video: wayland: Display non-native fullscreen aspect ratios centered …

…with a black border

Employ subsurfaces and viewports to maintain a proper aspect ratio for fullscreen modes that don't match the display's native aspect ratio, and display the content centered, with a black border.  The mask surface uses a 1x1 SHM buffer, which is scaled to the display output dimensions using a viewport.  The draw surface becomes a subsurface of the parent mask surface and runs in desynced mode.

CMakeLists.txt

@@ -905,6 +905,22 @@ if(SDL_LIBC)
     check_symbol_exists(getauxval "sys/auxv.h" HAVE_GETAUXVAL)
     check_symbol_exists(elf_aux_info "sys/auxv.h" HAVE_ELF_AUX_INFO)
     check_symbol_exists(poll "poll.h" HAVE_POLL)
+    check_symbol_exists(posix_fallocate "fcntl.h" HAVE_POSIX_FALLOCATE)
+
+    # memfd_create() and mkostemp() require _GNU_SOURCE to be defined on Linux
+    if(LINUX)
+      list(FIND CMAKE_REQUIRED_DEFINITIONS "-D_GNU_SOURCE" GNU_SOURCE_DEFINED)
+    else()
+      set(GNU_SOURCE_DEFINED 0)
+    endif()
+    if(GNU_SOURCE_DEFINED EQUAL -1)
+      list(APPEND CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
+    endif()
+    check_symbol_exists(memfd_create "sys/mman.h" HAVE_MEMFD_CREATE)
+    check_symbol_exists(mkostemp "stdlib.h" HAVE_MKOSTEMP)
+    if(GNU_SOURCE_DEFINED EQUAL -1)
+      list(REMOVE_ITEM CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
+    endif()
 
     check_library_exists(m pow "" HAVE_LIBM)
     if(HAVE_LIBM)

include/SDL_config.h.cmake

@@ -202,6 +202,9 @@
 #cmakedefine HAVE_GETAUXVAL 1
 #cmakedefine HAVE_ELF_AUX_INFO 1
 #cmakedefine HAVE_POLL 1
+#cmakedefine HAVE_POSIX_FALLOCATE 1
+#cmakedefine HAVE_MEMFD_CREATE 1
+#cmakedefine HAVE_MKOSTEMP 1
 #cmakedefine HAVE__EXIT 1
 
 #elif defined(__WIN32__)

src/video/wayland/SDL_waylandevents.c

@@ -391,8 +391,8 @@ pointer_handle_motion(void *data, struct wl_pointer *pointer,
     if (input->pointer_focus) {
         const float sx_f = (float)wl_fixed_to_double(sx_w);
         const float sy_f = (float)wl_fixed_to_double(sy_w);
-        const int   sx   = (int)SDL_lroundf(sx_f * window->pointer_scale_x);
-        const int   sy   = (int)SDL_lroundf(sy_f * window->pointer_scale_y);
+        const int   sx   = (int)SDL_lroundf((sx_f - window->pointer_offset_x) * window->pointer_scale_x);
+        const int   sy   = (int)SDL_lroundf((sy_f - window->pointer_offset_y) * window->pointer_scale_y);
         SDL_SendMouseMotion(window->sdlwindow, 0, 0, sx, sy);
     }
 }
@@ -719,10 +719,10 @@ touch_handler_down(void *data, struct wl_touch *touch, unsigned int serial,
                    int id, wl_fixed_t fx, wl_fixed_t fy)
 {
     SDL_WindowData *window_data = (SDL_WindowData *)wl_surface_get_user_data(surface);
-    const double dblx = wl_fixed_to_double(fx) * window_data->pointer_scale_x;
-    const double dbly = wl_fixed_to_double(fy) * window_data->pointer_scale_y;
-    const float x = dblx / window_data->sdlwindow->w;
-    const float y = dbly / window_data->sdlwindow->h;
+    const double dblx = (wl_fixed_to_double(fx) - window_data->pointer_offset_x) * window_data->pointer_scale_x;
+    const double dbly = (wl_fixed_to_double(fy) - window_data->pointer_offset_y) * window_data->pointer_scale_y;
+    const float x = dblx / (float)window_data->sdlwindow->w;
+    const float y = dbly / (float)window_data->sdlwindow->h;
 
     touch_add(id, x, y, surface);
 
@@ -752,8 +752,8 @@ touch_handler_motion(void *data, struct wl_touch *touch, unsigned int timestamp,
                      int id, wl_fixed_t fx, wl_fixed_t fy)
 {
     SDL_WindowData *window_data = (SDL_WindowData *)wl_surface_get_user_data(touch_surface(id));
-    const double dblx = wl_fixed_to_double(fx) * window_data->pointer_scale_x;
-    const double dbly = wl_fixed_to_double(fy) * window_data->pointer_scale_y;
+    const double dblx = (wl_fixed_to_double(fx) - window_data->pointer_offset_x) * window_data->pointer_scale_x;
+    const double dbly = (wl_fixed_to_double(fy) - window_data->pointer_offset_y) * window_data->pointer_scale_y;
     const float x = dblx / window_data->sdlwindow->w;
     const float y = dbly / window_data->sdlwindow->h;
 
@@ -1824,8 +1824,8 @@ tablet_tool_handle_motion(void* data, struct zwp_tablet_tool_v2* tool, wl_fixed_
     input->sx_w = sx_w;
     input->sy_w = sy_w;
     if (input->tool_focus) {
-        const float sx_f = (float)wl_fixed_to_double(sx_w);
-        const float sy_f = (float)wl_fixed_to_double(sy_w);
+        const float sx_f = (float)wl_fixed_to_double(sx_w) - window->pointer_offset_x;
+        const float sy_f = (float)wl_fixed_to_double(sy_w) - window->pointer_offset_y;
         const int   sx   = (int)SDL_lroundf(sx_f * window->pointer_scale_x);
         const int   sy   = (int)SDL_lroundf(sy_f * window->pointer_scale_y);
         SDL_SendMouseMotion(window->sdlwindow, 0, 0, sx, sy);
@@ -2197,6 +2197,13 @@ static const struct zwp_relative_pointer_v1_listener relative_pointer_listener =
     relative_pointer_handle_relative_motion,
 };
 
+SDL_FORCE_INLINE struct wl_surface *
+get_input_lock_surface(SDL_Window *window)
+{
+    SDL_WindowData *data = window->driverdata;
+    return data->parent_surface ? data->parent_surface : data->surface;
+}
+
 static void
 locked_pointer_locked(void *data,
                       struct zwp_locked_pointer_v1 *locked_pointer)
@@ -2227,7 +2234,7 @@ lock_pointer_to_window(SDL_Window *window,
 
     locked_pointer =
         zwp_pointer_constraints_v1_lock_pointer(d->pointer_constraints,
-                                                w->surface,
+                                                get_input_lock_surface(window),
                                                 input->pointer,
                                                 NULL,
                                                 ZWP_POINTER_CONSTRAINTS_V1_LIFETIME_PERSISTENT);
@@ -2371,7 +2378,7 @@ int Wayland_input_confine_pointer(struct SDL_WaylandInput *input, SDL_Window *wi
 
     confined_pointer =
         zwp_pointer_constraints_v1_confine_pointer(d->pointer_constraints,
-                                                   w->surface,
+                                                   get_input_lock_surface(window),
                                                    input->pointer,
                                                    confine_rect,
                                                    ZWP_POINTER_CONSTRAINTS_V1_LIFETIME_PERSISTENT);
@@ -2406,7 +2413,7 @@ int Wayland_input_grab_keyboard(SDL_Window *window, struct SDL_WaylandInput *inp
 
     w->key_inhibitor =
         zwp_keyboard_shortcuts_inhibit_manager_v1_inhibit_shortcuts(d->key_inhibitor_manager,
-                                                                    w->surface,
+                                                                    get_input_lock_surface(window),
                                                                     input->seat);
 
     return 0;

src/video/wayland/SDL_waylandvideo.c

@@ -850,6 +850,8 @@ display_handle_global(void *data, struct wl_registry *registry, uint32_t id,
         Wayland_init_xdg_output(d);
     } else if (SDL_strcmp(interface, "wp_viewporter") == 0) {
         d->viewporter = wl_registry_bind(d->registry, id, &wp_viewporter_interface, 1);
+    } else if (SDL_strcmp(interface, "wl_subcompositor") == 0) {
+        d->subcompositor = wl_registry_bind(d->registry, id, &wl_subcompositor_interface, 1);
 
 #ifdef SDL_VIDEO_DRIVER_WAYLAND_QT_TOUCH
     } else if (SDL_strcmp(interface, "qt_touch_extension") == 0) {
@@ -1066,6 +1068,10 @@ Wayland_VideoQuit(_THIS)
         wp_viewporter_destroy(data->viewporter);
     }
 
+    if (data->subcompositor) {
+        wl_subcompositor_destroy(data->subcompositor);
+    }
+
     if (data->compositor)
         wl_compositor_destroy(data->compositor);
 

src/video/wayland/SDL_waylandvideo.h

@@ -75,6 +75,7 @@ typedef struct {
     struct zwp_text_input_manager_v3 *text_input_manager;
     struct zxdg_output_manager_v1 *xdg_output_manager;
     struct wp_viewporter *viewporter;
+    struct wl_subcompositor *subcompositor;
 
     EGLDisplay edpy;
     EGLContext context;