Wayland: Add support for dropping files when sandboxed

Adds support for receiving drops that make use
of the [File Transfer][1] portal. This is the case
in sandboxed environments such as Flatpak or Snap.

[1]: https://flatpak.github.io/xdg-desktop-portal/docs/doc-org.freedesktop.portal.FileTransfer.html

.github/workflows/build.yml

@@ -21,7 +21,7 @@ jobs:
             - name: Install dependencies
               run: |
                   sudo apt update
-                  sudo apt install libxrandr-dev libxinerama-dev libxcursor-dev libxi-dev libxext-dev libwayland-dev libxkbcommon-dev
+                  sudo apt install libxrandr-dev libxinerama-dev libxcursor-dev libxi-dev libxext-dev libwayland-dev libxkbcommon-dev libdbus-1-dev
 
             - name: Configure Null shared library
               run: cmake -B build-null-shared -D GLFW_BUILD_WAYLAND=OFF -D GLFW_BUILD_X11=OFF -D BUILD_SHARED_LIBS=ON

README.md

@@ -143,6 +143,7 @@ information on what to include when reporting a bug.
    a modal to a fallback decoration
  - [Wayland] Bugfix: The cursor position was not updated when clicking through
    from a modal to the content area
+ - [Wayland]: Add support for dropping files when sandboxed
  - [X11] Bugfix: Running without a WM could trigger an assert (#2593,#2601,#2631)
  - [Null] Added Vulkan 'window' surface creation via `VK_EXT_headless_surface`
  - [Null] Added EGL context creation on Mesa via `EGL_MESA_platform_surfaceless`

src/CMakeLists.txt

@@ -161,6 +161,10 @@ if (GLFW_BUILD_WAYLAND)
         wayland-egl>=0.2.7
         xkbcommon>=0.5.0)
 
+    pkg_check_modules(DBUS REQUIRED dbus-1)
+    target_include_directories(glfw PRIVATE ${DBUS_INCLUDE_DIRS})
+    target_link_libraries(glfw PRIVATE ${DBUS_LIBRARIES})
+
     target_include_directories(glfw PRIVATE ${Wayland_INCLUDE_DIRS})
 
     if (NOT CMAKE_SYSTEM_NAME STREQUAL "Linux")

src/wl_platform.h

@@ -338,6 +338,7 @@ typedef struct _GLFWofferWayland
     struct wl_data_offer*       offer;
     GLFWbool                    text_plain_utf8;
     GLFWbool                    text_uri_list;
+    GLFWbool                    portal_file_transfer;
 } _GLFWofferWayland;
 
 typedef struct _GLFWscaleWayland
@@ -450,6 +451,7 @@ typedef struct _GLFWlibraryWayland
     struct wl_data_offer*       dragOffer;
     _GLFWwindow*                dragFocus;
     uint32_t                    dragSerial;
+    GLFWbool                    dragUsePortal;
 
     const char*                 tag;
 

src/wl_window.c

@@ -41,6 +41,7 @@
 #include <sys/timerfd.h>
 #include <poll.h>
 #include <linux/input-event-codes.h>
+#include <dbus/dbus.h>
 
 #include "wayland-client-protocol.h"
 #include "xdg-shell-client-protocol.h"
@@ -54,6 +55,7 @@
 
 #define GLFW_BORDER_SIZE    4
 #define GLFW_CAPTION_HEIGHT 24
+#define FILE_TRANSFER_PORTAL_MIME_TYPE "application/vnd.portal.filetransfer"
 
 static int createTmpfileCloexec(char* tmpname)
 {
@@ -1969,6 +1971,8 @@ static void dataOfferHandleOffer(void* userData,
                 _glfw.wl.offers[i].text_plain_utf8 = GLFW_TRUE;
             else if (strcmp(mimeType, "text/uri-list") == 0)
                 _glfw.wl.offers[i].text_uri_list = GLFW_TRUE;
+            else if (strcmp(mimeType, FILE_TRANSFER_PORTAL_MIME_TYPE) == 0)
+                _glfw.wl.offers[i].portal_file_transfer = GLFW_TRUE;
 
             break;
         }
@@ -2031,13 +2035,19 @@ static void dataDeviceHandleEnter(void* userData,
         _GLFWwindow* window = wl_surface_get_user_data(surface);
         if (window->wl.surface == surface)
         {
-            if (_glfw.wl.offers[i].text_uri_list)
+            GLFWbool portal = _glfw.wl.offers[i].portal_file_transfer;
+            if (_glfw.wl.offers[i].text_uri_list || portal)
             {
                 _glfw.wl.dragOffer = offer;
                 _glfw.wl.dragFocus = window;
                 _glfw.wl.dragSerial = serial;
+                _glfw.wl.dragUsePortal = portal;
 
-                wl_data_offer_accept(offer, serial, "text/uri-list");
+                if (portal) {
+                    wl_data_offer_accept(offer, serial, FILE_TRANSFER_PORTAL_MIME_TYPE);
+                } else {
+                    wl_data_offer_accept(offer, serial, "text/uri-list");
+                }
             }
         }
     }
@@ -2071,12 +2081,126 @@ static void dataDeviceHandleMotion(void* userData,
 {
 }
 
+// Receives a dropped file that was sent using the
+// [File Transfer](https://flatpak.github.io/xdg-desktop-portal/docs/doc-org.freedesktop.portal.FileTransfer.html) portal.
+// This enables us to receive files when running as a Flatpak or Snap.
+static void dataDeviceHandleFileTransferPortalDrop(void* userData,
+                                                   struct wl_data_device* device)
+{
+    char* key = readDataOfferAsString(_glfw.wl.dragOffer, FILE_TRANSFER_PORTAL_MIME_TYPE);
+    if (!key)
+        return;
+
+    DBusError error;
+    dbus_error_init(&error);
+    DBusConnection* connection = dbus_bus_get(DBUS_BUS_SESSION, &error);
+    if (dbus_error_is_set(&error))
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR, "DBus: %s", error.message);
+        dbus_error_free(&error);
+        _glfw_free(key);
+        return;
+    }
+    dbus_connection_set_exit_on_disconnect(connection, FALSE);
+
+    DBusMessage* message = dbus_message_new_method_call(
+        "org.freedesktop.portal.Documents",
+        "/org/freedesktop/portal/documents",
+        "org.freedesktop.portal.FileTransfer",
+        "RetrieveFiles"
+    );
+    if (!message)
+    {
+        _glfwInputError(GLFW_OUT_OF_MEMORY, NULL);
+        _glfw_free(key);
+        return;
+    }
+    DBusMessageIter args, options;
+    dbus_message_iter_init_append(message, &args);
+    if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_STRING, &key))
+    {
+        _glfwInputError(GLFW_OUT_OF_MEMORY, NULL);
+        dbus_message_unref(message);
+        _glfw_free(key);
+        return;
+    }
+    if (!dbus_message_iter_open_container(&args, DBUS_TYPE_ARRAY, "{sv}", &options))
+    {
+        _glfwInputError(GLFW_OUT_OF_MEMORY, NULL);
+        dbus_message_unref(message);
+        _glfw_free(key);
+        return;
+    }
+    if (!dbus_message_iter_close_container(&args, &options))
+    {
+        _glfwInputError(GLFW_OUT_OF_MEMORY, NULL);
+        dbus_message_unref(message);
+        _glfw_free(key);
+        return;
+    }
+
+    DBusMessage* reply = dbus_connection_send_with_reply_and_block(connection, message, DBUS_TIMEOUT_INFINITE, &error);
+    if (dbus_error_is_set(&error))
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR, "DBus: %s", error.message);
+        dbus_error_free(&error);
+        dbus_message_unref(message);
+        _glfw_free(key);
+        return;
+    }
+
+    DBusMessageIter out, array;
+    if (!dbus_message_iter_init(reply, &out))
+    {
+        _glfwInputError(GLFW_OUT_OF_MEMORY, NULL);
+        dbus_message_unref(reply);
+        dbus_message_unref(message);
+        _glfw_free(key);
+        return;
+    }
+    if (dbus_message_iter_get_arg_type(&out) != DBUS_TYPE_ARRAY
+        || dbus_message_iter_get_element_type(&out) != DBUS_TYPE_STRING) {
+        _glfwInputError(GLFW_PLATFORM_ERROR, "DBus: Reply is not an array of strings");
+        dbus_message_unref(reply);
+        dbus_message_unref(message);
+        _glfw_free(key);
+        return;
+    }
+    dbus_message_iter_recurse(&out, &array);
+    int elements = dbus_message_iter_get_element_count(&out);
+    char** paths = _glfw_calloc(elements, sizeof(char*));
+    if (!paths) {
+        _glfwInputError(GLFW_OUT_OF_MEMORY, NULL);
+        dbus_message_unref(reply);
+        dbus_message_unref(message);
+        _glfw_free(key);
+        return;
+    }
+    int i = 0;
+    do {
+        dbus_message_iter_get_basic(&array, &paths[i++]);
+    } while (dbus_message_iter_next(&array));
+
+    _glfwInputDrop(_glfw.wl.dragFocus, elements, (const char**) paths);
+
+    _glfw_free(paths);
+    dbus_message_unref(reply);
+    dbus_message_unref(message);
+    _glfw_free(key);
+}
+
 static void dataDeviceHandleDrop(void* userData,
                                  struct wl_data_device* device)
 {
     if (!_glfw.wl.dragOffer)
         return;
 
+    if (_glfw.wl.dragUsePortal)
+    {
+        dataDeviceHandleFileTransferPortalDrop(userData, device);
+        return;
+    }
+
     char* string = readDataOfferAsString(_glfw.wl.dragOffer, "text/uri-list");
     if (string)
     {