during Qt bootstrapping QLibraryInfo is not available yet.
The -installdir option still allows us to specify
QLibraryInfo::DocumentationPath  on the command line.

Change-Id: Ic4729f4daad112f0d175931467cf09cfcf5145a3
Reviewed-by: Martin Smith <martin.smith@nokia.com>

src/tools/qdoc/config.cpp

@@ -150,6 +150,7 @@ QStringList MetaStack::getExpanded(const Location& location)
 QT_STATIC_CONST_IMPL QString Config::dot = QLatin1String(".");
 bool Config::generateExamples = true;
 QString Config::overrideOutputDir;
+QString Config::installDir;
 QSet<QString> Config::overrideOutputFormats;
 QMap<QString, QString> Config::extractedDirs;
 int Config::numInstances;

src/tools/qdoc/config.h

@@ -111,6 +111,7 @@ public:
     QT_STATIC_CONST QString dot;
 
     static bool generateExamples;
+    static QString installDir;
     static QString overrideOutputDir;
     static QSet<QString> overrideOutputFormats;
 

src/tools/qdoc/main.cpp

@@ -116,10 +116,12 @@ static void printHelp()
                              "Display this information and exit\n"
                              "    -highlighting  "
                              "Turn on syntax highlighting (makes qdoc run slower)\n"
-                             "    -no-examples   "
-                             "Do not generate documentation for examples\n"
                              "    -indexdir      "
                              "Specify a directory where QDoc should search for indices to link to\n"
+                             "    -installdir    "
+                             "Specify the directory where the output will be after running \"make install\"\n"
+                             "    -no-examples   "
+                             "Do not generate documentation for examples\n"
                              "    -obsoletelinks "
                              "Report links from obsolete items to non-obsolete items\n"
                              "    -outputdir     "
@@ -488,6 +490,10 @@ int main(int argc, char **argv)
             }
             i++;
         }
+        else if (opt == "-installdir") {
+            Config::installDir = argv[i];
+            i++;
+        }
         else if (opt == "-obsoletelinks") {
             obsoleteLinks = true;
         }

src/tools/qdoc/tree.cpp

@@ -967,7 +967,18 @@ void Tree::readIndexFile(const QString& path)
         file.close();
 
         QDomElement indexElement = document.documentElement();
-        QString indexUrl = indexElement.attribute("url", "");
+
+        // Generate a relative URL between the install dir and the index file
+        // when the -installdir command line option is set.
+        QString indexUrl;
+        if (Config::installDir.isEmpty()) {
+            indexUrl = indexElement.attribute("url", "");
+        }
+        else {
+            QDir installDir(Config::installDir);
+            indexUrl = installDir.relativeFilePath(path).section('/', 0, -2);
+        }
+
         priv->basesList.clear();
         priv->relatedList.clear();