Correct way to use multiple .IDL (MIDL) files within a single "Windows Runtime Component C++/WinRT" project

user_8047069 0
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Visual Studio 2019. Windows Runtime Component C++/WinRT project.

How do I follow and implement the recommendation: "We recommend that you declare each runtime class in its own Interface Definition Language (IDL) (.idl) file, in order to optimize build performance when you edit an IDL file, and for logical correspondence of an IDL file to its generated source code files. Visual Studio merges all of the resulting .winmd files into a single file with the same name as the root namespace. That final .winmd file will be the one that the consumers of your component will reference."

https://docs.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/author-apis

Within the same project I can add a second (third and so on) .IDL file using Project->Add New Item->Midl File (.idl). This seems to work ok?! I then manually add associated .h and .cpp files for each .IDL file. Build to generate stub files then manually copy and "fill in" these files before a final build which is successful. In this way I have a single IDL file per runtime class with its associated headers and implementation files including any other files (c++ .h and .cpp files) needed for the implementation. As I need to add functionality to the interface I just edit the IDL file, rebuild and add functionality to the header and implementation C++ files.

Is this what was recommended?!?

When I add the .IDL file and then manually add an associated .h and .cpp they do not appear "under" the .IDL file as the original ones did when I created the new project. Is this just a visual nicety of Solution Explorer OR is this indicating that I have something wrong?!?

I plan to have multiple "C++/WinRT WRC" projects (one for each namespace, each consisting of multiple runtimeclass interfaces with separate .IDL/.h/.cpp files as described above. Then I reference all of the projects (project to project) in my single C#/UWP App.

I am actually trying to implement a user interface to allow me to utilise a large code base of math/engineering C++ classes that implement a very specific & proprietary type of electronic circuit simulation already existing and programmed in C++ and compiled as a console app. The user data in and out is relatively small compared to the processing that takes place to generate the output.

c++-winrt windows-runtime visual-studio
2 Answers

It looks like you are handling the idl files correctly and that behavior is the same as I experienced when just adding a new Midl file directly.

If you like the look of having the .h and .cpp files "under" the .idl file in the tree you can try adding a new View Model instead of a new Midl file. This will create the .idl/.h/.cpp files all with the same name and place the .h and .cpp files visually under the Midl file. The idl template you get this way is for a basic runtime class.

user_108683040

When creating a new Windows Runtime Component, the .idl and the .h are usually grouped under the .cpp, not the .idl, but whatever your preference. There isn't a template to add a Runtime Class, which is pretty dumb. One fix for this could be as follows:

This is not a perfect solution, but is the easiest. Create a new Windows Runtime Component. Open Project>Export Template. Select Export Item. Select the Runtime Class under the new component. Export with Automatic Import option checked. Save your project and exit VS. Open your project. You can now add a fully templated Windows Runtime Class by simply adding item>Runtime Class. However, there will still be no dependencies (there may be a tool for custom nesting, but not in community as far as I can see). To fix this, after adding the files, save the project. Edit the project file (use notepad++ or even unload project, edit) and add the property <DependentUpon>Runtime Class.idl</DependentUpon> between your .cpp and .h file delimiters. Save the project file and reload. Probably want to do this in batches.

The alternative is to write a .vsix to either add the files and edit the project file, or have a right click command that runs on a .cpp and edits the project file, adding the DependentUpon directive. I can't find a 2022 functional .vsix for this. I will post one if I make one.

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