guides:machine_code:com

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guides:machine_code:com [2025-03-26 15:55] – Various comment improvements geekguides:machine_code:com [2025-03-28 13:28] (current) – [Using COM with MCode] Link MCode guide geek
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 ====== Using COM with MCode ====== ====== Using COM with MCode ======
 +
 +Please read the basic [[guides:machine_code|MCode]] guide before this one!
 +
 +If you have not, consider referencing the [[guides:com:start|COM APIs]] guide to learn more about how COM works.
  
 When building integrations for AutoHotkey using MCode, it is often convenient to be able to work with COM objects. Either consuming COM objects in your MCode, or exporting COM objects from your MCode so they can be consumed by AHK. When building integrations for AutoHotkey using MCode, it is often convenient to be able to work with COM objects. Either consuming COM objects in your MCode, or exporting COM objects from your MCode so they can be consumed by AHK.
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 By implementing the IDispatch interface, your custom COM object can be wrapped by AHK. Once wrapped, users can interact with the object using native object syntax. By implementing the IDispatch interface, your custom COM object can be wrapped by AHK. Once wrapped, users can interact with the object using native object syntax.
 +
 +IDispatch extends IUnknown, so it has the three IUnknown methods. After those, it includes these four methods:
 +  * ''GetTypeInfoCount'' - Allows debug-style inspection of the COM object. ([[https://learn.microsoft.com/en-us/windows/win32/api/oaidl/nf-oaidl-idispatch-gettypeinfocount|MSDN]])
 +  * ''GetTypeInfo'' - Allows debug-style inspection of the COM object. ([[https://learn.microsoft.com/en-us/windows/win32/api/oaidl/nf-oaidl-idispatch-gettypeinfo|MSDN]])
 +  * ''GetIDsOfNames'' - Translates script-given method and property names to unique DISPID values. ([[https://learn.microsoft.com/en-us/windows/win32/api/oaidl/nf-oaidl-idispatch-getidsofnames|MSDN]])
 +  * ''Invoke'' - Dispatches MyObj's method and property implementations. ([[https://learn.microsoft.com/en-us/windows/win32/api/oaidl/nf-oaidl-idispatch-invoke|MSDN]])
 +
 +The methods ''GetTypeInfo'' and ''GetTypeInfoCount'' are optional. We will leave as unimplemented stubs.
 +
 +The ''GetIDsOfNames'' method accesses the object's internal name store, and returns an object-specific "DISPID" number. For objects which have a fixed set of properties, this can be implemented by hard coding some constants into the MCode. As an example, if you were creating an object which just had a single method called ''Compute'', you might make ''GetIDsOfNames'' return ''1'' when given the name ''"Compute"''. When the script makes a call to your object like ''object.Compute()'', the string ''"Compute"'' is passed to this ''GetIDsOfNames'' function. AutoHotkey will take the result (''1'') and cache it for the lifetime of the object.
 +
 +If your object allows for new properties to be created dynamically, ''GetIDsOfNames'' might implement something like a counter and hash map. Whenever a new property is created, the counter would be incremented and then its value will be saved inside the hash map so that the mapping can be resolved again later.
 +
 +The ''Invoke'' method is where all the magic happens. This function takes the DISPID specified by ''GetIDsOfNames'' and runs the custom code associated with the DISPID/name. ''Invoke'' receives a set of flags, which can be one or more of the following:
 +  * ''DISPATCH_METHOD'' - The name was invoked as a method, as in ''object.Name(...)''.
 +  * ''DISPATCH_PROPERTYGET'' - The name was invoked as a property retrieval, as in ''MsgBox object.Name''.
 +  * ''DISPATCH_PROPERTYPUT'' - The name was invoked as a property put, as in ''object.Name := "New Name"''.
 +  * ''DISPATCH_PROPERTYPUTREF'' - The name was invoked as a property put "by reference". This is uncommon.
 +
 +''Invoke'' also receives a ''DISPPARAMS'' argument, which contains an array of VARIANTs passed as arguments, and an array of VARIANTs passed as keyword arguments (not applicable when calling from AHK). ''Invoke'' has three output parameters,
 +
 +  * ''VARIANT *pVarResult'' - The result of the call, if any
 +  * ''EXCEPINFO *pExcepInfo'' - Any exception to return to the caller
 +  * ''UINT       *puArgErr'' - If an argument was bad, which argument was it?
 +
 +By implementing ''Invoke'' to check the DISPIDs against the constants you created for each field that you want to be available on your object, and checking the flags against the appropriate flags for those fields, you can create virtual methods that AutoHotkey can call with regular object syntax.
  
 <runner ahk2> <runner ahk2>
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 MsgBox MyObj.FirstAddend " + " MyObj.SecondAddend " = " MyObj.GetSum() MsgBox MyObj.FirstAddend " + " MyObj.SecondAddend " = " MyObj.GetSum()
 </runner> </runner>
 +
 +===== Consuming AHK Objects from MCode =====
 +
 +AutoHotkey objects are, at their basic, IDispatch objects. Just like we can create IDispatch objects using basic C code, we can interact with IDispatch objects using basic C code.
 +
 +<runner ahk2>
 +#Requires AutoHotkey v2.0
 +#include <MCL>
 +
 +lib := MCL.FromC("
 +(
 +#include <mcl.h>
 +#include <stdlib.h>
 +#include <oaidl.h>
 +
 +MCL_IMPORT(HRESULT, OleAut32, VariantChangeType, (VARIANT*, const VARIANT*, USHORT, VARTYPE));
 +
 +static IID IID_NULL = { 0x00000000, 0x0000, 0x0000, { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } };
 +
 +MCL_EXPORT(SumValues, Ptr, Cdecl_Int);
 +int SumValues(IDispatch* pObj) {
 +    // Get the ID of the "Length" property
 +    DISPID dispidLength = DISPID_UNKNOWN;
 +    LPOLESTR strLength = L"Length";
 +    pObj->lpVtbl->GetIDsOfNames(pObj, &IID_NULL, &strLength, 1, 0, &dispidLength);
 +    if (dispidLength == DISPID_UNKNOWN) {
 +        return 0;
 +    }
 +
 +    // Invoke the "Length" property
 +    DISPPARAMS dpLength = { .cArgs = 0, .cNamedArgs = 0 };
 +    VARIANT vLength = { .vt = VT_EMPTY };
 +    if (S_OK != pObj->lpVtbl->Invoke(
 +        pObj, dispidLength, NULL, 0, DISPATCH_PROPERTYGET,
 +        &dpLength, &vLength, NULL, NULL) ||
 +        vLength.vt != VT_I4) {
 +        return 0;
 +    }
 +
 +    // Loop from i = 0 to Length
 +    int out = 0;
 +    for (int i = 0; i < vLength.lVal; i++) {
 +        // Invoke the value property, with argument `i+1`. This is equivalent
 +        // to `object[i+1]`
 +        VARIANT vargGet = { .vt = VT_I4, .lVal = i + 1 };
 +        DISPPARAMS dpGet = { .cArgs = 1, .cNamedArgs = 0, .rgvarg = &vargGet };
 +        VARIANT vGet = { .vt = VT_EMPTY };
 +        if (S_OK != pObj->lpVtbl->Invoke(
 +            pObj, DISPID_VALUE, NULL, 0, DISPATCH_PROPERTYGET,
 +            &dpGet, &vGet, NULL, NULL)) {
 +            return 0;
 +        }
 +
 +        // Coerce to 4-byte integer (LONG)
 +        if (S_OK != VariantChangeType(&vGet, &vGet, 0, VT_I4)) {
 +            return 0;
 +        }
 +
 +        out += vGet.lVal;
 +    }
 +
 +    return out;
 +}
 +)")
 +
 +input := [1, 2, 3]
 +MsgBox lib.SumValues(ObjPtr(input))
 +</runner>
 +
 +==== Implementing QuickSort ====
 +
 +By invoking ''DISPID_VALUE'' with ''DISPATCH_PROPERTYGET'' and ''DISPATCH_PROPERTYPUT'', we can get and set values from an object's item store. This allows us to implement a basic Quicksort algorithm that applies to a provided array:
 +
 +<runner ahk2>
 +#Requires AutoHotkey v2.0
 +#include <MCL>
 +
 +lib := MCL.FromC("
 +(
 +#include <mcl.h>
 +#include <stdlib.h>
 +#include <oaidl.h>
 +
 +#define E_FAIL 0x80004005
 +
 +MCL_IMPORT(HRESULT, OleAut32, VarCmp, (VARIANT* left, VARIANT* right, DWORD lcid, ULONG dwFlags));
 +MCL_IMPORT(HRESULT, OleAut32, VariantClear, (VARIANT* pvarg));
 +
 +HRESULT GetItem(IDispatch* array, ULONG index, VARIANT* pvarResult) {
 +    VARIANT vargGet = { .vt = VT_I4, .lVal = index };
 +    DISPPARAMS dpGet = { .cArgs = 1, .cNamedArgs = 0, .rgvarg = &vargGet };
 +    return array->lpVtbl->Invoke(
 +        array, DISPID_VALUE, NULL, 0, DISPATCH_PROPERTYGET,
 +        &dpGet, pvarResult, NULL, NULL);
 +}
 +
 +HRESULT PutItem(IDispatch* array, ULONG index, VARIANT* pvarItem) {
 +    VARIANT vargIndex = { .vt = VT_I4, .lVal = index };
 +    VARIANT rgvargArgs[] = { *pvarItem, vargIndex };
 +    DISPPARAMS dpPut = { .cArgs = 2, .cNamedArgs = 0, .rgvarg = rgvargArgs };
 +    return array->lpVtbl->Invoke(
 +        array, DISPID_VALUE, NULL, 0, DISPATCH_PROPERTYPUT,
 +        &dpPut, NULL, NULL, NULL);
 +}
 +
 +HRESULT partition(IDispatch *array, ULONG lo, ULONG hi, ULONG* newPartition) {
 +    HRESULT result = E_FAIL;
 +
 +    VARIANT varHi = { .vt = VT_EMPTY };
 +    VARIANT varI = { .vt = VT_EMPTY };
 +    VARIANT varJ = { .vt = VT_EMPTY };
 +
 +    // Use highest index value as pivot
 +    if (S_OK != GetItem(array, hi, &varHi)) goto fail;
 +
 +    ULONG i = lo;
 +    for (ULONG j = lo; j < hi; j++) {
 +        if (S_OK != GetItem(array, j, &varJ)) goto fail;
 +        // lcid = LOCALE_INVARIANT, dwFlags = NORM_IGNORECASE
 +        if (
 +            (varJ.vt != varHi.vt) ? (varJ.vt <= varHi.vt) :
 +            VarCmp(&varJ, &varHi, 0x7F, 0x1) < 2) {
 +            if (S_OK != GetItem(array, i, &varI)) goto fail;
 +            if (S_OK != PutItem(array, i, &varJ)) goto fail;
 +            if (S_OK != PutItem(array, j, &varI)) goto fail;
 +            i = i + 1;
 +            VariantClear(&varI);
 +        }
 +        VariantClear(&varJ);
 +    }
 +
 +    // Center the pivot value
 +    if (S_OK != GetItem(array, i, &varI)) goto fail;
 +    if (S_OK != PutItem(array, i, &varHi)) goto fail;
 +    if (S_OK != PutItem(array, hi, &varI)) goto fail;
 +
 +    *newPartition = i;
 +    result = S_OK;
 +
 +    fail:
 +    VariantClear(&varHi);
 +    VariantClear(&varI);
 +    VariantClear(&varJ);
 +    return result;
 +}
 +
 +MCL_EXPORT(quicksort, Ptr, array, UInt, lo, UInt, hi, CDecl_Int);
 +HRESULT quicksort(IDispatch *array, ULONG lo, ULONG hi) {
 +    if (lo >= hi) return S_OK;
 +    ULONG p = 0;
 +    if (S_OK != partition(array, lo, hi, &p)) return E_FAIL;
 +    if (S_OK != quicksort(array, lo, p - 1)) return E_FAIL;
 +    if (S_OK != quicksort(array, p + 1, hi)) return E_FAIL;
 +    return S_OK;
 +}
 +
 +)")
 +
 +x := ["c", 6, 3.0, 3, 8, "b", 9, 2.0, 4, 5, "a", 1,2, 1.0, 7]
 +
 +MsgBox "Before Sorting: " JSON.Dump(x)
 +
 +lib.quicksort(ObjPtr(x), 1, x.Length)
 +
 +MsgBox "After Sorting: " JSON.Dump(x)
 +</runner>
 +