update bbcode in RichTextLabel page for Godot 3.2 (#2846)

* update bbcode in RichTextLabel page for Godot 3.2

* Reorder content, improve language and fix invalid code

Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

tutorials/gui/bbcode_in_richtextlabel.rst

@@ -6,19 +6,43 @@ BBCode in RichTextLabel
 Introduction
 ------------
 
-:ref:`class_RichTextLabel` allows the display of complex text markup in a control.
+Label nodes are great for displaying basic text but they have limits. If you want
+to change the color of the text, or its alignment, that change affects all of the
+text in the Label node. You can't have only one part of the text be one color, or
+only one part of the text be centered. To get around this limitation you would use
+a :ref:`class_RichTextLabel`.
+
+:ref:`class_RichTextLabel` allows the display of complex text markup in a Control.
 It has a built-in API for generating the markup, but can also parse a BBCode.
 
 Note that the BBCode tags can also be used, to some extent, in the
 :ref:`XML source of the class reference <doc_updating_the_class_reference>`.
 
-Setting up
-----------
+Using BBCode
+------------
 
-For a ``RichTextLabel`` to work properly, it must be set up. That means loading
-the intended fonts in the relevant properties:
+For uniformly formatted text you can write in the "Text" property, but if you want
+to use BBCode markup you should use the "Text" property in the "Bb Code" section
+instead (``bbcode_text``). Writing to this property will trigger the parsing of your
+markup to format the text as requested. Before this happens, you need to toggle the
+"Enabled" checkbox in the "Bb Code" section (``bbcode_enabled``).
 
-.. image:: img/rtl_setup.png
+.. image:: img/bbcodeText.png
+
+For example, ``BBCode [color=blue]blue[/color]`` would render the word "blue" with
+a blue color.
+
+.. iamge:: img/bbcodeDemo.png
+
+You'll notice that after writing in the BBCode "Text" property the regular "Text"
+property now has the text without the BBCode. While the text property will be updated
+by the BBCode property, you can't edit the text property or you'll lose the BBCode
+markup. All changes to the text must be done in the BBCode parameter.
+
+.. node::
+
+    For BBCode tags such as ``[b]`` (bold) or ``[i]`` (italics) to work you must
+    set up custom fonts for the RichTextLabel node first.
 
 Reference
 ---------
@@ -83,3 +107,193 @@ For opaque RGB colors, any valid 6-digit hexadecimal code is supported, e.g. ``[
 
 For transparent RGB colors, any 8-digit hexadecimal code can be used, e.g. ``[color=#88ffffff]translucent white[/color]``.
 In this case, note that the alpha channel is the **first** component of the color code, not the last one.
+
+Animation effects
+-----------------
+
+BBCode can also be used to create different text animation effects. Five customizable
+effects are provided out of the box, and you can easily create your own.
+
+Wave
+++++
+
+.. image:: img/wave.png
+
+Wave makes the text go up and down. Its tag format is ``[wave amp=50 freq=2][/wave]``.
+``amp`` controls how high and low the effect goes, and ``freq`` controls how fast the
+text goes up and down.
+
+Tornado
++++++++
+
+.. image:: img/tornado.png
+
+Tornao makes the text move around in a circle. Its tag format is
+``[tornado radius=5 freq=2][/tornado]``.
+``radius`` is the radius of the circle that controls the offset, ``freq`` is how
+fast the text moves in a circle.
+
+Shake
++++++
+
+.. image:: img/shake.png
+
+Shake makes the text shake. Its tag format is ``[shake rate=5 level=10][/shake]``.
+``rate`` controls how fast the text shakes, ``level`` controls how far the text is
+offset from the origin.
+
+Fade
+++++
+
+.. image:: img/fade.png
+
+Fade creates a fade effect over the text that is not animated. Its tag format is
+``[fade start=4 length=14][/fade]``.
+``start`` controls the starting position of the falloff relative to where the fade
+command is inserted, ``length`` controls over how many characters should the fade
+out take place.
+
+Rainbow
++++++++
+
+.. image:: img/rainbow.png
+
+Rainbow gives the text a rainbow color that changes over time. Its tag format is
+``[rainbow freq=0.2 sat=10 val=20][/rainbow].
+``freq`` is the number of full rainbow cycles per second, ``sat`` is the saturation
+of the rainbow, ``val`` is the value of the rainbow.
+
+Custom BBCode tags and text effects
+-----------------------------------
+
+You can extend the :ref:`class_RichTextEffect` resource type to create your own custom
+BBCode tags. You begin by extending the :ref:`class_RichTextEffect` resource type. Add
+the ``tool`` prefix to your GDScript file if you wish to have these custom effects run
+within the editor itself. The RichTextLabel does not need to have a script attached,
+nor does it need to be running in ``tool`` mode.
+
+There is only one function that you need to extend: ``_process_custom_fx(char_fx)``.
+Optionally, you can also provide a custom BBCode identifier simply by adding a member
+name ``bbcode``. The code will check the ``bbcode`` property automatically or will
+use the name of the file to determine what the BBCode tag should be.
+
+_process_custom_fx
+++++++++++++++++++
+
+This is where the logic of each effect takes place and is called once per character
+during the draw phase of text rendering. This passes in a :ref:`class_CharFXTransform`
+object, which holds a few variables to control how the associated character is rendered:
+
+- ``identity`` specifies which custom effect is being processed. You should use that for
+  code flow control.
+- ``relative_index`` tells you how far into a given custom effect block you are in as an
+  index.
+- ``absolute_index`` tells you how far into the entire text you are as an index.
+- ``elapsed_time`` is the total amount of time the text effect has been running.
+- ``visible`` will tell you whether the character is visible or not and will also allow you
+  to hide a given portion of text.
+- ``offset`` is an offset position relative to where the given character should render under
+  normal circumstances.
+- ``color`` is the color of a given character.
+- Finally, ``env`` is a :ref:`class_Dictionary` of parameters assigned to a given custom
+  effect. You can use `:ref:`class_Dictionary_method_get` with an optional default value
+  to retrieve each parameter, if specified by the user. For example ``[custom_fx spread=0.5
+  color=#FFFF00]test[/custom_fx]`` would have a float ``spread`` and Color ``color``
+  parameters in its ` `env`` Dictionary. See below for more usage examples.
+
+The last thing to note about this function is that it is necessary to return a boolean
+``true`` value to verify that the effect processed correctly. This way, if there's a problem
+with rendering a given character, it will back out of rendering custom effects entirely until
+the user fixes whatever error cropped up in their custom effect logic.
+
+Here are some examples of custom effects:
+
+Ghost
++++++
+
+::
+
+    tool
+    extends RichTextEffect
+
+    # Syntax: [ghost freq=5.0 span=10.0][/ghost]
+
+    # Define the tag name.
+    var bbcode = "ghost"
+
+    func _process_custom_fx(char_fx):
+        # Get parameters, or use the provided default value if missing.
+        var speed = char_fx.env.get("freq", 5.0)
+        var span = char_fx.env.get("span", 10.0)
+
+        var alpha = sin(char_fx.elapsed_time * speed + (char_fx.absolute_index / span)) * 0.5 + 0.5
+        char_fx.color.a = alpha
+        return true
+
+Pulse
++++++
+
+::
+
+    tool
+    extends RichTextEffect
+
+    # Syntax: [pulse color=#00FFAA height=0.0 freq=2.0][/pulse]
+
+    # Define the tag name.
+    var bbcode = "pulse"
+
+    func _process_custom_fx(char_fx):
+        # Get parameters, or use the provided default value if missing.
+        var color = char_fx.env.get("color", char_fx.color)
+        var height = char_fx.env.get("height", 0.0)
+        var freq = char_fx.env.get("freq", 2.0)
+
+        var sined_time = (sin(char_fx.elapsed_time * freq) + 1.0) / 2.0
+        var y_off = sined_time * height
+        color.a = 1.0
+        char_fx.color = char_fx.color.linear_interpolate(color, sined_time)
+        char_fx.offset = Vector2(0, -1) * y_off
+        return true
+
+Matrix
+++++++
+
+::
+
+    tool
+    extends RichTextEffect
+
+    # Syntax: [matrix clean=2.0 dirty=1.0 span=50][/matrix]
+
+    # Define the tag name.
+    var bbcode = "matrix"
+
+    func _process_custom_fx(char_fx):
+        # Get parameters, or use the provided default value if missing.
+        var clear_time = char_fx.env.get("clean", 2.0)
+        var dirty_time = char_fx.env.get("dirty", 1.0)
+        var text_span = char_fx.env.get("span", 50)
+		
+        var value = char_fx.character
+		
+        var matrix_time = fmod(char_fx.elapsed_time + (char_fx.absolute_index / float(text_span)), \
+                               clear_time + dirty_time)
+		
+        matrix_time = 0.0 if matrix_time < clear_time else \
+                      (matrix_time - clear_time) / dirty_time
+
+        if value >= 65 && value < 126 && matrix_time > 0.0:
+            value -= 65
+            value = value + int(1 * matrix_time * (126 - 65))
+            value %= (126 - 65)
+            value += 65
+        char_fx.character = value
+        return true
+
+This will add a few new BBCode commands, which can be used like so:
+
+::
+
+    [center][ghost]This is a custom [matrix]effect[/matrix][/ghost] made in
+    [pulse freq=5.0 height=2.0][pulse color=#00FFAA freq=2.0]GDScript[/pulse][/pulse].[/center]