[epiphany/mcatanzaro/#1733] ephy-download: use a nested main loop in decide-destination

[Michael Catanzaro <mcatanzaro src gnome org>]

commit cea40eb6eec07d4cfbc40e01e1c38b1582a5381a
Author: Michael Catanzaro <mcatanzaro redhat com>
Date:   Mon Apr 4 15:43:20 2022 -0500

    ephy-download: use a nested main loop in decide-destination
    
    d2620578 broke the "ask on download" setting: WebKit expects a download
    destination to be provided synchronously, which means using
    gtk_dialog_run() was important and switching to use gtk_window_present()
    was not OK. Now the results of the destination selection file chooser
    are ignored, and the download is actually started before displaying the
    file chooser. Fixing this properly requires WebKit API changes, so for
    now let's manually implement our own nested main loop.
    
    Fixes #1747
    
    Also incidentally/accidentally fixes #1749

 embed/ephy-download.c | 47 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 30 insertions(+), 17 deletions(-)
---
diff --git a/embed/ephy-download.c b/embed/ephy-download.c
index 1d3b2d552..652d52512 100644
--- a/embed/ephy-download.c
+++ b/embed/ephy-download.c
@@ -752,6 +752,7 @@ typedef struct {
   GtkWindow *dialog;
   GFile *directory;
   GtkLabel *directory_label;
+  GMainLoop *nested_loop;
 } SuggestedFilenameData;
 
 static void
@@ -777,10 +778,7 @@ filename_suggested_dialog_cb (GtkDialog             *dialog,
   }
 
   gtk_widget_destroy (GTK_WIDGET (dialog));
-
-  g_object_unref (data->directory);
-  g_free (data->suggested_filename);
-  g_free (data);
+  g_main_loop_quit (data->nested_loop);
 }
 
 static void
@@ -848,7 +846,7 @@ filename_suggested_cb (EphyDownload *download,
   g_autofree gchar *display_name = NULL;
   const gchar *content_type;
   const char *directory_path;
-  SuggestedFilenameData *data;
+  SuggestedFilenameData data;
 
   application = G_APPLICATION (ephy_embed_shell_get_default ());
   toplevel = gtk_application_get_active_window (GTK_APPLICATION (application));
@@ -908,26 +906,41 @@ filename_suggested_cb (EphyDownload *download,
 
   directory_path = g_settings_get_string (EPHY_SETTINGS_WEB, EPHY_PREFS_WEB_LAST_DOWNLOAD_DIRECTORY);
 
-  data = g_new0 (SuggestedFilenameData, 1);
-  data->download = download;
-  data->webkit_download = webkit_download;
-  data->suggested_filename = g_strdup (suggested_filename);
-  data->dialog = GTK_WINDOW (dialog);
+  data.download = download;
+  data.webkit_download = webkit_download;
+  data.suggested_filename = g_strdup (suggested_filename);
+  data.dialog = GTK_WINDOW (dialog);
   if (!directory_path || !directory_path[0])
-    data->directory = g_file_new_for_path (ephy_file_get_downloads_dir ());
+    data.directory = g_file_new_for_path (ephy_file_get_downloads_dir ());
   else
-    data->directory = g_file_new_for_path (directory_path);
-  data->directory_label = GTK_LABEL (button_label);
+    data.directory = g_file_new_for_path (directory_path);
+  data.directory_label = GTK_LABEL (button_label);
+  data.nested_loop = g_main_loop_new (NULL, FALSE);
 
-  display_name = ephy_file_get_display_name (data->directory);
-  gtk_label_set_label (data->directory_label, display_name);
+  display_name = ephy_file_get_display_name (data.directory);
+  gtk_label_set_label (data.directory_label, display_name);
 
   g_signal_connect (button, "clicked",
-                    G_CALLBACK (filename_suggested_button_cb), data);
+                    G_CALLBACK (filename_suggested_button_cb), &data);
   g_signal_connect (dialog, "response",
-                    G_CALLBACK (filename_suggested_dialog_cb), data);
+                    G_CALLBACK (filename_suggested_dialog_cb), &data);
 
   gtk_window_present (GTK_WINDOW (dialog));
+
+  /* Here we need to wait for the final filename from the file chooser. Sadly,
+   * there is no safe way to do this. Ideally, we would indicate to WebKit that
+   * we wish to handle this asynchronously, but there is no way to do that:
+   * https://bugs.webkit.org/show_bug.cgi?id=238748
+   *
+   * So instead let's run a nested main loop here. This is not particularly safe
+   * or good, but allows emulating gtk_dialog_run() and doesn't require new
+   * WebKit API.
+   */
+  g_main_loop_run (data.nested_loop);
+
+  g_main_loop_unref (data.nested_loop);
+  g_object_unref (data.directory);
+  g_free (data.suggested_filename);
 }
 
 EphyDownload *