On Wednesday, 15 June 2016 at 21:06:01 UTC, Joerg Joergonson
wrote:
My thinking is that CoCreateinstance is suppose to give us a
pointer to the interface so we can use it, if all this stuff is
crashing does that mean the interface is invalid or not being
assigned properly or is there far more to it than this?
The problem is Photoshop hasn't provided an interface with
methods that can be called directly. They don't exist on the
interface, hence them being commented out. It's a mechanism known
as late binding (everything is done at runtime rather than
compile time). You need to ask the interface for the method's ID,
marshal the parameters into a specific format, and then "invoke"
the method using that ID.
And you're not going to like it. Here's an example just to call
the "Load" method:
// Initialize the Photoshop class instance
IDispatch psApp;
auto iid = IID__Application;
auto clsid = CLSID_Application;
assert(SUCCEEDED(CoCreateInstance(&clsid, null, CLSCTX_ALL,
&iid, cast(void**)&psApp)));
scope(exit) psApp.Release();
// Get the ID of the Load method
auto methodName = "Load"w.ptr;
auto dispId = DISPID_UNKNOWN;
iid = IID_NULL;
assert(SUCCEEDED(psApp.GetIDsOfNames(&iid, &methodName, 1, 0,
&dispId)));
// Put the parameters into the expected format
VARIANT fileName = {
vt: VARENUM.VT_BSTR,
bstrVal: SysAllocString("ps.psd"w.ptr)
};
scope(exit) VariantClear(&fileName);
DISPPARAMS params = {
rgvarg: &fileName,
cArgs: 1
};
// Finally call the method
assert(SUCCEEDED(psApp.Invoke(dispId, &iid, 0, DISPATCH_METHOD,
¶ms, null, null, null)));
tlb2d only outputs the late-bound methods as a hint to the user
so they know the names of the methods and the expected parameters
(well, it saves looking them up in OleView). Had Photoshop
supplied a compile-time binding, you could have just called
psApp.Load(fileName) like you tried.
It's possible to wrap that ugly mess above in less verbose code
using native D types, and the Juno COM library mentioned earlier
enabled that, but the code is quite ancient (and is part of and
depends on a larger library). I've been slowly working on a more
modern library. You'd be able to just write this:
auto psApp = makeReference!"Photoshop.Application"();
psApp.Load("ps.psd");
But I don't know when it'll be ready.
