[vtkusers] Catching arrow keys in linux

[Liam Kurmos]

On Fri, Jan 22, 2010 at 9:17 PM, David Gobbi <david.gobbi at gmail.com> wrote:
> On Fri, Jan 22, 2010 at 2:06 PM, David Doria <daviddoria+vtk at gmail.com> wrote:
>> On Fri, Jan 22, 2010 at 3:47 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>>
>>> It's failing because you are doing this:
>>>
>>>  rwi->GetKeySym() == "Up"
>>>
>>> Throw in a strcmp or something.
>>>
>>>  - David
>>>
>>>
>>> On Fri, Jan 22, 2010 at 1:36 PM, David Doria <daviddoria+vtk at gmail.com>
>>> wrote:
>>> > On Fri, Jan 22, 2010 at 3:21 PM, David Gobbi <david.gobbi at gmail.com>
>>> > wrote:
>>> >>
>>> >> I'm not sure what #defines you are talking about, but why not use the
>>> >> interactor "GetKeySym" method to detect arrow keys?  They have the
>>> >> names "Up", "Down", "Left", "Right".
>>> >>
>>> >>    David
>>> >>
>>> >>
>>> >> On Fri, Jan 22, 2010 at 1:18 PM, David Doria <daviddoria+vtk at gmail.com>
>>> >> wrote:
>>> >> > It seems that for win32, there are some #defines for arrow keys like
>>> >> > VK_RIGHT. I can't seem to find what should be done for non win32 -
>>> >> > any
>>> >> > thoughts?
>>> >> >
>>> >> > Thanks,
>>> >> >
>>> >> > David
>>> >>
>>> >
>>> > So typically I do this from inside my InteractorStyle subclass:
>>> >
>>> >     virtual void OnChar()
>>> >     {
>>> >       vtkRenderWindowInteractor *rwi = this->Interactor;
>>> >
>>> >       char ch = rwi->GetKeyCode() ;
>>> >       switch (ch)
>>> >       {
>>> >         case 's':
>>> >           cout << "Pressed s." << endl;
>>> >           break;
>>> >         case 'a':
>>> >           cout << "Pressed a." << endl;
>>> >           break ;
>>> >         default:
>>> >           cout << "Pressed an unhandled key: " << rwi->GetKeyCode() <<
>>> > endl;
>>> >           break;
>>> >       }
>>> > The problem is that OnChar() doesn't fire when the arrow keys are
>>> > pressed. I
>>> > tried to use
>>> >     virtual void OnKeyDown()
>>> >     {
>>> >       vtkRenderWindowInteractor *rwi = this->Interactor;
>>> >
>>> >       if(rwi->GetKeySym() == "Up")
>>> >       {
>>> >         cout << "Pressed up." << endl;
>>> >       }
>>> >
>>> >       // forward events
>>> >       vtkInteractorStyleTrackballCamera::OnKeyDown();
>>> >     }
>>> > But it doesn't seem to compare to true. It also doesn't seem to flush
>>> > the
>>> > buffer when I would expect?
>>> > Also, what is the difference between KeyPress and KeyDown? The
>>> > documentation
>>> > is kind of broken
>>> >
>>> > here: http://www.vtk.org/doc/nightly/html/classvtkInteractorStyle.html#a65fcd9765c162a6021434386037ca641
>>> > Thanks,
>>> >
>>> > David
>>
>> Yes, that was certainly a bug, but not as confusing as the following
>> problem.
>> With these two functions:
>>
>>     virtual void OnKeyPress()
>>     {
>>       vtkRenderWindowInteractor *rwi = this->Interactor;
>>
>>       std::string key = rwi->GetKeySym();
>>       if(key.compare("Up") == 0)
>>         {
>>         cout << "Pressed up." << endl;
>>         }
>>
>>       // forward events
>>       vtkInteractorStyleTrackballCamera::OnKeyPress();
>>     }
>>
>>     virtual void OnChar()
>>     {
>>       vtkRenderWindowInteractor *rwi = this->Interactor;
>>
>>       char ch = rwi->GetKeyCode() ;
>>       switch (ch)
>>       {
>>         case 's':
>>           cout << "Pressed s." << endl;
>>           break;
>>         case 'a':
>>           cout << "Pressed a." << endl;
>>           break ;
>>         default:
>>           cout << "Pressed an unhandled key: " << ch << endl;
>>           break;
>>       }
>>  // forward events
>>       vtkInteractorStyleTrackballCamera::OnChar();
>>     }
>> The output of pressing:
>> a, b, up, a
>> Is:
>> Pressed a.
>> Pressed an unhandled key: b
>> Pressed up.
>> Pressed an unhandled key: Pressed a.
>> You can see that there is an "unhandled key" in the mix when there was
>> actually no unhandled key. There were only 4 keypresses, and 5 outputs.
>> Thanks,
>>
>> David
>
> Print out the keycode of the mystery key as a hexidecimal value.  My
> guess is that you're seeing an output from the arrow key in both the
> OnKeyPress and in OnChar.  The KeyCode values aren't guaranteed to be
> ascii.
>
>   David

off topic, but I found it interesting to learn that sending a
non-ascii char to cout can cause the <<endl not to function without
throwing an error.

Liam