X11 Modal window support (solution based on windows code).

src/dlangui/platforms/x11/x11app.d

@@ -1193,6 +1193,7 @@ class X11Platform : Platform {
     }
 
     private X11Window[XWindow] _windowMap;
+    private X11Window[] _windowList;
 
     /**
      * create window
@@ -1210,6 +1211,7 @@ class X11Platform : Platform {
         int newheight = height;
         X11Window window = new X11Window(this, windowCaption, parent, flags, newwidth, newheight);
         _windowMap[window._win] = window;
+        _windowList ~= window;
         return window;
     }
 
@@ -1238,6 +1240,17 @@ class X11Platform : Platform {
         XSendEvent(x11display2, window._win, false, StructureNotifyMask, &ev);
         XFlush(x11display2);
         XUnlockDisplay(x11display2);
+        
+        for (uint i = 0; i < _windowList.length; i++) {
+            if (w is _windowList[i]) {
+                for (uint j = i; j + 1 < _windowList.length; j++)
+                    _windowList[j] = _windowList[j + 1];
+                _windowList[$ - 1] = null;
+                _windowList.length--;
+                break;
+            }
+        }
+        
     }
 
     bool handleTimers() {
@@ -1648,6 +1661,21 @@ class X11Platform : Platform {
         }
     }
     
+    /// returns true if there is some modal window opened above this window, and this window should not process mouse/key input and should not allow closing
+    override bool hasModalWindowsAbove(DWindow w) {
+        // override in platform specific class
+        for (uint i = 0; i + 1 < _windowList.length; i++) {
+            if (_windowList[i] is w) {
+                for (uint j = i + 1; j < _windowList.length; j++) {
+                    if (_windowList[j].flags & WindowFlag.Modal)
+                        return true;
+                }
+                return false;
+            }
+        }
+        return false;
+    }
+    
     /// handle theme change: e.g. reload some themed resources
     override void onThemeChanged() {
         foreach(w; _windowMap)