Wayland: restore support of Fl_Tile with subwindow widget

FL/Fl_Tile.H

@@ -25,6 +25,9 @@
 */
 
 class FL_EXPORT Fl_Tile : public Fl_Group {
+  friend class Fl_Window_Driver;
+private:
+  static bool in_drag_intersection_;
 public:
   int handle(int event) FL_OVERRIDE;
   Fl_Tile(int X, int Y, int W, int H, const char *L=0);

src/Fl_Tile.cxx

@@ -482,6 +482,8 @@ void Fl_Tile::move_intersection(int oldx, int oldy, int newx, int newy) {
   }
 }
 
+bool Fl_Tile::in_drag_intersection_ = false;
+
 /**
  Drags the intersection at (\p oldx,\p oldy) to (\p newx,\p newy).
 
@@ -532,10 +534,12 @@ void Fl_Tile::drag_intersection(int oldx, int oldy, int newx, int newy) {
       }
     }
     // resize all children that have changed in size
+    in_drag_intersection_ = true;
     for (i = 0; i < children(); i++) {
       Fl_Rect &r = final_size[i];
       child(i)->damage_resize(r.x(), r.y(), r.w(), r.h());
     }
+    in_drag_intersection_ = false;
     delete[] final_size;
   } else {
     move_intersection(oldx, oldy, newx, newy);

src/Fl_Window_Driver.H

@@ -31,6 +31,7 @@
 #include <FL/Fl_Export.H>
 #include <FL/Fl_Window.H>
 #include <FL/Fl_Overlay_Window.H>
+#include <FL/Fl_Tile.H>
 
 #include <stdlib.h>
 
@@ -208,6 +209,7 @@ public:
 
   virtual fl_uintptr_t os_id() { return 0; }
   virtual void allow_expand_outside_parent() {}
+  static bool in_tile_intersection_drag() { return Fl_Tile::in_drag_intersection_; }
 };
 
 #endif // FL_WINDOW_DRIVER_H

src/drivers/Wayland/Fl_Wayland_Window_Driver.cxx

@@ -1831,7 +1831,7 @@ void Fl_Wayland_Window_Driver::resize(int X, int Y, int W, int H) {
   // When moving or resizing a non-GL subwindow independently from its parent, this condition
   // delays application of X,Y,W,H values until the compositor signals
   // it's ready for a new frame using the frame callback mechanism.
-  if (depth > 1 || pWindow->as_gl_window() || !parent_xid || wait_for_expose_value || (parent_xid->frame_cb && !xid_rect)) {
+  if (in_tile_intersection_drag() || depth > 1 || pWindow->as_gl_window() || !parent_xid || wait_for_expose_value || (parent_xid->frame_cb && !xid_rect)) {
     if (is_a_resize) {
       if (pWindow->parent()) {
         if (W < 1) W = 1;
@@ -1909,7 +1909,7 @@ void Fl_Wayland_Window_Driver::resize(int X, int Y, int W, int H) {
       }
       Fl_Wayland_Graphics_Driver::buffer_commit(parent_xid);
     } else {
-      if (!parent_xid->frame_cb) {
+      if (!in_tile_intersection_drag() && !parent_xid->frame_cb) {
         // use the frame callback mechanism and memorize current X,Y,W,H values
         xid_rect = new xid_and_rect;
         xid_rect->xid = parent_xid;