Fix "New Wayland subwindow code creates issues with resizes of opengl windows…" (#1311)

src/Fl_Gl_Window.cxx

@@ -300,6 +300,7 @@ void Fl_Gl_Window::resize(int X,int Y,int W,int H) {
   if (is_a_resize) valid(0);
   pGlWindowDriver->resize(is_a_resize, W, H);
   Fl_Window::resize(X,Y,W,H);
+  if (is_a_resize) pGlWindowDriver->after_resize();
 }
 
 /**

src/Fl_Gl_Window_Driver.H

@@ -67,6 +67,7 @@ public:
   virtual void make_current_after() {}
   virtual void swap_buffers() {}
   virtual void resize(int /*is_a_resize*/, int /*w*/, int /*h*/) {}
+  virtual void after_resize() {}
   virtual char swap_type();
   virtual void swap_interval(int) { }
   virtual int swap_interval() const { return -1; }

src/drivers/Wayland/Fl_Wayland_Gl_Window_Driver.H

@@ -38,6 +38,7 @@ private:
   int mode_(int m, const int *a) FL_OVERRIDE;
   void swap_buffers() FL_OVERRIDE;
   void resize(int is_a_resize, int w, int h) FL_OVERRIDE;
+  void after_resize() FL_OVERRIDE;
   char swap_type() FL_OVERRIDE;
   void swap_interval(int) FL_OVERRIDE;
   int swap_interval() const FL_OVERRIDE;

src/drivers/Wayland/Fl_Wayland_Gl_Window_Driver.cxx

@@ -406,6 +406,14 @@ void Fl_Wayland_Gl_Window_Driver::resize(int is_a_resize, int W, int H) {
   }*/
 }
 
+void Fl_Wayland_Gl_Window_Driver::after_resize() {
+  Fl_Window *parent = (pWindow->parent() ? pWindow->window() : NULL);
+  struct wld_window *xid = (parent ? fl_wl_xid(parent) : NULL);
+  if (xid && !xid->frame_cb) {
+    eglSwapBuffers(Fl_Wayland_Gl_Window_Driver::egl_display, egl_surface);
+  }
+}
+
 char Fl_Wayland_Gl_Window_Driver::swap_type() {
   return copy;
 }

src/drivers/Wayland/Fl_Wayland_Window_Driver.H

@@ -149,7 +149,6 @@ struct wld_window {
   struct wl_callback *frame_cb;
   struct Fl_Wayland_Graphics_Driver::wld_buffer *buffer;
   struct xdg_surface *xdg_surface;
-  enum Fl_Wayland_Window_Driver::kind kind;
   union { // for each value of kind
     struct libdecor_frame *frame;
     struct wl_subsurface *subsurface;
@@ -158,6 +157,7 @@ struct wld_window {
   };
   // non-null when using custom cursor
   struct Fl_Wayland_Window_Driver::custom_cursor *custom_cursor;
+  enum Fl_Wayland_Window_Driver::kind kind;
   int configured_width;
   int configured_height;
   int floating_width;

src/drivers/Wayland/Fl_Wayland_Window_Driver.cxx

@@ -1452,7 +1452,7 @@ void Fl_Wayland_Window_Driver::makeWindow()
   Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
 
   new_window->wl_surface = wl_compositor_create_surface(scr_driver->wl_compositor);
-  //Fl::warning("makeWindow:%p wayland-scale=%d user-scale=%.2f\n", pWindow, new_window->scale, Fl::screen_scale(0));
+//printf("makeWindow:%p %s %s\n", pWindow, pWindow->parent()?"SUB":"", pWindow->as_gl_window()?"GL":"");
   wl_surface_add_listener(new_window->wl_surface, &surface_listener, new_window);
 
   if (!shape()) { // rectangular FLTK windows are opaque
@@ -1841,9 +1841,14 @@ void Fl_Wayland_Window_Driver::resize(int X, int Y, int W, int H) {
   }
   Fl_Window *parent = this->parent() ? pWindow->window() : NULL;
   struct wld_window *parent_xid = parent ? fl_wl_xid(parent) : NULL;
-  // When moving or resizing a subwindow independently from its parent, skip the move/resize
-  // operation if the parent window is being redrawn, in line with the frame callback mechanism.
-  if (depth == 1 && fl_win && parent_xid && parent_xid->frame_cb && is_a_move) {
+//printf("resize[%p] %dx%d is_a_resize=%d is_a_move=%d depth=%d parent_xid->frame_cb=%p\n", pWindow,W,H,is_a_resize,is_a_move,depth, (parent_xid?parent_xid->frame_cb:0) );
+  if (depth == 1 && fl_win && parent_xid && parent_xid->frame_cb && can_expand_outside_parent_) {
+    // When moving or resizing a subwindow independently from its parent while the parent window
+    // is being redrawn, the processing depends on whether the moved/resize window
+    // is a draggable-subwindow. For a draggable subwindow having can_expand_outside_parent_ != 0,
+    // skip the X,Y,W,H tuple to process only tuples received when parent window is ready.
+    // This smoothes the movement of the draggable subwindow.
+    // Process regular subwindows normally.
     depth--;
     return;
   }
@@ -1917,13 +1922,19 @@ void Fl_Wayland_Window_Driver::resize(int X, int Y, int W, int H) {
         wl_subsurface_set_position(fl_win->subsurface, X * f, Y * f);
         wl_surface_commit(parent_xid->wl_surface);
       }
-    } else if (is_a_move && !parent_xid->frame_cb) {
-      // Use the frame callback mechanism applied to the object's parent window
-      parent_xid->frame_cb = wl_surface_frame(parent_xid->wl_surface);
-      wl_callback_add_listener(parent_xid->frame_cb,
-                               Fl_Wayland_Graphics_Driver::p_surface_frame_listener, parent_xid);
+    } else if (parent_xid->buffer && is_a_move) {
       if (fl_win->subsurface) wl_subsurface_set_position(fl_win->subsurface, X * f, Y * f);
-      wl_surface_commit(parent_xid->wl_surface);
+      if (!parent_xid->buffer->wl_buffer || parent_xid->buffer->draw_buffer_needs_commit) {
+        if (!parent_xid->frame_cb) Fl_Wayland_Graphics_Driver::buffer_commit(parent_xid);
+      } else {
+        if (!parent_xid->frame_cb) {
+          // Use the frame callback mechanism applied to the object's parent window
+          parent_xid->frame_cb = wl_surface_frame(parent_xid->wl_surface);
+          wl_callback_add_listener(parent_xid->frame_cb,
+                                   Fl_Wayland_Graphics_Driver::p_surface_frame_listener, parent_xid);
+        }
+        wl_surface_commit(parent_xid->wl_surface);
+      }
     }
     checkSubwindowFrame(); // make sure subwindow doesn't leak outside parent
   }