x11: Support _NET_WM_USER_TIME and give _NET_ACTIVE_WINDOW a valid timestamp.

Fixes Bugzilla #3056.

src/video/x11/SDL_x11events.c

@@ -512,6 +512,23 @@ ProcessHitTest(_THIS, const SDL_WindowData *data, const XEvent *xev)
     return SDL_FALSE;
 }
 
+static void
+X11_UpdateUserTime(SDL_WindowData *data, const unsigned long latest)
+{
+    if (latest && (latest != data->user_time)) {
+        SDL_VideoData *videodata = data->videodata;
+        Display *display = videodata->display;
+        X11_XChangeProperty(display, data->xwindow, videodata->_NET_WM_USER_TIME,
+                            XA_CARDINAL, 32, PropModeReplace,
+                            (const unsigned char *) &latest, 1);
+        #if DEBUG_XEVENTS
+        printf("window %p: updating _NET_WM_USER_TIME to %lu\n", data, latest);
+        #endif
+        data->user_time = latest;
+    }
+}
+
+
 static void
 X11_DispatchEvent(_THIS)
 {
@@ -773,6 +790,7 @@ X11_DispatchEvent(_THIS)
                 }
             }
 
+            X11_UpdateUserTime(data, xevent.xkey.time);
         }
         break;
 
@@ -1001,6 +1019,7 @@ X11_DispatchEvent(_THIS)
                 }
                 SDL_SendMouseButton(data->window, 0, SDL_PRESSED, button);
             }
+            X11_UpdateUserTime(data, xevent.xbutton.time);
         }
         break;
 
@@ -1027,7 +1046,7 @@ X11_DispatchEvent(_THIS)
 
             char *name = X11_XGetAtomName(display, xevent.xproperty.atom);
             if (name) {
-                printf("window %p: PropertyNotify: %s %s\n", data, name, (xevent.xproperty.state == PropertyDelete) ? "deleted" : "changed");
+                printf("window %p: PropertyNotify: %s %s time=%lu\n", data, name, (xevent.xproperty.state == PropertyDelete) ? "deleted" : "changed", xevent.xproperty.time);
                 X11_XFree(name);
             }
 
@@ -1095,6 +1114,17 @@ X11_DispatchEvent(_THIS)
             }
 #endif /* DEBUG_XEVENTS */
 
+            /* Take advantage of this moment to make sure user_time has a
+                valid timestamp from the X server, so if we later try to
+                raise/restore this window, _NET_ACTIVE_WINDOW can have a
+                non-zero timestamp, even if there's never been a mouse or
+                key press to this window so far. Note that we don't try to
+                set _NET_WM_USER_TIME here, though. That's only for legit
+                user interaction with the window. */
+            if (!data->user_time) {
+                data->user_time = xevent.xproperty.time;
+            }
+
             if (xevent.xproperty.atom == data->videodata->_NET_WM_STATE) {
                 /* Get the new state from the window manager.
                    Compositing window managers can alter visibility of windows

src/video/x11/SDL_x11video.c

@@ -397,6 +397,7 @@ X11_VideoInit(_THIS)
     GET_ATOM(_NET_WM_ICON_NAME);
     GET_ATOM(_NET_WM_ICON);
     GET_ATOM(_NET_WM_PING);
+    GET_ATOM(_NET_WM_USER_TIME);
     GET_ATOM(_NET_ACTIVE_WINDOW);
     GET_ATOM(UTF8_STRING);
     GET_ATOM(PRIMARY);

src/video/x11/SDL_x11video.h

@@ -100,6 +100,7 @@ typedef struct SDL_VideoData
     Atom _NET_WM_ICON_NAME;
     Atom _NET_WM_ICON;
     Atom _NET_WM_PING;
+    Atom _NET_WM_USER_TIME;
     Atom _NET_ACTIVE_WINDOW;
     Atom UTF8_STRING;
     Atom PRIMARY;

src/video/x11/SDL_x11window.c

@@ -944,6 +944,8 @@ SetWindowActive(_THIS, SDL_Window * window)
     Atom _NET_ACTIVE_WINDOW = data->videodata->_NET_ACTIVE_WINDOW;
 
     if (X11_IsWindowMapped(_this, window)) {
+        SDL_assert(data->user_time != 0);  /* should be set by _some_ event by now. */
+        /*printf("SDL Window %p: sending _NET_ACTIVE_WINDOW with timestamp %lu\n", window, data->user_time);*/
         XEvent e;
 
         SDL_zero(e);
@@ -952,7 +954,7 @@ SetWindowActive(_THIS, SDL_Window * window)
         e.xclient.format = 32;
         e.xclient.window = data->xwindow;
         e.xclient.data.l[0] = 1;  /* source indication. 1 = application */
-        e.xclient.data.l[1] = CurrentTime;
+        e.xclient.data.l[1] = data->user_time;
         e.xclient.data.l[2] = 0;
 
         X11_XSendEvent(display, RootWindow(display, displaydata->screen), 0,

src/video/x11/SDL_x11window.h

@@ -60,6 +60,7 @@ typedef struct
     Uint32 pending_focus_time;
     XConfigureEvent last_xconfigure;
     struct SDL_VideoData *videodata;
+    unsigned long user_time;
     Atom xdnd_req;
     Window xdnd_source;
 #if SDL_VIDEO_OPENGL_EGL