Fail to create instance of ITaskbarList3

Question

I'm learning the new Java FFM API. During the learning, I decided to use Windows SDK to control Taskbar.

The interface ITtaskbarList3 represents the Taskbar and provides functions to control it.

I used the jextract tool to generate necessary classes:

jextract --output target/generated-sources/jextract -t "taskbar_test.gen" -l :shell32 -l :Explorerframe -l :ole32 -I "C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\shared" -I "C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um" -I "C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\km" -I "C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\km\crt" "C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um\ShObjIdl_core.h"

In the code below, I'm trying to obtain CLSID and IID from string and use them to obtain an instance of ITaskbarList3:


package taskbar_test;

import taskbar_test.gen.CLSID;
import taskbar_test.gen.ShObjIdl_core_h;

import java.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;

public class ComStart {

    public static final String GUID_FORMAT = "{%s}";
    
    // CLSID of ITaskbarList3
    public static final String CLSID_CONST = "56FDF344-FD6D-11d0-958A-006097C9A090";
    // IID of ITaskbarList3
    public static final String IID_CONST = "EA1AFB91-9E28-4B86-90E9-9E9F8A5EEFAF";

    public static void main(String[] args) {

            try (var arena = Arena.ofConfined()) {
                // https://learn.microsoft.com/en-us/windows/win32/api/combaseapi/nf-combaseapi-clsidfromstring#remarks
                // The CLSID format is {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}.
                var clsidString = arena.allocateFrom(GUID_FORMAT.formatted(CLSID_CONST));
                var iidString = arena.allocateFrom(GUID_FORMAT.formatted(IID_CONST));
                var clsid = arena.allocate(CLSID.layout());
                var iid = arena.allocate(CLSID.layout());
                var taskbarPtr = arena.allocate(ShObjIdl_core_h.C_POINTER);

                int hr = ShObjIdl_core_h.CoInitializeEx(MemorySegment.NULL, ShObjIdl_core_h.COINIT_MULTITHREADED());
                if (hr != ShObjIdl_core_h.S_OK()) {
                    throw new RuntimeException("CoInitialize failed with error code: " + hr);
                }

                hr = ShObjIdl_core_h.CLSIDFromString(clsidString, clsid);
                if (hr != ShObjIdl_core_h.S_OK()) {
                    throw new RuntimeException("CLSIDFromString failed with error code: " + hr);
                }
                
                hr = ShObjIdl_core_h.IIDFromString(iidString, iid);
                if (hr != ShObjIdl_core_h.S_OK()) {
                    throw new RuntimeException("IIDFromString failed with error code: " + hr);
                }

                hr = ShObjIdl_core_h.CoCreateInstance(clsid, MemorySegment.NULL, ShObjIdl_core_h.CLSCTX_REMOTE_SERVER(), iid, taskbarPtr);
                if (hr != ShObjIdl_core_h.S_OK()) {
                    if (hr == ShObjIdl_core_h.REGDB_E_CLASSNOTREG()) {
                        System.out.println("COM class is not registered!");
                    }
                    throw new RuntimeException("CoCreateInstance failed with error code: " + hr);
                }

            } finally {
                ShObjIdl_core_h.CoUninitialize();
            }
    }

}

I expect to get the instance, but instead I get error from function CLSIDFromString that the string does not have correct format. I do not understand why, because the format is following documentation.

How the code should look like to be able to obtain instance correctly so I can manage taskbar, namely set progress value.

Thank you.

On a side note - per MSDN documentation, your app must wait to receive the TaskbarButtonCreated message before it can use the ITaskBarList... interfaces. — Remy Lebeau
– Remy Lebeau, Commented Jan 19 at 16:50
@PetrŠtechmüller - you should answer yourself with all details/changes if your problem is solved — Simon Mourier
– Simon Mourier, Commented Jan 19 at 17:10
Oh my bad. It works in the way I'm able to create an instance. I will post the final code asap. — Petr Štechmüller
– Petr Štechmüller, Commented Jan 19 at 17:31

Petr Štechmüller · Accepted Answer · 2025-01-19 19:33:56Z

Thanks to advices from all, I was able to create following code:

package taskbar_test;

import taskbar_test.gen.CLSID;
import taskbar_test.gen.ShObjIdl_core_h;

import java.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;
import java.nio.charset.StandardCharsets;

public class ComStart {

    public static final String GUID_FORMAT = "{%s}";
    
    // CLSID of ITaskbarList3
    public static final String CLSID_CONST = "56FDF344-FD6D-11d0-958A-006097C9A090";
    // IID of ITaskbarList3
    public static final String IID_CONST = "EA1AFB91-9E28-4B86-90E9-9E9F8A5EEFAF";

    public static void main(String[] args) {

            try (var arena = Arena.ofConfined()) {
                // https://learn.microsoft.com/en-us/windows/win32/api/combaseapi/nf-combaseapi-clsidfromstring#remarks
                // The CLSID format is {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}.
                var clsidString = arena.allocateFrom(GUID_FORMAT.formatted(CLSID_CONST), StandardCharsets.UTF_16LE);
                var iidString = arena.allocateFrom(GUID_FORMAT.formatted(IID_CONST), StandardCharsets.UTF_16LE);
                var clsid = arena.allocate(CLSID.layout());
                var iid = arena.allocate(CLSID.layout());
                var taskbarPtr = arena.allocate(ShObjIdl_core_h.C_POINTER);

                int hr = ShObjIdl_core_h.CoInitializeEx(MemorySegment.NULL, ShObjIdl_core_h.COINIT_MULTITHREADED());
                if (hr != ShObjIdl_core_h.S_OK()) {
                    throw new RuntimeException("CoInitialize failed with error code: " + hr);
                }

                hr = ShObjIdl_core_h.CLSIDFromString(clsidString, clsid);
                if (hr != ShObjIdl_core_h.S_OK()) {
                    throw new RuntimeException("CLSIDFromString failed with error code: " + hr);
                }
                
                hr = ShObjIdl_core_h.IIDFromString(iidString, iid);
                if (hr != ShObjIdl_core_h.S_OK()) {
                    throw new RuntimeException("IIDFromString failed with error code: " + hr);
                }

                hr = ShObjIdl_core_h.CoCreateInstance(clsid, MemorySegment.NULL, ShObjIdl_core_h.CLSCTX_ALL(), iid, taskbarPtr);
                if (hr != ShObjIdl_core_h.S_OK()) {
                    if (hr == ShObjIdl_core_h.REGDB_E_CLASSNOTREG()) {
                        System.out.println("COM class is not registered!");
                    }
                    throw new RuntimeException("CoCreateInstance failed with error code: " + hr);
                }

            } finally {
                ShObjIdl_core_h.CoUninitialize();
            }
    }

}

Now the instance is created correctly.

Just a tip: you can add import static taskbar_test.gen.ShObjIdl_core_h.*; so you don't have to prefix everything with ShObjIdl_core_h. if you want. Also, CLSID should have an allocate method that you can use to be a bit more concise CLSID.allocate(arena);

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