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Basic concepts


The Windows Runtime (WinRT) is a suite of APIs and architectural model, introduced in Windows 8, that powers the latest generation of Windows APIs. It is an evolution of the COM API that is designed for access from a variety of languages. WinRT introduces standardized interfaces for collections (e.g. IVector), as well as support for generic types and asynchronous programming models.

dartwinrt provides an idiomatic Dart projection of modern WinRT APIs using FFI. This allows you to use WinRT APIs in your Dart applications, including Flutter apps with minimal effort. It consists of 18 packages, each of which corresponds to a top-level namespace (e.g. windows_globalization package contains the WinRT APIs from the Windows.Globalization namespace).

Typically, you would import only the packages that provide the specific WinRT APIs that your application requires. For example, to use the Calendar class from the Windows.Globalization namespace, you would import the windows_globalization package as follows:

import 'package:windows_globalization/windows_globalization.dart';

The WinRT APIs that are projected by dartwinrt are limited, but additional APIs will be added based on user demand, especially if it helps facilitate the development of new Dart packages for Windows.

If you encounter any issues or have any feature requests, please submit them through the issue tracker.


dartwinrt is under active development and is considered unstable, which means breaking changes are expected. Additionally, it is worth noting that there are some known limitations associated with it.

Initializing the WinRT

dartwinrt automatically initializes WinRT using a multi-threaded apartment (MTA) when necessary. Therefore, in most cases, you do not need to undertake any extra measures to begin calling WinRT APIs.


Keep in mind that, if you need to call WinRT APIs that only work in a single-threaded apartment (STA), you must initialize WinRT with a STA by calling the RoInitialize(RO_INIT_TYPE.RO_INIT_SINGLETHREADED) function.

Calling WinRT APIs

Calling WinRT APIs is pretty straightforward. To illustrate, here is a simple example that demonstrates how to retrieve the current DateTime from the Calendar class:

import 'package:windows_globalization/windows_globalization.dart';

void main() {
final calendar = Calendar(); // Create a new Calendar object
final currentDateTime = calendar.getDateTime(); // Get the current DateTime
print(currentDateTime); // e.g. 2023-05-11 13:47:21.380001Z

Releasing WinRT objects

In general, releasing WinRT objects isn't something you need to worry about, because when the object becomes inaccessible to the program, the Finalizer automatically releases it for you.


If you are manually managing the lifetime of an object, such as by calling the .detach() method, then it is important to ensure that you release it properly by calling the .release() method. Additionally, you should free up the memory that was allocated for the object by calling the free() helper function as follows:

calendar.release(); // Release the WinRT object
free(calendar.ptr); // Release the allocated memory for the object

This is necessary to prevent memory leaks and ensure that the memory used by the object is properly released.


It is important to include this code as part of a try / finally block to ensure that the object is released properly, even if an exception is thrown during the execution of your code.