[gnome-builder] devhelp: Redirect any non local link to the user's browser

[Christian Hergert <chergert src gnome org>]

commit aa4e56d47d3e665a2bce3b3f78f4ccb80d496eb7
Author: vanadiae <vanadiae35 gmail com>
Date:   Sun Aug 1 19:48:45 2021 +0200

    devhelp: Redirect any non local link to the user's browser
    
    And block any remote page resource (e.g. javascript, CSS). The point
    here is to make sure that opening a project's homepage will open the
    web browser. Since it's easy to block the rest of the possible URI
    requests (remote resources), then do that too since we don't expect to
    have any remote things since it's supposed to be entirely offline
    documentation.

 src/plugins/devhelp/gbp-devhelp-page.c | 77 ++++++++++++++++++++++++++++++----
 1 file changed, 70 insertions(+), 7 deletions(-)
---
diff --git a/src/plugins/devhelp/gbp-devhelp-page.c b/src/plugins/devhelp/gbp-devhelp-page.c
index fbb499c0f..8d74b6a1f 100644
--- a/src/plugins/devhelp/gbp-devhelp-page.c
+++ b/src/plugins/devhelp/gbp-devhelp-page.c
@@ -228,21 +228,84 @@ gbp_devhelp_page_class_init (GbpDevhelpPageClass *klass)
   g_type_ensure (WEBKIT_TYPE_WEB_VIEW);
 }
 
+static gboolean
+webview_decide_policy_cb (WebKitWebView           *web_view,
+                          WebKitPolicyDecision    *decision,
+                          WebKitPolicyDecisionType decision_type,
+                          gpointer                 user_data)
+{
+  WebKitURIRequest *request = NULL;
+  g_autoptr(GUri) uri = NULL;
+  gboolean launch_in_browser;
+
+  g_assert (WEBKIT_IS_WEB_VIEW (web_view));
+
+  switch (decision_type) {
+    case WEBKIT_POLICY_DECISION_TYPE_NEW_WINDOW_ACTION:
+    case WEBKIT_POLICY_DECISION_TYPE_NAVIGATION_ACTION:
+      {
+        WebKitNavigationAction *navigation_action =
+          webkit_navigation_policy_decision_get_navigation_action (WEBKIT_NAVIGATION_POLICY_DECISION 
(decision));
+        request = webkit_navigation_action_get_request (navigation_action);
+        launch_in_browser = TRUE;
+      }
+      break;
+    case WEBKIT_POLICY_DECISION_TYPE_RESPONSE:
+      request = webkit_response_policy_decision_get_request (WEBKIT_RESPONSE_POLICY_DECISION (decision));
+      launch_in_browser = FALSE;
+      break;
+    default:
+      return FALSE;
+  }
+
+  uri = g_uri_parse (webkit_uri_request_get_uri (request), G_URI_FLAGS_NONE, NULL);
+  if (!uri)
+    /* Don't let invalid URIs go through the firewall. */
+    {
+      webkit_policy_decision_ignore (decision);
+      return TRUE;
+    }
+  else
+    {
+      /* Allow the integrated devhelp web view to handle local documentation links,
+       * but open any non-local ones with the user's web browser (e.g. library's homepage),
+       * and deny any other remote resource.
+       */
+      if (g_strcmp0 (g_uri_get_scheme (uri), "file") == 0)
+        return FALSE;
+      else
+        {
+          if (launch_in_browser)
+            {
+              GAppLaunchContext *launch_ctx = G_APP_LAUNCH_CONTEXT (gdk_display_get_app_launch_context 
(gdk_display_get_default ()));
+              g_app_info_launch_default_for_uri (webkit_uri_request_get_uri (request),
+                                                 launch_ctx,
+                                                 NULL);
+            }
+          webkit_policy_decision_ignore (decision);
+          return TRUE;
+        }
+    }
+}
+
 static void
-setup_webview_styling (WebKitWebView *web_view)
+setup_webview (WebKitWebView *web_view)
 {
+  g_autoptr(WebKitUserStyleSheet) stylesheet = NULL;
+
   /* Both gi-docgen and gtk-doc use the devhelp-hidden style class to give indications of what
    * elements should be hidden for use by devhelp. Generally it's for the sidebar but it allows
    * to hide really anything not useful for devhelp (e.g. the TOC which already has native GTK
    * widgets in Builder/Devhelp. So follow Devhelp here and hide them.
    */
-  g_autoptr(WebKitUserStyleSheet) stylesheet =
-    webkit_user_style_sheet_new (".devhelp-hidden { display: none; }",
-                                 WEBKIT_USER_CONTENT_INJECT_ALL_FRAMES,
-                                 WEBKIT_USER_STYLE_LEVEL_USER,
-                                 NULL, NULL);
+  stylesheet = webkit_user_style_sheet_new (".devhelp-hidden { display: none; }",
+                                            WEBKIT_USER_CONTENT_INJECT_ALL_FRAMES,
+                                            WEBKIT_USER_STYLE_LEVEL_USER,
+                                            NULL, NULL);
   webkit_user_content_manager_add_style_sheet (webkit_web_view_get_user_content_manager (web_view),
                                                stylesheet);
+
+  g_signal_connect (web_view, "decide-policy", G_CALLBACK (webview_decide_policy_cb), NULL);
 }
 
 static const GActionEntry actions[] = {
@@ -266,7 +329,7 @@ gbp_devhelp_page_init (GbpDevhelpPage *self)
   self->clipboard = gtk_clipboard_get (GDK_SELECTION_PRIMARY);
   self->web_controller = webkit_web_view_get_find_controller (self->web_view);
 
-  setup_webview_styling (self->web_view);
+  setup_webview (self->web_view);
 
   gtk_overlay_add_overlay (self->devhelp_overlay,
                            GTK_WIDGET (self->search_revealer));