Doc: Restore links to the Plug & Paint example sources

The three examples, 'Plug & Paint' and its plugins, have been moved to
manual tests. This example is tightly integrated to the deployment
documentation for Windows, macOS, and Linux platforms, where it serves
as a tutorial for deploying a Qt application that has plugins of its
own.

While the deployment tools for each platform automates much of the
process, it makes sense to maintain documentation for users who need
to create deployment packages manually.

Add \externalpage links to a source repository for the examples,
remove excess linking to them. In passing, fix a few issues in
deployment and plugin-related docs.

These changes fix around 30 documentation warnings for broken
links to the Plug & Paint example docs.

Fixes: QTBUG-115988
Pick-to: 6.6 6.5
Change-Id: Ifd29ae2a9f16796a520ca7ab4eb6702ccb295326
Reviewed-by: Andreas Eliasson <andreas.eliasson@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 8 insertions, 10 deletions

diff --git a/doc/src/howtos/plugins-howto.qdoc b/doc/src/howtos/plugins-howto.qdoc
index 94d92cd09..f11237090 100644
--- a/doc/src/howtos/plugins-howto.qdoc
+++ b/doc/src/howtos/plugins-howto.qdoc
@@ -216,7 +216,6 @@
     \li Use the Q_INTERFACES() macro to tell Qt's \l{meta-object
        system} about the interfaces.
     \li Export the plugin using the Q_PLUGIN_METADATA() macro.
-    \li Build the plugin using a suitable \c .pro file.
     \endlist
 
     For example, here's the definition of an interface class:
@@ -228,14 +227,13 @@
 
     \snippet plugins/extrafiltersplugin.h 0
 
-    The \l{tools/plugandpaint/app}{Plug & Paint} example documentation
-    explains this process in detail. See also \l{Creating Custom
-    Widgets for Qt Designer} for information about issues that are
-    specific to Qt Designer. You can also take a look at the
-    \l{Echo Plugin Example} which is a more trivial example on
-    how to implement a plugin that extends Qt applications.
-    Please note that a QCoreApplication must have been initialized
-    before plugins can be loaded.
+    You can take a look at the \l{Echo Plugin Example} which is a trivial
+    example on how to implement a plugin that extends Qt applications.
+    Note that a QCoreApplication instance must be initialized before
+    plugins can be loaded.
+
+    See also \l{Creating Custom Widgets for Qt Designer} for information
+    about issues that are specific to Qt Designer.
 
     \section1 Locating Plugins
 
@@ -372,5 +370,5 @@
     The \l{Deploying Plugins} document covers the process of deploying
     plugins with applications and debugging them when problems arise.
 
-    \sa QPluginLoader, QLibrary, {Plug & Paint Example}
+    \sa QPluginLoader, QLibrary
 */