When building content for the web, you might need to communicate with other elements on your web page. Or you might want to implement functionality using Web APIs which Unity doesn’t expose by default. In both cases, you need to directly interface with the browser’s JavaScript engine. Unity WebGL provides different methods to do this.
The recommended way of using browser JavaScript in your project is to add your JavaScript sources to your project, and then call those functions directly from your script code. To do so, place files with JavaScript code using the .jslib extension in the Assets folder > Plugins subfolder. The plugin file needs to have a syntax like this:
mergeInto(LibraryManager.library, {
Hello: function () {
window.alert("Hello, world!");
},
HelloString: function (str) {
window.alert(UTF8ToString(str));
},
PrintFloatArray: function (array, size) {
for(var i = 0; i < size; i++)
console.log(HEAPF32[(array >> 2) + i]);
},
AddNumbers: function (x, y) {
return x + y;
},
StringReturnValueFunction: function () {
var returnStr = "bla";
var bufferSize = lengthBytesUTF8(returnStr) + 1;
var buffer = _malloc(bufferSize);
stringToUTF8(returnStr, buffer, bufferSize);
return buffer;
},
BindWebGLTexture: function (texture) {
GLctx.bindTexture(GLctx.TEXTURE_2D, GL.textures[texture]);
},
});
Then, you can call these functions from your C# scripts as follows:
using UnityEngine;
using System.Runtime.InteropServices;
public class NewBehaviourScript : MonoBehaviour {
[DllImport("__Internal")]
private static extern void Hello();
[DllImport("__Internal")]
private static extern void HelloString(string str);
[DllImport("__Internal")]
private static extern void PrintFloatArray(float[] array, int size);
[DllImport("__Internal")]
private static extern int AddNumbers(int x, int y);
[DllImport("__Internal")]
private static extern string StringReturnValueFunction();
[DllImport("__Internal")]
private static extern void BindWebGLTexture(int texture);
void Start() {
Hello();
HelloString("This is a string.");
float[] myArray = new float[10];
PrintFloatArray(myArray, myArray.Length);
int result = AddNumbers(5, 7);
Debug.Log(result);
Debug.Log(StringReturnValueFunction());
var texture = new Texture2D(1, 1, TextureFormat.ARGB32, false);
BindWebGLTexture(texture.GetNativeTexturePtr());
}
}
More Details:
UTF8ToString helper function to convert to a JavaScript string._malloc to allocate some memory and the stringToUTF8 helper function to write a JavaScript string to it. If the string is a return value, then the IL2CPP runtime automatically frees up the memory for you.emscripten provides different ArrayBufferViews into its heap for different sizes of integer, unsigned integer or floating point representations of memory: HEAP8, HEAPU8, HEAP16, HEAPU16, HEAP32, HEAPU32, HEAPF32, HEAPF64.GL.textures array which maps native texture IDs from Unity to WebGL texture objects. You can call WebGL functions on emscripten’s WebGL context, GLctx.JavaScript と相互作用する方法に関して詳しくは、emscripten ドキュメント を参照してください。
In addition, there are several plugins in the Unity installation folder that you can use as reference: PlaybackEngines/WebGLSupport/BuildTools/lib and PlaybackEngines/WebGLSupport/BuildTools/Emscripten/src/library*.
The recommended approach is to execute all the build code in its own scope. This allows you to embed your content on an arbitrary page without causing conflicts with the embedding page code, and lets you embed more than one build on the same page.
If you have all your JavaScript code in the form of .jslib plugins inside your project, then this JavaScript code will run inside the same scope as the compiled build and your code should work the same way as in previous versions of Unity. For example, the following objects and functions should be directly visible from the JavaScript plugin code: Module, SendMessage, HEAP8, ccall etc..
However, if you are planning to call the internal JavaScript functions from the global scope of the embedding page, you must use the unityInstance variable in your WebGL Template index.html. Do this after the Unity engine instantiation succeeds, for example:
var myGameInstance = null;
script.onload = () => {
createUnityInstance(canvas, config, (progress) => {...}).then((unityInstance) => {
myGameInstance = unityInstance;
…
Then, you can send a message to the build using myGameInstance.SendMessage(), or access the build Module object using myGameInstance.Module.
The recommended way of sending data or notification to the Unity script from the browser’s JavaScript is to call methods on GameObjects in your content. If you are making the call from a JavaScript plugin, embedded in your project, you can use the following code:
MyGameInstance.SendMessage(objectName, methodName, value);
objectName はシーンのオブジェクトの名。 methodName は、現在オブジェクトにアタッチされているスクリプトのメソッド名です。value には文字列、数字などで、以下の例のように空にしておくことも可能です。
MyGameInstance.SendMessage('MyGameObject', 'MyFunction');
MyGameInstance.SendMessage('MyGameObject', 'MyFunction', 5);
MyGameInstance.SendMessage('MyGameObject', 'MyFunction', 'MyString');
If you would like to make a call from the global scope of the embedding page, see the Code Visibility section.
Unity compiles your sources into JavaScript from C/C++ code using emscripten, so you can also write plugins in C/C++ code, and call these functions from C#. Therefore, instead of the .jslib file in the example above, you could have a C/C++ file in your project, which is automatically get compiled with your scripts, and you can call functions from it, just like in the JavaScript example above.
If you are using C++ (.cpp) to implement the plugin, then you must ensure the functions are declared with C linkage to avoid name mangling issues:
# include <stdio.h>
extern "C" void Hello ()
{
printf("Hello, world!\n");
}
extern "C" int AddNumbers (int x, int y)
{
return x + y;
}
Note: Unity is using the Emscripten version 2.0.19 toolchain.
replaced Pointer__stringify() with UTF8ToString in 2021.2 onwards
2020.1 で unity.Instance が createUnityInstance に変更されました。
コード例の誤りを修正
2019.1 で WebGL インスタンスの名称が gameInstance から unityInstance に変更されました。