using lua scripted objects from c++

[nelsoncs]

can someone point me to a tutorial or reference showing how to use lua scripted objects from c++? thanks

[AggrorJorn]

http://leadwerks.wikidot.com/ has some good articles. Among them are a lot of references to topics covering interesting stuff.

 

http://leadwerks.wikidot.com/wiki:communication-from-lua-to-c

[Charrua]

hi

 

i am getting some troubles, due to my lack of knowledge.

 

the easy part is:

 

add

#include "lua.h"

in your App.h

 

so, any scripted object will work, but:

if you create a camera in your map (via editor) you have to make some tricks to use that camera and not create another via c++

 

your initila c++ code, creates a context, window etc, you have to write your scripts using those objects...

 

you may write something like this on your Scripts functions:

 

function Script:PostRender()

 

local window = Window:GetCurrent()

local context = Context:GetCurrent()

 

if window:KeyHit(Key.M) then

self.showtext = not(self.showtext)

end

 

if self.showtext

 

context:SetBlendMode(Blend.Alpha)

context:SetColor(255,255, 255)

context:DrawText("hello", x, y)

end

 

end

 

as i get some troubles using a camera defined in c from lua scripts (sure i am doing something wrong) i define the camera inside the editor and then i use that camera from c++

see:

http://www.leadwerks.com/werkspace/topic/10154-set-camera-to-a-camera-in-the-scenelevelmap/

 

Juan

[nelsoncs]

Juan,

Thanks for the reference to your solution to obtain the camera from the editor/map in C++. this kind of pushed me in the right direction addressing my current problem.

 

I have a design where new entities will be created after the map has been loaded, so I wanted to be able to use the World::ForEachEntity....() functions from within a given, non-Leadwerks::Object class. This turned out to be somewhat difficult to figure out but I think I have a solution.

 

The code below is what I used as an experiment to get the entity class names printed on my console widget.

 

1.

 

SomeClass.h

 

... (prototype)

static void entityClass ( Leadwerks::Entity * entity,

Leadwerks::Object* extra ); // this is the declaration for a callback function, it has to be static

 

2.

SomeClass.cpp

 

... (using the callback function, maybe in the constructor, notice that the 'this' pointer for the classinstance is

cast to a leadwerks object pointer and passed in as a parameter)

 

world->ForEachEntityInAABBDo( aabb,

&entityClass,

(Leadwerks::Object *) this

);

 

3.

SomeClass.cpp

 

...

void SomeClass::entityClass(Leadwerks::Entity * entity,

Leadwerks::Object* extra) {

 

std::string str ( entity->GetClassName() );

 

cout << "Attack::entityClass: " << str << '\n';

((SomeClass *) extra)->getConsole()->addText( &str );

}

 

// Note: "ForEachEntityInAABBDo" seems to require that the

// callback function be static. This creates a really big problem

// if trying to get data back into a C++ class because a static function

// has no idea what class instance you are interested in. So, this solution

// casts the current class instance pointer (this) to a Leadwerks Object

// and then casts back to the cognate Class *. Seems to work but

// the assumption is that there is never a problem with pointer

// Implementations at runtime.

 

 

I was going take the time to confirm that the pointer thunks were ok using Valgrind, but I get so many reported memory leaks from within the engine, thus obsfucating my inspection, that I may wait till something breaks.

 

So, now that I can access basic data for entites created in the Leadwerks editor at anytime, it is on towards making use of their Lua scripts from C++.......

[Rick]

After your map is loaded you can also loop over the entities in the world.

 

list<Entity*>::iteration iter;
for(iter = world->entities.begin(); iter != world->entities.end(); ++iter)
{
}

 

This saves you from having to mess with passing a this pointer as I you can loop over this in any class. Your idea is good for other things like collisions as you have no other options but to use a callback, but with going over entities loaded from the map you have this more straight forward way.

[nelsoncs]

Nice, thanks Rick. I can see I glossed over the members section when I read Command Reference > World.

[AggrorJorn]

All of is did in the beginning.