webview2-rs

https://github.com/wravery/webview2-rs
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webview2-rs provides Rust bindings for the WebView2 COM APIs, allowing Rust applications to embed...
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### Run sample app with cargo run --example sample

Source: https://github.com/wravery/webview2-rs/blob/main/README.md

Run the sample app from anywhere in the repository using the cargo run command with the sample example.

```cmd
> cargo run --example sample
```

--------------------------------

### GetAvailableCoreWebView2BrowserVersionString - Get installed runtime version

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Unsafe function that returns the version of the installed WebView2 runtime. The versioninfo parameter receives a pointer to the version string. Source: crates/bindings/src/bindings.rs:53.

```rust
pub unsafe fn GetAvailableCoreWebView2BrowserVersionString<P0>(
    browserexecutablefolder: P0,
    versioninfo: *mut windows_core::PWSTR,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<windows_core::PCWSTR>,

```

--------------------------------

### GetAvailableCoreWebView2BrowserVersionString

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Returns the version of the installed WebView2 runtime as a string.

```APIDOC
## GetAvailableCoreWebView2BrowserVersionString

### Description
Returns the version of the installed WebView2 runtime.

### Function Signature
rust
pub unsafe fn GetAvailableCoreWebView2BrowserVersionString<P0>(
    browserexecutablefolder: P0,
    versioninfo: *mut windows_core::PWSTR,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<windows_core::PCWSTR>,


### Parameters
- **browserexecutablefolder** (P0) - Required - Path to the browser executable folder.
- **versioninfo** (*mut windows_core::PWSTR) - Required - Pointer to receive the version string.

### Return Value
- `windows_core::Result<()>` - Indicates success or failure.

### Remarks
This function is unsafe and must be called within an unsafe block.
```

--------------------------------

### Basic wait_with_pump example

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com.md

Basic usage of wait_with_pump: spawns a thread that sends a value after 100ms, then waits while pumping messages. The function returns the received value, and the example asserts it equals 42.

```rust
use std::sync::mpsc;
use webview2_com::{wait_with_pump, Error};

let (tx, rx) = mpsc::channel();
std::thread::spawn(move || {
    std::thread::sleep(std::time::Duration::from_millis(100));
    tx.send(42u32).unwrap();
});

// Pumps UI messages until the spawned thread delivers 42.
let value: u32 = wait_with_pump(rx)?;
assert_eq!(value, 42);
# Ok::<(), webview2_com::Error>(())
```

--------------------------------

### wait_with_pump error handling example

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com.md

Example with error handling: drops the sender to simulate a worker failure, then matches on the result. Shows handling of TaskCanceled and other errors. Note that a dropped sender alone does not produce SendError.

```rust
use webview2_com::Error;

let (tx, rx) = mpsc::channel();
// Simulate a worker that fails before sending.
drop(tx);

match wait_with_pump::<u32>(rx) {
    Ok(value) => println!("got {value}"),
    Err(Error::TaskCanceled) => println!("message loop quit before the result arrived"),
    Err(err) => println!("other error: {err:?}"),
}
```

--------------------------------

### GetAvailableCoreWebView2BrowserVersionStringWithOptions - Version lookup with options

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Unsafe function that retrieves the installed WebView2 runtime version while honoring release-channel options. The versioninfo parameter receives the version string. Source: crates/bindings/src/bindings.rs:70.

```rust
pub unsafe fn GetAvailableCoreWebView2BrowserVersionStringWithOptions<P0, P1>(
    browserexecutablefolder: P0,
    environmentoptions: P1,
    versioninfo: *mut windows_core::PWSTR,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<windows_core::PCWSTR>,
    P1: windows_core::Param<ICoreWebView2EnvironmentOptions>,

```

--------------------------------

### Catching webview2_com::Error variants

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/errors.md

Shows how to catch and match on each variant of webview2_com::Error. The example drops the sender before calling wait_with_pump to force a SendError, but the match handles all variants. Use this pattern when you need to distinguish COM failures, application errors, task cancellation, and channel send failures.

```rust
use webview2_com::{Error, wait_with_pump};
use std::sync::mpsc;

let (tx, rx) = mpsc::channel();
drop(tx); // receiver gone before any value

match wait_with_pump::<u32>(rx) {
    Ok(v) => println!("{v}"),
    Err(err) => match err {
        Error::WindowsError(werr) => println!("COM failure: {werr}"),
        Error::CallbackError(msg) => println!("app error: {msg}"),
        Error::TaskCanceled => println!("WM_QUIT while waiting"),
        Error::SendError => println!("channel send failed"),
    },
}
```

--------------------------------

### WebView2 NuGet package constants

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/update-bindings.md

Constants defining the WebView2 SDK NuGet package name and version used by the update-bindings tool. The package is installed into OUT_DIR/Microsoft.Web.WebView2.1.0.3800.47 from https://api.nuget.org/v3/index.json.

```rust
const WEBVIEW2_NAME: &str = "Microsoft.Web.WebView2";
const WEBVIEW2_VERSION: &str = "1.0.3800.47";
```

--------------------------------

### CreateCoreWebView2EnvironmentWithOptions

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Creates a WebView2 environment with custom browser folder, user data folder, and options.

```APIDOC
## CreateCoreWebView2EnvironmentWithOptions

### Description
Creates a WebView2 environment with a custom browser executable folder, user data folder, and environment options.

### Function Signature
rust
pub unsafe fn CreateCoreWebView2EnvironmentWithOptions<P0, P1, P2, P3>(
    browserexecutablefolder: P0,
    userdatafolder: P1,
    environmentoptions: P2,
    environmentcreatedhandler: P3,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<windows_core::PCWSTR>,
    P1: windows_core::Param<windows_core::PCWSTR>,
    P2: windows_core::Param<ICoreWebView2EnvironmentOptions>,
    P3: windows_core::Param<ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler>,


### Parameters
- **browserexecutablefolder** (P0) - Required - Path to the browser executable folder.
- **userdatafolder** (P1) - Required - Path to the user data folder.
- **environmentoptions** (P2) - Required - Environment options.
- **environmentcreatedhandler** (P3) - Required - Handler invoked when the environment is created.

### Return Value
- `windows_core::Result<()>` - Indicates success or failure.

### Remarks
This function is unsafe and must be called within an unsafe block.
```

--------------------------------

### RAII variant of in-param example with CoTaskMemPWSTR

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/pwstr.md

RAII variant of the in-param example: CoTaskMemPWSTR automatically frees the allocated string when it goes out of scope, so no manual CoTaskMemFree call is needed.

```rust
use webview2_com::{
    pwstr::CoTaskMemPWSTR,
    Microsoft::Web::WebView2::Win32::*,
};

let webview: ICoreWebView2 = /* ... */ todo!();

let url = CoTaskMemPWSTR::from("https://example.com");
unsafe { webview.Navigate(*url.as_ref().as_pcwstr()) }?;
// url is freed automatically when it goes out of scope.
# Ok::<(), windows::core::Error>(())
```

--------------------------------

### CreateCoreWebView2Environment

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Creates a WebView2 environment with default options using the provided completed handler.

```APIDOC
## CreateCoreWebView2Environment

### Description
Creates a WebView2 environment with default options.

### Function Signature
rust
pub unsafe fn CreateCoreWebView2Environment<P0>(
    environmentcreatedhandler: P0,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler>,


### Parameters
- **environmentcreatedhandler** (P0) - Required - Handler invoked when the environment is created.

### Return Value
- `windows_core::Result<()>` - Indicates success or failure.

### Remarks
This function is unsafe and must be called within an unsafe block.
```

--------------------------------

### CreateCoreWebView2EnvironmentWithOptions - Create environment with custom options

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Unsafe function that creates a WebView2 environment with a custom browser executable folder, user data folder, and environment options. All parameters are required. Source: crates/bindings/src/bindings.rs:29.

```rust
pub unsafe fn CreateCoreWebView2EnvironmentWithOptions<P0, P1, P2, P3>(
    browserexecutablefolder: P0,
    userdatafolder: P1,
    environmentoptions: P2,
    environmentcreatedhandler: P3,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<windows_core::PCWSTR>,
    P1: windows_core::Param<windows_core::PCWSTR>,
    P2: windows_core::Param<ICoreWebView2EnvironmentOptions>,
    P3: windows_core::Param<ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler>,

```

--------------------------------

### Run update-bindings tool with cargo run update-bindings

Source: https://github.com/wravery/webview2-rs/blob/main/README.md

Build and run the update-bindings tool from the root of the repository to regenerate bindings after updating the winmd file.

```cmd
> cargo run update-bindings
```

--------------------------------

### event_callback usage example

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-macros.md

Example usage of the #[event_callback] attribute on a struct that implements a COM event-sink interface. The struct holds the event handler interface and optional WebView2 objects. The macro requires exactly two argument types.

```rust
#[event_callback]
pub struct NavigationCompletedEventHandler(
    ICoreWebView2NavigationCompletedEventHandler,
    Option<ICoreWebView2>,
    Option<ICoreWebView2NavigationCompletedEventArgs>,
);
```

--------------------------------

### Module structure of webview2-com-sys

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Shows the top-level module layout of the generated bindings crate, including the Microsoft.Web.WebView2.Win32 module and the declared_interfaces module. The include! macro pulls in the generated bindings.rs file.

```rust
pub mod Microsoft {
    pub mod Web {
        pub mod WebView2 {
            pub mod Win32 {
                mod windows_core {
                    macro_rules! link_webview2 { ... }
                    pub(crate) use ::windows_core::*;
                    pub(crate) use link_webview2 as link;
                }
                include!("bindings.rs");
            }
        }
    }
}

pub mod declared_interfaces;
```

--------------------------------

### Configure CoreWebView2EnvironmentOptions with custom scheme and release channels

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/options.md

Sets additional browser arguments, language, release channels, and a custom scheme registration on CoreWebView2EnvironmentOptions. The options struct is then converted into ICoreWebView2EnvironmentOptions for use with the async environment creation API. All operations are within an unsafe block as required by the COM API.

```rust
use webview2_com::{
    pwstr::pwstr_from_str,
    CoreWebView2CustomSchemeRegistration, CoreWebView2EnvironmentOptions,
    Microsoft::Web::WebView2::Win32::*,
};

let mut options = CoreWebView2EnvironmentOptions::default();

unsafe {
    options.set_additional_browser_arguments(String::from("--disable-features=Foo"));
    options.set_language(String::from("en-US"));
    options.set_release_channels(
        COREWEBVIEW2_RELEASE_CHANNELS_STABLE | COREWEBVIEW2_RELEASE_CHANNELS_BETA,
    );

    let mut scheme = CoreWebView2CustomSchemeRegistration::new(String::from("custom"));
    scheme.set_treat_as_secure(true);
    scheme.set_allowed_origins(vec![String::from("https://example.com")]);
    options.set_scheme_registrations(vec![Some(scheme.into())]);
}

// Pass to the async environment creation API. The options struct converts into
// ICoreWebView2EnvironmentOptions (and every other implemented interface).
let options: ICoreWebView2EnvironmentOptions = options.into();
# Ok::<(), webview2_com::Error>(())
```

--------------------------------

### Usage of #[completed_callback] on a tuple struct

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-macros.md

Example usage of the #[completed_callback] attribute on a tuple struct, as seen in callback.rs. The struct fields are parsed as (interface, arg_1, arg_2?) where arg_2 is optional.

```rust
#[completed_callback]
pub struct CreateCoreWebView2EnvironmentCompletedHandler(
    ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler,
    HRESULT,
    Option<ICoreWebView2Environment>,
);
```

--------------------------------

### Root module re-exports (src/lib.rs)

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com.md

This is the entire `src/lib.rs` file. It re-exports the `Microsoft` namespace from `webview2-com-sys` and the `pub use` statements for `callback`, `options`, and `pwstr` submodules. The `#[macro_use] extern crate webview2_com_macros;` makes the `#[completed_callback]` and `#[event_callback]` attribute macros available inside the crate only.

```rust
extern crate webview2_com_sys;
pub use webview2_com_sys::Microsoft;

#[macro_use]
extern crate webview2_com_macros;

mod callback;
mod options;
mod pwstr;

pub use callback::*;
pub use options::*;
pub use pwstr::*;
```

--------------------------------

### Environment Options Accessors

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/options.md

Documentation for all accessor methods on the environment options type, including getters and setters for each option.

```APIDOC
## additional_browser_arguments

### Description
Returns the value of the `AdditionalBrowserArguments` option.

### Signature
`pub unsafe fn additional_browser_arguments(&self) -> &str`

### Parameters
None

### Returns
- `&str` - The additional browser arguments string.

### COM Equivalent
`ICoreWebView2EnvironmentOptions::AdditionalBrowserArguments`
```

```APIDOC
## set_additional_browser_arguments

### Description
Sets the value of the `AdditionalBrowserArguments` option.

### Signature
`pub unsafe fn set_additional_browser_arguments(&self, value: String)`

### Parameters
- `value` (String) - The additional browser arguments string.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions::SetAdditionalBrowserArguments`
```

```APIDOC
## language

### Description
Returns the value of the `Language` option.

### Signature
`pub unsafe fn language(&self) -> &str`

### Parameters
None

### Returns
- `&str` - The language string.

### COM Equivalent
`ICoreWebView2EnvironmentOptions::Language`
```

```APIDOC
## set_language

### Description
Sets the value of the `Language` option.

### Signature
`pub unsafe fn set_language(&self, value: String)`

### Parameters
- `value` (String) - The language string.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions::SetLanguage`
```

```APIDOC
## target_compatible_browser_version

### Description
Returns the value of the `TargetCompatibleBrowserVersion` option.

### Signature
`pub unsafe fn target_compatible_browser_version(&self) -> &str`

### Parameters
None

### Returns
- `&str` - The target compatible browser version string.

### COM Equivalent
`ICoreWebView2EnvironmentOptions::TargetCompatibleBrowserVersion`
```

```APIDOC
## set_target_compatible_browser_version

### Description
Sets the value of the `TargetCompatibleBrowserVersion` option.

### Signature
`pub unsafe fn set_target_compatible_browser_version(&self, value: String)`

### Parameters
- `value` (String) - The target compatible browser version string.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions::SetTargetCompatibleBrowserVersion`
```

```APIDOC
## allow_single_sign_on_using_os_primary_account

### Description
Returns the value of the `AllowSingleSignOnUsingOSPrimaryAccount` option.

### Signature
`pub unsafe fn allow_single_sign_on_using_os_primary_account(&self) -> bool`

### Parameters
None

### Returns
- `bool` - Whether single sign-on using the OS primary account is allowed.

### COM Equivalent
`ICoreWebView2EnvironmentOptions::AllowSingleSignOnUsingOSPrimaryAccount`
```

```APIDOC
## set_allow_single_sign_on_using_os_primary_account

### Description
Sets the value of the `AllowSingleSignOnUsingOSPrimaryAccount` option.

### Signature
`pub unsafe fn set_allow_single_sign_on_using_os_primary_account(&self, value: bool)`

### Parameters
- `value` (bool) - Whether single sign-on using the OS primary account is allowed.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions::SetAllowSingleSignOnUsingOSPrimaryAccount`
```

```APIDOC
## exclusive_user_data_folder_access

### Description
Returns the value of the `ExclusiveUserDataFolderAccess` option.

### Signature
`pub unsafe fn exclusive_user_data_folder_access(&self) -> bool`

### Parameters
None

### Returns
- `bool` - Whether exclusive user data folder access is enabled.

### COM Equivalent
`ICoreWebView2EnvironmentOptions2::ExclusiveUserDataFolderAccess`
```

```APIDOC
## set_exclusive_user_data_folder_access

### Description
Sets the value of the `ExclusiveUserDataFolderAccess` option.

### Signature
`pub unsafe fn set_exclusive_user_data_folder_access(&self, value: bool)`

### Parameters
- `value` (bool) - Whether exclusive user data folder access is enabled.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions2::SetExclusiveUserDataFolderAccess`
```

```APIDOC
## is_custom_crash_reporting_enabled

### Description
Returns the value of the `IsCustomCrashReportingEnabled` option.

### Signature
`pub unsafe fn is_custom_crash_reporting_enabled(&self) -> bool`

### Parameters
None

### Returns
- `bool` - Whether custom crash reporting is enabled.

### COM Equivalent
`ICoreWebView2EnvironmentOptions3::IsCustomCrashReportingEnabled`
```

```APIDOC
## set_is_custom_crash_reporting_enabled

### Description
Sets the value of the `IsCustomCrashReportingEnabled` option.

### Signature
`pub unsafe fn set_is_custom_crash_reporting_enabled(&self, value: bool)`

### Parameters
- `value` (bool) - Whether custom crash reporting is enabled.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions3::SetIsCustomCrashReportingEnabled`
```

```APIDOC
## scheme_registrations

### Description
Returns the custom scheme registrations.

### Signature
`pub unsafe fn scheme_registrations(&self) -> Vec<Option<ICoreWebView2CustomSchemeRegistration>>`

### Parameters
None

### Returns
- `Vec<Option<ICoreWebView2CustomSchemeRegistration>>` - The list of custom scheme registrations.

### COM Equivalent
`IFixedEnvironmentOptions4::GetCustomSchemeRegistrations`
```

```APIDOC
## set_scheme_registrations

### Description
Sets the custom scheme registrations.

### Signature
`pub unsafe fn set_scheme_registrations(&self, value: Vec<Option<ICoreWebView2CustomSchemeRegistration>>)`

### Parameters
- `value` (Vec<Option<ICoreWebView2CustomSchemeRegistration>>) - The list of custom scheme registrations.

### Returns
None

### COM Equivalent
`IFixedEnvironmentOptions4::SetCustomSchemeRegistrations`
```

```APIDOC
## enable_tracking_prevention

### Description
Returns the value of the `EnableTrackingPrevention` option.

### Signature
`pub unsafe fn enable_tracking_prevention(&self) -> bool`

### Parameters
None

### Returns
- `bool` - Whether tracking prevention is enabled.

### COM Equivalent
`ICoreWebView2EnvironmentOptions5::EnableTrackingPrevention`
```

```APIDOC
## set_enable_tracking_prevention

### Description
Sets the value of the `EnableTrackingPrevention` option.

### Signature
`pub unsafe fn set_enable_tracking_prevention(&self, value: bool)`

### Parameters
- `value` (bool) - Whether tracking prevention is enabled.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions5::SetEnableTrackingPrevention`
```

```APIDOC
## are_browser_extensions_enabled

### Description
Returns the value of the `AreBrowserExtensionsEnabled` option.

### Signature
`pub unsafe fn are_browser_extensions_enabled(&self) -> bool`

### Parameters
None

### Returns
- `bool` - Whether browser extensions are enabled.

### COM Equivalent
`ICoreWebView2EnvironmentOptions6::AreBrowserExtensionsEnabled`
```

```APIDOC
## set_are_browser_extensions_enabled

### Description
Sets the value of the `AreBrowserExtensionsEnabled` option.

### Signature
`pub unsafe fn set_are_browser_extensions_enabled(&self, value: bool)`

### Parameters
- `value` (bool) - Whether browser extensions are enabled.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions6::SetAreBrowserExtensionsEnabled`
```

```APIDOC
## channel_search_kind

### Description
Returns the value of the `ChannelSearchKind` option.

### Signature
`pub unsafe fn channel_search_kind(&self) -> COREWEBVIEW2_CHANNEL_SEARCH_KIND`

### Parameters
None

### Returns
- `COREWEBVIEW2_CHANNEL_SEARCH_KIND` - The channel search kind.

### COM Equivalent
`ICoreWebView2EnvironmentOptions7::ChannelSearchKind`
```

```APIDOC
## set_channel_search_kind

### Description
Sets the value of the `ChannelSearchKind` option.

### Signature
`pub unsafe fn set_channel_search_kind(&self, value: COREWEBVIEW2_CHANNEL_SEARCH_KIND)`

### Parameters
- `value` (COREWEBVIEW2_CHANNEL_SEARCH_KIND) - The channel search kind.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions7::SetChannelSearchKind`
```

```APIDOC
## release_channels

### Description
Returns the value of the `ReleaseChannels` option.

### Signature
`pub unsafe fn release_channels(&self) -> COREWEBVIEW2_RELEASE_CHANNELS`

### Parameters
None

### Returns
- `COREWEBVIEW2_RELEASE_CHANNELS` - The release channels.

### COM Equivalent
`ICoreWebView2EnvironmentOptions7::ReleaseChannels`
```

```APIDOC
## set_release_channels

### Description
Sets the value of the `ReleaseChannels` option.

### Signature
`pub unsafe fn set_release_channels(&self, value: COREWEBVIEW2_RELEASE_CHANNELS)`

### Parameters
- `value` (COREWEBVIEW2_RELEASE_CHANNELS) - The release channels.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions7::SetReleaseChannels`
```

```APIDOC
## scroll_bar_style

### Description
Returns the value of the `ScrollBarStyle` option.

### Signature
`pub unsafe fn scroll_bar_style(&self) -> COREWEBVIEW2_SCROLLBAR_STYLE`

### Parameters
None

### Returns
- `COREWEBVIEW2_SCROLLBAR_STYLE` - The scroll bar style.

### COM Equivalent
`ICoreWebView2EnvironmentOptions8::ScrollBarStyle`
```

```APIDOC
## set_scroll_bar_style

### Description
Sets the value of the `ScrollBarStyle` option.

### Signature
`pub unsafe fn set_scroll_bar_style(&self, value: COREWEBVIEW2_SCROLLBAR_STYLE)`

### Parameters
- `value` (COREWEBVIEW2_SCROLLBAR_STYLE) - The scroll bar style.

### Returns
None

### COM Equivalent
`ICoreWebView2EnvironmentOptions8::SetScrollBarStyle`
```

--------------------------------

### Callback API

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/callback.md

Documentation for closure type aliases and generated callback structs in the webview2-com crate.

```APIDOC
## `CompletedClosure<Arg1, Arg2>`

### Description
Generic closure signature for `completed_callback` types. It is a `FnOnce` closure that is stored in an `UnsafeCell<Option<...>>` and taken on the first COM `Invoke`. Subsequent `Invoke` calls are no-ops returning `Ok(())`.

### Type Alias
```rust
pub type CompletedClosure<Arg1, Arg2> = Box<
    dyn FnOnce(
        <Arg1 as ClosureArg>::Output,
        <Arg2 as ClosureArg>::Output,
    ) -> ::windows::core::Result<()>,
>;
```

### Parameters
- `Arg1` - A type implementing `ClosureArg`; its `Output` is the first argument to the closure.
- `Arg2` - A type implementing `ClosureArg`; its `Output` is the second argument to the closure.

### Return Value
- `::windows::core::Result<()>` - The closure returns a Windows result indicating success or failure.

## `EventClosure<Arg1, Arg2>`

### Description
Generic closure signature for `event_callback` types. It is a `FnMut` closure that is stored directly in an `UnsafeCell<...>` and called on every COM `Invoke`.

### Type Alias
```rust
pub type EventClosure<Arg1, Arg2> = Box<
    dyn FnMut(
        <Arg1 as ClosureArg>::Output,
        <Arg2 as ClosureArg>::Output,
    ) -> windows::core::Result<()>,
>;
```

### Parameters
- `Arg1` - A type implementing `ClosureArg`; its `Output` is the first argument to the closure.
- `Arg2` - A type implementing `ClosureArg`; its `Output` is the second argument to the closure.

### Return Value
- `windows::core::Result<()>` - The closure returns a Windows result indicating success or failure.

## Generated callback structs

### Description
Every generated callback struct has the shape shown below. The struct implements a COM interface and provides `create` and (for completed callbacks) `wait_for_async_operation` methods.

### Struct Definition
```rust
type <Name>Closure = CompletedClosure<Arg1, Arg2>;   // private module-level alias

#[implement(<COM interface>)]
pub struct <Name>(::std::cell::UnsafeCell<Option<<Name>Closure>>);

impl <Name> {
    pub fn create(closure: <Name>Closure) -> <COM interface>;
    pub fn wait_for_async_operation(
        closure: Box<dyn FnOnce(<COM interface>) -> crate::Result<()>>,
        completed: <Name>Closure,
    ) -> crate::Result<()>;
}

impl <Name>_Impl for <Name>_Impl {
    fn Invoke<'a>(&self, arg1: ..., arg2: ...) -> ::windows::core::Result<()>;
}
```

### `create`

#### Description
Wraps the closure in the struct and converts it into the COM interface pointer. Return the interface and hand it to the raw binding, e.g. `webview.add_NavigationCompleted(&handler, &mut token)`.

#### Signature
```rust
pub fn create(closure: <Name>Closure) -> <COM interface>
```

#### Parameters
- `closure` (`<Name>Closure`) - The closure to wrap.

#### Return Value
- `<COM interface>` - The COM interface pointer.

### `wait_for_async_operation`

#### Description
Only exists on `#[completed_callback]` types. Combines the pattern of calling an async COM operation that receives a completed handler, then synchronously waiting for the handler to fire. It creates an `mpsc` channel, wraps the `completed` closure to send its result over the channel, calls the caller's closure with the handler interface, and then blocks on the UI thread while pumping messages until the handler fires (or `WM_QUIT` aborts).

#### Signature
```rust
pub fn wait_for_async_operation(
    closure: Box<dyn FnOnce(<COM interface>) -> crate::Result<()>>,
    completed: <Name>Closure,
) -> crate::Result<()>
```

#### Parameters
- `closure` (`Box<dyn FnOnce(<COM interface>) -> crate::Result<()>>`) - The caller's closure that receives the handler interface and must invoke the async WebView2 method with it.
- `completed` (`<Name>Closure`) - The completed handler closure.

#### Return Value
- `crate::Result<()>` - Returns `Err(Error::WindowsError(...))` if the closure's error mapping produced one, `Err(Error::TaskCanceled)` if the message loop quit, or otherwise transports the closure's own error result.

```

--------------------------------

### Using the generated callback in consumer code

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-macros.md

Consumer code that uses the generated ZoomFactorChangedEventHandler. It creates a handler with a closure that receives the controller and unknown arguments, then adds it to the controller. The example returns a Result with windows::core::Error.

```rust
use webview2_com::ZoomFactorChangedEventHandler;

let handler = ZoomFactorChangedEventHandler::create(Box::new(|controller, _unknown| {
    if let Some(controller) = controller {
        unsafe { println!("zoom now {}", controller.ZoomFactor()?) };
    }
    Ok(())
}));

let mut token = 0;
unsafe { controller.add_ZoomFactorChanged(&handler, &mut token)? };
# Ok::<(), windows::core::Error>(())
```

--------------------------------

### CreateCoreWebView2Environment - Create environment with default options

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Unsafe function that creates a WebView2 environment using default options. The environmentcreatedhandler callback is required. Source: crates/bindings/src/bindings.rs:19.

```rust
pub unsafe fn CreateCoreWebView2Environment<P0>(
    environmentcreatedhandler: P0,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler>,

```

--------------------------------

### Run all tests with cargo test

Source: https://github.com/wravery/webview2-rs/blob/main/README.md

Run all tests from the root of the repository using the cargo test command.

```cmd
> cargo test
```

--------------------------------

### Generate bindings.rs with windows-bindgen

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/update-bindings.md

Invokes the windows-bindgen 0.66 CLI to regenerate bindings.rs. Inputs are the built-in 'default' metadata plus the winmd file; the output is compared byte-for-byte with the existing bindings.rs and only copied if different.

```rust
bindgen([
    "--in", "default",
    "--in", winmd_path,
    "--out", source_path,
    "--rustfmt",
    "--reference", "windows,skip-root,Windows",
    "--filter", "Microsoft.Web.WebView2.Win32",
    "--implement",
    "--flat",
    "--no-allow",
]).unwrap();
```

--------------------------------

### Wait for async operation with AddScriptToExecuteOnDocumentCreatedCompletedHandler::wait_for_async_operation

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/callback.md

Synchronously waits for an async operation using wait_for_async_operation on AddScriptToExecuteOnDocumentCreatedCompletedHandler. The first closure starts the async call, the second receives the result and sends it through an mpsc channel. Errors from the completed closure map to Error::WindowsError; on pump exit via WM_QUIT it returns Err(Error::TaskCanceled), and on GetMessageA failure it returns Err(Error::WindowsError(...)).

```rust
use std::sync::mpsc;
use windows::core::PCWSTR;
use webview2_com::{
    pwstr::pwstr_from_str,
    Microsoft::Web::WebView2::Win32::*, AddScriptToExecuteOnDocumentCreatedCompletedHandler, Error,
};

let webview: ICoreWebView2 = /* from ICoreWebView2Controller::CoreWebView2() */ todo!();

let (tx, rx) = mpsc::channel::<String>();

AddScriptToExecuteOnDocumentCreatedCompletedHandler::wait_for_async_operation(
    Box::new(move |handler| unsafe {
        // Kick the message pump afterwards if this runs on another thread.
        let js = pwstr_from_str("window.version = 1;");
        webview
            .AddScriptToExecuteOnDocumentCreated(PCWSTR(js.0), &handler)
            .map_err(Error::WindowsError)
    }),
    Box::new(move |error_code, id| {
        error_code?; // surface HRESULT failures
        let _ = tx.send(string_from_pcwstr(&id)); // id: String, produced by the PCWSTR conversion
        Ok(())
    }),
)?;

// wait_with_pump inside wait_for_async_operation pumped messages until Invoke fired.
# Ok::<(), webview2_com::Error>(())
```

--------------------------------

### create method signature

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/callback.md

Wraps the closure in the struct and converts it into the COM interface pointer. Return the interface and hand it to the raw binding, e.g. `webview.add_NavigationCompleted(&handler, &mut token)`.

```rust
pub fn create(closure: <Name>Closure) -> <COM interface>

```

--------------------------------

### take_pwstr

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/pwstr.md

Copies a PWSTR allocated with CoTaskMemAlloc to a String and frees the original buffer.

```APIDOC
## take_pwstr

### Description
Copies a PWSTR allocated with CoTaskMemAlloc to a String and frees the original buffer.

### Signature
pub fn take_pwstr(source: PWSTR) -> String

### Parameters
- **source** (PWSTR) - Required - The PWSTR to copy and free.

### Return Value
- **String** - The copied string.

### Behavior
Wraps in CoTaskMemPWSTR::from(source), converts via Display, and frees the buffer on drop.

```

--------------------------------

### CoTaskMemPWSTR

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/pwstr.md

Documentation for the CoTaskMemPWSTR RAII holder, including its methods and trait implementations.

```APIDOC
## CoTaskMemPWSTR

### Description
RAII holder for a PWSTR which is allocated with Com::CoTaskMemAlloc and freed with Com::CoTaskMemFree when dropped. An owned, nullable PWSTR. The lifetime parameter ties it to the borrow of the buffer it wraps.

### Methods

#### as_mut
- **Signature**: `pub fn as_mut(&'a mut self) -> CoTaskMemMut<'a>`
- **Description**: Get a mutable PWSTR guard which borrows the pointer.

#### as_ref
- **Signature**: `pub fn as_ref(&'a self) -> CoTaskMemRef<'a>`
- **Description**: Get a constant PCWSTR guard which borrows the pointer.

#### take
- **Signature**: `pub fn take(&mut self) -> PWSTR`
- **Description**: Take the PWSTR pointer and hand off ownership so that it is not freed when the CoTaskMemPWSTR is dropped.

### Trait Implementations

#### Drop
- **Behavior**: Calls Com::CoTaskMemFree(Some(self.0.as_ptr() ...)) unless the pointer is null.

#### Default
- **Behavior**: Produces CoTaskMemPWSTR(PWSTR::null(), PhantomData).

#### From<PWSTR>
- **Behavior**: Adopts ownership of an existing PWSTR (freed on drop).

#### From<&str>
- **Behavior**: Allocates a CoTaskMemAlloc buffer, encodes the string as UTF-16 with a trailing NUL, and wraps it. The empty string produces the null pointer (Default::default()).

#### Display
- **Behavior**: Formats the pointed-to string via string_from_pcwstr (null pointer renders as the empty string).
```

--------------------------------

### CoreWebView2CustomSchemeRegistration::new

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/options.md

Creates a new CoreWebView2CustomSchemeRegistration for the given scheme name with default settings.

```APIDOC
## CoreWebView2CustomSchemeRegistration::new

### Description
Creates a registration for the given scheme name (e.g. `"custom"`). Initial state: `treat_as_secure = false`, `allowed_origins = []`, `has_authority_component = false`.

### Method
Constructor

### Signature
`pub fn new(scheme_name: String) -> Self`

### Parameters
- `scheme_name` (String) - Required - The scheme name to register.

### Returns
- `Self` - The new registration instance.
```

--------------------------------

### GetAvailableCoreWebView2BrowserVersionStringWithOptions

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Version lookup honoring release-channel options.

```APIDOC
## GetAvailableCoreWebView2BrowserVersionStringWithOptions

### Description
Version lookup honoring release-channel options.

### Function Signature
rust
pub unsafe fn GetAvailableCoreWebView2BrowserVersionStringWithOptions<P0, P1>(
    browserexecutablefolder: P0,
    environmentoptions: P1,
    versioninfo: *mut windows_core::PWSTR,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<windows_core::PCWSTR>,
    P1: windows_core::Param<ICoreWebView2EnvironmentOptions>,


### Parameters
- **browserexecutablefolder** (P0) - Required - Path to the browser executable folder.
- **environmentoptions** (P1) - Required - Environment options.
- **versioninfo** (*mut windows_core::PWSTR) - Required - Pointer to receive the version string.

### Return Value
- `windows_core::Result<()>` - Indicates success or failure.

### Remarks
This function is unsafe and must be called within an unsafe block.
```

--------------------------------

### CORE_WEBVIEW_TARGET_PRODUCT_VERSION constant

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

String constant for the default TargetCompatibleBrowserVersion used by CoreWebView2EnvironmentOptions::default(). Source: crates/bindings/src/bindings.rs:1013.

```rust
pub const CORE_WEBVIEW_TARGET_PRODUCT_VERSION: windows_core::PCWSTR =
    windows_core::w!("145.0.3800.47");
```

--------------------------------

### COREWEBVIEW2_WEB_RESOURCE_REQUEST_SOURCE_KINDS flags

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/types.md

Flags for the COREWEBVIEW2_WEB_RESOURCE_REQUEST_SOURCE_KINDS type, each defined as a constant with the given i32 value.

```rust
ALL = -1i32
DOCUMENT = 1i32
NONE = 0i32
SERVICE_WORKER = 4i32
SHARED_WORKER = 2i32
```

--------------------------------

### Plain structs from webview2-com-sys

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/types.md

Defines the COREWEBVIEW2_COLOR and COREWEBVIEW2_PHYSICAL_KEY_STATUS structs. COREWEBVIEW2_COLOR is the ARGB color used by ICoreWebView2Controller2::SetDefaultBackgroundColor; COREWEBVIEW2_PHYSICAL_KEY_STATUS is the key state passed to ICoreWebView2AcceleratorKeyPressedEventArgs.

```rust
pub struct COREWEBVIEW2_COLOR {
    pub A: u8,
    pub R: u8,
    pub G: u8,
    pub B: u8,
}

pub struct COREWEBVIEW2_PHYSICAL_KEY_STATUS {
    pub RepeatCount: u32,
    pub ScanCode: u32,
    pub IsExtendedKey: windows_core::BOOL,
    pub IsMenuKeyDown: windows_core::BOOL,
    pub WasKeyDown: windows_core::BOOL,
    pub IsKeyReleased: windows_core::BOOL,
}
```

--------------------------------

### Free functions for string conversion

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/pwstr.md

Free functions for converting between PCWSTR/PWSTR and String. string_from_pcwstr copies a const pointer, take_pwstr copies and frees a mutable pointer, and pwstr_from_str allocates a new PWSTR from a Rust string.

```rust
/// Copy a [`PCWSTR`] from an input param to a [`String`].
pub fn string_from_pcwstr(source: &PCWSTR) -> String

/// Copy a [`PWSTR`] allocated with [`Com::CoTaskMemAlloc`] from an input param to a [`String`]
/// and free the original buffer with [`Com::CoTaskMemFree`].
pub fn take_pwstr(source: PWSTR) -> String

/// Allocate a [`PWSTR`] with [`Com::CoTaskMemAlloc`] and copy a [`&str`] into it.
pub fn pwstr_from_str(source: &str) -> PWSTR
```

--------------------------------

### pwstr_from_str

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/pwstr.md

Allocates a PWSTR with CoTaskMemAlloc and copies a &str into it.

```APIDOC
## pwstr_from_str

### Description
Allocates a PWSTR with CoTaskMemAlloc and copies a &str into it.

### Signature
pub fn pwstr_from_str(source: &str) -> PWSTR

### Parameters
- **source** (&str) - Required - The string to copy.

### Return Value
- **PWSTR** - The allocated pointer. The caller owns it. Empty string yields a null pointer.

### Behavior
CoTaskMemPWSTR::from(source).take() — allocates and returns the raw pointer.

```

--------------------------------

### link_webview2! macro linking attributes

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Shows the cfg_attr attributes used by the link_webview2! macro to link against the correct WebView2 loader library. On MSVC targets it links the static library, on other targets it links the DLL import library.

```rust
#[cfg_attr(target_env = "msvc", link(name = "WebView2LoaderStatic", kind = "static"))]
#[cfg_attr(not(target_env = "msvc"), link(name = "WebView2Loader.dll"))]
```

--------------------------------

### CompareBrowserVersions

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/webview2-com-sys.md

Compares two browser version strings and stores the result (-1, 0, or 1) in the provided pointer.

```APIDOC
## CompareBrowserVersions

### Description
Compares two browser version strings; `result` receives `-1`, `0`, or `1`.

### Function Signature
rust
pub unsafe fn CompareBrowserVersions<P0, P1>(
    version1: P0,
    version2: P1,
    result: *mut i32,
) -> windows_core::Result<()>
where
    P0: windows_core::Param<windows_core::PCWSTR>,
    P1: windows_core::Param<windows_core::PCWSTR>,


### Parameters
- **version1** (P0) - Required - First version string.
- **version2** (P1) - Required - Second version string.
- **result** (*mut i32) - Required - Pointer to receive the comparison result (-1, 0, or 1).

### Return Value
- `windows_core::Result<()>` - Indicates success or failure.

### Remarks
This function is unsafe and must be called within an unsafe block.
```

--------------------------------

### CoTaskMemMut::as_pwstr

Source: https://github.com/wravery/webview2-rs/blob/main/_autodocs/api-reference/pwstr.md

Borrows the inner PWSTR for use as a COM out-parameter.

```APIDOC
## CoTaskMemMut::as_pwstr

### Description
Borrows the inner PWSTR for use as a COM out-parameter.

### Method
as_pwstr

### Signature
pub fn as_pwstr(&mut self) -> &'a PWSTR

### Parameters
None

### Return Value
- **&'a PWSTR** - A reference to the inner PWSTR.

```
Tokens:
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