wayland: Adjust popup adjoining check

The previous calculation could result in a window whose original position was positioned exactly corner-to-corner with the parent not being adjusted to be adjoining, and thus subject to spurious closure.

(cherry picked from commit b0cdb7143fb423b808e3b2c010368e6d49550054)

src/video/wayland/SDL_waylandwindow.c

@@ -215,32 +215,32 @@ static void EnsurePopupPositionIsValid(SDL_Window *window, int *x, int *y)
     int adj_count = 0;
 
     /* Per the xdg-positioner spec, child popup windows must intersect or at
-     * least be partially adjacent to the parent window.
+     * least be partially adjoining the parent window.
      *
      * Failure to ensure this on a compositor that enforces this restriction
      * can result in behavior ranging from the window being spuriously closed
      * to a protocol violation.
      */
-    if (*x + window->w < 0) {
+    if (*x + window->w <= 0) {
         *x = -window->w;
         ++adj_count;
     }
-    if (*y + window->h < 0) {
+    if (*y + window->h <= 0) {
         *y = -window->h;
         ++adj_count;
     }
-    if (*x > window->parent->w) {
+    if (*x >= window->parent->w) {
         *x = window->parent->w;
         ++adj_count;
     }
-    if (*y > window->parent->h) {
+    if (*y >= window->parent->h) {
         *y = window->parent->h;
         ++adj_count;
     }
 
     /* If adjustment was required on the x and y axes, the popup is aligned with
-     * the parent corner-to-corner and is neither overlapping nor adjacent, so it
-     * must be nudged by 1 to be considered adjacent.
+     * the parent corner-to-corner and is neither overlapping nor adjoining, so it
+     * must be nudged by 1 to be considered adjoining.
      */
     if (adj_count > 1) {
         *x += *x < 0 ? 1 : -1;