🔒 Locked

Passing function pointers to DXUTSetCallback* methods

Started by BlackGhost Oct 5, 2004 at 11:56 AM 2 replies 2.4k views

Original Post

Oct 5, 2004 at 11:56 AM

Hi, I'm having a problem with function pointers in C++. The directX 9 sample framework allows us to create callbacks for significant events, e.g. the create device event can be handled by a function with this declaration:


HRESULT CALLBACK onCreateDevice(IDirect3DDevice9* pd3dDevice, const D3DSURFACE_DESC* pBackBufferSurfaceDesc);

and we declare to the framework that this will be the callback with the command DXUTSetCallbackDeviceCreated(onCreateDevice). This function takes a function pointer as a parameter. The problem is that if the function passed in is not global, and instead is a member function of a class, the conversion of the parameter to the correct type does not work as before -I get a type cast error. The type that is expected is the function pointer HRESULT (CALLBACK *LPDXUTCALLBACKDEVICECREATED)( IDirect3DDevice9* pd3dDevice, const D3DSURFACE_DESC* pBackBufferSurfaceDesc ); Can anyone with more experience on function pointers provide any insight on this situation? Furthermore, what happens if the function is virtual -can pointers to that function work in this case? Thanks for any replies.

Muhammad Haggag

156

Muhammad Haggag

Oct 5, 2004 at 4:44 PM

Class member functions have an implicit first parameter, the this pointer. That's why the compiler sees them as having a different signature than the callback's.
e.g.

class Boo{public:    HRESULT on_create_device(IDirect3DDevice9* device, const D3DSURFACE_DESC* bbs_desc); };

Is seen by the compiler as:

HRESULT on_create_device(Boo* this, IDirect3DDevice9* device, ...);

To work around this, you can make it a static function. However, you won't be able to access non-static class members that way.

jasonsa

Oct 8, 2004 at 2:48 AM

Ya, you can do something like this:

class CFoo{    void Init()     {         DXUTSetCallbackDeviceReset( StaticOnDeviceReset );         // etc...    }     // static methods which handle the DXUT callbacks and pass the calls to non-static class methods     // so they can easily access member methods    static HRESULT StaticOnDeviceReset( ... )  { g_Foo.OnDeviceReset(); }         HRESULT OnDeviceReset( .. )    {        // code from old framework's app method RestoreDeviceObjects() here    }}

IFooBar

119

IFooBar

Oct 8, 2004 at 7:56 AM

If only the dx library made use of boost eh?

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.