From ab916a959e096a3af9502b50a622eda0e8f83253 Mon Sep 17 00:00:00 2001
From: Joshua Ashton <[EMAIL REDACTED]>
Date: Wed, 27 Mar 2024 18:33:50 +0000
Subject: [PATCH] video: Only prefer Wayland if fifo-v1 and commit-timing-v1
are available
Wayland has a myriad of unresolved problems regarding surface suspension
blocking forever in QueuePresent/SwapBuffers when occludedand the FIFO
(vsync) implementation being fundamentally broken leading to reduced
GPU-bound performance and 'barcoding' frametimes due to swapchain
starvation.
There are two protocols used to solve these two problems together --
fifo-v1 and commit-timing-v1, which implement the commit queue on the
compositor side, and a timestamp that frames are intended to be
displayed for/discarded respectfully.
To avoid severe performance regressions for developers targeting SDL3,
only pick Wayland as the default backend when these two protocols are
supported -- otherwise fallback to X11/XWayland.
We do this by having two VideoBootStraps, one which is tests the
preferred case, "wayland_preferred" (ie. if fifo-v1 + commit-timing-v1
are available init time), and the fallback, which is just "wayland",
the same name as before, which does no such tests.
Thus, forcing with SDL_VIDEO_DRIVER=wayland will go onto the fallback
option, and pick Wayland always, as usual, so there is no behaviour
change.
In the case that X11/XWayland is not available (ie. no DISPLAY), we will
still fallback to using Wayland without these protocols available.
Signed-off-by: Joshua Ashton <joshua@froggi.es>
---
src/video/SDL_sysvideo.h | 3 +-
src/video/SDL_video.c | 5 +-
src/video/wayland/SDL_waylandvideo.c | 82 +++++++++++++++++++++++++++-
3 files changed, 85 insertions(+), 5 deletions(-)
diff --git a/src/video/SDL_sysvideo.h b/src/video/SDL_sysvideo.h
index 6554191225eab..9e03a86687ed5 100644
--- a/src/video/SDL_sysvideo.h
+++ b/src/video/SDL_sysvideo.h
@@ -503,7 +503,8 @@ extern VideoBootStrap RPI_bootstrap;
extern VideoBootStrap KMSDRM_bootstrap;
extern VideoBootStrap DUMMY_bootstrap;
extern VideoBootStrap DUMMY_evdev_bootstrap;
-extern VideoBootStrap Wayland_bootstrap;
+extern VideoBootStrap Wayland_preferred_bootstrap;
+extern VideoBootStrap Wayland_fallback_bootstrap;
extern VideoBootStrap VIVANTE_bootstrap;
extern VideoBootStrap Emscripten_bootstrap;
extern VideoBootStrap OFFSCREEN_bootstrap;
diff --git a/src/video/SDL_video.c b/src/video/SDL_video.c
index 47677944d7a4a..353e110403819 100644
--- a/src/video/SDL_video.c
+++ b/src/video/SDL_video.c
@@ -71,11 +71,14 @@ static VideoBootStrap *bootstrap[] = {
&COCOA_bootstrap,
#endif
#ifdef SDL_VIDEO_DRIVER_WAYLAND
- &Wayland_bootstrap,
+ &Wayland_preferred_bootstrap,
#endif
#ifdef SDL_VIDEO_DRIVER_X11
&X11_bootstrap,
#endif
+#ifdef SDL_VIDEO_DRIVER_WAYLAND
+ &Wayland_fallback_bootstrap,
+#endif
#ifdef SDL_VIDEO_DRIVER_VIVANTE
&VIVANTE_bootstrap,
#endif
diff --git a/src/video/wayland/SDL_waylandvideo.c b/src/video/wayland/SDL_waylandvideo.c
index db0d40a7a7be6..7a5f2cb8747bc 100644
--- a/src/video/wayland/SDL_waylandvideo.c
+++ b/src/video/wayland/SDL_waylandvideo.c
@@ -68,6 +68,7 @@
#include <libdecor.h>
#endif
+#define WAYLANDVID_PREFERRED_DRIVER_NAME "wayland_preferred"
#define WAYLANDVID_DRIVER_NAME "wayland"
/* Clamp certain core protocol versions on older versions of libwayland. */
@@ -372,7 +373,54 @@ static void Wayland_DeleteDevice(SDL_VideoDevice *device)
SDL_WAYLAND_UnloadSymbols();
}
-static SDL_VideoDevice *Wayland_CreateDevice(void)
+typedef struct
+{
+ SDL_bool has_fifo_v1;
+ SDL_bool has_commit_timing_v1;
+} SDL_WaylandPreferredData;
+
+static void wayland_preferred_check_handle_global(void *data, struct wl_registry *registry, uint32_t id,
+ const char *interface, uint32_t version)
+{
+ SDL_WaylandPreferredData *d = data;
+
+ if (SDL_strcmp(interface, "wp_fifo_manager_v1") == 0) {
+ d->has_fifo_v1 = SDL_TRUE;
+ } else if (SDL_strcmp(interface, "wp_commit_timing_manager_v1") == 0) {
+ d->has_commit_timing_v1 = SDL_TRUE;
+ }
+}
+
+static void wayland_preferred_check_remove_global(void *data, struct wl_registry *registry, uint32_t id)
+{
+ /* No need to do anything here. */
+}
+
+static const struct wl_registry_listener preferred_registry_listener = {
+ wayland_preferred_check_handle_global,
+ wayland_preferred_check_remove_global
+};
+
+static SDL_bool Wayland_IsPreferred(struct wl_display *display)
+{
+ struct wl_registry *registry = wl_display_get_registry(display);
+ SDL_WaylandPreferredData preferred_data = { 0 };
+
+ if (!registry) {
+ SDL_SetError("Failed to get the Wayland registry");
+ return SDL_FALSE;
+ }
+
+ wl_registry_add_listener(registry, &preferred_registry_listener, &preferred_data);
+
+ WAYLAND_wl_display_roundtrip(display);
+
+ wl_registry_destroy(registry);
+
+ return preferred_data.has_fifo_v1 && preferred_data.has_commit_timing_v1;
+}
+
+static SDL_VideoDevice *Wayland_CreateDevice(SDL_bool fallback)
{
SDL_VideoDevice *device;
SDL_VideoData *data;
@@ -401,6 +449,18 @@ static SDL_VideoDevice *Wayland_CreateDevice(void)
}
}
+ /*
+ * If we are checking for preferred Wayland, then let's query for
+ * fifo-v1 and commit-timing-v1's existance so we don't regress
+ * GPU-bound performance and frame-pacing by default due to
+ * swapchain starvation.
+ */
+ if (!fallback && !Wayland_IsPreferred(display)) {
+ WAYLAND_wl_display_disconnect(display);
+ SDL_WAYLAND_UnloadSymbols();
+ return NULL;
+ }
+
data = SDL_calloc(1, sizeof(*data));
if (!data) {
WAYLAND_wl_display_disconnect(display);
@@ -534,9 +594,25 @@ static SDL_VideoDevice *Wayland_CreateDevice(void)
return device;
}
-VideoBootStrap Wayland_bootstrap = {
+static SDL_VideoDevice *Wayland_Preferred_CreateDevice(void)
+{
+ return Wayland_CreateDevice(SDL_FALSE);
+}
+
+static SDL_VideoDevice *Wayland_Fallback_CreateDevice(void)
+{
+ return Wayland_CreateDevice(SDL_TRUE);
+}
+
+VideoBootStrap Wayland_preferred_bootstrap = {
+ WAYLANDVID_PREFERRED_DRIVER_NAME, "SDL Wayland video driver",
+ Wayland_Preferred_CreateDevice,
+ Wayland_ShowMessageBox
+};
+
+VideoBootStrap Wayland_fallback_bootstrap = {
WAYLANDVID_DRIVER_NAME, "SDL Wayland video driver",
- Wayland_CreateDevice,
+ Wayland_Fallback_CreateDevice,
Wayland_ShowMessageBox
};