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NAME

       wxKeyEvent - Functions for wxKeyEvent class

DESCRIPTION

       This event class contains information about key press and release events.

       The main information carried by this event is the key being pressed or released. It can be
       accessed  using  either  getKeyCode/1  function  or  getUnicodeKey/1.  For  the  printable
       characters,  the  latter  should  be  used as it works for any keys, including non-Latin-1
       characters that can be entered when using national keyboard layouts.  getKeyCode/1  should
       be used to handle special characters (such as cursor arrows keys or HOME or INS and so on)
       which  correspond  to  ?wxKeyCode  enum  elements  above  the  WXK_START  constant.  While
       getKeyCode/1  also  returns  the  character  code  for  Latin-1 keys for compatibility, it
       doesn't work for Unicode characters in general and  will  return  WXK_NONE  for  any  non-
       Latin-1  ones.  For  this  reason, it's recommended to always use getUnicodeKey/1 and only
       fall back to getKeyCode/1 if getUnicodeKey/1 returned  WXK_NONE  meaning  that  the  event
       corresponds to a non-printable special keys.

       While  both of these functions can be used with the events of wxEVT_KEY_DOWN, wxEVT_KEY_UP
       and wxEVT_CHAR types, the values returned by them are different for the first  two  events
       and the last one. For the latter, the key returned corresponds to the character that would
       appear in e.g. a text zone if the user pressed the key in it. As such, its  value  depends
       on  the  current  state  of  the Shift key and, for the letters, on the state of Caps Lock
       modifier. For example, if A key is pressed without Shift being held  down,  wxKeyEvent  of
       type  wxEVT_CHAR  generated  for  this  key press will return (from either getKeyCode/1 or
       getUnicodeKey/1  as  their  meanings  coincide  for  ASCII  characters)  key  code  of  97
       corresponding  the  ASCII  value of a. And if the same key is pressed but with Shift being
       held (or Caps Lock being active), then the key could would be  65,  i.e.  ASCII  value  of
       capital A.

       However  for  the  key  down  and  up  events  the  returned  key  code  will instead be A
       independently of the state of the modifier keys i.e. it depends only on physical key being
       pressed  and  is  not  translated to its logical representation using the current keyboard
       state. Such untranslated key codes are defined as follows:

       Notice that the first rule applies to all Unicode letters,  not  just  the  usual  Latin-1
       ones. However for non-Latin-1 letters only getUnicodeKey/1 can be used to retrieve the key
       code as getKeyCode/1 just returns WXK_NONE in this case.

       To  summarize:  you  should  handle  wxEVT_CHAR  if  you  need  the  translated  key   and
       wxEVT_KEY_DOWN  if  you  only need the value of the key itself, independent of the current
       keyboard state.

       Note: Not all key down events may be generated by the user. As an example,  wxEVT_KEY_DOWN
       with  =  key code can be generated using the standard US keyboard layout but not using the
       German one because the = key corresponds to Shift-0 key combination in this layout and the
       key code for it is 0, not =. Because of this you should avoid requiring your users to type
       key events that might be impossible to enter on their keyboard.

       Another difference between key and char events is that another kind of translation is done
       for the latter ones when the Control key is pressed: char events for ASCII letters in this
       case carry codes corresponding to the ASCII value of Ctrl-Latter, i.e. 1 for Ctrl-A, 2 for
       Ctrl-B  and  so  on until 26 for Ctrl-Z. This is convenient for terminal-like applications
       and can be completely ignored by all the other ones (if you need to handle  Ctrl-A  it  is
       probably  a  better  idea  to  use  the  key  event rather than the char one). Notice that
       currently no translation is done for the presses of [, \, ], ^ and _ keys which  might  be
       mapped to ASCII values from 27 to 31. Since version 2.9.2, the enum values WXK_CONTROL_A -
       WXK_CONTROL_Z can be used instead of the non-descriptive constant values 1-26.

       Finally, modifier keys only generate key events but no char events at all.  The  modifiers
       keys are WXK_SHIFT, WXK_CONTROL, WXK_ALT and various WXK_WINDOWS_XXX from ?wxKeyCode enum.

       Modifier  keys  events  are  special  in one additional aspect: usually the keyboard state
       associated with a key press is well defined, e.g. shiftDown/1 returns  true  only  if  the
       Shift  key  was  held  pressed  when the key that generated this event itself was pressed.
       There is an ambiguity  for  the  key  press  events  for  Shift  key  itself  however.  By
       convention, it is considered to be already pressed when it is pressed and already released
       when it is released. In other words, wxEVT_KEY_DOWN event for the Shift  key  itself  will
       have wxMOD_SHIFT in getModifiers/1 and shiftDown/1 will return true while the wxEVT_KEY_UP
       event for Shift itself will not have wxMOD_SHIFT in its  modifiers  and  shiftDown/1  will
       return false.

       Tip: You may discover the key codes and modifiers generated by all the keys on your system
       interactively by running the page_samples_keyboard wxWidgets sample and pressing some keys
       in it.

       Note:  If  a  key  down (EVT_KEY_DOWN) event is caught and the event handler does not call
       event.Skip() then the corresponding char event (EVT_CHAR) will  not  happen.  This  is  by
       design  and  enables the programs that handle both types of events to avoid processing the
       same key twice. As a consequence, if you do not want to suppress the wxEVT_CHAR events for
       the  keys  you  handle, always call event.Skip() in your wxEVT_KEY_DOWN handler. Not doing
       may also prevent accelerators defined using this key from working.

       Note: If a key is maintained in  a  pressed  state,  you  will  typically  get  a  lot  of
       (automatically  generated) key down events but only one key up one at the end when the key
       is released so it is wrong to assume that there is one up event corresponding to each down
       one.

       Note:  For  Windows  programmers:  The key and char events in wxWidgets are similar to but
       slightly different from Windows  WM_KEYDOWN  and  WM_CHAR  events.  In  particular,  Alt-x
       combination  will generate a char event in wxWidgets (unless it is used as an accelerator)
       and almost all keys, including ones without ASCII equivalents, generate char events too.

       See: wxKeyboardState (not implemented in wx)

       This class is derived (and can use functions) from: wxEvent

       wxWidgets docs: wxKeyEvent

EVENTS

       Use wxEvtHandler:connect/3 with wxKeyEventType to subscribe to events of this type.

DATA TYPES

       wxKeyEvent() = wx:wx_object()

       wxKey() =
           #wxKey{type = wxKeyEvent:wxKeyEventType(),
                  x = integer(),
                  y = integer(),
                  keyCode = integer(),
                  controlDown = boolean(),
                  shiftDown = boolean(),
                  altDown = boolean(),
                  metaDown = boolean(),
                  uniChar = integer(),
                  rawCode = integer(),
                  rawFlags = integer()}

       wxKeyEventType() = char | char_hook | key_down | key_up

EXPORTS

       altDown(This) -> boolean()

              Types:

                 This = wxKeyEvent()

              Returns true if the Alt key is pressed.

              Notice that getModifiers/1 should usually be used instead of this one.

       cmdDown(This) -> boolean()

              Types:

                 This = wxKeyEvent()

              Returns true if the key used for command accelerators is pressed.

              Same as controlDown/1. Deprecated.

              Notice that getModifiers/1 should usually be used instead of this one.

       controlDown(This) -> boolean()

              Types:

                 This = wxKeyEvent()

              Returns true if the Control key or Apple/Command key under macOS is pressed.

              This function doesn't distinguish between right and left control keys.

              Notice that getModifiers/1 should usually be used instead of this one.

       getKeyCode(This) -> integer()

              Types:

                 This = wxKeyEvent()

              Returns the key code of the key that generated this event.

              ASCII symbols return normal ASCII values, while events from special  keys  such  as
              "left  cursor  arrow"  (WXK_LEFT)  return  values  outside  of the ASCII range. See
              ?wxKeyCode for a full list of the virtual key codes.

              Note that this method returns a meaningful value only for special  non-alphanumeric
              keys  or  if  the  user  entered  a  Latin-1 character (this includes ASCII and the
              accented letters found in Western European  languages  but  not  letters  of  other
              alphabets  such  as e.g. Cyrillic). Otherwise it simply method returns WXK_NONE and
              getUnicodeKey/1 should be used to obtain the corresponding Unicode character.

              Using getUnicodeKey/1 is in general the right thing to do if you are interested  in
              the characters typed by the user, getKeyCode/1 should be only used for special keys
              (for which getUnicodeKey/1 returns WXK_NONE). To handle  both  kinds  of  keys  you
              might write:

       getModifiers(This) -> integer()

              Types:

                 This = wxKeyEvent()

              Return the bit mask of all pressed modifier keys.

              The  return  value  is  a  combination of wxMOD_ALT, wxMOD_CONTROL, wxMOD_SHIFT and
              wxMOD_META bit masks. Additionally, wxMOD_NONE is defined as 0, i.e. corresponds to
              no  modifiers  (see  HasAnyModifiers()  (not  implemented  in wx)) and wxMOD_CMD is
              either wxMOD_CONTROL (MSW  and  Unix)  or  wxMOD_META  (Mac),  see  cmdDown/1.  See
              ?wxKeyModifier for the full list of modifiers.

              Notice   that  this  function  is  easier  to  use  correctly  than,  for  example,
              controlDown/1 because when using the latter you also have to remember to test  that
              none of the other modifiers is pressed:

              and  forgetting  to  do  it  can  result  in serious program bugs (e.g. program not
              working with European keyboard layout where AltGr key which is seen by the  program
              as combination of CTRL and ALT is used). On the other hand, you can simply write:

              with this function.

       getPosition(This) -> {X :: integer(), Y :: integer()}

              Types:

                 This = wxKeyEvent()

              Obtains the position (in client coordinates) at which the key was pressed.

              Notice  that under most platforms this position is simply the current mouse pointer
              position and has no special relationship to the key event itself.

              x and y may be NULL if the corresponding coordinate is not needed.

       getRawKeyCode(This) -> integer()

              Types:

                 This = wxKeyEvent()

              Returns the raw key code for this event.

              The flags are platform-dependent and should  only  be  used  if  the  functionality
              provided by other wxKeyEvent methods is insufficient.

              Under  MSW,  the raw key code is the value of wParam parameter of the corresponding
              message.

              Under GTK, the raw key code is the keyval field of the corresponding GDK event.

              Under macOS, the raw key code is the keyCode field of the corresponding NSEvent.

              Note: Currently the raw key codes are  not  supported  by  all  ports,  use  #ifdef
              wxHAS_RAW_KEY_CODES to determine if this feature is available.

       getRawKeyFlags(This) -> integer()

              Types:

                 This = wxKeyEvent()

              Returns the low level key flags for this event.

              The  flags  are  platform-dependent  and  should  only be used if the functionality
              provided by other wxKeyEvent methods is insufficient.

              Under  MSW,  the  raw  flags  are  just  the  value  of  lParam  parameter  of  the
              corresponding message.

              Under  GTK,  the  raw flags contain the hardware_keycode field of the corresponding
              GDK event.

              Under macOS, the raw flags contain the modifiers state.

              Note: Currently the raw key flags are  not  supported  by  all  ports,  use  #ifdef
              wxHAS_RAW_KEY_CODES to determine if this feature is available.

       getUnicodeKey(This) -> integer()

              Types:

                 This = wxKeyEvent()

              Returns the Unicode character corresponding to this key event.

              If the key pressed doesn't have any character value (e.g. a cursor key) this method
              will return WXK_NONE. In this case you should  use  getKeyCode/1  to  retrieve  the
              value of the key.

              This function is only available in Unicode build, i.e. when wxUSE_UNICODE is 1.

       getX(This) -> integer()

              Types:

                 This = wxKeyEvent()

              Returns the X position (in client coordinates) of the event.

              See: getPosition/1

       getY(This) -> integer()

              Types:

                 This = wxKeyEvent()

              Returns the Y position (in client coordinates) of the event.

              See: getPosition/1

       hasModifiers(This) -> boolean()

              Types:

                 This = wxKeyEvent()

              Returns true if Control or Alt are pressed.

              Checks  if  Control, Alt or, under macOS only, Command key are pressed (notice that
              the real Control key is still taken into account under OS X too).

              This method returns false if only Shift is pressed for  compatibility  reasons  and
              also  because  pressing  Shift  usually  doesn't  change  the interpretation of key
              events, see HasAnyModifiers() (not implemented in wx) if you  want  to  take  Shift
              into account as well.

       metaDown(This) -> boolean()

              Types:

                 This = wxKeyEvent()

              Returns true if the Meta/Windows/Apple key is pressed.

              This  function  tests  the  state  of  the key traditionally called Meta under Unix
              systems, Windows keys under MSW Notice that getModifiers/1 should usually  be  used
              instead of this one.

              See: cmdDown/1

       shiftDown(This) -> boolean()

              Types:

                 This = wxKeyEvent()

              Returns true if the Shift key is pressed.

              This function doesn't distinguish between right and left shift keys.

              Notice that getModifiers/1 should usually be used instead of this one.