Add gtk_show_uri_win32 ()

This is a new internal utility to open/show/launch/execute URIs and
files on Windows, using Windows's native ShellExecuteEx () and
SHOpenWithDialog () APIs.

The advantages this has over using the win32 implementation of
g_app_info_launch_default_for_uri ():

* the implementation here is fairly simple;
* it doesn't involve trying to grok the registry for app / file	type
  registrations (at least not inside GLib/GTK side, the implementations
  of ShellExecuteEx/SHOpenWithDialog presumably do that internally);
* it doesn't require convoluted formatting / escaping of invocation
  command lines that GWin32AppInfo / gspawn-win32 has to do otherwise
  (again, presumably the Windows libraries implement this internally);
* it's certain to end up opening the file/URI the same way other apps
  in the system would;
* it can/will open the native system UI for picking an app in case there
  are multiple options (or when so requested programmatically with the
  always-ask flag), or if there is no app installed that can handle the
  URI scheme / file type;
* it lets us pass the parent window handle, much like the portal APIs;
  presumably Windows would use this for positioning the picking UI, or
  placing the launched app's window;
* presumably, this will properly elevate privileges with a User Access
  Control (UAC) prompt if the app being launched requires administrator
  access; this presumably is impossible with the wspawn* APIs that
  gspawn-win32 uses;
* this has a much better chance to work properly with the win32 app
  isolation (AppContainer) technology.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>

gtk/gtkshowwin32.c

@@ -0,0 +1,185 @@
+/*
+ * GTK - The GIMP Toolkit
+ * Copyright (C) 2024 Sergey Bugaev
+ * All rights reserved.
+ *
+ * This Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This Library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "gtkshowwin32.h"
+#include <gtk/gtknative.h>
+#include <gdk/win32/gdkwin32misc.h>
+
+#include <shellapi.h>
+#include <shlobj.h>
+
+typedef struct {
+  gunichar2 *uri_or_path;
+  gboolean always_ask;
+} ShowData;
+
+static void
+show_data_free (ShowData *data)
+{
+  g_free (data->uri_or_path);
+  g_slice_free (ShowData, data);
+}
+
+static void
+show_uri_win32_in_thread (GTask        *task,
+                          gpointer      source_object,
+                          gpointer      task_data,
+                          GCancellable *cancellable)
+{
+  ShowData *data = task_data;
+  GdkSurface *parent_surface;
+  HWND parent_hwnd;
+  HMONITOR monitor;
+  HRESULT hr;
+
+  if (source_object)
+    {
+      parent_surface = gtk_native_get_surface (GTK_NATIVE (source_object));
+      parent_hwnd = GDK_SURFACE_HWND (parent_surface);
+      monitor = MonitorFromWindow (parent_hwnd, MONITOR_DEFAULTTONULL);
+    }
+  else
+    {
+      parent_hwnd = 0;
+      monitor = (HMONITOR) NULL;
+    }
+
+  if (!data->always_ask)
+    {
+      BOOL res;
+      SHELLEXECUTEINFOW shex_info;
+
+      /* Attempt to initialize COM, in the off chance that there
+       * are ShellExecute hooks. */
+      hr = CoInitializeEx (NULL, COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE);
+
+      memset (&shex_info, 0, sizeof (shex_info));
+
+      shex_info.cbSize = sizeof (shex_info);
+      shex_info.fMask = SEE_MASK_NOASYNC | SEE_MASK_HMONITOR;
+      shex_info.hwnd = parent_hwnd;
+      shex_info.lpVerb = NULL;
+
+      shex_info.lpFile = data->uri_or_path;
+      shex_info.lpParameters = NULL;
+      shex_info.lpDirectory = NULL;
+      shex_info.nShow = SW_SHOWNORMAL;
+      shex_info.hMonitor = monitor;
+
+      /* Us passing the monitor derived from the parent window shouldn't
+       * break any custom window positioning logic in the app being
+       * launched, since the passed monitor is only used as a fallback
+       * for apps that use CW_USEDEFAULT. */
+
+      res = ShellExecuteExW (&shex_info);
+
+      /* Un-initialize COM if we have successfully initialized it earlier. */
+      if (SUCCEEDED (hr))
+        CoUninitialize ();
+
+      if (res)
+        g_task_return_boolean (task, TRUE);
+      else
+        {
+          int errsv = GetLastError ();
+          gchar *emsg = g_win32_error_message (errsv);
+
+          g_task_return_new_error (task, G_IO_ERROR,
+                                   g_io_error_from_win32_error (errsv),
+                                   "%s", emsg);
+          g_free (emsg);
+        }
+    }
+  else
+    {
+      OPENASINFO openas_info;
+
+      memset (&openas_info, 0, sizeof (openas_info));
+
+      openas_info.pcszFile = data->uri_or_path;
+      openas_info.pcszClass = NULL;
+      openas_info.oaifInFlags = OAIF_ALLOW_REGISTRATION | OAIF_REGISTER_EXT | OAIF_EXEC;
+
+      hr = SHOpenWithDialog (parent_hwnd, &openas_info);
+
+      if (SUCCEEDED (hr))
+        g_task_return_boolean (task, TRUE);
+      else
+        g_task_return_new_error (task, G_IO_ERROR,
+                                 G_IO_ERROR_FAILED,
+                                 "Failed to display Open With dialog: 0x%lx", hr);
+    }
+}
+
+void
+gtk_show_uri_win32 (GtkWindow          *parent,
+                    const char         *uri_or_path,
+                    gboolean            always_ask,
+                    GCancellable       *cancellable,
+                    GAsyncReadyCallback callback,
+                    gpointer            user_data)
+{
+  ShowData *show_data;
+  GTask *task;
+  GError *error = NULL;
+  char *owned_path = NULL;
+
+  g_return_if_fail (uri_or_path != NULL);
+
+  task = g_task_new (parent, cancellable, callback, user_data);
+  g_task_set_source_tag (task, gtk_show_uri_win32);
+
+  /* ShellExecute doesn't quite like file:// URLs, so convert
+   * those to file paths now. */
+  if (g_str_has_prefix (uri_or_path, "file://"))
+    {
+      GFile *file = g_file_new_for_uri (uri_or_path);
+      uri_or_path = owned_path = g_file_get_path (file);
+      g_object_unref (file);
+    }
+
+  show_data = g_slice_new (ShowData);
+  show_data->always_ask = always_ask;
+  /* Note: uri_or_path is UTF-8 encoded here. */
+  show_data->uri_or_path = g_utf8_to_utf16 (uri_or_path, -1, NULL, NULL, &error);
+  g_clear_pointer(&owned_path, g_free);
+  if (G_UNLIKELY (error))
+    {
+      g_task_return_error (task, error);
+      g_slice_free (ShowData, show_data);
+      g_object_unref (task);
+      return;
+    }
+
+  g_task_set_task_data (task, show_data, (GDestroyNotify) show_data_free);
+  g_task_run_in_thread (task, show_uri_win32_in_thread);
+  g_object_unref (task);
+}
+
+gboolean
+gtk_show_uri_win32_finish (GtkWindow    *parent,
+                           GAsyncResult *result,
+                           GError      **error)
+{
+  g_return_val_if_fail (g_task_is_valid (result, parent), FALSE);
+
+  return g_task_propagate_boolean (G_TASK (result), error);
+}

gtk/gtkshowwin32.h

@@ -0,0 +1,39 @@
+/*
+ * GTK - The GIMP Toolkit
+ * Copyright (C) 2024 Sergey Bugaev
+ * All rights reserved.
+ *
+ * This Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This Library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <gio/gio.h>
+
+typedef struct _GtkWindow GtkWindow;
+
+G_BEGIN_DECLS
+
+void gtk_show_uri_win32 (GtkWindow          *parent,
+                         const char         *uri_or_path,
+                         gboolean            always_ask,
+                         GCancellable       *cancellable,
+                         GAsyncReadyCallback callback,
+                         gpointer            user_data);
+
+gboolean gtk_show_uri_win32_finish (GtkWindow    *parent,
+                                    GAsyncResult *result,
+                                    GError      **error);
+
+G_END_DECLS

gtk/meson.build

@@ -663,6 +663,7 @@ if os_win32
     'gtkimcontextime.c',
     'gtkfilechoosernativewin32.c',
     'gtkwin32.c',
+    'gtkshowwin32.c',
   ]
 endif