Dart/Win32

A package that wraps some of the most common Win32 API calls using FFI to make them accessible to Dart code without requiring a C compiler or the Windows SDK.

pub package Language Build

In addition to exposing the APIs themselves, this package offers a variety of instructive examples for more complex FFI usage scenarios.

By design, this package provides minimal modifications to the Win32 API to support Dart idioms. The goal is to provide high familiarity to an existing Win32 developer. Other plugins may build on these primitives to provide a friendly API for Dart and Flutter developers. A good example of that is filepicker_windows, which offers a common item dialog suitable for incorporation into an existing Flutter app.

Usage

This package lets you write apps that use the Windows API directly from Dart, by wrapping common Win32, COM and Windows Runtime APIs using Dart FFI.

You could use it to call a Win32 API like EnumFontFamiliesEx to enumerate all locally-installed fonts:

Fonts screenshot

or access system information that is not exposed directly by the Dart framework libraries:

System information screenshot

You could use it to build a Windows app with Flutter that relies on Win32 APIs:

Disk explorer screenshot

You could even use it to build a traditional Win32 app, written purely in Dart, that could have come straight out of a classic Charles Petzold book on programming Windows apps:

Dart notepad screenshot

or even, perhaps, a fully-fledged game using GDI:

Dart Tetris for Win32 screenshot

You might even build a package that depends upon it, like dart_console, which enables advanced console manipulation:

Dart console ANSI color demo screenshot

or filepicker_windows, which provides a modern Windows file picker for Flutter:

Windows file picker screenshot

Getting started

Many more samples can be found in the example\ subdirectory, along with a test suite in the test\ subdirectory that shows other API calls.

A good starting point is hello.dart. This example demonstrates creating a Win32 window and responding to common messages such as WM_PAINT through a WindowProc callback function.

To run it, type:

dart example\hello.dart

This should display a window with a text message.

This can be compiled into a standalone Win32 executable by running:

dart compile exe example\hello.dart -o example\bin\hello.exe

Samples

Dart samples

The package includes a number of examples in the example subdirectory. These examples use the Win32 API for all UI display and do not require Flutter.

ExampleDescription
hello.dartBasic Petzoldian "hello world" Win32 app
calendar.dartGets information about the calendar from a WinRT API
console.dartShows usage of console APIs
credentials.dartAdds a credential to the store and retrieves it
customwin.dartDisplays a non-rectangular window
devices.dartUses volume management APIs to list all disk devices
dialog.dartCreate a custom dialog box in code
dialogshow.dartCreates a common item dialog (file picker) using COM
dump.dartUse debugger libraries to print DLL exported functions
dynamic_load.dartDemonstrate loading a DLL and calling it at runtime
filever.dartGetting file version information from the file resource
guid.dartCreates a globally unique identifier (GUID)
knownfolder.dartRetrieves known folders from the current user profile
manifest\Demonstrates the use of app manifests for compiled apps
modules.dartEnumerates all loaded modules on the current system
monitor.dartUses DDC and monitor-config API to get monitor caps
msgbox.dartDemonstrates a MessageBox from the console
notepad\notepad.dartLightweight replica of the Windows notepad applet
paint.dartDemonstrates simple GDI drawing and min/max window sizing
play_sound.dartPlays a WAV file through the Windows PlaySound API
screenshot.dartTakes a screenshot of the current desktop
scroll.dartExample of horizontal and vertical scrolling text window
sendinput.dartSends keyboard and mouse input to another window
snake.dartSnake game using various GDI features
sysinfo.dartExamples of getting device information from native C APIs
tetris\main.dartPort of an open-source Tetris game to Dart
wallpaper.dartShows what wallpaper and background color are set
window.dartEnumerates open windows and basic window manipulation
winmd.dartInterrogate Windows Runtime types
wmi.dartUsing WMI from COM to retrieve device/OS information

Flutter samples

The explorer\ subdirectory contains an example of a simple Flutter app that uses the volume management Win32 APIs to find the disk drives connected to your computer and their volume IDs and attached paths.

Requirements

This package assumes the Dart 64-bit compiler, running on Windows. Many commands are tested on 32-bit Windows, but due to the lack of a compiler for 32-bit executables and the increasing lack of machines running 32-bit OSes, this is inevitably a low priority. The package is also tested on Windows-on-ARM architecture, running in x64 emulation mode.

Features and bugs

The current package only projects a subset of the Win32 API, but new APIs will be add based on user demand. I'm particularly interested in unblocking plugins for Windows. Please file feature requests and bugs at the issue tracker.

Disclaimer: This is a hobby project, and should not be viewed as having the same level of quality assurance as an official package from the Dart team. I'm a product manager having fun on my weekends!

Backwards compatibility

The library version uses semver, but you should not assume a strict guarantee of no breaking changes between minor versions. That guarantee is not possible to make, for several reasons:

  • Several times, my fixing a bug in the fidelity of the Win32 API has tightened the constraints over a parameter (for example, Pointer becomes Pointer<INPUT>). These changes should be signalled in the log.
  • Adding new features may itself cause a breaking change. For example, if you declare a missing Windows constant in your own code that is then added, Dart will complain about the duplicate definition.

One solution is to pin to a specific version of Win32, or declare a more tightly-bounded version dependency (e.g. '>=1.7.0 <1.8.0' rather than merely ^1.7.0). But the best approach is simply to test regularly with the latest version of this package, and continue to move your minimum forward. As the package matures, these issues should gradually fade away.

Acknowledgements

The Tetris example listed above is a fuller worked example of a reasonably complete program that uses the Dart Win32 package. It is a port of a C version of the game by Chang-Hung Liang. More information...

The C implementation of Snake is by David Jones, and is ported with his permission.

The original C version of the Notepad example was authored by Charles Petzold, and is kindly licensed by him without restriction.

The summary Win32 API documentation comments are licensed by Microsoft under the Creative Commons Attribution 4.0 International Public License.

Libraries

win32
Support for programming against the Win32 API on Windows operating systems. [...]