Typos fixes for documentation and source code comments. This commit is a follow up to:   vtk/vtk!3424

- made vtkScalarsToColors::SetRange(double[2]) virtual, since the other SetRange() is.  Likewise vtkLookupTable::SetTableRange(double[2]).
- changed most uses of dangerous GetTableValue() (that returns inner buffer) in favour of version that copies the values out.
- use fixed-size memcpy in a few places for a potential speedup
- improved some comments
- added a few consts, especially with buffers
- removed const on plain old ints
- moved a nan check earlier, saving work when true
- moved some variable declarations closer to initialization
- removed some unneeded semi colons
- removed some useless casts, added others for clarity

When the point are modified, Modified() must be called on the points
as well.

Specifically:

very strange braces!
syntaxError,Common/DataModel/vtkHyperTreeGrid.cxx:699,error,syntax error

changed size()>0 to !empty()
stlSize,Filters/General/vtkLoopBooleanPolyDataFilter.cxx:1426,performance,Possible inefficient checking for 'nocellregion' emptiness.

This useless flag has been there since code was added in 2000 in f50b0909
knownConditionTrueFalse,Common/DataModel/vtkPointLocator.cxx:323,style,Condition 'flag' is always true
knownConditionTrueFalse,Common/DataModel/vtkPointLocator.cxx:415,style,Condition 'flag' is always true
knownConditionTrueFalse,Common/DataModel/vtkStaticPointLocator.cxx:788,style,Condition 'flag' is always true
knownConditionTrueFalse,Common/DataModel/vtkStaticPointLocator.cxx:879,style,Condition 'flag' is always true

This useless 'result' has been there since code was added in 2003 in dd39b9e4
knownConditionTrueFalse,IO/XML/vtkXMLRectilinearGridReader.cxx:236,style,Condition 'result' is always true
knownConditionTrueFalse,IO/XML/vtkXMLRectilinearGridReader.cxx:245,style,Condition 'result' is always true
knownConditionTrueFalse,IO/XML/vtkXMLRectilinearGridReader.cxx:254,style,Condition 'result' is always true

New check in cppcheck 1.81, block is indeed dead code:
oppositeInnerCondition,Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx:272,warning,Opposite inner 'if' condition leads to a dead code block.
oppositeInnerCondition,Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx:293,warning,Opposite inner 'if' condition leads to a dead code block.
oppositeInnerCondition,Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx:349,warning,Opposite inner 'if' condition leads to a dead code block.

false positive, suppressed with zero initialization:
uninitvar,Filters/Statistics/vtkKMeansStatistics.cxx:810,error,Uninitialized variable: curDistance
uninitvar,Filters/Statistics/vtkKMeansStatistics.cxx:812,error,Uninitialized variable: curDistance

free(NULL) is allowed, so just remove null check
knownConditionTrueFalse,IO/Geometry/Testing/Cxx/TestIncrementalOctreePointLocator.cxx:920,style,Condition 'truthIds' is always false
knownConditionTrueFalse,IO/Geometry/Testing/Cxx/TestIncrementalOctreePointLocator.cxx:956,style,Condition 'diskFile' is always false

Simplified the calculation, verified same codegen on x86_64 with godbolt
shiftTooManyBitsSigned,Rendering/Volume/vtkHAVSVolumeMapper.cxx:53,error,Shifting signed 32-bit value by 31 bits is undefined behaviour

These have all been thus since their inception, but a global search find the same pattern in TestDijkstraGraphGeodesicPath.cxx, from which I copied the apparent solution
knownConditionTrueFalse,Interaction/Widgets/Testing/Cxx/TestPolygonalRepresentationHandleWidget.cxx:119,style,Condition 'distanceOffsetSpecified' is always false
knownConditionTrueFalse,Interaction/Widgets/Testing/Cxx/TestPolygonalRepresentationHandleWidget.cxx:199,style,Condition 'distanceOffsetSpecified' is always false
knownConditionTrueFalse,Interaction/Widgets/Testing/Cxx/TestPolygonalSurfaceConstrainedDistanceWidget.cxx:244,style,Condition 'distanceOffsetSpecified' is always false
knownConditionTrueFalse,Interaction/Widgets/Testing/Cxx/TestPolygonalSurfaceConstrainedDistanceWidget.cxx:325,style,Condition 'distanceOffsetSpecified' is always false
knownConditionTrueFalse,Interaction/Widgets/Testing/Cxx/TestSurfaceConstrainedHandleWidget.cxx:117,style,Condition 'distanceOffsetSpecified' is always false
knownConditionTrueFalse,Interaction/Widgets/Testing/Cxx/TestSurfaceConstrainedHandleWidget.cxx:189,style,Condition 'distanceOffsetSpecified' is always false

Toggle with #if instead
knownConditionTrueFalse,Imaging/Hybrid/vtkSurfaceReconstructionFilter.cxx:300,style,Condition 'orientationPropagation' is always true

Added parens
clarifyCalculation,Common/DataModel/vtkLagrangeWedge.cxx:906,style,Clarify calculation precedence for '/' and '?'.

This topic catches another batch of NULL conversions that
clang did not handle for various reasons. It also includes
a number of changes to comments and strings where NULL was
used. It also catches some recent code changes where NULL
was used instead of nullptr.

Now that VTK requires a C++11 compiler we can ditch using custom typedefs to
wrap =delete;

Does not make sense for OpenGL2 and is not implemented
Also deprecate PainterDelegate

Now that VTK requires a C++11 compiler we can ditch using custom typedefs

Adding in functionality to allow inserting vtkNew objects into
stl containers of vtkSmartPointer objects as well as comparisons
between vtkNew objects and raw pointers. Also removing Get() and
GetPointer() calls from vtkNew objects since in most instances we
can just pass in the vtkNew<> object instead of having to use the
Get() or GetPointer() methods to get the raw pointer.

This change was caused by commit
BUG: Back buffer is not cleared if multiple renderers

Was causing a shadowed ivar warning, removed subclass ivar
after examining code.

Add 3d event support into these classes. Also
add some additional options to the rep to give it a bit
more customizaiton.

The margin and cursor actors were not updating during interaction.
This calls Modified() on the point arrays to update the buffers.

Deprecated MapColorScalarsThroughLookupTable and setters/getters in
favor of new ColorMode that is analagous to the color mode in
vtkMapper, i.e., it adds a mode where additional scalar types such as
float and double can be used for direct coloring.

A couple more places where arrays were being modified
without calling Modified

The test was disabled when deprecating volume texture mapper.

vtkTexturedButtonRepresentation2D is a composite representation that
uses vtkBalloonRepresentation internally. The representation would need
to compensate the active viewport origin when deciding whether the
button was clicked.

For vtkKCoreLayout, just alloc & copy the string.

For vtkInteractorStyleUser, init to nullptr instead of empty string.
It’s taking the char* owned by the vtkRenderWindowInteractor, which looks like it can be null anyway.
Adjusted usage to be prepared for null.

Also fixed some related indentation and comments.

The size of the handles in the vtkImplicitPlaneRepresentation and
vtkImplicitCylinderRepresentation were not being updated when the
RenderWindow changed size. This could make the handles smaller or
larger than they should be in some cases.  Rebuilding the
representation when the RenderWindow changes ensures the handles are
the correct size in such cases.

also add some new states that subclasses can use
move PICK state into InteractorStyle from Image
subclass.

The old event signatures were limited to X Y mouse
events and not flexible enough for general event handling.
These updated signatures allow for much more flexibility.

This topic also switches the distance withget to use a
double representation for the glyph to avoid float
resolution issues with large coordinate systems.

This topic adds handling for 3D events to the point handle
and distance representations and widgets.

updating the tests to follow modern standards

This topic is the result of running clang-tidy to
modernize our usage of NULL and 0 to nullptr. It also
includes some manual and semi manual changes where
clang-tidy would not be expected to work (such as in
comments, or classes not compiled on this build)

There are definitely many comments and occurances that
this topic misses that we will need to fix over time.

This topic introduces support for events in VTK to pass a
vtkEventData instance as their calldata. This instance can
be used to hold event specific data that would otherwise
complicate the render window interactor. The event specific
data also allows us to have fewer vtkCommands as we do not
need a specific command for each button on a controller but
rather can include the controller button as data in the
appropriate vtkEventData subclass.

Currently this is only implemented for 3D events but it could
be updated to handle mouse, keyboard or events as desired.

This commit cleans up offscreen rendering support in VTK. This includes
several changes.

1. It makes EGL support independent of onscreen GL
   support. It's now possible to enable EGL and GLX in same build of
   VTK, for example, so long as the two use shared GL-dispatch
   mechanism.  Previously, EGL could not be enabled together with GLX
   (i.e.  `VTK_USE_X` set to ON). These changes allow for that
   configuration.

2. `VTK_USE_OFFSCREEN_EGL` is replaced by `VTK_OPENGL_HAS_EGL`.
    This is consistent with `VTK_OPENGL_HAS_OSMESA` flag. And also
    in similar vein to changes to `FindOpenGL.cmake` where EGL
    becomes a component of `find_package(OpenGL)`.

3. `VTK_EGL_DEVICE_INDEX` has been replaced by
   `VTK_DEFAULT_EGL_DEVICE_INDEX` since it only affect the default
   value, and doesn't preclude users from manually specifying the
   device index.

4. `VTK_USE_OFFSCREEN` has been replaced by
   `VTK_DEFAULT_RENDER_WINDOW_OFFSCREEN`, since similar to `3`
   this option was only intended to affect the default value.

5. Simplified `FindEGL.cmake`. Apps don't need to link against
   `gldispatch` library and hence removed it and created an
   imported target to simplify use.

6. For all changes to CMake variables, we put out `DEPRECATION`
   messages if old variables are used.

7. When `VTK_USE_X` and `VTK_OPENGL_HAS_EGL` or
   `VTK_OPENGL_HAS_OSMESA` in ON, following things happen:
   i.   The object-factory simply returns the X-based (or
        onscreen) render window i.e. `vtkXOpenGLRenderWindow`.
   ii.  To create one of the offscreen render windows, one can
        manually instantiate them e.g. by explicitly
        instantiating `vtkEGLRenderWindow`.
        `vtkXOpenGLRenderWindow` has implementation to swap to
        OSMesa if `SetUseOffscreen(true)` is called.
   iii. As soon any off-screen features are enabled, `glew`
        uses the offscreen library APIs to get OpenGL function pointers
        irrespective of how the active context was initialized.

Tests various new modes added to vtkInteractorStyleRubberBandZoom.

vtkInteractorStyleRubberBandZoom is highly unreliable
(paraview/paraview#17511). Added new options to make it a little easier
to use and more consistent.

1. Added option to lock aspect ratio of the box to that of the viewport.
   Thus user get a better understanding of what would actually be zoomed
   to.
2. Added option to center the box at the start position rather than
   having the start position be one of the corners of the box. This
   makes it easier to focus on point of interest.
3. Added option to use "zoom" instead of "dolly" for perspective camera.
   This avoid cases where the camera travels into the dataset when
   zooming into small regions.
4. When not dollying, instead changing camera view angle to zoom in
   perspective mode, we reorient the camera to point to the center of
   the target box rather than panning which ends up giving more reliable
   results in real world scenarios.
5. The code has been cleaned up to use vtkVector, vtkRect to make it
   more readable.

The default behavior is left unchanged.

Changes C style header names to C++

Checked with blame that deleted code is truely dead.

These changes are more invasive than my previous conversions.
a) Some private/protected method signatures now take a size parameter.
b) Deleted vtkMPEG2Writer entirely, because 1) it uses sprintf and I can’t find the size of the buffer, I think it’s been removed. 2) The class hasn’t been built in years.
c) some new defines introduced to avoid copy-pasting magic numbers.

The only remaining sprintf, I think, are in third party or C code.

Found and auto-fixed by clang-tidy’s readability-redundant-control-flow check.

Though I did have to manualy fix whitespace after it.

Found & auto-fixed by clang-tidy’s readability-container-size-empty check.

empty() is guaranteed O(1) while size() is not, thus could be faster in some cases.