MacOSX: Ensure that main window is visible on screen when About is display as a way to workaround for situations where UI is not visible or can't be move (for example, when changing display monitor with a different resolution).

src/Main/Forms/MainFrame.cpp

@@ -725,6 +725,7 @@ namespace VeraCrypt
 #ifdef TC_MACOSX
 		if (Gui->IsInBackgroundMode())
 			Gui->SetBackgroundMode (false);
+		EnsureVisible ();
 #endif
 		AboutDialog dialog (this);
 		dialog.ShowModal();

src/Main/Forms/MainFrame.h

@@ -15,6 +15,7 @@
 
 #include "Forms.h"
 #include "ChangePasswordDialog.h"
+#include <wx/display.h>
 
 namespace VeraCrypt
 {
@@ -161,6 +162,26 @@ namespace VeraCrypt
 		void UpdateVolumeList ();
 		void UpdateWipeCacheButton ();
 		void WipeCache ();
+        
+        void EnsureVisible()
+        {
+        	wxDisplay display (this);
+        	wxRect displayRect = display.GetClientArea();
+        	    
+        	bool bMove = false;
+        	wxPoint p = GetScreenPosition();
+        	wxRect r = GetRect ();
+        	if (p.x < displayRect.x)
+        		p.x = 0, bMove = true;
+        	if (p.y < displayRect.y)
+        		p.y = displayRect.y, bMove = true;
+        	if (p.x + r.width > displayRect.x + displayRect.width)
+        		p.x = displayRect.x + displayRect.width - r.width, bMove = true;
+        	if (p.y + r.height > displayRect.y + displayRect.height)
+        		p.y = displayRect.y + displayRect.height - r.height, bMove = true;
+        	if (bMove)
+        		Move (p);
+        }
 
 		struct VolumeActivityMapEntry
 		{