[vtk-developers] vtk-developers Digest, Vol 158, Issue 21

Andras Lasso lasso at queensu.ca
Fri Jun 23 07:04:19 EDT 2017 

I find vtkNew<…> to be the shortest and most readable way of creating a new VTK object. However, it is rather inconvenient that GetPointer() must be called to get the pointer. Is there a specific reason for requiring using GetPointer()? Could we change vtkNew to have automatic conversion to pointer type - the same way as in vtkSmartPointer?



Andras



From: David Cole via vtk-developers<mailto:vtk-developers at vtk.org>
Sent: Friday, June 23, 2017 5:29 AM
To: Elvis Stansvik<mailto:elvis.stansvik at orexplore.com>
Cc: VTK Developers<mailto:vtk-developers at vtk.org>; Andrew Maclean<mailto:andrew.amaclean at gmail.com>
Subject: Re: [vtk-developers] vtk-developers Digest, Vol 158, Issue 21



One thing I would point out is some folks who might want to compile
the VTK examples may be using a slightly older version of VTK, and
perhaps one that is not even being compiled with a modern compiler
capable of compiling C++ 11...

So I would refrain from using "auto" in the examples until such time
as all the people who want to build an example are pretty much
guaranteed to be using a VTK which requires C++ 11, and therefore a
compiler capable of dealing with C++ 11 constructs.

I wouldn't do the "auto" thing just yet.


David C.



On Fri, Jun 23, 2017 at 4:47 AM, Elvis Stansvik
<elvis.stansvik at orexplore.com> wrote:
> 2017-06-23 10:33 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>> Sorry, accidently hit send. Fixes below.
>>
>> 2017-06-23 10:29 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>>> 2017-06-23 1:21 GMT+02:00 Andrew Maclean <andrew.amaclean at gmail.com>:
>>>> Hi Bill, Elvis,
>>>>    Elvis, personally I wouldn't like to see the homogenisation of the
>>>> examples by doing what you propose.
>>>> The reasons are:
>>>> 1) One of the advantages of the examples is seeing the different approaches
>>>> used by the contributors.
>>>> 2) It may dissuade contributors by implicitly forcing them to use a
>>>> particular approach.
>>>> 3) One of the really useful things in the example is the different ways VTK
>>>> is used.
>>>
>>> I absolutely agree with 1 and 3 (which I think are the same?), but I
>>> don't see how changing to auto would in affect anything in this
>>> regard.
>>>
>>> I also don't see how it would be a homogenization. The declarations I
>>> would change are already homogeneous in that they're all
>>> vtkSmartPointer<Foo> a = vtkSmartPointer<Foo>::New(). Changing to auto
>>> would not make it more or less homogeneous.
>>>
>>> It would be a
>>
>> ... It would be homogenisation if I'd change all
>> vtkNew/vtkSmartPointer to auto a = vtkSmartPointer..., but that's not
>> what this is about.
>>
>>> Note that this is not about changing vtkNew to vtkSmartPointer.
>>>
>>> And how would changing to auto in any way affect the approach taken by
>>> the example?
>>>
>>>
>>>
>>>> To me it matters little whether:
>>>> auto actor = vtkSmartPointer<vtkActor>::New();
>>>> vtkSmartPointer<vtkActor> actor =
>>>>     vtkSmartPointer<vtkActor>::New();
>>>>
>>>> or whether "ren/renWin" is used instead of "renderer" or "rendererWindow" in
>>>> the examples.
>>
>> It matters little to me too, but it does matter. I think it's almost
>> indisputable that
>>
>>     auto someVar = vtkSmartPointer<SomeLongTypeName>::New()
>>
>> is more readable than
>>
>>     vtkSmartPointer<SomeLongTypeName> someVar =
>>         vtkSmartPointer<SomeLongTypeName>::New();
>>
>> especially since the latter leads to many more lines to scan across
>> when looking for something in the examples.
>
> Another small plus I see with using auto is it's a keyword which would
> be highlighted, so the declarations would stand out more.
>
> E.g. looking at the code for this example
>
>     https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Florensen.github.io%2FVTKExamples%2Fsite%2FCxx%2FFiltering%2FConnectivityFilter%2F&data=02%7C01%7Classo%40queensu.ca%7C0ced79d0c7c54d7f0f2808d4ba1a6217%7Cd61ecb3b38b142d582c4efb2838b925c%7C1%7C0%7C636338069854146481&sdata=ha%2BCR8CriMPmQqz%2FxrAgI6lQ7RKn21tuZ6Z%2FitzKD%2Fg%3D&reserved=0
>
> I find it hard to quickly answer "what are the declarations?", since
> they have no highlighting compared to the surrounding statements. Had
> they been auto, it would have been easier since I think auto would
> have been highlighted.
>
> I think quickly identifying the variables involved helps the reading
> of the examples.
>
> Elvis
>
>>
>> So, in short I agree with everything you say, but I can't see how
>> changing one way of doing declarations to another is a homogenization.
>> And I do think spelling matters.
>>
>> I'm perfectly OK with leaving the examples exactly like they are
>> though, just wanted to explain how I see it.
>>
>> Elvis
>>
>>>>
>>>> Of more importance are explanatory notes in the examples.
>>>>
>>>> Bill, I see you are using vtkNamedColors. This example shows what other
>>>> things you can do with this class:
>>>> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Florensen.github.io%2FVTKExamples%2Fsite%2FCxx%2FVisualization%2FNamedColors%2F&data=02%7C01%7Classo%40queensu.ca%7C0ced79d0c7c54d7f0f2808d4ba1a6217%7Cd61ecb3b38b142d582c4efb2838b925c%7C1%7C0%7C636338069854146481&sdata=jnbJJe87OvOErNapbQL2HiAt6DnbOWifp67W4lNVqfo%3D&reserved=0
>>>>
>>>> For example, assign colors by name:
>>>> renderer->SetBackground(namedColors->GetColor3d("SteelBlue").GetData
>>>> ());
>>>> Create your own named color (in this case a red with an alpha of 0.5):
>>>> namedColors->GetColor("Red", rgba);
>>>> rgba[3] = 0.5; namedColors->SetColor("My Red", rgba);
>>>>
>>>> Regards
>>>>    Andrew
>>>>
>>>>>
>>>>> ---------- Forwarded message ----------
>>>>> From: Bill Lorensen <bill.lorensen at gmail.com>
>>>>> To: Elvis Stansvik <elvis.stansvik at orexplore.com>
>>>>> Cc: vtkdev <vtk-developers at vtk.org>
>>>>> Bcc:
>>>>> Date: Thu, 22 Jun 2017 13:32:55 -0400
>>>>> Subject: Re: [vtk-developers] vtkNew in examples (or auto?)
>>>>> Let's leave them as is for now. I want to make sure I understand this.
>>>>>
>>>>>
>>>>> On Thu, Jun 22, 2017 at 1:13 PM, Elvis Stansvik
>>>>> <elvis.stansvik at orexplore.com> wrote:
>>>>> > 2017-06-22 19:09 GMT+02:00 Bill Lorensen <bill.lorensen at gmail.com>:
>>>>> >> I'm not sure what you mean by auto-fying
>>>>> >
>>>>> > Sorry, I should have been clearer. What I mean is changing declarations
>>>>> > such as
>>>>> >
>>>>> >
>>>>> vtkSmartPointer<vtkActor> actor =
>>>>> >     vtkSmartPointer<vtkActor>::New();
>>>>> >
>>>>> > into
>>>>> >
>>>>> >   auto actor = vtkSmartPointer<vtkActor>::New();
>>>>> >
>>>>> > I think it would cut down on the number of lines in many examples, and
>>>>> > make them more readable. (This would only be done in places where the
>>>>> > type of the variable is still clear from the declaration.)
>>>>> >
>>>>> > Elvis
>>>>> >
>>>>> >>
>>>>> >>
>>>>> >>
>>>>> >> On Thu, Jun 22, 2017 at 1:07 PM, Elvis Stansvik
>>>>> >> <elvis.stansvik at orexplore.com> wrote:
>>>>> >>> 2017-06-22 19:01 GMT+02:00 Bill Lorensen <bill.lorensen at gmail.com>:
>>>>> >>>> I prefer vtkSmartPointer because it can be used like any other vtk
>>>>> >>>> pointer. No need for a GetPointer() is some cases. The example writer
>>>>> >>>> is free to use vtkSmartPointer or vtkNew. But I would leave them as
>>>>> >>>> there are.
>>>>> >>>
>>>>> >>> Right, that's a valid point. But how about auto-fying the
>>>>> >>> declarations? (but keep using vtkSmartPointer)
>>>>> >>>
>>>>> >>> My motivation is that when reading an example, I'm often squinting to
>>>>> >>> find the variable names in the declarations, wedged in there somewhere
>>>>> >>> between all those type names and angle brackets. Especially as the
>>>>> >>> lines are often broken due to running long.
>>>>> >>>
>>>>> >>>>
>>>>> >>>>
>>>>> >>>> Other cleanup's sound great. I've also started using vtkNamedColors
>>>>> >>>> instead of setting float values.
>>>>> >>>
>>>>> >>> Great.
>>>>> >>>
>>>>> >>> Elvis
>>>>> >>>
>>>>> >>>>
>>>>> >>>> On Thu, Jun 22, 2017 at 12:57 PM, Elvis Stansvik
>>>>> >>>> <elvis.stansvik at orexplore.com> wrote:
>>>>> >>>>> Hi all,
>>>>> >>>>>
>>>>> >>>>> How about a refactor of the examples to use vtkNew instead of
>>>>> >>>>> vtkSmartPointer (where it makes sense)?
>>>>> >>>>>
>>>>> >>>>> E.g.
>>>>> >>>>>
>>>>> >>>>>   vtkNew<vtkActor> actor;
>>>>> >>>>>   actor->SetMapper(mapper);
>>>>> >>>>>
>>>>> >>>>>   vtkNew<vtkRenderer> renderer;
>>>>> >>>>>   renderer->AddActor(actor);
>>>>> >>>>>
>>>>> >>>>> instead of
>>>>> >>>>>
>>>>> >>>>>   vtkSmartPointer<vtkActor> actor =
>>>>> >>>>>     vtkSmartPointer<vtkActor>::New();
>>>>> >>>>>   actor->SetMapper(mapper);
>>>>> >>>>>
>>>>> >>>>>   vtkSmartPointer<vtkRenderer> renderer =
>>>>> >>>>>     vtkSmartPointer<vtkRenderer>::New();
>>>>> >>>>>   renderer->AddActor(actor);
>>>>> >>>>>
>>>>> >>>>> I think it would help with the readability of the examples. Or are
>>>>> >>>>> there other reasons for the prevalent use of vtkSmartPointer?
>>>>> >>>>>
>>>>> >>>>> Another option would be to use auto, e.g.
>>>>> >>>>>
>>>>> >>>>>   auto actor = vtkSmartPointer<vtkActor>::New();
>>>>> >>>>>
>>>>> >>>>> Also, would anyone mind if I did a little naming cleanup, mostly
>>>>> >>>>> things like "renwin" -> "window" and "iren" -> "interactor"? Those
>>>>> >>>>> abbreviations are not that bad, but I think it's better in examples
>>>>> >>>>> to
>>>>> >>>>> spell out the variables in proper English.
>>>>> >>>>>
>>>>> >>>>> If there are no objections, I could try to prepare an MR when time
>>>>> >>>>> permits. If so, vtkNew, or auto?
>>>>> >>>>>
>>>>> >>>>> Elvis
>>>>> >>>>> _______________________________________________
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>>>>
>>>>
>>>> --
>>>> ___________________________________________
>>>> Andrew J. P. Maclean
>>>>
>>>> ___________________________________________
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