feat: Implement navigation event and cancellation, closes #456

.changes/nav-handler.md

@@ -0,0 +1,5 @@
+---
+"wry": patch
+---
+
+Add navigation handler to decide if a url is allowed to navigate.

Cargo.toml

@@ -76,6 +76,7 @@ sys-info = "0.9"
 ]
 
 [target."cfg(any(target_os = \"ios\", target_os = \"macos\"))".dependencies]
+block = "0.1"
 cocoa = "0.24"
 core-graphics = "0.22"
 objc = { version = "0.2", features = [ "exception" ] }

examples/navigation_event.rs

@@ -0,0 +1,51 @@
+// Copyright 2019-2021 Tauri Programme within The Commons Conservancy
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: MIT
+
+fn main() -> wry::Result<()> {
+  use wry::{
+    application::{
+      event::{Event, StartCause, WindowEvent},
+      event_loop::{ControlFlow, EventLoop},
+      window::WindowBuilder,
+    },
+    webview::WebViewBuilder,
+  };
+
+  enum UserEvent {
+    Navigation(String),
+  }
+
+  let event_loop: EventLoop<UserEvent> = EventLoop::with_user_event();
+  let proxy = event_loop.create_proxy();
+  let window = WindowBuilder::new()
+    .with_title("Hello World")
+    .build(&event_loop)?;
+  let webview = WebViewBuilder::new(window)?
+    .with_url("http://neverssl.com")?
+    .with_navigation_handler(move |uri: String| {
+      let submitted = proxy.send_event(UserEvent::Navigation(uri.clone())).is_ok();
+
+      submitted && uri.contains("neverssl")
+    })
+    .build()?;
+
+  #[cfg(debug_assertions)]
+  webview.devtool();
+
+  event_loop.run(move |event, _, control_flow| {
+    *control_flow = ControlFlow::Wait;
+
+    match event {
+      Event::NewEvents(StartCause::Init) => println!("Wry has started!"),
+      Event::WindowEvent {
+        event: WindowEvent::CloseRequested,
+        ..
+      } => *control_flow = ControlFlow::Exit,
+      Event::UserEvent(UserEvent::Navigation(uri)) => {
+        println!("{}", uri);
+      }
+      _ => (),
+    }
+  });
+}

src/webview/mod.rs

@@ -110,6 +110,12 @@ pub struct WebViewAttributes {
   #[cfg(not(feature = "file-drop"))]
   file_drop_handler: Option<Box<dyn Fn(&Window, FileDropEvent) -> bool>>,
 
+  /// Set a navigation handler to decide if incoming url is allowed to navigate.
+  ///
+  /// The closure take a `String` parameter as url and return `bool` to determine the url. True is
+  /// allow to nivagate and false is not.
+  pub navigation_handler: Option<Box<dyn Fn(String) -> bool>>,
+
   /// Enables clipboard access for the page rendered on **Linux** and **Windows**.
   ///
   /// macOS doesn't provide such method and is always enabled by default. But you still need to add menu
@@ -139,6 +145,7 @@ impl Default for WebViewAttributes {
       custom_protocols: vec![],
       ipc_handler: None,
       file_drop_handler: None,
+      navigation_handler: None,
       clipboard: false,
       devtool: false,
     }
@@ -296,6 +303,15 @@ impl<'a> WebViewBuilder<'a> {
     self
   }
 
+  /// Set a navigation handler to decide if incoming url is allowed to navigate.
+  ///
+  /// The closure takes a `String` parameter as url and return `bool` to determine the url. True is
+  /// allowed to nivagate and false is not.
+  pub fn with_navigation_handler(mut self, callback: impl Fn(String) -> bool + 'static) -> Self {
+    self.webview.navigation_handler = Some(Box::new(callback));
+    self
+  }
+
   /// Consume the builder and create the [`WebView`].
   ///
   /// Platform-specific behavior:

src/webview/web_context.rs

@@ -64,7 +64,7 @@ impl Default for WebContext {
 }
 
 /// Data that all [`WebContext`] share regardless of platform.
-#[derive(Debug, Default)]
+#[derive(Default, Debug)]
 pub struct WebContextData {
   data_directory: Option<PathBuf>,
 }

src/webview/webkitgtk/mod.rs

@@ -13,11 +13,12 @@ use gio::Cancellable;
 use glib::signal::Inhibit;
 use gtk::prelude::*;
 use webkit2gtk::{
-  traits::*, UserContentInjectedFrames, UserScript, UserScriptInjectionTime, WebView,
-  WebViewBuilder,
+  traits::*, NavigationPolicyDecision, PolicyDecisionType, UserContentInjectedFrames, UserScript,
+  UserScriptInjectionTime, WebView, WebViewBuilder,
 };
 use webkit2gtk_sys::{
   webkit_get_major_version, webkit_get_micro_version, webkit_get_minor_version,
+  webkit_policy_decision_ignore, webkit_policy_decision_use,
 };
 
 use web_context::WebContextExt;
@@ -198,6 +199,31 @@ impl InnerWebView {
       Inhibit(false)
     });
 
+    if let Some(nav_handler) = attributes.navigation_handler {
+      webview.connect_decide_policy(move |_webview, policy_decision, policy_type| {
+        if let PolicyDecisionType::NavigationAction = policy_type {
+          if let Some(policy) = policy_decision.dynamic_cast_ref::<NavigationPolicyDecision>() {
+            if let Some(nav_action) = policy.navigation_action() {
+              if let Some(uri_req) = nav_action.request() {
+                if let Some(uri) = uri_req.uri() {
+                  let allow = nav_handler(uri.to_string());
+                  let pointer = policy_decision.as_ptr();
+                  unsafe {
+                    if allow {
+                      webkit_policy_decision_use(pointer)
+                    } else {
+                      webkit_policy_decision_ignore(pointer)
+                    }
+                  }
+                }
+              }
+            }
+          }
+        }
+        true
+      });
+    }
+
     // Gtk application window can only contain one widget at a time.
     // In tao, we add a GtkBox to pack menu bar. So we check if
     // there's a box widget here.

src/webview/webview2/mod.rs

@@ -299,6 +299,29 @@ window.addEventListener('mousemove', (e) => window.chrome.webview.postMessage('_
     }
     .map_err(webview2_com::Error::WindowsError)?;
 
+    if let Some(nav_callback) = attributes.navigation_handler {
+      unsafe {
+        webview
+          .NavigationStarting(
+            NavigationStartingEventHandler::create(Box::new(move |_, args| {
+              if let Some(args) = args {
+                let mut uri = PWSTR::default();
+                args.Uri(&mut uri)?;
+                let uri = take_pwstr(uri);
+
+                let allow = nav_callback(uri);
+
+                args.SetCancel(!allow)?;
+              }
+
+              Ok(())
+            })),
+            &mut token,
+          )
+          .map_err(webview2_com::Error::WindowsError)?;
+      }
+    }
+
     let mut custom_protocol_names = HashSet::new();
     if !attributes.custom_protocols.is_empty() {
       for (name, _) in &attributes.custom_protocols {

src/webview/wkwebview/mod.rs

@@ -15,7 +15,7 @@ use cocoa::{
 };
 use cocoa::{
   base::id,
-  foundation::{NSDictionary, NSFastEnumeration},
+  foundation::{NSDictionary, NSFastEnumeration, NSInteger},
 };
 
 use std::{
@@ -62,6 +62,7 @@ pub struct InnerWebView {
   // Note that if following functions signatures are changed in the future,
   // all fucntions pointer declarations in objc callbacks below all need to get updated.
   ipc_handler_ptr: *mut (Box<dyn Fn(&Window, String)>, Rc<Window>),
+  nav_handler_ptr: *mut Box<dyn Fn(String) -> bool>,
   #[cfg(target_os = "macos")]
   file_drop_ptr: *mut (Box<dyn Fn(&Window, FileDropEvent) -> bool>, Rc<Window>),
   protocol_ptrs: Vec<*mut Box<dyn Fn(&HttpRequest) -> Result<HttpResponse>>>,
@@ -309,6 +310,52 @@ impl InnerWebView {
         null_mut()
       };
 
+      // Navigation handler
+      extern "C" fn navigation_policy(this: &Object, _: Sel, _: id, action: id, handler: id) {
+        unsafe {
+          let request: id = msg_send![action, request];
+          let url: id = msg_send![request, URL];
+          let url: id = msg_send![url, absoluteString];
+          let url = NSString(Id::from_ptr(url));
+          let handler = handler as *mut block::Block<(NSInteger,), c_void>;
+
+          let function = this.get_ivar::<*mut c_void>("function");
+          if !function.is_null() {
+            let function = &mut *(*function as *mut Box<dyn for<'s> Fn(String) -> bool>);
+            match (function)(url.to_str().to_string()) {
+              true => (*handler).call((1,)),
+              false => (*handler).call((0,)),
+            };
+          } else {
+            log::warn!("WebView instance is dropped! This navigation handler shouldn't be called.");
+            (*handler).call((1,));
+          }
+        }
+      }
+
+      let nav_handler_ptr = if let Some(nav_handler) = attributes.navigation_handler {
+        let cls = match ClassDecl::new("UIViewController", class!(NSObject)) {
+          Some(mut cls) => {
+            cls.add_ivar::<*mut c_void>("function");
+            cls.add_method(
+              sel!(webView:decidePolicyForNavigationAction:decisionHandler:),
+              navigation_policy as extern "C" fn(&Object, Sel, id, id, id),
+            );
+            cls.register()
+          }
+          None => class!(UIViewController),
+        };
+
+        let handler: id = msg_send![cls, new];
+        let nav_handler_ptr = Box::into_raw(Box::new(nav_handler));
+        (*handler).set_ivar("function", nav_handler_ptr as *mut _ as *mut c_void);
+
+        let _: () = msg_send![webview, setNavigationDelegate: handler];
+        nav_handler_ptr
+      } else {
+        null_mut()
+      };
+
       // File drop handling
       #[cfg(target_os = "macos")]
       let file_drop_ptr = match attributes.file_drop_handler {
@@ -330,6 +377,7 @@ impl InnerWebView {
         ns_window,
         manager,
         ipc_handler_ptr,
+        nav_handler_ptr,
         #[cfg(target_os = "macos")]
         file_drop_ptr,
         protocol_ptrs,
@@ -498,6 +546,10 @@ impl Drop for InnerWebView {
         let _ = Box::from_raw(self.ipc_handler_ptr);
       }
 
+      if !self.nav_handler_ptr.is_null() {
+        let _ = Box::from_raw(self.ipc_handler_ptr);
+      }
+
       #[cfg(target_os = "macos")]
       if !self.file_drop_ptr.is_null() {
         let _ = Box::from_raw(self.file_drop_ptr);