Backport to 1.9: fix for distance sorting with gl-coordinate-system changed

doc/ReleaseNotes

@@ -49,6 +49,7 @@ This issue fixes several bugs that were still found in 1.9.2.
 * Fix error when trying to raise vectors to a power
 * GLSL: fix error when legacy matrix generator inputs are mat3
 * Now tries to preserve refresh rate when switching fullscreen on Windows
+* Fix back-to-front sorting when gl-coordinate-system is changed
 
 ------------------------  RELEASE 1.9.2  ------------------------
 

panda/src/display/graphicsStateGuardian.cxx

@@ -148,6 +148,10 @@ GraphicsStateGuardian(CoordinateSystem internal_coordinate_system,
   _coordinate_system = CS_invalid;
   _internal_transform = TransformState::make_identity();
 
+  if (internal_coordinate_system == CS_default) {
+    _internal_coordinate_system = get_default_coordinate_system();
+  }
+
   set_coordinate_system(get_default_coordinate_system());
 
   _data_reader = (GeomVertexDataPipelineReader *)NULL;

panda/src/glstuff/glGraphicsStateGuardian_src.cxx

@@ -5485,19 +5485,6 @@ make_geom_munger(const RenderState *state, Thread *current_thread) {
   return GeomMunger::register_munger(munger, current_thread);
 }
 
-////////////////////////////////////////////////////////////////////
-//     Function: GLGraphicsStateGuardian::compute_distance_to
-//       Access: Public, Virtual
-//  Description: This function will compute the distance to the
-//               indicated point, assumed to be in eye coordinates,
-//               from the camera plane.  The point is assumed to be
-//               in the GSG's internal coordinate system.
-////////////////////////////////////////////////////////////////////
-PN_stdfloat CLP(GraphicsStateGuardian)::
-compute_distance_to(const LPoint3 &point) const {
-  return -point[2];
-}
-
 ////////////////////////////////////////////////////////////////////
 //     Function: GLGraphicsStateGuardian::framebuffer_copy_to_texture
 //       Access: Public, Virtual

panda/src/glstuff/glGraphicsStateGuardian_src.h

@@ -336,8 +336,6 @@ public:
   virtual PT(GeomMunger) make_geom_munger(const RenderState *state,
                                           Thread *current_thread);
 
-  virtual PN_stdfloat compute_distance_to(const LPoint3 &point) const;
-
   virtual void clear(DrawableRegion *region);
 
   virtual bool framebuffer_copy_to_texture