[OSX] [VTK6.3] PCLVisualizer::wasStopped() doesn't return true after closing window when using multiple PCLVisualizers in a program

The same error reported in #1390 happens when using multiple PCLVisualizers in a program. A minimal test case is as follows:

#include <iostream>
#include <pcl/visualization/pcl_visualizer.h>

void f1() {
  auto viewer = pcl::visualization::PCLVisualizer::Ptr(
      new pcl::visualization::PCLVisualizer("Test"));
  while (!viewer->wasStopped()) {
    viewer->spinOnce();
  }
}

int main() {
  f1(); // First time, it works as expected
  f1(); // Second time, ERROR happens
  return 0;
}

Error messages:

ERROR: In /tmp/vtk20151007-78273-1tax4sc/VTK-6.3.0/Rendering/OpenGL/vtkOpenGLPolyDataMapper2D.cxx, line 442
vtkOpenGLPolyDataMapper2D (0x7fd1fc70a410): failed after RenderOverlay 1 OpenGL errors detected
  0 : (1286) Invalid framebuffer operation


ERROR: In /tmp/vtk20151007-78273-1tax4sc/VTK-6.3.0/Rendering/OpenGL/vtkOpenGLRenderer.cxx, line 1202
vtkOpenGLRenderer (0x7fd1fc7069b0): failed after Clear 1 OpenGL errors detected
  0 : (1286) Invalid framebuffer operation

After a little digging into the problem, I found that win_->IsDrawable () (pcl_visualizer.cpp#L472) returns false for the first time when I close the window, but true for the second time.

I'm testing on osx 10.10.4.

Start with the minimal C++ reproduction and inspect visualization/src/pcl_visualizer.cpp around the referenced win_->IsDrawable() check. Trace the window lifecycle across the two PCLVisualizer instances on macOS, then verify that closing the second window makes wasStopped() return true without the reported OpenGL framebuffer errors.