Re: Fwd: Google Summer of Code 2012 DEADLINE: 2012-02-27

[Dylan Smith]

On Sat, Feb 11, 2012 at 2:27 PM, Maarten Lankhorst
wrote:
> Are you sure? I don't see any example calls being wrapped to ITextHost
> for example..

Yup, I worked on it myself.  All those ITextHost_*(...), which you can
easily grep for in editor.c, are using macros in editor.h:

--- snip ---
#ifdef __i386__ /* Use wrappers to perform thiscall on i386 */
#define TXTHOST_VTABLE(This) (&itextHostStdcallVtbl)
#else /* __i386__ */
#define TXTHOST_VTABLE(This) (This)->lpVtbl
#endif /* __i386__ */
 /*** ITextHost methods ***/
#define ITextHost_TxGetDC(This) TXTHOST_VTABLE(This)->TxGetDC(This)
...
--- end snip ---

So for i386 it will use the itextHostStdcallVtbl, which is defined in
txthost.c to pop the This pointer off the stack and into a register, then
grab the pointer to the vtable, and jump to the thiscall method.

--- snip ---
#define STDCALL(func) __stdcall_ ## func
#define DEFINE_STDCALL_WRAPPER(num,func,args) \
   extern typeof(func) __stdcall_ ## func; \
   __ASM_STDCALL_FUNC(__stdcall_ ## func, args, \
                   "popl %eax\n\t" \
                   "popl %ecx\n\t" \
                   "pushl %eax\n\t" \
                   "movl (%ecx), %eax\n\t" \
                   "jmp *(4*(" #num "))(%eax)" )

DEFINE_STDCALL_WRAPPER(3,ITextHostImpl_TxGetDC,4)
...

const ITextHostVtbl itextHostStdcallVtbl = {
    NULL,
    NULL,
    NULL,
    __stdcall_ITextHostImpl_TxGetDC,
...
--- end snip ---

The ITextHost interface is also implemented in txthost.c for non-windowless
richedit controls.  That interface is implemented using thiscall wrappers
which do the reverse of the standard call wrappers.