HGE and Python

[Prahaai]

Good day.

I've been trying to port HGE (http://hge.relishgames.com) to Python for more than 4 months now...
HGE is a hardware accelerated 2D game engine.
It comes with the source and examples. In the folder "include", you can find "hge.h", the file that i am talking about in all the post.

#
I tried to load the DLL functions with Python Ctypes like this :

>>> from ctypes import *
>>> HGE = cdll.LoadLibrary("C:/hge181/hge")
>>> HGE.hgeCreate(0x180)

But i get this error : "Procedure called with not enough arguments (4 bytes missing) or wrong calling convention".
The call should be done with hgeCreate(HGE_VERSION) and the constant is defined as "#define HGE_VERSION 0x180"...
Number 0x180 means 384 in Python. I don't mean what it means in C.
So i am stuck.

I also tried to modify the "hge.h" file on line 408, and export the rest of the classes...

__declspec (dllexport) hgeVertex;
__declspec (dllexport) hgeTriple;
__declspec (dllexport) hgeQuad;
__declspec (dllexport) hgeInputEvent;

But after compilation, i am not able to access them from Python "ctypes". They seem to remain invisible. Perhaps i am not doing it right?...

#
I tried Cython.
I tried to load "hge.h" in Cython and use the structures.
The first error i get is at line 173: "typedef bool (*hgeCallback)();". I am not that good in C/C++ to understand what it means. So i commented it...
The second big error is at line 408: "extern "C" { EXPORT HGE * CALL hgeCreate(int ver); }". This should be the DLL export. I comented that too...

I used this code in Cython, loading from "hge.h":

# file HGE.pyx
cdef extern from "windows.h":
   pass

cdef extern from "hge.h":
   pass

And i get this errors:

..\hge.h(215) : error C2061: syntax error : identifier 'hgeVertex'
..\hge.h(218) : error C2059: syntax error : '}'
..\hge.h(226) : error C2061: syntax error : identifier 'hgeVertex'
..\hge.h(229) : error C2059: syntax error : '}'
..\hge.h(274) : error C2061: syntax error : identifier 'HGE'
..\hge.h(274) : error C2059: syntax error : ';'
..\hge.h(275) : error C2449: found '{' at file scope (missing function header?)
..\hge.h(407) : error C2059: syntax error : '}'

Then i tried to define hgeVertex in Cython like:

struct hgeVertex:
   float x, y      # screen position   
   float z         # Z-buffer depth 0..1
   DWORD col      # color
   float tx, ty      # texture coordinates

But i get the exact same errors.
If i comment all the structures hgeVertex and Triple and Quad and the HGE class, the Cython file compiles !... But it's not useful at all.
My Cython is okay, i compiled a few programs before, so that's not a problem...

#
Then i tried Swig (and it worked with the examples )... But the problems with "hge,h" seem to be somewhat similar.
I call swig like this : "swig -c++ -python hge.i"
And the file "hge.i" contains:

/* File : hge.i */
%module hge

%{
#include "hge.h"
%}

/* Let's just grab the original header file here */
%include "hge.h"

And the error i get after commenting the HGE callback and DLL export is this : "hge.h(276): Error: Syntax error in input(3)." Line 276 is exactly the first call of HGE class : "virtual void CALL Release() = 0;".

#
I tried Boost.Python (and it works with embedding and extending examples), but i could't compile "hge.h" even after commenting the structures and classes. I have to write some wrapper code in "hge.h" and i am probably doing it completely wrong.

BOOST_PYTHON_MODULE(hge)
{
	using namespace boost::python;
	class_<hgeVertex> base("hgeVertex");
}

So i am stuck again...

I am not that good in neither C or Python.

Can anyone suggest any ideas? Please?
I really really really want to port HGE in Python. It's the greatest game engine i have ever seen. The particle engine is EXCELLENT and i need it.

Thank you in advance.

[EAnder]

Im not into ctypes yet but I do know that in "#define HGE_VERSION 0x180" 0x180 is not just for python. It is a hex number so it should be represented in most if not all programming languages. All else fails you could do the conversion your self i guess...

[Murtan]

I did some initial review, and I was able to load the library and call hgeCreate using ctypes:

Run this from a directory with the hge.dll in it, I was in the hge181 directory.

from ctypes import *
hge = windll.hge
hgeCreate = hge.hgeCreate
hgeCreate.restype = c_void_p

hge = hgeCreate(0x180)

But from there, it would seem ctypes does not support making calls into c++ classes, and that appears to be how you interface to the rest of hge. (hgeCreate returns a pointer to an instance of the class)

[Stefano Mtangoo]

I have problems too in learning ctypes. They are powerful way to port C++ power into python, but seems to lack begginers tutorial which is very sad. For man like me with little knowledge in c++, it is big burded.

Anyway, so far what I know is that, in order to rightly call any function in Python using ctypes are
1. define result type using restype
2. define arguments types using argtype
3. call the function with right arguments

But so far I haven't been successful to do anything useful with ctypes. I believe sometimes I will do!

[Prahaai]

Good day.

Thank you so much for your answers!

I managed to call HGE dll the way you told:
>>> HGE = windll.LoadLibrary("C:/hge181/hge")
>>> HGE.hgeCreate(0x180)
But it's not helpful. It would mean that i have to re-create all the header files from "include" directory in python, and all helper functions from the "libs" to be able to use hge in the same way as the original.
So ctypes is not what i need. Anyway, it's a big step!

I also tried swig, a lot.
A lot, a lot, a lot of examples. Hacking examples and stuff.
And i managed to compile "hge.h" header and call the structs and HGE main class from python. I don't seem to be able to acces the "enums", but that's not a big problem.
How i did that, if anyone wants to know: There are 4 files.
- There is "example.cxx", that includes "hge.h" in the proper C++ way and defines a HGE* hge=0 just like in the tutorials.
- Then is "hge.h", the original file, with ONE line commented: line 408 with the DLL EXPORT. Ah, and one more thing. I had to delete ALL "CALL" keywords from HGE class, because if one CALL appears, the swig compiler flags the line as error. So, for now, no stdcall.
- Then is "example.i", with "#include "hge.h"" and "%include "hge.h"". Simple as that.
- And then, there is setup.py. "example_module = Extension('_example', sources=,)"
That's it. I compile it all like this:

swig -c++ -python example.i
setup build_ext --inplace

So it's a huge step for me. The compiler i have in my system is mingw-3.4.5. I don't know if it's good for this. Maybe i should try a MS compiler instead?

Next things i want to do:
- try to compile the project with a MS compiles. Visual studio 7.1 or somethin.
- learn if i can do stdcalls from swig.
- try to compile one normal hge tutorial WITHOUT including "hge.lib" and "hgehelp.lib". All functions defined there can be included just like normal headers, the source is there and i compiled the libs myself. I need this step because i don't think i can include lib files in a swig project.
- try to do all i did in swig, with Cython. It's pretty easy to use and faster from what i know.

That's all for now.
It would be of great help if anyone could tell how to deal with the __stdcall thingy...

Thank you very much.