webview2-rs

Rust bindings for the WebView2 COM APIs

Crates in this repo

The root of this repo defines a virtual workspace in Cargo.toml which includes three crates:

• webview2-com: The main crate, which depends on webview2-com-macros and webview2-com-sys.
• webview2-com-macros: Macros used to build boilerplate implementations of all the ICoreWebView2...Handler interfaces declared in WebView2.h.
• webview2-com-sys: Unsafe bindings built with the Windows crate.
• update-bindings: Utility to regenerate the bindings in webview2-com-sys from a new winmd file.

Windows Metadata

The Windows crate requires a Windows Metadata (winmd) file describing the API. The one used in this repo was generated with the webview2-win32md project.

Getting started

Run all the tests from the root of the repo:

> cargo test

Or run the sample app from anywhere in the repo:

> cargo run --example sample

See the README.md in webview2-com for more details about using that crate in your own project.

Cross-compilation

The update-bindings tool automatically downloads and extracts the NuGet package for the SDK and links against the libraries from that package. If you build on a Windows machine, you probably won't need to do anything special to enable this, but if you are building on a Linux or macOS machine, you need to have mono installed and on your $PATH to execute the nuget.exe CLI tool.

By default this crate uses the WebView2LoaderStatic.lib static library and does not need to redistribute WebView2Loader.dll. However, this doesn't work with the *-pc-windows-gnu targets instead of *-pc-windows-msvc (for example, when cross-compiling). For the gnu targets, it will link against the import lib for WebView2Loader.dll instead, and you will need to place this DLL next to your executable or in your $PATH so it can find the DLL at runtime.

Updating the WebView2 SDK

You can tell the update-bindings tool to use a different version by updating WEBVIEW2_VERSION in main.rs:

    const WEBVIEW2_VERSION: &str = "1.0.3296.44";

It will also regenerate declared_interfaces.rs if they change in a new version. This file is used in webview2-com, and in particular, the tests in callback.rs and options.rs verify that all of the interfaces listed in declared_interfaces.rs are implemented.

If a new version of the SDK declared additional callback interfaces, you will need to add those interfaces to callback.rs using the #[completed_callback] (for ICoreWebView2...CompletedHandler interfaces) and #[event_callback] (for ICoreWebView2...EventHandler interfaces) macros.

There is a special case for ICoreWebView2EnvironmentOptions4 which replaces that interface declaration with IFixedEnvironmentOptions4 because the windows_bindgen crate misunderstands the method signature on SetCustomSchemeRegistrations as having an out-param. Otherwise, when new ICoreWebView2EnvironmentOptions... interfaces are added, you will need to:

• Add the interface to the #[implement(...)] attribute on pub struct CoreWebView2EnvironmentOptions.
• Declare UnsafeCell<...> members in CoreWebView2EnvironmentOptions to hold the field values and initialize the defaults in impl Default for CoreWebView2EnvironmentOptions.
• Implement accessors in impl CoreWebView2EnvironmentOptions to get and set the UnsafeCell<...> member with appropriate Rust types.
• Add a trait impl ICoreWebView2EnvironmentOptions..._Impl for CoreWebView2EnvironmentOptions_Impl block to define the COM interface methods (typically in terms of the accessors in impl CoreWebView2EnvironmentOptions).

It does not regenerate the winmd file automatically because that would depend on having the dotnet CLI installed. New versions of the SDK should be backwards compatible, but you may want to regenerate the Microsoft.Web.WebView2.Win32.winmd file using webview2-win32md if you need functionality which was added in a new version. You should then copy the file to ./crates/update-bindings/winmd/Microsoft.Web.WebView2.Win32.winmd, which is where the update-bindings tool looks for it.

To run the update-bindings tool after updating the winmd file, build and run the tool without any additional arguments from the root of this repo:

> cargo run update-bindings