webview2/

lib.rs

#![doc = r###"
Rust bindings for
[WebView2](https://docs.microsoft.com/en-us/microsoft-edge/hosting/webview2):

> The Microsoft Edge WebView2 control enables you to embed web technologies
(HTML, CSS, and JavaScript) in your native applications. The WebView2 control
uses Microsoft Edge (Chromium) as the rendering engine to display the web
content in native applications. With WebView2, you may embed web code in
different parts of your native application, or build the entire native
application within a single WebView. For information on how to start building a
WebView2 application, see [Get
Started](https://docs.microsoft.com/en-us/microsoft-edge/webview2/#getting-started).

# API

The `webview2` crate contains high-level, idiomatic wrappers for the raw COM
APIs, which can be found in the `webview2-sys` crate.

The API mapping should be quite straightforward.

The `CreateCoreWebView2EnvironmentWithDetails` function does not have a direct
equivalent. It is replaced with a nicer `EnvironmentBuilder` API. The
`GetAvailableCoreWebView2BrowserVersionString` and `CompareBrowserVersions`
functions are also exposed through the builder.

# Runtime

The Edge browser from beta, dev or canary channels (>= 86.0.622.0) or the
[Evergreen WebView2
Runtime](https://docs.microsoft.com/en-us/microsoft-edge/webview2/concepts/distribution#understand-the-webview2-runtime-and-installer-preview)
need to be installed for this to actually work. Or the
[`build`](struct.EnvironmentBuilder.html#method.build) method will return an
error.

# WebView2Loader

A binary library `WebView2Loader` from the WebView2 SDK need to be used, either
the DLL `WebView2Loader.dll` or the static library `WebView2LoaderStatic.lib`.
This brings some complexities:

* When using the **gnu** toolchain, the static library does not seem to work so
  the `WebView2Loader.dll` DLL is used. You need to make sure that the DLL can
  be loaded at runtime, e.g. by **putting it alongside the built exe files**.

* When using the **msvc** toolchain, the static library is used. Make sure you
  have the **v142** toolset (or **visual studio 2019**), because the static
  library seem to be built with visual studio 2019 and could not be correctly
  linked by earlier versions of the visual studio. See [C++ binary compatibility
  between Visual Studio 2015, 2017, and
  2019](https://docs.microsoft.com/en-us/cpp/porting/binary-compat-2015-2017?view=vs-2019).

# Examples

See the `examples` directory, especially the heavily commented `win32` example.
"###]
#![cfg(windows)]
// Caused by the `com_interface` macro.
#![allow(clippy::cmp_null)]
#![allow(clippy::type_complexity)]
#![allow(clippy::upper_case_acronyms)]
#![allow(non_camel_case_types)]

use com::{interfaces::IUnknown, ComInterface, ComPtr, ComRc};
use std::cell::{Cell, RefCell};
use std::fmt;
use std::io;
use std::mem::{self, MaybeUninit};
use std::path::Path;
use std::ptr;
use webview2_sys::*;
use widestring::{NulError, WideCStr, WideCString};
use winapi::shared::minwindef::*;
use winapi::shared::ntdef::*;
use winapi::shared::windef::*;
use winapi::shared::winerror::{
    E_FAIL, E_INVALIDARG, E_NOINTERFACE, FACILITY_WIN32, HRESULT_CODE, HRESULT_FROM_WIN32,
    MAKE_HRESULT, SEVERITY_ERROR, SUCCEEDED, S_OK,
};
use winapi::um::combaseapi::{CoTaskMemAlloc, CoTaskMemFree};

static DEFAULT_TARGET_COMPATIBLE_BROWSER_VERSION: &str = "89.0.765";

/// Returns a pointer that implements the COM callback interface with the specified closure.
/// Inspired by C++ Microsoft::WRT::Callback.
#[macro_export]
macro_rules! callback {
    ($name:ident, move | $($arg:ident : $arg_type:ty),* $(,)?| -> $ret_type:ty { $($body:tt)* }) => {{
        #[com::co_class(implements($name))]
        struct Impl {
            cb: Box<dyn Fn($($arg_type),*) -> $ret_type>,
        }

        impl $name for Impl {
            unsafe fn invoke(&self, $($arg : $arg_type),*) -> $ret_type {
                let r = std::panic::catch_unwind(std::panic::AssertUnwindSafe(move || {
                    (self.cb)($($arg),*)
                }));
                match r {
                    Ok(r) => r,
                    Err(_) => {
                        eprintln!("webview2: panic in callback function. Aborting because it's UB to unwind across FFI boundaries.");
                        std::process::abort()
                    }
                }
            }
        }

        impl Impl {
            // It is never used.
            pub fn new() -> Box<Self> {
                unreachable!()
            }
            // Returns an owning ComPtr. Suitable for passing over FFI.
            // The receiver is responsible for releasing it.
            pub fn new_ptr(cb: impl Fn($($arg_type),*) -> $ret_type + 'static) -> com::ComPtr<dyn $name> {
                let e = Self::allocate(Box::new(cb));
                unsafe {
                    use com::interfaces::IUnknown;
                    e.add_ref();
                    com::ComPtr::<dyn $name>::new(Box::into_raw(e) as _)
                }
            }
        }

        Impl::new_ptr(move |$($arg : $arg_type),*| -> $ret_type { $($body)* })
    }}
}

// Call `AddRef` and convert to `ComRc`.
unsafe fn add_ref_to_rc<T: ComInterface + ?Sized>(
    ptr: *mut *mut <T as ComInterface>::VTable,
) -> ComRc<T> {
    let ptr = ComPtr::new(ptr);
    ptr.add_ref();
    ptr.upgrade()
}

include!("interfaces.rs");

// Put it in a module so that the `EnvironmentOptionsImplClassFactory` struct
// does not leak into our public API.
mod environment_options {
    use super::*;

    #[com::co_class(implements(ICoreWebView2EnvironmentOptions))]
    pub struct EnvironmentOptionsImpl {
        additional_browser_arguments: RefCell<Option<WideCString>>,
        language: RefCell<Option<WideCString>>,
        target_compatible_browser_version: RefCell<Option<WideCString>>,
        allow_single_sign_on_using_osprimary_account: Cell<bool>,
    }

    impl EnvironmentOptionsImpl {
        fn new() -> Box<Self> {
            unreachable!()
        }

        pub fn from_builder(
            builder: &EnvironmentBuilder,
        ) -> Result<*mut *mut ICoreWebView2EnvironmentOptionsVTable> {
            let additional_browser_arguments = if let Some(v) = builder.additional_browser_arguments
            {
                Some(WideCString::from_str(v)?)
            } else {
                None
            };
            let language = if let Some(v) = builder.language {
                Some(WideCString::from_str(v)?)
            } else {
                None
            };
            // Strangely, `CreateCoreWebView2EnvironmentWithDetails` will fail
            // with 0x80070057 (`E_INVALIDARG`) if the
            // `TargetCompatibleBrowserVersion` property is `NULL`.
            let version = builder
                .target_compatible_browser_version
                .unwrap_or(DEFAULT_TARGET_COMPATIBLE_BROWSER_VERSION);
            let version = Some(WideCString::from_str(version)?);

            let allow_single_sign_on_using_osprimary_account =
                builder.allow_single_sign_on_using_osprimary_account;

            let instance = Self::allocate(
                additional_browser_arguments.into(),
                language.into(),
                version.into(),
                allow_single_sign_on_using_osprimary_account.into(),
            );
            unsafe {
                instance.add_ref();
            }
            Ok(Box::into_raw(instance) as _)
        }
    }

    fn clone_wide_cstr_with_co_task_mem_alloc(s: &WideCStr) -> LPWSTR {
        let len = s.len() + 1;
        unsafe {
            let s1 = CoTaskMemAlloc(len * 2) as *mut u16;
            assert!(!s1.is_null());
            ptr::copy_nonoverlapping(s.as_ptr(), s1, len);
            s1
        }
    }

    impl ICoreWebView2EnvironmentOptions for EnvironmentOptionsImpl {
        unsafe fn get_additional_browser_arguments(
            &self,
            /* out, retval */ value: *mut LPWSTR,
        ) -> HRESULT {
            if let Some(v) = self.additional_browser_arguments.borrow().as_ref() {
                value.write(clone_wide_cstr_with_co_task_mem_alloc(&v));
            } else {
                value.write(ptr::null_mut());
            }
            S_OK
        }

        unsafe fn put_additional_browser_arguments(&self, /* in */ value: LPCWSTR) -> HRESULT {
            *self.additional_browser_arguments.borrow_mut() =
                Some(WideCString::from_ptr_str(value));
            S_OK
        }

        unsafe fn get_language(&self, /* out, retval */ value: *mut LPWSTR) -> HRESULT {
            if let Some(v) = self.language.borrow().as_ref() {
                value.write(clone_wide_cstr_with_co_task_mem_alloc(&v));
            } else {
                value.write(ptr::null_mut());
            }
            S_OK
        }

        unsafe fn put_language(&self, /* in */ value: LPCWSTR) -> HRESULT {
            *self.language.borrow_mut() = Some(WideCString::from_ptr_str(value));
            S_OK
        }

        unsafe fn get_target_compatible_browser_version(
            &self,
            /* out, retval */ value: *mut LPWSTR,
        ) -> HRESULT {
            if let Some(v) = self.target_compatible_browser_version.borrow().as_ref() {
                value.write(clone_wide_cstr_with_co_task_mem_alloc(&v));
            } else {
                value.write(ptr::null_mut());
            }
            S_OK
        }

        unsafe fn put_target_compatible_browser_version(
            &self,
            /* in */ value: LPCWSTR,
        ) -> HRESULT {
            *self.target_compatible_browser_version.borrow_mut() =
                Some(WideCString::from_ptr_str(value));
            S_OK
        }

        unsafe fn get_allow_single_sign_on_using_osprimary_account(&self, value: *mut i32) -> i32 {
            value.write(if self.allow_single_sign_on_using_osprimary_account.get() {
                1
            } else {
                0
            });
            S_OK
        }

        unsafe fn put_allow_single_sign_on_using_osprimary_account(&self, value: i32) -> i32 {
            self.allow_single_sign_on_using_osprimary_account
                .set(value != 0);
            S_OK
        }
    }
}

pub fn get_available_browser_version_string(
    browser_executable_folder: Option<&Path>,
) -> Result<String> {
    let browser_executable_folder = if let Some(p) = browser_executable_folder {
        Some(WideCString::from_os_str(p)?)
    } else {
        None
    };

    let mut result = MaybeUninit::<LPWSTR>::uninit();

    check_hresult(unsafe {
        GetAvailableCoreWebView2BrowserVersionString(
            browser_executable_folder
                .as_ref()
                .map_or(ptr::null(), |x| x.as_ptr()),
            result.as_mut_ptr(),
        )
    })?;
    let result = unsafe { result.assume_init() };
    let result1 = unsafe { WideCStr::from_ptr_str(result) }
        .to_string()
        .map_err(|_| Error::new(E_FAIL));
    unsafe { CoTaskMemFree(result as _) };
    result1
}

pub fn compare_browser_versions(version1: &str, version2: &str) -> Result<std::cmp::Ordering> {
    let version1 = WideCString::from_str(version1)?;
    let version2 = WideCString::from_str(version2)?;
    let mut result = MaybeUninit::<i32>::uninit();

    check_hresult(unsafe {
        CompareBrowserVersions(version1.as_ptr(), version2.as_ptr(), result.as_mut_ptr())
    })?;
    let result = unsafe { result.assume_init() };

    Ok(result.cmp(&0))
}

/// A builder for calling the `CreateCoreWebView2EnvironmentWithOptions`
/// function.
///
/// Use [Environment::builder()](./struct.Environment.html#method.builder) to create one.
#[derive(Default)]
pub struct EnvironmentBuilder<'a> {
    browser_executable_folder: Option<&'a Path>,
    user_data_folder: Option<&'a Path>,
    additional_browser_arguments: Option<&'a str>,
    language: Option<&'a str>,
    target_compatible_browser_version: Option<&'a str>,
    allow_single_sign_on_using_osprimary_account: bool,
}

impl<'a> EnvironmentBuilder<'a> {
    // Hidden. Prefer `Environment::builder()`.
    #[doc(hidden)]
    #[inline]
    pub fn new() -> Self {
        Self::default()
    }

    #[inline]
    pub fn with_browser_executable_folder(self, browser_executable_folder: &'a Path) -> Self {
        Self {
            browser_executable_folder: Some(browser_executable_folder),
            ..self
        }
    }

    #[inline]
    pub fn with_user_data_folder(self, user_data_folder: &'a Path) -> Self {
        Self {
            user_data_folder: Some(user_data_folder),
            ..self
        }
    }

    #[inline]
    pub fn with_additional_browser_arguments(self, additional_browser_arguments: &'a str) -> Self {
        Self {
            additional_browser_arguments: Some(additional_browser_arguments),
            ..self
        }
    }

    #[inline]
    pub fn with_language(mut self, language: &'a str) -> Self {
        self.language = Some(language);
        self
    }

    #[inline]
    pub fn with_target_compatible_browser_version(mut self, version: &'a str) -> Self {
        self.target_compatible_browser_version = Some(version);
        self
    }

    #[inline]
    pub fn with_allow_single_sign_on_using_osprimary_account(mut self, allow: bool) -> Self {
        self.allow_single_sign_on_using_osprimary_account = allow;
        self
    }

    /// Get available browser version string (within the
    /// browser_executable_folder if it is specified.)
    #[inline]
    pub fn get_available_browser_version_string(&self) -> Result<String> {
        get_available_browser_version_string(self.browser_executable_folder)
    }

    #[deprecated = "use webview2::compare_browser_versions instead"]
    #[inline]
    pub fn compare_browser_versions(
        &self,
        version1: &str,
        version2: &str,
    ) -> Result<std::cmp::Ordering> {
        compare_browser_versions(version1, version2)
    }

    #[inline]
    pub fn build(
        &self,
        completed: impl FnOnce(Result<Environment>) -> Result<()> + 'static,
    ) -> Result<()> {
        let browser_executable_folder = if let Some(p) = self.browser_executable_folder {
            Some(WideCString::from_os_str(p)?)
        } else {
            None
        };
        let user_data_folder = if let Some(p) = self.user_data_folder {
            Some(WideCString::from_os_str(p)?)
        } else {
            None
        };
        let options = environment_options::EnvironmentOptionsImpl::from_builder(&self)?;

        let completed = Cell::new(Some(completed));
        let completed = callback!(
            ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler,
            move |result: HRESULT,
                  created_environment: *mut *mut ICoreWebView2EnvironmentVTable|
                  -> HRESULT {
                let result = check_hresult(result).map(move |_| Environment {
                    inner: unsafe { add_ref_to_rc(created_environment) },
                });
                if let Some(completed) = completed.take() {
                    to_hresult(completed(result))
                } else {
                    S_OK
                }
            }
        );

        check_hresult(unsafe {
            CreateCoreWebView2EnvironmentWithOptions(
                browser_executable_folder
                    .as_ref()
                    .map(|p| p.as_ptr())
                    .unwrap_or(ptr::null()),
                user_data_folder
                    .as_ref()
                    .map(|p| p.as_ptr())
                    .unwrap_or(ptr::null()),
                options,
                completed.as_raw(),
            )
        })
    }
}

macro_rules! get {
    ($get_method:ident, $T: ident) => {
        pub fn $get_method(&self) -> Result<$T> {
            let mut value = MaybeUninit::<$T>::uninit();
            check_hresult(unsafe { self.inner.$get_method(value.as_mut_ptr()) })?;
            Ok(unsafe { value.assume_init() })
        }
    };
}

macro_rules! put {
    ($put_method:ident, $arg_name:ident : $T:ident) => {
        pub fn $put_method(&self, $arg_name: $T) -> Result<()> {
            check_hresult(unsafe { self.inner.$put_method($arg_name) })
        }
    };
}

macro_rules! get_interface {
    ($get_method:ident, $T: ident) => {
        pub fn $get_method(&self) -> Result<$T> {
            let mut ppv = ptr::null_mut();
            check_hresult(unsafe { self.inner.$get_method(&mut ppv) })?;
            if ppv.is_null() {
                Err(Error::new(E_FAIL))
            } else {
                Ok(unsafe {
                    $T {
                        inner: add_ref_to_rc(ppv),
                    }
                })
            }
        }
    };
}

macro_rules! put_interface {
    ($put_method:ident, $T: ident) => {
        pub fn $put_method(&self, i: $T) -> Result<()> {
            check_hresult(unsafe {
                // Convert to `ComPtr` so that it is not automatically released.
                self.inner.$put_method(ComPtr::from(i.inner).as_raw())
            })
        }
    };
}

macro_rules! get_bool {
    ($get_method:ident) => {
        pub fn $get_method(&self) -> Result<bool> {
            let mut enabled = MaybeUninit::<BOOL>::uninit();
            check_hresult(unsafe { self.inner.$get_method(enabled.as_mut_ptr()) })?;
            Ok(unsafe { enabled.assume_init() } != 0)
        }
    };
}

macro_rules! put_bool {
    ($put_method:ident) => {
        pub fn $put_method(&self, enabled: bool) -> Result<()> {
            let enabled = if enabled { 1 } else { 0 };
            check_hresult(unsafe { self.inner.$put_method(enabled) })
        }
    };
}

macro_rules! get_string {
    ($get_string_method:ident) => {
        pub fn $get_string_method(&self) -> Result<String> {
            let mut result: LPWSTR = ptr::null_mut();
            check_hresult(unsafe { self.inner.$get_string_method(&mut result) })?;
            let result1 = unsafe { WideCStr::from_ptr_str(result) };
            let result1 = result1.to_string().map_err(|_| Error { hresult: E_FAIL });
            unsafe {
                CoTaskMemFree(result as _);
            }
            result1
        }
    };
}

macro_rules! put_string {
    ($put_string_method:ident) => {
        pub fn $put_string_method(&self, message_string: &str) -> Result<()> {
            let message = WideCString::from_str(message_string)?;
            check_hresult(unsafe { self.inner.$put_string_method(message.as_ptr()) })
        }
    };
}

macro_rules! call {
    ($method:ident) => {
        pub fn $method(&self) -> Result<()> {
            check_hresult(unsafe { self.inner.$method() })
        }
    };
}

macro_rules! add_event_handler_controller {
    ($method:ident, $arg_type:ident) => {
        pub fn $method(
            &self,
            event_handler: impl Fn(Controller) -> Result<()> + 'static,
        ) -> Result<EventRegistrationToken> {
            let mut token = MaybeUninit::<EventRegistrationToken>::uninit();

            let event_handler = callback!(
                $arg_type,
                move |sender: *mut *mut ICoreWebView2ControllerVTable,
                      _args: *mut *mut com::interfaces::iunknown::IUnknownVTable|
                      -> HRESULT {
                    let sender = Controller {
                        inner: unsafe { add_ref_to_rc(sender) },
                    };
                    to_hresult(event_handler(sender))
                }
            );

            check_hresult(unsafe {
                self.inner
                    .$method(event_handler.as_raw(), token.as_mut_ptr())
            })?;
            Ok(unsafe { token.assume_init() })
        }
    };
}

macro_rules! add_event_handler_view {
    ($method:ident, $arg_type:ident) => {
        pub fn $method(
            &self,
            event_handler: impl Fn(WebView) -> Result<()> + 'static,
        ) -> Result<EventRegistrationToken> {
            let mut token = MaybeUninit::<EventRegistrationToken>::uninit();

            let event_handler = callback!(
                $arg_type,
                move |sender: *mut *mut ICoreWebView2VTable,
                      _args: *mut *mut com::interfaces::iunknown::IUnknownVTable|
                      -> HRESULT {
                    let sender = WebView {
                        inner: unsafe { add_ref_to_rc(sender) },
                    };
                    to_hresult(event_handler(sender))
                }
            );

            check_hresult(unsafe {
                self.inner
                    .$method(event_handler.as_raw(), token.as_mut_ptr())
            })?;
            Ok(unsafe { token.assume_init() })
        }
    };
}

macro_rules! add_event_handler {
    ($method:ident, $arg_type:ident, $arg_args:ident, $arg_args_type:ident) => {
        pub fn $method(
            &self,
            handler: impl Fn(WebView, $arg_args) -> Result<()> + 'static,
        ) -> Result<EventRegistrationToken> {
            let mut token = MaybeUninit::<EventRegistrationToken>::uninit();

            let handler = callback!($arg_type, move |sender: *mut *mut ICoreWebView2VTable,
                                                     args: *mut *mut $arg_args_type|
                  -> HRESULT {
                let sender = WebView {
                    inner: unsafe { add_ref_to_rc(sender) },
                };
                let args = $arg_args {
                    inner: unsafe { add_ref_to_rc(args) },
                };
                to_hresult(handler(sender, args))
            });

            check_hresult(unsafe { self.inner.$method(handler.as_raw(), token.as_mut_ptr()) })?;
            Ok(unsafe { token.assume_init() })
        }
    };
}

macro_rules! remove_event_handler {
    ($method:ident) => {
        pub fn $method(&self, token: EventRegistrationToken) -> Result<()> {
            check_hresult(unsafe { self.inner.$method(token) })
        }
    };
}

impl Environment {
    pub fn builder<'a>() -> EnvironmentBuilder<'a> {
        EnvironmentBuilder::new()
    }

    pub fn create_controller(
        &self,
        parent_window: HWND,
        completed: impl FnOnce(Result<Controller>) -> Result<()> + 'static,
    ) -> Result<()> {
        let completed = Cell::new(Some(completed));
        let completed = callback!(
            ICoreWebView2CreateCoreWebView2ControllerCompletedHandler,
            move |result: HRESULT,
                  created_host: *mut *mut ICoreWebView2ControllerVTable|
                  -> HRESULT {
                let result = check_hresult(result).map(|_| Controller {
                    inner: unsafe { add_ref_to_rc(created_host) },
                });
                if let Some(completed) = completed.take() {
                    to_hresult(completed(result))
                } else {
                    S_OK
                }
            }
        );
        check_hresult(unsafe {
            self.inner
                .create_core_web_view2_controller(parent_window, completed.as_raw())
        })
    }
    pub fn create_web_resource_response(
        &self,
        content: Stream,
        status_code: i32,
        reason_phrase: &str,
        headers: &str,
    ) -> Result<WebResourceResponse> {
        let content = ComPtr::from(content.into_inner());
        let reason_phrase = WideCString::from_str(reason_phrase)?;
        let headers = WideCString::from_str(headers)?;
        let mut response =
            MaybeUninit::<*mut *mut ICoreWebView2WebResourceResponseVTable>::uninit();
        check_hresult(unsafe {
            self.inner.create_web_resource_response(
                content.as_raw(),
                status_code,
                reason_phrase.as_ptr(),
                headers.as_ptr(),
                response.as_mut_ptr(),
            )
        })?;
        Ok(WebResourceResponse::from(unsafe {
            ComRc::from_raw(response.assume_init())
        }))
    }
    get_string!(get_browser_version_string);
    pub fn add_new_browser_version_available(
        &self,
        event_handler: impl Fn(Environment) -> Result<()> + 'static,
    ) -> Result<EventRegistrationToken> {
        let mut token = MaybeUninit::<EventRegistrationToken>::uninit();

        let event_handler = callback!(
            ICoreWebView2NewBrowserVersionAvailableEventHandler,
            move |sender: *mut *mut ICoreWebView2EnvironmentVTable,
                  _args: *mut *mut com::interfaces::iunknown::IUnknownVTable|
                  -> HRESULT {
                let sender = Environment {
                    inner: unsafe { add_ref_to_rc(sender) },
                };
                to_hresult(event_handler(sender))
            }
        );

        check_hresult(unsafe {
            self.inner
                .add_new_browser_version_available(event_handler.as_raw(), token.as_mut_ptr())
        })?;
        Ok(unsafe { token.assume_init() })
    }
    remove_event_handler!(remove_new_browser_version_available);
}

impl Controller {
    get_bool!(get_is_visible);
    put_bool!(put_is_visible);
    get!(get_bounds, RECT);
    put!(put_bounds, bounds: RECT);
    get!(get_zoom_factor, f64);
    put!(put_zoom_factor, zoom_factor: f64);
    add_event_handler_controller!(
        add_zoom_factor_changed,
        ICoreWebView2ZoomFactorChangedEventHandler
    );
    remove_event_handler!(remove_zoom_factor_changed);
    pub fn set_bounds_and_zoom_factor(&self, bounds: RECT, zoom_factor: f64) -> Result<()> {
        check_hresult(unsafe { self.inner.set_bounds_and_zoom_factor(bounds, zoom_factor) })
    }
    pub fn move_focus(&self, reason: MoveFocusReason) -> Result<()> {
        check_hresult(unsafe { self.inner.move_focus(reason) })
    }
    pub fn add_move_focus_requested(
        &self,
        handler: impl Fn(Controller, MoveFocusRequestedEventArgs) -> Result<()> + 'static,
    ) -> Result<EventRegistrationToken> {
        let mut token = MaybeUninit::<EventRegistrationToken>::uninit();

        let handler = callback!(
            ICoreWebView2MoveFocusRequestedEventHandler,
            move |sender: *mut *mut ICoreWebView2ControllerVTable,
                  args: *mut *mut ICoreWebView2MoveFocusRequestedEventArgsVTable|
                  -> HRESULT {
                let sender = Controller {
                    inner: unsafe { add_ref_to_rc(sender) },
                };
                let args = MoveFocusRequestedEventArgs {
                    inner: unsafe { add_ref_to_rc(args) },
                };
                to_hresult(handler(sender, args))
            }
        );

        check_hresult(unsafe {
            self.inner
                .add_move_focus_requested(handler.as_raw(), token.as_mut_ptr())
        })?;
        Ok(unsafe { token.assume_init() })
    }
    remove_event_handler!(remove_move_focus_requested);
    add_event_handler_controller!(add_got_focus, ICoreWebView2FocusChangedEventHandler);
    remove_event_handler!(remove_got_focus);
    add_event_handler_controller!(add_lost_focus, ICoreWebView2FocusChangedEventHandler);
    remove_event_handler!(remove_lost_focus);
    pub fn add_accelerator_key_pressed(
        &self,
        handler: impl Fn(Controller, AcceleratorKeyPressedEventArgs) -> Result<()> + 'static,
    ) -> Result<EventRegistrationToken> {
        let mut token = MaybeUninit::<EventRegistrationToken>::uninit();

        let handler = callback!(
            ICoreWebView2AcceleratorKeyPressedEventHandler,
            move |sender: *mut *mut ICoreWebView2ControllerVTable,
                  args: *mut *mut ICoreWebView2AcceleratorKeyPressedEventArgsVTable|
                  -> HRESULT {
                let sender = Controller {
                    inner: unsafe { add_ref_to_rc(sender) },
                };
                let args = AcceleratorKeyPressedEventArgs {
                    inner: unsafe { add_ref_to_rc(args) },
                };
                to_hresult(handler(sender, args))
            }
        );

        check_hresult(unsafe {
            self.inner
                .add_accelerator_key_pressed(handler.as_raw(), token.as_mut_ptr())
        })?;
        Ok(unsafe { token.assume_init() })
    }
    remove_event_handler!(remove_accelerator_key_pressed);
    get!(get_parent_window, HWND);
    put!(put_parent_window, top_level_window: HWND);
    call!(notify_parent_window_position_changed);
    call!(close);
    pub fn get_webview(&self) -> Result<WebView> {
        let mut ppv: *mut *mut ICoreWebView2VTable = ptr::null_mut();
        check_hresult(unsafe { self.inner.get_core_web_view2(&mut ppv) })?;
        Ok(WebView {
            inner: unsafe { add_ref_to_rc(ppv) },
        })
    }
    pub fn get_controller2(&self) -> Result<Controller2> {
        let inner = self
            .inner
            .get_interface::<dyn ICoreWebView2Controller2>()
            .ok_or_else(|| Error::new(E_NOINTERFACE))?;
        Ok(Controller2 { inner })
    }
}

impl Controller2 {
    get!(get_default_background_color, Color);
    put!(put_default_background_color, color: Color);
}

impl WebView {
    pub fn get_settings(&self) -> Result<Settings> {
        let mut ppv: *mut *mut ICoreWebView2SettingsVTable = ptr::null_mut();
        check_hresult(unsafe { self.inner.get_settings(&mut ppv) })?;
        Ok(Settings {
            inner: unsafe { add_ref_to_rc(ppv) },
        })
    }
    get_string!(get_source);
    put_string!(navigate);
    put_string!(navigate_to_string);
    add_event_handler!(
        add_navigation_starting,
        ICoreWebView2NavigationStartingEventHandler,
        NavigationStartingEventArgs,
        ICoreWebView2NavigationStartingEventArgsVTable
    );
    remove_event_handler!(remove_navigation_starting);
    add_event_handler!(
        add_content_loading,
        ICoreWebView2ContentLoadingEventHandler,
        ContentLoadingEventArgs,
        ICoreWebView2ContentLoadingEventArgsVTable
    );
    remove_event_handler!(remove_content_loading);
    add_event_handler!(
        add_source_changed,
        ICoreWebView2SourceChangedEventHandler,
        SourceChangedEventArgs,
        ICoreWebView2SourceChangedEventArgsVTable
    );
    remove_event_handler!(remove_source_changed);
    add_event_handler_view!(add_history_changed, ICoreWebView2HistoryChangedEventHandler);
    remove_event_handler!(remove_history_changed);
    add_event_handler!(
        add_navigation_completed,
        ICoreWebView2NavigationCompletedEventHandler,
        NavigationCompletedEventArgs,
        ICoreWebView2NavigationCompletedEventArgsVTable
    );
    remove_event_handler!(remove_navigation_completed);
    add_event_handler!(
        add_frame_navigation_starting,
        ICoreWebView2NavigationStartingEventHandler,
        NavigationStartingEventArgs,
        ICoreWebView2NavigationStartingEventArgsVTable
    );
    remove_event_handler!(remove_frame_navigation_starting);
    add_event_handler!(
        add_script_dialog_opening,
        ICoreWebView2ScriptDialogOpeningEventHandler,
        ScriptDialogOpeningEventArgs,
        ICoreWebView2ScriptDialogOpeningEventArgsVTable
    );
    remove_event_handler!(remove_script_dialog_opening);
    add_event_handler!(
        add_permission_requested,
        ICoreWebView2PermissionRequestedEventHandler,
        PermissionRequestedEventArgs,
        ICoreWebView2PermissionRequestedEventArgsVTable
    );
    remove_event_handler!(remove_permission_requested);
    add_event_handler!(
        add_process_failed,
        ICoreWebView2ProcessFailedEventHandler,
        ProcessFailedEventArgs,
        ICoreWebView2ProcessFailedEventArgsVTable
    );
    remove_event_handler!(remove_process_failed);
    // Don't take an `Option<impl FnOnce>`:
    // https://users.rust-lang.org/t/solved-how-to-pass-none-to-a-function-when-an-option-closure-is-expected/10956/8
    pub fn add_script_to_execute_on_document_created(
        &self,
        script: &str,
        callback: impl FnOnce(String) -> Result<()> + 'static,
    ) -> Result<()> {
        let script = WideCString::from_str(script)?;
        let callback = Cell::new(Some(callback));
        let callback = callback!(
            ICoreWebView2AddScriptToExecuteOnDocumentCreatedCompletedHandler,
            move |error_code: HRESULT, id: LPCWSTR| -> HRESULT {
                to_hresult(check_hresult(error_code).and_then(|_| {
                    let id = unsafe { WideCStr::from_ptr_str(id) }
                        .to_string()
                        .map_err(|_| Error::new(E_FAIL))?;
                    if let Some(callback) = callback.take() {
                        callback(id)
                    } else {
                        Ok(())
                    }
                }))
            }
        );
        check_hresult(unsafe {
            self.inner
                .add_script_to_execute_on_document_created(script.as_ptr(), callback.as_raw())
        })
    }
    pub fn remove_script_to_execute_on_document_created(&self, id: &str) -> Result<()> {
        let id = WideCString::from_str(id)?;
        check_hresult(unsafe {
            self.inner
                .remove_script_to_execute_on_document_created(id.as_ptr())
        })
    }
    pub fn execute_script(
        &self,
        script: &str,
        callback: impl FnOnce(String) -> Result<()> + 'static,
    ) -> Result<()> {
        let script = WideCString::from_str(script)?;
        let callback = Cell::new(Some(callback));
        let callback = callback!(
            ICoreWebView2ExecuteScriptCompletedHandler,
            move |error_code: HRESULT, result_object_as_json: LPCWSTR| -> HRESULT {
                to_hresult(check_hresult(error_code).and_then(|_| {
                    let result_object_as_json_string =
                        unsafe { WideCStr::from_ptr_str(result_object_as_json) }
                            .to_string()
                            .map_err(|_| Error::new(E_FAIL))?;
                    if let Some(callback) = callback.take() {
                        callback(result_object_as_json_string)
                    } else {
                        Ok(())
                    }
                }))
            }
        );
        check_hresult(unsafe {
            self.inner
                .execute_script(script.as_ptr(), callback.as_raw())
        })
    }
    add_event_handler_view!(
        add_document_title_changed,
        ICoreWebView2DocumentTitleChangedEventHandler
    );
    remove_event_handler!(remove_document_title_changed);
    pub fn capture_preview(
        &self,
        image_format: CapturePreviewImageFormat,
        image_stream: Stream,
        handler: impl FnOnce(Result<()>) -> Result<()> + 'static,
    ) -> Result<()> {
        let handler = Cell::new(Some(handler));
        let handler = callback!(
            ICoreWebView2CapturePreviewCompletedHandler,
            move |result: HRESULT| -> HRESULT {
                if let Some(handler) = handler.take() {
                    to_hresult(handler(check_hresult(result)))
                } else {
                    S_OK
                }
            }
        );
        let image_stream = ComPtr::from(image_stream.inner);

        check_hresult(unsafe {
            self.inner
                .capture_preview(image_format, image_stream.as_raw(), handler.as_raw())
        })
    }
    call!(reload);
    put_string!(post_web_message_as_json);
    put_string!(post_web_message_as_string);
    add_event_handler!(
        add_web_message_received,
        ICoreWebView2WebMessageReceivedEventHandler,
        WebMessageReceivedEventArgs,
        ICoreWebView2WebMessageReceivedEventArgsVTable
    );
    remove_event_handler!(remove_web_message_received);
    // TODO: call_dev_tools_protocol_method
    get!(get_browser_process_id, u32);
    get_bool!(get_can_go_back);
    get_bool!(get_can_go_forward);
    call!(go_back);
    call!(go_forward);
    // TODO: get_dev_tools_protocol_event_receiver
    call!(stop);
    add_event_handler!(
        add_new_window_requested,
        ICoreWebView2NewWindowRequestedEventHandler,
        NewWindowRequestedEventArgs,
        ICoreWebView2NewWindowRequestedEventArgsVTable
    );
    remove_event_handler!(remove_new_window_requested);
    get_string!(get_document_title);
    // TODO: add_host_object_to_script ??
    // TODO: remove_host_object_to_script ??
    call!(open_dev_tools_window);
    add_event_handler_view!(
        add_contains_full_screen_element_changed,
        ICoreWebView2ContainsFullScreenElementChangedEventHandler
    );
    remove_event_handler!(remove_contains_full_screen_element_changed);
    get_bool!(get_contains_full_screen_element);
    add_event_handler!(
        add_web_resource_requested,
        ICoreWebView2WebResourceRequestedEventHandler,
        WebResourceRequestedEventArgs,
        ICoreWebView2WebResourceRequestedEventArgsVTable
    );
    remove_event_handler!(remove_web_resource_requested);
    pub fn add_web_resource_requested_filter(
        &self,
        uri: &str,
        resource_context: WebResourceContext,
    ) -> Result<()> {
        let uri = WideCString::from_str(uri)?;
        check_hresult(unsafe {
            self.inner
                .add_web_resource_requested_filter(uri.as_ptr(), resource_context)
        })
    }
    pub fn remove_web_resource_requested_filter(
        &self,
        uri: &str,
        resource_context: WebResourceContext,
    ) -> Result<()> {
        let uri = WideCString::from_str(uri)?;
        check_hresult(unsafe {
            self.inner
                .remove_web_resource_requested_filter(uri.as_ptr(), resource_context)
        })
    }
    add_event_handler_view!(
        add_window_close_requested,
        ICoreWebView2WindowCloseRequestedEventHandler
    );
    remove_event_handler!(remove_window_close_requested);
}

impl Settings {
    get_bool!(get_is_script_enabled);
    put_bool!(put_is_script_enabled);

    get_bool!(get_is_web_message_enabled);
    put_bool!(put_is_web_message_enabled);

    get_bool!(get_are_default_script_dialogs_enabled);
    put_bool!(put_are_default_script_dialogs_enabled);

    get_bool!(get_is_status_bar_enabled);
    put_bool!(put_is_status_bar_enabled);

    get_bool!(get_are_dev_tools_enabled);
    put_bool!(put_are_dev_tools_enabled);

    get_bool!(get_are_default_context_menus_enabled);
    put_bool!(put_are_default_context_menus_enabled);

    get_bool!(get_are_host_objects_allowed);
    put_bool!(put_are_host_objects_allowed);

    get_bool!(get_is_zoom_control_enabled);
    put_bool!(put_is_zoom_control_enabled);

    get_bool!(get_is_built_in_error_page_enabled);
    put_bool!(put_is_built_in_error_page_enabled);

    pub fn get_settings2(&self) -> Result<Settings2> {
        let inner = self
            .inner
            .get_interface::<dyn ICoreWebView2Settings2>()
            .ok_or_else(|| Error::new(E_NOINTERFACE))?;
        Ok(Settings2 { inner })
    }
}

impl Settings2 {
    get_string!(get_user_agent);
    put_string!(put_user_agent);
}

impl ContentLoadingEventArgs {
    get_bool!(get_is_error_page);
    get!(get_navigation_id, u64);
}

impl WebMessageReceivedEventArgs {
    get_string!(get_source);
    get_string!(try_get_web_message_as_string);
    get_string!(get_web_message_as_json);
}

impl HttpHeadersCollectionIterator {
    pub fn get_current_header(&self) -> Result<(String, String)> {
        let mut name = MaybeUninit::<LPWSTR>::uninit();
        let mut value = MaybeUninit::<LPWSTR>::uninit();
        unsafe {
            check_hresult(
                self.inner
                    .get_current_header(name.as_mut_ptr(), value.as_mut_ptr()),
            )?;
            let name = name.assume_init();
            let value = value.assume_init();
            let name1 = WideCStr::from_ptr_str(name)
                .to_string()
                .map_err(|_| Error::new(E_FAIL));
            let value1 = WideCStr::from_ptr_str(value)
                .to_string()
                .map_err(|_| Error::new(E_FAIL));

            CoTaskMemFree(name as _);
            CoTaskMemFree(value as _);

            Ok((name1?, value1?))
        }
    }
    get_bool!(get_has_current_header);
    get_bool!(move_next);
}

impl Iterator for HttpHeadersCollectionIterator {
    type Item = (String, String);

    fn next(&mut self) -> Option<(String, String)> {
        if self.get_has_current_header() != Ok(true) {
            return None;
        }
        let v = self.get_current_header().ok();
        let _ = self.move_next();
        v
    }
}

impl HttpRequestHeaders {
    pub fn get_header(&self, name: &str) -> Result<String> {
        let name = WideCString::from_str(name)?;
        let mut value = MaybeUninit::<LPWSTR>::uninit();
        unsafe {
            check_hresult(self.inner.get_header(name.as_ptr(), value.as_mut_ptr()))?;
            let value = value.assume_init();
            let value1 = WideCStr::from_ptr_str(value)
                .to_string()
                .map_err(|_| Error::new(E_FAIL));

            CoTaskMemFree(value as _);

            value1
        }
    }
    pub fn get_headers(&self, name: &str) -> Result<HttpHeadersCollectionIterator> {
        let name = WideCString::from_str(name)?;
        let mut iterator: *mut *mut ICoreWebView2HttpHeadersCollectionIteratorVTable =
            ptr::null_mut();
        check_hresult(unsafe { self.inner.get_headers(name.as_ptr(), &mut iterator) })?;
        Ok(HttpHeadersCollectionIterator {
            inner: unsafe { add_ref_to_rc(iterator) },
        })
    }
    pub fn contains(&self, name: &str) -> Result<bool> {
        let name = WideCString::from_str(name)?;
        let mut result = MaybeUninit::<BOOL>::uninit();
        check_hresult(unsafe { self.inner.contains(name.as_ptr(), result.as_mut_ptr()) })?;
        Ok(unsafe { result.assume_init() } != 0)
    }
    pub fn set_header(&self, name: &str, value: &str) -> Result<()> {
        let name = WideCString::from_str(name)?;
        let value = WideCString::from_str(value)?;
        check_hresult(unsafe { self.inner.set_header(name.as_ptr(), value.as_ptr()) })
    }
    put_string!(remove_header);
    get_interface!(get_iterator, HttpHeadersCollectionIterator);
}

impl HttpResponseHeaders {
    pub fn get_header(&self, name: &str) -> Result<String> {
        let name = WideCString::from_str(name)?;
        let mut value = MaybeUninit::<LPWSTR>::uninit();
        unsafe {
            check_hresult(self.inner.get_header(name.as_ptr(), value.as_mut_ptr()))?;
            let value = value.assume_init();
            let value1 = WideCStr::from_ptr_str(value)
                .to_string()
                .map_err(|_| Error::new(E_FAIL));

            CoTaskMemFree(value as _);

            value1
        }
    }
    pub fn contains(&self, name: &str) -> Result<bool> {
        let name = WideCString::from_str(name)?;
        let mut result = MaybeUninit::<BOOL>::uninit();
        check_hresult(unsafe { self.inner.contains(name.as_ptr(), result.as_mut_ptr()) })?;
        Ok(unsafe { result.assume_init() } != 0)
    }
    pub fn append_header(&self, name: &str, value: &str) -> Result<()> {
        let name = WideCString::from_str(name)?;
        let value = WideCString::from_str(value)?;
        check_hresult(unsafe { self.inner.append_header(name.as_ptr(), value.as_ptr()) })
    }
    pub fn get_headers(&self, name: &str) -> Result<HttpHeadersCollectionIterator> {
        let name = WideCString::from_str(name)?;
        let mut iterator: *mut *mut ICoreWebView2HttpHeadersCollectionIteratorVTable =
            ptr::null_mut();
        check_hresult(unsafe { self.inner.get_headers(name.as_ptr(), &mut iterator) })?;
        Ok(HttpHeadersCollectionIterator {
            inner: unsafe { add_ref_to_rc(iterator) },
        })
    }
    get_interface!(get_iterator, HttpHeadersCollectionIterator);
}

impl Deferral {
    call!(complete);
}

impl WebResourceRequest {
    get_string!(get_uri);
    put_string!(put_uri);
    get_string!(get_method);
    put_string!(put_method);
    get_interface!(get_content, Stream);
    put_interface!(put_content, Stream);
    get_interface!(get_headers, HttpRequestHeaders);
}

impl WebResourceResponse {
    get_interface!(get_content, Stream);
    put_interface!(put_content, Stream);
    get_interface!(get_headers, HttpResponseHeaders);
    get!(get_status_code, i32);
    put!(put_status_code, status_code: i32);
    get_string!(get_reason_phrase);
    put_string!(put_reason_phrase);
}

impl WebResourceRequestedEventArgs {
    get_interface!(get_request, WebResourceRequest);
    get_interface!(get_response, WebResourceResponse);
    put_interface!(put_response, WebResourceResponse);
    get_interface!(get_deferral, Deferral);
    get!(get_resource_context, WebResourceContext);
}

impl NavigationCompletedEventArgs {
    get_bool!(get_is_success);
    get!(get_web_error_status, WebErrorStatus);
    get!(get_navigation_id, u64);
}

impl NavigationStartingEventArgs {
    get_string!(get_uri);
    get_bool!(get_is_user_initiated);
    get_bool!(get_is_redirected);
    get_interface!(get_request_headers, HttpRequestHeaders);
    get_bool!(get_cancel);
    put_bool!(put_cancel);
    get!(get_navigation_id, u64);
}

impl SourceChangedEventArgs {
    get_bool!(get_is_new_document);
}

impl ScriptDialogOpeningEventArgs {
    get_string!(get_uri);
    get!(get_kind, ScriptDialogKind);
    get_string!(get_message);
    call!(accept);
    get_string!(get_default_text);
    get_string!(get_result_text);
    put_string!(put_result_text);
    get_interface!(get_deferral, Deferral);
}

impl PermissionRequestedEventArgs {
    get_string!(get_uri);
    get!(get_permission_kind, PermissionKind);
    get_bool!(get_is_user_initiated);
    get!(get_state, PermissionState);
    put!(put_state, state: PermissionState);
    get_interface!(get_deferral, Deferral);
}

impl ProcessFailedEventArgs {
    get!(get_process_failed_kind, ProcessFailedKind);
}

impl NewWindowRequestedEventArgs {
    get_string!(get_uri);
    put_interface!(put_new_window, WebView);
    get_interface!(get_new_window, WebView);
    put_bool!(put_handled);
    get_bool!(get_handled);
    get_bool!(get_is_user_initiated);
    get_interface!(get_deferral, Deferral);
    get_interface!(get_window_features, WindowFeatures);
}

impl WindowFeatures {
    get_bool!(get_has_position);
    get_bool!(get_has_size);
    get!(get_left, u32);
    get!(get_top, u32);
    get!(get_height, u32);
    get!(get_width, u32);
    get_bool!(get_should_display_menu_bar);
    get_bool!(get_should_display_status);
    get_bool!(get_should_display_toolbar);
    get_bool!(get_should_display_scroll_bars);
}

impl MoveFocusRequestedEventArgs {
    get!(get_reason, MoveFocusReason);
    get_bool!(get_handled);
    put_bool!(put_handled);
}

impl AcceleratorKeyPressedEventArgs {
    get!(get_key_event_kind, KeyEventKind);
    get!(get_virtual_key, u32);
    get!(get_key_event_lparam, i32);
    get!(get_physical_key_status, PhysicalKeyStatus);
    get_bool!(get_handled);
    put_bool!(put_handled);
}

// Missing in winapi APIs. But present in its import libraries.
extern "stdcall" {
    fn SHCreateMemStream(p_init: *const u8, cb_init: UINT) -> *mut *mut IStreamVTable;
}

impl Stream {
    /// Create a stream from a byte buffer. (`SHCreateMemStream`)
    pub fn from_bytes(buf: &[u8]) -> Self {
        let ppv = unsafe { SHCreateMemStream(buf.as_ptr(), buf.len() as _) };
        assert!(!ppv.is_null());
        Self {
            // Do not need to add ref for this pointer.
            inner: unsafe { ComRc::from_raw(ppv) },
        }
    }

    /// Create a `Stream` from an owning raw pointer to an `IStream`.
    ///
    /// # Safety
    ///
    /// See `ComRc::from_raw`.
    pub unsafe fn from_raw(ppv: *mut *mut IStreamVTable) -> Self {
        Self {
            inner: ComRc::from_raw(ppv),
        }
    }
}

impl io::Read for Stream {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let mut read_bytes = MaybeUninit::uninit();
        check_hresult(unsafe {
            self.inner.read(
                buf.as_mut_ptr() as *mut _,
                buf.len() as _,
                read_bytes.as_mut_ptr(),
            )
        })
        .map_err(|e| e.into_io_error())?;
        Ok(unsafe { read_bytes.assume_init() } as _)
    }
}

impl io::Write for Stream {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        let mut written_bytes = MaybeUninit::uninit();
        check_hresult(unsafe {
            self.inner.write(
                buf.as_ptr() as *mut _,
                buf.len() as _,
                written_bytes.as_mut_ptr(),
            )
        })
        .map_err(|e| e.into_io_error())?;
        Ok(unsafe { written_bytes.assume_init() } as _)
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

impl io::Seek for Stream {
    fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
        use std::convert::TryInto;

        let (origin, amount) = match pos {
            io::SeekFrom::Start(x) => (/* STREAM_SEEK_SET */ 0, x.try_into().unwrap()),
            io::SeekFrom::Current(x) => (/* STREAM_SEEK_CUR */ 1, x),
            io::SeekFrom::End(x) => (/* STREAM_SEEK_END */ 2, x),
        };

        let mut new_pos = MaybeUninit::<u64>::uninit();

        check_hresult(unsafe {
            self.inner.seek(
                mem::transmute(amount),
                origin,
                new_pos.as_mut_ptr() as *mut _,
            )
        })
        .map_err(|e| e.into_io_error())?;
        Ok(unsafe { new_pos.assume_init() })
    }
}

#[doc(inline)]
pub use webview2_sys::{
    CapturePreviewImageFormat, EventRegistrationToken, KeyEventKind, MoveFocusReason,
    PermissionKind, PermissionState, PhysicalKeyStatus, ProcessFailedKind, ScriptDialogKind,
    WebErrorStatus, WebResourceContext,
};

/// WebView2 Error.
///
/// Actually it's just an `HRESULT`.
#[derive(Eq, PartialEq)]
pub struct Error {
    hresult: HRESULT,
}

pub type Result<T> = std::result::Result<T, Error>;

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "webview2 error, HRESULT {:#X}", self.hresult as u32)
    }
}

impl fmt::Debug for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "webview2 error, HRESULT {:#X}", self.hresult as u32)
    }
}

impl std::error::Error for Error {}

impl From<NulError<u16>> for Error {
    fn from(_: NulError<u16>) -> Error {
        Error {
            hresult: E_INVALIDARG,
        }
    }
}

impl From<io::Error> for Error {
    fn from(e: io::Error) -> Error {
        match e.raw_os_error() {
            Some(e) => Error::new(HRESULT_FROM_WIN32(e as u32)),
            _ => Error::new(E_FAIL),
        }
    }
}

impl Error {
    pub fn new(hresult: HRESULT) -> Self {
        Self { hresult }
    }

    fn into_io_error(self) -> io::Error {
        if (self.hresult & (0xffff_0000_u32 as i32))
            == MAKE_HRESULT(SEVERITY_ERROR, FACILITY_WIN32, 0)
        {
            io::Error::from_raw_os_error(HRESULT_CODE(self.hresult))
        } else {
            io::Error::new(io::ErrorKind::Other, self)
        }
    }

    pub fn hresult(&self) -> HRESULT {
        self.hresult
    }
}

/// Check a `HRESULT`, if it is `SUCCEEDED`, return `Ok(())`. Otherwide return
/// an error containing the `HRESULT`.
pub fn check_hresult(hresult: HRESULT) -> Result<()> {
    if SUCCEEDED(hresult) {
        Ok(())
    } else {
        Err(Error { hresult })
    }
}

fn to_hresult<T>(r: Result<T>) -> HRESULT {
    match r {
        Ok(_) => S_OK,
        Err(Error { hresult }) => hresult,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::{Read, Seek, Write};

    #[test]
    fn test_stream() {
        let mut stream = Stream::from_bytes(b"hello,");
        stream.seek(io::SeekFrom::End(0)).unwrap();
        stream.write_all(b" world").unwrap();

        let mut buf = Vec::new();
        stream.seek(io::SeekFrom::Start(0)).unwrap();
        stream.read_to_end(&mut buf).unwrap();
        assert_eq!(buf, b"hello, world");
    }

    #[test]
    fn test_cmp_version() {
        assert_eq!(
            compare_browser_versions("84.0.498.0 canary", "84.0.498.0 canary").unwrap(),
            std::cmp::Ordering::Equal,
        );
        assert_eq!(
            compare_browser_versions("84.0.430.0 canary", "84.0.498.0 canary").unwrap(),
            std::cmp::Ordering::Less,
        );
        assert_eq!(
            compare_browser_versions("84.0.498.0", "84.0.440.0").unwrap(),
            std::cmp::Ordering::Greater,
        );
    }
}