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Update the "Customizing the HTML5 Shell" page (#4748)

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Co-authored-by: Hugo Locurcio <hugo.locurcio@hugo.pro>
This commit is contained in:
Fabio Alessandrelli
2021-03-12 18:59:17 +01:00
committed by GitHub
parent 36c9302533
commit d47b8617c4
1 changed files with 99 additions and 93 deletions
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192
tutorials/platform/customizing_html5_shell.rst
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@@ -5,7 +5,7 @@ Custom HTML page for Web export
While Web export templates provide a default HTML page fully capable of launching
the project without any further customization, it may be beneficial to create a custom
HTML page. While the game itself cannot be directly controlled from the outside,
HTML page. While the game itself cannot easily be directly controlled from the outside yet,
such page allows to customize the initialization process for the engine.
Some use-cases where customizing the default page is useful include:
@@ -20,32 +20,48 @@ Some use-cases where customizing the default page is useful include:
The default HTML page is available in the Godot Engine repository at
`/misc/dist/html/full-size.html <https://github.com/godotengine/godot/blob/master/misc/dist/html/full-size.html>`__
and can be used as a reference implementation. Another sample HTML page is available at
`/misc/dist/html/fixed-size.html <https://github.com/godotengine/godot/blob/master/misc/dist/html/fixed-size.html>`__.
It differs from the default one by having a fixed size canvas area and an output widget below it.
but the following template can be used as a much simpler example:
.. note:: It is recommended to use developer tools provided by browser vendors to debug
exported projects. Output generated by the engine may be limited and does not
include WebGL errors.
.. code-block:: html
<!DOCTYPE html>
<html>
<head>
<title>My Template</title>
<meta charset="UTF-8">
</head>
<body>
<canvas id="canvas"></canvas>
<script src="$GODOT_URL"></script>
<script>
var engine = new Engine($GODOT_CONFIG);
engine.startGame();
</script>
</body>
</html>
Setup
-----
As evident by the default HTML page, it is mostly a regular HTML document. To work with
Godot projects it needs to be fully realized, to have a control code that calls
the :js:class:`Engine` class, and to provide places for several placeholders, which are
replaced with their actual values during export.
As shown by the example above, it is mostly a regular HTML document, with few placeholders
which needs to be replaced during export, an html ``<canvas>`` element, and some simple
JavaScript code that calls the :js:class:`Engine` class.
.. image:: img/html5_export_options.png
The only required placeholders are:
- ``$GODOT_BASENAME``:
The base name from the *Export Path*, as set up in the export options; suffixes are omitted
(e.g. ``game.html`` becomes ``game``). This variable can be used to generate a path
to the main JavaScript file ``$GODOT_BASENAME.js``, which provides the :js:class:`Engine`
class. A splash image shown during the booting process can be accessed using this variable
as well: ``$GODOT_BASENAME.png``.
- ``$GODOT_URL``:
The name of the main JavaScript file, which provides the :js:class:`Engine` class required
to start the engine and that must be included in the HTML as a ``<script>``.
The name is generated from the *Export Path* during the export process.
- ``$GODOT_CONFIG``:
A JavaScript object, containing the export options and can be later overridden.
See :js:attr:`EngineConfig` for the full list of overrides.
The following optional placeholders will enable some extra features in your cusstom HTML template.
- ``$GODOT_PROJECT_NAME``:
The project name as defined in the Project Settings.
The project name as defined in the Project Settings. It is a good idea to use it as a ``<title>``
in your template.
- ``$GODOT_HEAD_INCLUDE``:
A custom string to include in the HTML document just before the end of the ``<head>`` tag. It
@@ -53,66 +69,74 @@ replaced with their actual values during export.
control the HTML page you create, this variable can be useful for configuring parts of the
HTML ``head`` element from the Godot Editor, e.g. for different Web export presets.
- ``$GODOT_DEBUG_ENABLED``:
A flag that tells if this is a debug build, or not. This variable is substituted by strings
``true`` and ``false``, and can be used to disable debug branches within your control code.
When the custom page is ready, it can be selected in the export options under the *Html / Custom Html Shell*
section.
.. image:: img/html5_export_options.png
Starting the project
--------------------
To be able to start the game, you need to write a script that initializes the engine — the control
code. This process consists of three steps, though some of them can be skipped and left for
a default behavior.
code. This process consists of three steps, but as shown here, most of them can be skipped depending on
how much customization is needed.
See the :ref:`HTML5 shell class reference <doc_html5_shell_classref>`, for the full list of methods and options available.
First, the engine must be loaded, then it needs to be initialized, and after this the project
can finally be started. You can perform every of these steps manually and with great control.
However, in the simplest case all you need to do is to create an instance of the :js:class:`Engine`
class and then call the :js:meth:`engine.startGame` method.
class with the exported configuration, and then call the :js:meth:`engine.startGame <Engine.prototype.startGame>` method
optionally overriding any :js:attr:`EngineConfig` parameters.
.. code-block:: js
const execName = "path://to/executable"
const mainPack = "path://to/main_pack"
const engine = new Engine();
engine.startGame(execName, mainPack)
const engine = new Engine($GODOT_CONFIG);
engine.startGame({
/* optional override configuration, eg. */
// unloadAfterInit: false,
// canvasResizePolicy: 0,
// ...
});
This snippet of code automatically loads and initializes the engine before starting the game.
It uses the given path to the executable to deduce the path to load the engine. The :js:meth:`engine.startGame`
It uses the given configuration to to load the engine. The :js:meth:`engine.startGame <Engine.prototype.startGame>`
method is asynchronous and returns a ``Promise``. This allows your control code to track if
the game was loaded correctly without blocking execution or relying on polling.
In case your project needs to have special arguments passed to it by the start-up script,
:js:meth:`engine.startGame` can be replaced by :js:meth:`engine.start`. This method takes an
arbitrary list of string arguments. As it does not have a defined list of arguments, :js:meth:`engine.start`
cannot automatically load the engine.
In case your project needs to have special control over the start arguments and dependency files,
the :js:meth:`engine.start <Engine.prototype.start>` method can be used instead. Note, that this method do not
automatically preload the ``pck`` file, so you will probably want to manually preload it
(and any other extra file) via the :js:meth:`engine.preloadFile <Engine.prototype.preloadFile>` method.
To load the engine manually the :js:meth:`Engine.load` static method must be called. As
this method is static, multiple engine instances can be spawned with the exact same ``basePath``.
If an instance requires a different ``basePath``, you can call the :js:meth:`engine.init`
method with that path before starting the game.
Optionally, you can also manually :js:meth:`engine.init <Engine.prototype.init>` to perform specific actions after
the module initialization, but before the engine starts.
.. note:: Multiple instances cannot be spawned by default, as the engine is immediately unloaded after it is initialized.
To prevent this from happening the :js:meth:`engine.setUnloadAfterInit` method can be called. It is still possible
to unload the engine manually afterwards by calling the :js:meth:`Engine.unload` static method. Unloading the engine
frees browser memory by unloading files that are no longer needed once the instance is initialized.
To correctly load the engine on some hosting providers and network configurations you may
need to change the default filename extension by using :js:meth:`Engine.setWebAssemblyFilenameExtension`.
By default, the extension is assumed to be ``wasm``. If your hosting provider blocks this
extension, this static method can be used to change it to something that is supported.
This process is a bit more complex, but gives you full control over the engine startup process.
.. code-block:: js
Engine.setWebAssemblyFilenameExtension("dat");
// Load mygame.dat as WebAssembly module.
Engine.load("mygame");
const myWasm = 'mygame.wasm';
const myPck = 'mygame.pck';
const engine = new Engine();
Promise.all([
// Load and init the engine
engine.init(myWasm),
// And the pck concurrently
engine.preloadFile(myPck),
]).then(() => {
// Now start the engine.
return engine.start({ args: ['--main-pack', myPck] });
}).then(() => {
console.log('Engine has started!');
});
.. warning:: If a different filename extension is used, some web servers may automatically
set the MIME-type of the file to something other than :mimetype:`application/wasm`.
In that case some start-up optimizations may be skipped.
To load the engine manually the :js:meth:`Engine.load` static method must be called. As
this method is static, multiple engine instances can be spawned if the share the same ``wasm``.
.. note:: Multiple instances cannot be spawned by default, as the engine is immediately unloaded after it is initialized.
To prevent this from happening see the :js:attr:`unloadAfterInit` override option. It is still possible
to unload the engine manually afterwards by calling the :js:meth:`Engine.unload` static method. Unloading the engine
frees browser memory by unloading files that are no longer needed once the instance is initialized.
Customizing the behavior
------------------------
@@ -125,46 +149,40 @@ allows to test for a specific major version of WebGL.
As the real executable file does not exist in the Web environment, the engine only stores a virtual
filename formed from the base name of loaded engine files. This value affects the output of the
:ref:`OS.get_executable_path() <class_OS_method_get_executable_path>` method and defines the name of
the automatically started main pack. The :js:meth:`engine.setExecutableName` method can be used
to override this value.
If your project requires some files to be available the moment it is loaded, you can preload
them by calling the :js:meth:`engine.preloadFile` method with a path to a file or by providing it
with an ``ArrayBuffer`` object. In case of the ``ArrayBuffer``, or one of its views, a second argument
must be specified to define an internal path for the loaded resource.
the automatically started main pack. The :js:attr:`executable` override option can be
used to override this value.
Customizing the presentation
----------------------------
Several methods can be used to further customize the look and behavior of the game on your page.
Several configuration options can be used to further customize the look and behavior of the game on your page.
By default, the first canvas element on the page is used for rendering. To use a different canvas
element the :js:meth:`engine.setCanvas` method can be used. It requires a reference to the DOM
element the :js:attr:`canvas` override option can be used. It requires a reference to the DOM
element itself.
.. code-block:: js
const canvasElement = document.querySelector("#my-canvas-element");
engine.setCanvas(canvasElement);
engine.startGame({ canvas: canvasElement });
If the width and height of this canvas element differ from values set in the project settings, it
will be resized on the project start. This behavior can be disabled by calling the :js:meth:`engine.setCanvasResizedOnStart`
method.
The way the engine resize the canvas can be configured via the :js:attr:`canvasResizePolicy`
override option.
If your game takes some time to load, it may be useful to display a custom loading UI which tracks
the progress. This can be achieved with the :js:meth:`engine.setProgressFunc` method which allows
to set up a callback function to be called regularly as the engine loads new bytes.
the progress. This can be achieved with the :js:attr:`onProgress` callback option, which
allows to set up a callback function that will be called regularly as the engine loads new bytes.
.. code-block:: js
function printProgress(current, total) {
console.log("Loaded " + current + " of " + total + " bytes");
}
engine.setProgressFunc(printProgress);
engine.startGame({ onProgress: printProgress });
Be aware that in some cases ``total`` can be ``0``. This means that it cannot be calculated.
If your game supports multiple languages, the :js:meth:`engine.setLocale` method can be used to set
a specific locale, provided you have a valid language code string. It may be good to use server-side
If your game supports multiple languages, the :js:attr:`locale` override option can be used to
force a specific locale, provided you have a valid language code string. It may be good to use server-side
logic to determine which languages a user may prefer. This way the language code can be taken from the
``Accept-Language`` HTTP header, or determined by a GeoIP service.
@@ -175,30 +193,18 @@ by the engine. This is similar to the output shown in the editor console window.
``console.log`` and ``console.warn`` are used for the output and error streams respectively. This
behavior can be customized by setting your own functions to handle messages.
Use the :js:meth:`engine.setStdoutFunc` method to set a callback function for the output stream. Default
behavior is similar to this:
Use the :js:attr:`onPrint` override option to set a callback function for the output stream,
and the :js:attr:`onPrintError` override option to set a callback function for the error stream.
.. code-block:: js
function printStdout(text) {
function print(text) {
console.log(text);
}
engine.setStdoutFunc(printStdout);
Use the :js:meth:`engine.setStderrFunc` method to set a callback function for the error stream. Default
behavior is similar to this:
.. code-block:: js
function printStderr(text) {
console.warn("Error: " + text);
function printError(text) {
console.warn(text);
}
engine.setStderrFunc(printStderr);
engine.startGame({ onPrint: print, onPrintError: printError });
When handling the engine output keep in mind, that it may not be desirable to print it out in the
finished product. To control whether or not the current execution is actually a debug build you can
use ``$GODOT_DEBUG_ENABLED`` placeholder.
Further debugging options and a low level access to the execution environment are available in a form
of Emscripten's ``Module`` object. It can be accessed using the :js:attr:`engine.rtenv` property on the
engine instance.
When handling the engine output, keep in mind that it may not be desirable to print it out in the
finished product.