HaikuBook: add remaining layout class documentation

This is the final contribution to #15368

* Tried to share more documentation in the various BLayoutBuilder classes
* Add missing GridView, GroupView, SpaceLayoutItem
* Also added AbstractLayoutItem, but hide the actual documentation behind
  an `INTERNAL` conditional block. This block identifier can be used to
  document parts of the API, to then hide them during a regular Doxygen run.
* Do some cleanup on other layout classes; add missing members, etc.
* The actual generated BLayoutBuilder::* html is a mess. I should investigate
  this at a later time. Especially the copied members seem to mix type
  definitions with member documentation. It is odd. Not unlikely to be a
  Doxygen bug.
* The general documentation for the layout system could use an overhaul as
  well, but this is for later.

Change-Id: I6db9ef105b4ae6de0f1ebb917f86f8b1c0d4ea2e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2491
Reviewed-by: waddlesplash <[email protected]>

docs/user/interface/GridView.dox

@@ -1,9 +1,9 @@
 /*
- * Copyright 2019 Haiku, Inc. All rights reserved.
+ * Copyright 2020 Haiku, Inc. All rights reserved.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
- *		Name, email@email.com
+ *		Niels Sascha Reedijk, niels.reedijk@gmail.com
  *
  * Corresponds to:
  *		headers/os/interface/GridView.h	hrev43514
@@ -14,7 +14,7 @@
 /*!
 	\file GridView.h
 	\ingroup layout
-	\brief Undocumented file.
+	\brief Provides the BGridView class.
 
 	\since Haiku R1
 */
@@ -24,36 +24,44 @@
 	\class BGridView
 	\ingroup layout
 	\ingroup libbe
-	\brief Undocumented class.
+	\brief Container view for a collection of views organized in a grid.
+
+	This class is a convencience class, that creates a BView with a BGridView
+	set up by default.
+
+	You place views in the grid in a table-like structure, that consists of
+	rows and columns. It is not required to put views in every cell in the
+	table. By default, the view has the default system grey background.
+
+	\see BGridLayout for more information on how and when to use this
+		type of container.
 
 	\since Haiku R1
 */
 
 
 /*!
-	\fn BGridView::BGridView(float horizontal=B_USE_DEFAULT_SPACING, float vertical=B_USE_DEFAULT_SPACING)
-	\brief Undocumented public method
+	\fn BGridView::BGridView(float horizontal, float vertical)
+	\brief Creates a new grid view.
 
-	\param horizontal Undocumented
-	\param vertical Undocumented
 
-	\return Undocumented
-	\retval <value> Undocumented
+	\param horizontal The horizontal padding between the columns that contain
+		views.
+	\param vertical The vertical padding between the rows that contain views.
 
 	\since Haiku R1
 */
 
 
 /*!
-	\fn BGridView::BGridView(const char *name, float horizontal=B_USE_DEFAULT_SPACING, float vertical=B_USE_DEFAULT_SPACING)
-	\brief Undocumented public method
+	\fn BGridView::BGridView(const char *name, float horizontal,
+		float vertical)
+	\brief Creates a new grid view with a \a name.
 
-	\param name Undocumented
-	\param horizontal Undocumented
-	\param vertical Undocumented
-
-	\return Undocumented
-	\retval <value> Undocumented
+	\param name The name for the view.
+	\param horizontal The horizontal padding between the columns that contain
+		views.
+	\param vertical The vertical padding between the rows that contain views.
 
 	\since Haiku R1
 */
@@ -61,33 +69,32 @@
 
 /*!
 	\fn BGridView::BGridView(BMessage *from)
-	\brief Undocumented public method
+	\brief Constructs a BGridView \a from an archive message.
 
-	\param from Undocumented
+	This method is usually not called directly, if you want to build a
+	grid view from an archived message you should call Instantiate() instead
+	because it can handle errors properly.
 
-	\return Undocumented
-	\retval <value> Undocumented
+	\param from The \ref BMessage that contains the grid view.
 
 	\since Haiku R1
 */
 
 
 /*!
-	\fn virtual virtual BGridView::~BGridView()
-	\brief Undocumented public method
-
-	\return Undocumented
-	\retval <value> Undocumented
+	\fn virtual BGridView::~BGridView()
+	\brief Destructor.
 
 	\since Haiku R1
 */
 
 
 /*!
-	\fn virtual virtual void BGridView::SetLayout(BLayout *layout)
-	\brief Undocumented public method
+	\fn virtual void BGridView::SetLayout(BLayout *layout)
+	\brief Adopt a given grid \a layout.
 
-	\param layout Undocumented
+	\param layout The layout to set to. This must be a BGridLayout, or a
+		derivative. Any other layout types will be ignored.
 
 	\since Haiku R1
 */
@@ -95,37 +102,27 @@
 
 /*!
 	\fn BGridLayout* BGridView::GridLayout() const
-	\brief Undocumented public method
+	\brief Get a pointer to the underlying BGridLayout.
 
-	\return Undocumented
-	\retval <value> Undocumented
+	\return A pointer to the underlying grid layout.
 
 	\since Haiku R1
 */
 
 
 /*!
-	\fn virtual virtual status_t BGridView::Perform(perform_code d, void *arg)
-	\brief Undocumented public method
+	\fn virtual status_t BGridView::Perform(perform_code d, void *arg)
+	\brief Perform some action. (Internal Method)
 
-	\param d Undocumented
-	\param arg Undocumented
-
-	\return Undocumented
-	\retval <value> Undocumented
+	Reimplemented from BView::Perform()
 
 	\since Haiku R1
 */
 
 
 /*!
-	\fn static static BArchivable* BGridView::Instantiate(BMessage *from)
-	\brief Undocumented public method
-
-	\param from Undocumented
-
-	\return Undocumented
-	\retval <value> Undocumented
+	\fn static BArchivable* BGridView::Instantiate(BMessage *from)
+	\brief Instantiate the view from the message \a from.
 
 	\since Haiku R1
 */