Fix build of math/vtk6 with Clang6 on -CURRENT.

The definition of NULL has changed in C++, and conversions have
gotten stricter, so using NULL where you mean 0 (or false) is
no longer an option. Detected by fallout from updating CMake 3.12.

No PORTREVISION bump because everywhere where it compiled previously
sees no change, and where it didn't compile before it does now
with the same result.

Reported by:	tcberner

1 files changed, 40 insertions, 0 deletions

diff --git a/math/vtk6/files/patch-Rendering_OpenGL_vtkXOpenGLRenderWindow.cxx b/math/vtk6/files/patch-Rendering_OpenGL_vtkXOpenGLRenderWindow.cxx
new file mode 100644
index 000000000000..e1a4bf0eaaef
--- /dev/null
+++ b/math/vtk6/files/patch-Rendering_OpenGL_vtkXOpenGLRenderWindow.cxx
@@ -0,0 +1,40 @@
+--- Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx.orig	2015-03-03 20:37:14 UTC
++++ Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx
+@@ -386,7 +386,7 @@ XVisualInfo *vtkXOpenGLRenderWindow::Get
+ 
+ vtkXOpenGLRenderWindow::vtkXOpenGLRenderWindow()
+ {
+-  this->ParentId = static_cast<Window>(NULL);
++  this->ParentId = static_cast<Window>(0);
+   this->ScreenSize[0] = 0;
+   this->ScreenSize[1] = 0;
+   this->OwnDisplay = 0;
+@@ -394,8 +394,8 @@ vtkXOpenGLRenderWindow::vtkXOpenGLRender
+   this->ForceMakeCurrent = 0;
+   this->UsingHardware = 0;
+   this->DisplayId = static_cast<Display *>(NULL);
+-  this->WindowId = static_cast<Window>(NULL);
+-  this->NextWindowId = static_cast<Window>(NULL);
++  this->WindowId = static_cast<Window>(0);
++  this->NextWindowId = static_cast<Window>(0);
+   this->ColorMap = static_cast<Colormap>(0);
+   this->OwnWindow = 0;
+ 
+@@ -776,7 +776,7 @@ void vtkXOpenGLRenderWindow::DestroyWind
+   if (this->OwnWindow && this->DisplayId && this->WindowId)
+     {
+     XDestroyWindow(this->DisplayId,this->WindowId);
+-    this->WindowId = static_cast<Window>(NULL);
++    this->WindowId = static_cast<Window>(0);
+     }
+ 
+   // if we create the display, we'll delete it
+@@ -1168,7 +1168,7 @@ void vtkXOpenGLRenderWindow::WindowRemap
+ 
+   // set the default windowid
+   this->WindowId = this->NextWindowId;
+-  this->NextWindowId = static_cast<Window>(NULL);
++  this->NextWindowId = static_cast<Window>(0);
+ 
+   // set everything up again
+   this->Initialize();