Improvements to Modules docs

Task-number: QTBUG-12430

4 files changed, 228 insertions, 93 deletions

diff --git a/doc/src/declarative/extending-tutorial.qdoc b/doc/src/declarative/extending-tutorial.qdoc
index bc849b0..d128d0f 100644
--- a/doc/src/declarative/extending-tutorial.qdoc
+++ b/doc/src/declarative/extending-tutorial.qdoc
@@ -421,7 +421,7 @@ To create a plugin library, we need:
 \list
 \o A plugin class that registers our QML types
 \o A project file that describes the plugin 
-\o A "qmldir" file that tells the QML engine to load the plugin
+\o A \l{Writing a qmldir file}{qmldir} file that tells the QML engine to load the plugin
 \endlist
 
 First, we create a plugin class named \c ChartsPlugin. It subclasses QDeclarativeExtensionPlugin
@@ -441,8 +441,8 @@ and specifies with DESTDIR that library files should be built into a "lib" subdi
 
 \quotefile declarative/tutorials/extending/chapter6-plugins/chapter6-plugins.pro
 
-Finally, we add a \c qmldir file that is automatically parsed by the QML engine.
-Here, we specify that a plugin named "chapter6-plugin" (the name
+Finally, we add a \l{Writing a qmldir file}{qmldir} file that is automatically parsed by the QML engine.
+In this file, we specify that a plugin named "chapter6-plugin" (the name
 of the example project) can be found in the "lib" subdirectory:
 
 \quotefile declarative/tutorials/extending/chapter6-plugins/qmldir
diff --git a/doc/src/declarative/modules.qdoc b/doc/src/declarative/modules.qdoc
index 938222a..9e51a40 100644
--- a/doc/src/declarative/modules.qdoc
+++ b/doc/src/declarative/modules.qdoc
@@ -30,152 +30,277 @@
 \title Modules
 \section1 QML Modules
 
-A \bold {QML module} is a collection of QML types. They allow you to organize your QML content
-into independent units. Modules have an optional versioning mechanism that allows for independent
+
+A module is a set of QML content files that can be imported as a unit into a QML 
+application. Modules can be used to organize QML content into independent units,
+and they can use a versioning mechanism that allows for independent 
 upgradability of the modules.
 
-There are two types of modules:
-location modules (defined by a URL),
-and
-installed modules (defined by a URI).
+While QML component files within the same directory are automatically accessible
+within the global namespace, components defined elsewhere must be imported 
+explicitly using the \c import statement to import them as modules. For 
+example, an \c import statement is required to use:
+
+\list
+\o A component defined in another QML file that is not in the same directory
+\o A component defined in a QML file located on a remote server
+\o A \l{QDeclarativeExtensionPlugin}{QML C++ plugin} library (unless the plugin is installed in the same directory)
+\o A JavaScript file (note this must be imported using \l {#namespaces}{named imports})
+\endlist
+
+An \c import statement includes the module name, and possibly a version number.
+This can be seen in the snippet commonly found at the top of QML files:
+
+\qml
+    import Qt 4.7
+\endqml
+    
+This imports version 4.7 of the "Qt" module into the global namespace. (The QML 
+library itself must be imported to use any of the \l {QML Elements}, as they
+are not included in the global namespace by default.)
+
+The \c Qt module is an \e installed module; it is found in the 
+\l{The QML import path}{import path}. There are two types of QML modules: 
+location modules (defined by a URL) and installed modules (defined by a URI).
+
+
+\section1 Location Modules
+
+Location modules can reside on the local filesystem or a network resource,
+and are referred to by a quoted location URL that specifies the filesystem
+or network URL. They allow any directory with QML content to be imported
+as a module, whether the directory is on the local filesystem or a remote
+server.
+
+For example, a QML project may have a separate directory for a set of
+custom UI components. These components can be accessed by importing the
+directory using a relative or absolute path, like this:
+
+\table
+\row
+\o Directory structure
+\o Contents of application.qml
+
+\row
+\o
+\code
+MyQMLProject
+    |- MyComponents
+        |- Slider.qml
+        |- CheckBox.qml       
+    |- Main    
+        |- application.qml
+\endcode
+
+\o
+\code
+import "../MyComponents"
+
+Slider { ... }
+CheckBox { ... }
+\endcode
+
+\endtable
 
-Location modules types are defined in QML files and \l{QDeclarativeExtensionPlugin}{QML C++ plugins}
-in a directory refered to directly by
-the location URL, either on the local filesystem, or as a network resource. The URL that locates them
-can be relative, in which case they actual URL is resolved by the QML file containing the import.
-When importing a location module, a quoted URL is used:
+Similarly, if the directory resided on a network source, it could
+be imported like this:
 
 \code
-import "https://qml.nokia.com/qml/example" 1.0
-import "https://qml.nokia.com/qml/example" as NokiaExample
-import "mymodule" 1.0
-import "mymodule"
+    import "https://qml.nokia.com/qml/qmlcomponents"
+    import "https://qml.nokia.com/qml/qmlcomponents" 1.0
 \endcode
 
-Installed modules can \e only be on the local file system or in application C++ code. Again they
-are defined in QML files and \l{QDeclarativeExtensionPlugin}{QML C++ plugins} in a directory,
-but the directory is indirectly referred to by the URI. The mapping to actual content is either
-by application C++ code registering a C++ type to a module URI (see \l{Extending QML in C++}),
-or in the referenced subdirectory of a path on the import path (see below).
-When importing a location module, an un-quoted URI is used:
+Remote location modules must have a \l{Writing a qmldir file}{qmldir file} in the
+same directory to specify which QML files should be made available. See the
+\l {#qmldirexample}{example} below. The qmldir file is optional for modules on 
+the local filesystem.
+
+
+
+\section1 Installed modules
+
+
+Installed modules are modules that are installed on the
+local filesystem within the QML import path, or modules defined in C++ 
+application code. When importing an installed module, an un-quoted URI is 
+used, with a mandatory version number:
 
 \code
-import com.nokia.qml.mymodule 1.0
-import com.nokia.qml.mymodule as MyModule
+    import Qt 4.7
+    import com.nokia.qml.mymodule 1.0
 \endcode
 
+Installed modules that are installed into the import path or created
+as a \l{QDeclarativeExtensionPlugin}{QML C++ plugin} must define a 
+\l{Writing a qmldir file}{qmldir file}.
+
+
+\section2 The QML import path
 
-For either type of module, a \c qmldir file in the module directory defines the content of the module. This file is
-optional for location modules, but only for local filesystem content or a single remote content with a namespace.
-The second exception is explained in more detail in the section below on Namespaces.
+The QML engine will search the import path for a requested installed module.
+The default import path includes:
 
-\section2 The Import Path
+\list
+\o The directory of the current file
+\o The location specified by QLibraryInfo::ImportsPath 
+\o Paths specified by the \c QML_IMPORT_PATH environment variable
+\endlist
 
-Installed modules are searched for on the import path.
-The \c -I option to the \l {QML Viewer} adds paths to the import path.
+The import path can be queried using QDeclarativeEngine::importPathList() and modified using QDeclarativeEngine::addImportPath().
 
-From C++, the path is available via \l QDeclarativeEngine::importPathList() and can be prepended to
-using \l QDeclarativeEngine::addImportPath().
+When running the \l {QML Viewer}, use the \c -I option to add paths to the import path.
 
-\section2 The \c qmldir File
 
-Installed QML modules and remote content without a namespace require a file \c qmldir which
-specifies the mapping from all type names to versioned QML files. It is a list of lines of the form:
+\section2 Creating installed modules in C++
+
+C++ applications can dynamically define installed modules using 
+qmlRegisterType(). 
+
+For \l{QDeclarativeExtensionPlugin}{QML C++ plugins}, the 
+module URI is automatically passed to QDeclarativeExtensionPlugin::registerTypes().
+The QDeclarativeExtensionPlugin documentation shows how to use this URI
+to call qmlRegisterType() to enable the plugin library to be built as
+an installed module. Once the plugin is built and installed, the module is importable
+in QML, like this:
+
+\code
+import com.nokia.TimeExample 1.0
+\endcode
+
+A \l{QDeclarativeExtensionPlugin}{QML C++ plugin} also requires a 
+\l{Writing a qmldir file}{qmldir file} to make it available to the
+QML engine.
+
+
+
+\target namespaces
+\section1 Namespaces: Using Named Imports
+
+By default, when a module is imported, its contents are imported into the global namespace. You may choose to import the module into another namespace, either to allow identically-named types to be referenced, or purely for readability.
+
+To import a module into a specific namespace, use the \e as keyword:
+
+\qml
+    import Qt 4.7 as QtLibrary
+    import "../MyComponents" as MyComponents
+    import com.nokia.qml.mymodule 1.0 as MyModule
+\endqml
+
+Types from these modules can then only be used when qualified by the namespace:
+
+\qml
+    QtLibrary.Rectangle { ... }
+    
+    MyComponents.Slider { ... }
+    
+    MyModule.SomeComponent { ... }
+\endqml
+
+Multiple modules can be imported into the same namespace in the same way that multiple modules can be imported into the global namespace:
+
+\qml
+    import Qt 4.7 as Nokia
+    import Ovi 1.0 as Nokia
+\endqml
+
+\section2 JavaScript files
+
+JavaScript files must always be imported with a named import:
+
+\qml
+    import "somescript.js" as MyScript
+    
+    Item {
+        //...
+        Component.onCompleted: MyScript.doSomething()
+    }
+\endqml
+
+
+
+\section1 Writing a qmldir file
+
+A \c qmldir file is a metadata file for a module that maps all type names in 
+the module to versioned QML files. It is required for installed modules, and 
+location modules that are loaded from a network source.
+
+It is defined by a plain text file named "qmldir" that contains one or more lines of the form:
 
 \code
 # <Comment>
 <TypeName> [<InitialVersion>] <File>
-internal <Name> <File>
+internal <TypeName> <File>
 plugin <Name> [<Path>]
 \endcode
 
-# <Comment> lines are ignored, and can be used for comments.
+\bold {# <Commment>} lines are used for comments. They are ignored by the QML engine.
 
-<TypeName> <InitialVersion> <File> lines are used to add QML files as types.
-<TypeName> is the type being made available; the optional <InitialVersion> is a version
-number like \c 4.0; <File> is the (relative)
-file name of the QML file defining the type. 
+\bold {<TypeName> [<InitialVersion>] <File>} lines are used to add QML files as types.
+<TypeName> is the type being made available, the optional <InitialVersion> is a version
+number, and <File> is the (relative) file name of the QML file defining the type. 
 
 Installed files do not need to import the module of which they are a part, as they can refer
 to the other QML files in the module as relative (local) files, but
 if the module is imported from a remote location, those files must nevertheless be listed in
 the \c qmldir file. Types which you do not wish to export to users of your module
-may be marked with the \c internal keyword: \c internal <TypeName> <File>.
+may be marked with the \c internal keyword: \bold {internal <TypeName> <File>}.
 
 The same type can be provided by different files in different versions, in which
 case later versions (eg. 1.2) must precede earlier versions (eg. 1.0),
 since the \e first name-version match is used and a request for a version of a type
 can be fulfilled by one defined in an earlier version of the module. If a user attempts
 to import a version earlier than the earliest provided or later than the latest provided,
-an error results, but if the user imports a version within the range of versions provided,
-even if no type is specific to that version, no error results.
+the import produces a runtime error, but if the user imports a version within the range of versions provided,
+even if no type is specific to that version, no error will occur.
 
 A single module, in all versions, may only be provided in a single directory (and a single \c qmldir file).
 If multiple are provided, only the first in the search path will be used (regardless of whether other versions
 are provided by directories later in the search path).
 
-Installed and remote files without a namespace \e must be referred to by version information described above,
-local files \e may have it.
-
 The versioning system ensures that a given QML file will work regardless of the version
 of installed software, since a versioned import \e only imports types for that version,
 leaving other identifiers available, even if the actual installed version might otherwise
 provide those identifiers.
 
-\c plugin <Name> [<Path>] lines are used to add \l{QDeclarativeExtensionPlugin}{QML C++ plugins}
-to the module. 
-
-<Name> is the name of the library.  It is usually not the same as the file name
-of the plugin binary, which is platform dependent; e.g. the library MyAppTypes would produce
-a libMyAppTypes.so on Linux and MyAppTypes.dll on Windows. 
-By default the engine searches for the plugin library in the directory containing the \c qmldir
-file.  The \c -P option to the \l {QML Viewer} adds paths to the 
-plugin search path. 
-From C++, the path is available via \l QDeclarativeEngine::pluginPathList() and can be prepended to
-using \l QDeclarativeEngine::addPluginPath().
+\bold {plugin <Name> [<Path>]} lines are used to add \l{QDeclarativeExtensionPlugin}{QML C++ plugins} to the module. <Name> is the name of the library.  It is usually not the same as the file name
+of the plugin binary, which is platform dependent; e.g. the library \c MyAppTypes would produce
+\c libMyAppTypes.so on Linux and \c MyAppTypes.dll on Windows. 
 
 <Path> is an optional argument specifying either an absolute path to the directory containing the
 plugin file, or a relative path from the directory containing the \c qmldir file to the directory 
-containing the plugin file.
-
+containing the plugin file. By default the engine searches for the plugin library in the directory that contains the \c qmldir
+file. The plugin search path can be queried with QDeclarativeEngine::pluginPathList() and modified using QDeclarativeEngine::addPluginPath(). When running the \l {QML Viewer}, use the \c -P option to add paths to the plugin search path.
 
-\section2 Namespaces - Named Imports
 
-When importing content it by default imports types into the global namespace.
-You may choose to import the module into another namespace, either to allow identically-named
-types to be referenced, or purely for readability.
+\target qmldirexample
+\section2 Example
 
-To import a module into a namespace:
+If the components in the \c MyComponents directory from the 
+\l{Location Modules}{earlier example} were to be made available as a network resource,
+the directory would need to contain a \c qmldir file similar to this:
 
 \code
-import Qt 4.7 as TheQtLibrary
+ComponentA 1.0 ComponentA.qml
+ComponentB 1.0 ComponentB.qml
 \endcode
 
-Types from the Qt 4.7 module may then be used, but only by qualifying them with the namespace:
+The \c MyComponents directory could then be imported as a module using: 
 
 \code
-TheQtLibrary.Rectangle { ... }
-\endcode
-
-Multiple modules can be imported into the same namespace in the same way that multiple
-modules can be imported into the global namespace:
+import "http://the-server-name.com/MyComponents"
 
-\code
-import Qt 4.7 as Nokia
-import Ovi 1.0 as Nokia
+Slider { ... }
+CheckBox { ... }
 \endcode
 
-While import statements are needed to make any types available in QML, the directory of the
-current file is implicitly loaded. This is the exact same as if you had added 'import "."' to
-the start of every QML file. The effect of this is that you can automatically use types defined in C++ plugins
-or QML files if they reside in the same directory. This is the last location searched for types - so if you
-happen to have a "Text.qml" file, or "text.qml" on case-insensitive file systems, it will not override
-the one from Qt if you import Qt.
-
-*/
+with an optional "1.0" version specification. Notice the import fails if
+a later version is used, as the \c qmldir file specifies that these elements
+are only available in the 1.0 version.
 
-/*
 
-Original requirement is QT-558.
+For examples of \c qmldir files for plugins, see the 
+\l {declarative/cppextensions/plugins}{Plugins} example and 
+\l {Tutorial: Writing QML extensions with C++}.
 
 */
+/
diff --git a/doc/src/declarative/qtdeclarative.qdoc b/doc/src/declarative/qtdeclarative.qdoc
index fb50286..413eb59 100644
--- a/doc/src/declarative/qtdeclarative.qdoc
+++ b/doc/src/declarative/qtdeclarative.qdoc
@@ -70,13 +70,23 @@
 
   Returns the QML type id.
 
-  Example: Register the C++ class \c MinehuntGame as the QML type
-  named \c Game for version 0.1 in the import library \c MinehuntCore:
+  For example, this registers a C++ class \c MySliderItem as a QML type
+  named \c Slider for version 1.0 of a \l{QML Modules}{module} called
+  "com.mycompany.qmlcomponents":
 
   \code
-  qmlRegisterType<MinehuntGame>("MinehuntCore", 0, 1, "Game");
+  qmlRegisterType<MySliderItem>("com.mycompany.qmlcomponents", 1, 0, "Slider");
   \endcode
 
+  Once this is registered, the type can be used in QML by importing the 
+  specified module name and version number:
+
+  \qml
+  imoprt com.mycompany.qmlcomponents 1.0
+
+  Slider { ... }
+  \endqml
+
   Note that it's perfectly reasonable for a library to register types to older versions
   than the actual version of the library. Indeed, it is normal for the new library to allow
   QML written to previous versions to continue to work, even if more advanced versions of
diff --git a/src/declarative/qml/qdeclarativeextensionplugin.cpp b/src/declarative/qml/qdeclarativeextensionplugin.cpp
index 448fde2..9b5eb61 100644
--- a/src/declarative/qml/qdeclarativeextensionplugin.cpp
+++ b/src/declarative/qml/qdeclarativeextensionplugin.cpp
@@ -60,7 +60,7 @@ QT_BEGIN_NAMESPACE
     \o Subclass QDeclarativeExtensionPlugin, implement registerTypes() method
     to register types using qmlRegisterType(), and export the class using the Q_EXPORT_PLUGIN2() macro
     \o Write an appropriate project file for the plugin
-    \o Create a \l{The qmldir file}{qmldir file} to describe the plugin
+    \o Create a \l{Writing a qmldir file}{qmldir file} to describe the plugin
     \endlist
 
     QML extension plugins can be used to provide either application-specific or
@@ -79,7 +79,7 @@ QT_BEGIN_NAMESPACE
     \dots
 
     To make this class available as a QML type, create a plugin that registers
-    this type using qmlRegisterType(). For this example the plugin
+    this type with a specific \l {QML Modules}{module} using qmlRegisterType(). For this example the plugin
     module will be named \c com.nokia.TimeExample (as defined in the project
     file further below).
 
@@ -104,7 +104,7 @@ QT_BEGIN_NAMESPACE
     ...
     \endcode    
 
-    Finally, a \l{The qmldir file}{qmldir file} is required in the \c com/nokia/TimeExample directory
+    Finally, a \l{Writing a qmldir file}{qmldir file} is required in the \c com/nokia/TimeExample directory
     that describes the plugin. This directory includes a \c Clock.qml file that
     should be bundled with the plugin, so it needs to be specified in the \c qmldir
     file: