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Callbacks

Any function from system, world or editor scripts can be called in a C# code. UnigineScript functions that are called from an external code are known as callbacks. Via callbacks scripts can communicate with each other, as well as with the external application.

The callback functions can receive optional arguments of the int or IntPtr type that are used to store user data. IntPtr values can be wrapped in classes, for example:

Source code (C#)
IntPtr ptr;
// create a node and then create a Unigine object
Unigine.Object.create(new Node(ptr));
See the article on Widget Dialog usage example for more details.

See also

An example can be found in <UnigineSDK>/source/csharp/samples/Api/Scripts/Callbacks/ directory.

Callbacks Usage Example

C# Side

To demonstrate how callbacks can be used, let's code the C# part first. Here's code from your_project_name.cs file:

Source code (C#)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Unigine;

namespace UnigineApp
{
	class UnigineApp
	{
		// world function
		private static Variable runWorldFunction(Variable name, Variable v)
		{
			Log.warning("runWorldFunction({0},{1}): called\n", name.getTypeName(), v.getTypeName());
			Engine engine = Engine.get();

			return engine.runWorldFunction(name, v);
		}

		static void Main(string[] args)
		{
			// export the runWorldFunction() function defined above
			Interpreter.addExternFunction("runWorldFunction", new Interpreter.Function2v(runWorldFunction));

			Wrapper.init();

			AppSystemLogic systemLogic = new AppSystemLogic();
			AppWorldLogic worldLogic = new AppWorldLogic();
			AppEditorLogic editorLogic = new AppEditorLogic();

			Engine engine = Engine.init(Engine.VERSION, args);

			engine.main(systemLogic, worldLogic, editorLogic);

			Engine.shutdown();
		}
	}
}

The following code should be in AppWorldLogic.cs

Source code (C#)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Unigine;

namespace UnigineApp
{
	class AppWorldLogic : WorldLogic
	{
		public AppWorldLogic()
		{
		}

		public override int init()
		{
			return 1;
		}

		public override int shutdown()
		{
			return 1;
		}

		public override int destroy()
		{
			return 1;
		}

		public override int update()
		{
			/*
			 * Callbacks usage example
			 */
			// call the counter() function of the script (defined below)
			Variable ret = Engine.get().runWorldFunction(new Variable("counter"));
			// print a message depending on the value returned by the counter() script function:
			// print the current value of the counter
			if (ret.getInt() != -1) Log.message("counter is: {0}\n", ret.getInt());
			// print the world name
			if (ret.getInt() == 3) Log.message("\nworld name is: \"{0}\"\n", Engine.get().runWorldFunction(new Variable("engine.world.getName")).getString());
			
		}

		public override int render()
		{
			return 1;
		}

		public override int flush()
		{
			return 1;
		}

		public override int save(Stream stream)
		{
			return 1;
		}

		public override int restore(Stream stream)
		{
			return 1;
		}
	}
}

Unigine Script Side

And now the UnigineScript side where callbacks are defined:

Source code (UnigineScript)
#include <core/unigine.h>

int callback(int value) {
	
	log.warning("callback(%s) is called\n",typeinfo(value));
	
	return value;
}

void counter() {
	
	for(int i = 0; i < 4; i++) {
		log.warning("counter(): called\n");
		yield i;
	}
	
	return -1;
}

int init() {
	Player player = new PlayerSpectator();
	player.setPosition(Vec3(0.0f,-3.401f,1.5f));
	player.setDirection(Vec3(0.0f,1.0f,-0.4f));
	engine.game.setPlayer(player);

	log.message("\n");
	
	// run the callback() script function via the API runWorldFunction() function
	log.message("result is: %s\n\n",typeinfo(runWorldFunction("callback",10)));
	log.message("result is: %s\n\n",typeinfo(runWorldFunction("callback",vec3(1,2,3))));
	log.message("result is: %s\n\n",typeinfo(runWorldFunction("callback","a string")));
	
	// show a console
	engine.console.setActivity(1);

	return 1;
}

int shutdown() {
	return 1;
}

int update() {
	return 1;
}

Calling Sequence

The sequence of function call will be as follows:

  1. The interpreter exports the runWorldFunction() function to make it available from the script.
  2. The engine is initialized, and the init() function of the script is called. This function calls the exported runWorldFunction() function.
  3. The exported runWorldFunction() function calls the callback() function from the script.
  4. The engine enters the main loop, where it calls the counter() function from the script by using the Unigine.Engine.runWorldFunction() function which has the same behavior as the Unigine::Engine::runWorldFunction() C++ API function.

Output

The following result will be printed into the console:

Output
runWorldFunction(string,int): called
callback(int: 10): called
result is: int: 10

runWorldFunction(string,vec3): called
callback(vec3: 1 2 3): called
result is: vec3: 1 2 3

runWorldFunction(string,string): called
callback(string: "a string"): called
result is: string: "a string"

counter(): called
counter is: 0
counter(): called
counter is: 1
counter(): called
counter is: 2
counter(): called
counter is: 3

world name is: "unigine_project/unigine_project"
Last update: 2018-04-26