kc3-lang/SDL

diff --git a/include/SDL_video.h b/include/SDL_video.h
index 65fd643..41c3e10 100644
--- a/include/SDL_video.h
+++ b/include/SDL_video.h
@@ -1795,7 +1795,7 @@ extern DECLSPEC void SDLCALL SDL_GL_GetDrawableSize(SDL_Window * window, int *w,
  * vsync. Adaptive vsync works the same as vsync, but if you've already missed
  * the vertical retrace for a given frame, it swaps buffers immediately, which
  * might be less jarring for the user during occasional framerate drops. If
- * application requests adaptive vsync and the system does not support it,
+ * an application requests adaptive vsync and the system does not support it,
  * this function will fail and return -1. In such a case, you should probably
  * retry the call with 1 for the interval.
  *
diff --git a/src/video/wayland/SDL_waylandopengles.c b/src/video/wayland/SDL_waylandopengles.c
index 5da365c..50f3368 100644
--- a/src/video/wayland/SDL_waylandopengles.c
+++ b/src/video/wayland/SDL_waylandopengles.c
@@ -22,6 +22,8 @@
 
 #if SDL_VIDEO_DRIVER_WAYLAND && SDL_VIDEO_OPENGL_EGL
 
+#include "SDL_timer.h"
+#include "../../core/unix/SDL_poll.h"
 #include "../SDL_sysvideo.h"
 #include "../../events/SDL_windowevents_c.h"
 #include "SDL_waylandvideo.h"
@@ -55,17 +57,82 @@ Wayland_GLES_CreateContext(_THIS, SDL_Window * window)
     SDL_GLContext context;
     context = SDL_EGL_CreateContext(_this, ((SDL_WindowData *) window->driverdata)->egl_surface);
     WAYLAND_wl_display_flush( ((SDL_VideoData*)_this->driverdata)->display );
-    
     return context;
 }
 
+/* Wayland wants to tell you when to provide new frames, and if you have a non-zero
+   swap interval, Mesa will block until a callback tells it to do so. On some
+   compositors, they might decide that a minimized window _never_ gets a callback,
+   which causes apps to hang during swapping forever. So we always set the official
+   eglSwapInterval to zero to avoid blocking inside EGL, and manage this ourselves.
+   If a swap blocks for too long waiting on a callback, we just go on, under the
+   assumption the frame will be wasted, but this is better than freezing the app.
+   I frown upon platforms that dictate this sort of control inversion (the callback
+   is intended for _rendering_, not stalling until vsync), but we can work around
+   this for now.  --ryan. */
+/* Addendum: several recent APIs demand this sort of control inversion: Emscripten,
+   libretro, Wayland, probably others...it feels like we're eventually going to have
+   to give in with a future SDL API revision, since we can bend the other APIs to
+   this style, but this style is much harder to bend the other way.  :/ */
+int
+Wayland_GLES_SetSwapInterval(_THIS, int interval)
+{
+    if (!_this->egl_data) {
+        return SDL_SetError("EGL not initialized");
+    }
+    
+    /* technically, this is _all_ adaptive vsync (-1), because we can't
+       actually wait for the _next_ vsync if you set 1, but things that
+       request 1 probably won't care _that_ much. I hope. No matter what
+       you do, though, you never see tearing on Wayland. */
+    if (interval > 1) {
+        interval = 1;
+    } else if (interval < -1) {
+        interval = -1;
+    }
+
+    /* !!! FIXME: technically, this should be per-context, right? */
+    _this->egl_data->egl_swapinterval = interval;
+    _this->egl_data->eglSwapInterval(_this->egl_data->egl_display, 0);
+    return 0;
+}
+
+int
+Wayland_GLES_GetSwapInterval(_THIS)
+{
+    if (!_this->egl_data) {
+        SDL_SetError("EGL not initialized");
+        return 0;
+    }
+
+    return _this->egl_data->egl_swapinterval;
+}
+
 int
 Wayland_GLES_SwapWindow(_THIS, SDL_Window *window)
 {
     SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
+    const int swap_interval = _this->egl_data->egl_swapinterval;
+
+    /* Control swap interval ourselves. See comments on Wayland_GLES_SetSwapInterval */
+    if (swap_interval != 0) {
+        const Uint32 max_wait = SDL_GetTicks() + 100;  /* ~10 fps, so we'll progress even if throttled to zero. */
+        struct wl_display *display = ((SDL_VideoData *)_this->driverdata)->display;
+        while ((SDL_AtomicGet(&data->swap_interval_ready) == 0) && (!SDL_TICKS_PASSED(SDL_GetTicks(), max_wait))) {
+            /* !!! FIXME: this is just the crucial piece of Wayland_PumpEvents */
+            WAYLAND_wl_display_flush(display);
+            if (SDL_IOReady(WAYLAND_wl_display_get_fd(display), SDL_FALSE, 0)) {
+                WAYLAND_wl_display_dispatch(display);
+            } else {
+                WAYLAND_wl_display_dispatch_pending(display);
+            }
+        }
+        SDL_AtomicSet(&data->swap_interval_ready, 0);
+    }
 
-    if (SDL_EGL_SwapBuffers(_this, data->egl_surface) < 0) {
-        return -1;
+    /* Feed the frame to Wayland. This will set it so the wl_surface_frame callback can fire again. */
+    if (!_this->egl_data->eglSwapBuffers(_this->egl_data->egl_display, data->egl_surface)) {
+        return SDL_EGL_SetError("unable to show color buffer in an OS-native window", "eglSwapBuffers");
     }
 
     // Wayland-EGL forbids drawing calls in-between SwapBuffers and wl_egl_window_resize
@@ -89,7 +156,9 @@ Wayland_GLES_MakeCurrent(_THIS, SDL_Window * window, SDL_GLContext context)
     }
     
     WAYLAND_wl_display_flush( ((SDL_VideoData*)_this->driverdata)->display );
-    
+
+    _this->egl_data->eglSwapInterval(_this->egl_data->egl_display, 0);  /* see comments on Wayland_GLES_SetSwapInterval. */
+
     return ret;
 }
 
diff --git a/src/video/wayland/SDL_waylandopengles.h b/src/video/wayland/SDL_waylandopengles.h
index cfa72e6..0dfe512 100644
--- a/src/video/wayland/SDL_waylandopengles.h
+++ b/src/video/wayland/SDL_waylandopengles.h
@@ -35,11 +35,11 @@ typedef struct SDL_PrivateGLESData
 #define Wayland_GLES_GetAttribute SDL_EGL_GetAttribute
 #define Wayland_GLES_GetProcAddress SDL_EGL_GetProcAddress
 #define Wayland_GLES_UnloadLibrary SDL_EGL_UnloadLibrary
-#define Wayland_GLES_SetSwapInterval SDL_EGL_SetSwapInterval
-#define Wayland_GLES_GetSwapInterval SDL_EGL_GetSwapInterval
 
 extern int Wayland_GLES_LoadLibrary(_THIS, const char *path);
 extern SDL_GLContext Wayland_GLES_CreateContext(_THIS, SDL_Window * window);
+extern int Wayland_GLES_SetSwapInterval(_THIS, int interval);
+extern int Wayland_GLES_GetSwapInterval(_THIS);
 extern int Wayland_GLES_SwapWindow(_THIS, SDL_Window * window);
 extern int Wayland_GLES_MakeCurrent(_THIS, SDL_Window * window, SDL_GLContext context);
 extern void Wayland_GLES_GetDrawableSize(_THIS, SDL_Window * window, int * w, int * h);
diff --git a/src/video/wayland/SDL_waylandwindow.c b/src/video/wayland/SDL_waylandwindow.c
index c06616b..50b16d1 100644
--- a/src/video/wayland/SDL_waylandwindow.c
+++ b/src/video/wayland/SDL_waylandwindow.c
@@ -199,6 +199,22 @@ static const struct wl_shell_surface_listener shell_surface_listener_wl = {
 };
 
 
+static const struct wl_callback_listener surface_frame_listener;
+
+static void
+handle_surface_frame_done(void *data, struct wl_callback *cb, uint32_t time)
+{
+    SDL_WindowData *wind = (SDL_WindowData *) data;
+    SDL_AtomicSet(&wind->swap_interval_ready, 1);  /* mark window as ready to present again. */
+
+    /* reset this callback to fire again once a new frame was presented and compositor wants the next one. */
+    wl_callback_destroy(cb);
+    wl_callback_add_listener(wl_surface_frame(wind->surface), &surface_frame_listener, data);
+}
+
+static const struct wl_callback_listener surface_frame_listener = {
+    handle_surface_frame_done
+};
 
 
 static void
@@ -996,6 +1012,9 @@ int Wayland_CreateWindow(_THIS, SDL_Window *window)
         wl_compositor_create_surface(c->compositor);
     wl_surface_add_listener(data->surface, &surface_listener, data);
 
+    /* fire a callback when the compositor wants a new frame rendered. */
+    wl_callback_add_listener(wl_surface_frame(data->surface), &surface_frame_listener, data);
+
 #ifdef SDL_VIDEO_DRIVER_WAYLAND_QT_TOUCH
     if (c->surface_extension) {
         data->extended_surface = qt_surface_extension_get_extended_surface(
diff --git a/src/video/wayland/SDL_waylandwindow.h b/src/video/wayland/SDL_waylandwindow.h
index baddeab..bcbed5b 100644
--- a/src/video/wayland/SDL_waylandwindow.h
+++ b/src/video/wayland/SDL_waylandwindow.h
@@ -67,6 +67,8 @@ typedef struct {
     struct zwp_keyboard_shortcuts_inhibitor_v1 *key_inhibitor;
     struct zwp_idle_inhibitor_v1 *idle_inhibitor;
 
+    SDL_atomic_t swap_interval_ready;
+
 #ifdef SDL_VIDEO_DRIVER_WAYLAND_QT_TOUCH
     struct qt_extended_surface *extended_surface;
 #endif /* SDL_VIDEO_DRIVER_WAYLAND_QT_TOUCH */