shiboken6: Brush up the code injection documentation

Link from the code injection page to the type system variables.
Link from conversion rule to templates.
Modernize the code a bit.

Change-Id: Ibc8e56a2e3313a0be50dc8bbc92f49a7afc775a2
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
(cherry picked from commit 4972d8cf6ea55884e501c452f32f558ad24240ae)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 22 insertions, 13 deletions

diff --git a/sources/shiboken6/doc/typesystem_codeinjection.rst b/sources/shiboken6/doc/typesystem_codeinjection.rst
index b0d5f3851..836609508 100644
--- a/sources/shiboken6/doc/typesystem_codeinjection.rst
+++ b/sources/shiboken6/doc/typesystem_codeinjection.rst
@@ -112,7 +112,8 @@ Below is the example C++ class for whom wrapper code will be generated.
 
     .. code-block:: c++
 
-        class InjectCode {
+        class InjectCode
+        {
         public:
             InjectCode();
             double overloadedMethod(int arg);
@@ -124,6 +125,10 @@ From the C++ class, |project| will generate a ``injectcode_wrapper.cpp`` file
 with the binding code. The next section will use a simplified version of the
 generated wrapper code with the injection spots marked with comments.
 
+There are a number of placeholders indicated by a percent sign ``%``, which
+will be expanded when inserting the code. For a list, see
+:ref:`typesystemvariables`.
+
 Noteworthy Cases
 ----------------
 
@@ -196,7 +201,7 @@ class is polymorphic.
 
         int InjectCodeWrapper::virtualMethod(int arg)
         {
-            PyObject* method = BindingManager::instance().getOverride(this, "virtualMethod");
+            PyObject *method = BindingManager::instance().getOverride(this, "virtualMethod");
             if (!py_override)
                 return this->InjectCode::virtualMethod(arg);
 
@@ -228,10 +233,9 @@ own ``beginning`` and ``end`` code injections.
 
     .. code-block:: c++
 
-            static PyObject*
-            PyInjectCode_overloadedMethod(PyObject* self, PyObject* arg)
+            static PyObject *PyInjectCode_overloadedMethod(PyObject *self, PyObject *arg)
             {
-                PyObject* py_result = 0;
+                PyObject* py_result{};
                 if (PyFloat_Check(arg)) {
                     double cpp_arg0 = Shiboken::Converter<double >::toCpp(arg);
 
@@ -250,13 +254,13 @@ own ``beginning`` and ``end`` code injections.
                 } else goto PyInjectCode_overloadedMethod_TypeError;
 
                 if (PyErr_Occurred() || !py_result)
-                    return 0;
+                    return {};
 
                 return py_result;
 
                 PyInjectCode_overloadedMethod_TypeError:
                     PyErr_SetString(PyExc_TypeError, "'overloadedMethod()' called with wrong parameters.");
-                    return 0;
+                    return {};
             }
 
 
@@ -371,7 +375,7 @@ to prevent bad custom code to pass unnoticed.
             // INJECT-CODE: <typesystem><inject-code class="target" position="beginning">
             // Uses: do something before the module is created.
 
-            PyObject* module = Py_InitModule("MODULENAME", MODULENAME_methods);
+            PyObject *module = Py_InitModule("MODULENAME", MODULENAME_methods);
 
             (... initialization of wrapped classes, namespaces, functions and enums ...)
 
diff --git a/sources/shiboken6/doc/typesystem_conversionrule.rst b/sources/shiboken6/doc/typesystem_conversionrule.rst
index 27e7a72de..430c4e4b3 100644
--- a/sources/shiboken6/doc/typesystem_conversionrule.rst
+++ b/sources/shiboken6/doc/typesystem_conversionrule.rst
@@ -32,6 +32,9 @@ conversion-rule
             </conversion-rule>
         </value-type>
 
+    The code can be inserted directly or via ``insert-template`` (see
+    :ref:`using-code-templates`).
+
     The example above show the structure of a complete conversion rule. Each of the
     child tags comprising the conversion rule are described in their own sections
     below.
diff --git a/sources/shiboken6/doc/typesystem_variables.rst b/sources/shiboken6/doc/typesystem_variables.rst
index 73d4dd12c..3d4638253 100644
--- a/sources/shiboken6/doc/typesystem_variables.rst
+++ b/sources/shiboken6/doc/typesystem_variables.rst
@@ -1,3 +1,5 @@
+.. _typesystemvariables:
+
 *********************
 Type System Variables
 *********************
@@ -24,9 +26,9 @@ Variables
 
 .. _arg_number:
 
-**%#**
+**%<number>**
 
-  Replaced by the name of a C++ argument in the position indicated by ``#``.
+  Replaced by the name of a C++ argument in the position indicated by ``<number>``.
   The argument counting starts with ``%1``, since ``%0`` represents the return
   variable name. If the number indicates a variable that was removed in the
   type system description, but there is a default value for it, this value will
@@ -214,13 +216,13 @@ Variables
 
 .. _pyarg:
 
-**%PYARG_#**
+**%PYARG_<number>**
 
-  Similar to ``%#``, but is replaced by the Python arguments (PyObjects)
+  Similar to ``%<number>``, but is replaced by the Python arguments (PyObjects)
   received by the Python wrapper method.
 
   If used in the context of a native code injection, i.e. in a virtual method
-  override, ``%PYARG_#`` will be translated to one item of the Python tuple
+  override, ``%PYARG_<number>`` will be translated to one item of the Python tuple
   holding the arguments that should be passed to the Python override for this
   virtual method.