Issue Passing String from ExtendScript to Custom After Effects Plugin via ExternalObject

Report · Nov 05, 2024

I'm attempting to pass a string, such as "testCommand," from a JavaScript (ExtendScript) script to a custom After Effects plugin written in C++. Below is my current JavaScript code:

var command = "testCommand";
var pluginPath = "C:/Program Files/Adobe/Common/Plug-ins/7.0/MediaCore/SaveImage/";
var libFilename = "SaveImage.aex";
var consoleLib = new ExternalObject("lib:" + pluginPath + libFilename);
var utf8Command = encodeURIComponent(command);
consoleLib.setCommandString(utf8Command);
consoleLib.unload();

I would appreciate guidance or examples on how to receive this string within the plugin using C++.

Report · Nov 05, 2024

How is the `.setCommandString` function implemented on the C++ side? Its function signature needs to have a parameter as `TaggedData` type. That data type has members that you set and then return the value.

The examples in the SDK show this function:

    /**
     * Appends a string onto the passed argument.
     *
     * This function only accepts a single argument, a String.  The passed argument
     * is appended with another string and then returned back to the scripting environment.
     * To call from Javascript&colon;
     *
     \code
     myObj.appendString("A String");
     \endcode
     *
     * If the arguments are not correct then a bad argument error code is returned.
     *
     * \param argv - The JavaScript argument
     * \param argc the argument count
     * \param retval The return value to be passed back to JavaScript
     */
    extern "C" BASICEXTERNALOBJECT_API long appendString(TaggedData* argv, long argc, TaggedData * retval)
    {
        // Accept 1 and only 1 argument
        if(argc != 1)
        {
            return kESErrBadArgumentList;
        }
        
        // The argument must be a string
        if(argv[0].type != kTypeString)
        {
            return kESErrBadArgumentList;
        }
        
        // The returned value type
        retval->type = kTypeString;
        
        // argv[0].data.string = the string passed in from the script
        string s (argv[0].data.string);
        
        // add a little bit of data onto the passed in string
        s.append("_appended by BasicExternalObject");
        
        retval->data.string = getNewBuffer(s);
        
        return kESErrOK;
    }

Report · Nov 18, 2024

I've tried different approaches, but so far I haven't been able to get a working result. I managed to pass a double variable, but I can't pass text. I've tried different text encodings, but it seems that's not the issue. Here are the characters I get instead of the text: �Q? �

here is my code

#include "SaveImage.h"
#include <Windows.h>
#include <string>

static AEGP_PluginID g_plugin_id = 0L;
static SPBasicSuite* g_sp_basic_suite = nullptr;

std::wstring ConvertToWString(const char* str) {

    int len = MultiByteToWideChar(CP_UTF8, 0, str, -1, nullptr, 0);
    std::wstring wide_string(len - 1, L' ');
    MultiByteToWideChar(CP_UTF8, 0, str, -1, &wide_string[0], len);

    return wide_string;
}

extern "C" __declspec(dllexport) const wchar_t* appendString(const char* input_string) {

    std::wstring modified_string = ConvertToWString(input_string);
    MessageBoxW(NULL, modified_string.c_str(), L"Debug", MB_OK);

    return 0;
}

A_Err EntryPointFunc(
    struct SPBasicSuite* pica_basicP,
    A_long major_versionL,
    A_long minor_versionL,
    AEGP_PluginID aegp_plugin_id,
    AEGP_GlobalRefcon* global_refconV
) {
    g_plugin_id = aegp_plugin_id;
    g_sp_basic_suite = pica_basicP;
    AEGP_SuiteHandler suites(pica_basicP);

    return A_Err_NONE;
}

var pluginPath = "C:/Program Files/Adobe/Common/Plug-ins/7.0/MediaCore/SaveImage/";
var pluginLibName = "SaveImage.aex";
var pluginLib = new ExternalObject("lib:" + pluginPath + pluginLibName);
                
var inputString = "My text";
pluginLib.appendString(inputString);