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WinRT: expanded the documentation on SDL_HINT_WINRT_HANDLE_BACK_BUTTON
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DavidLudwig committed Oct 4, 2014
1 parent 498690f commit 411e0f9dac2043e0ac2afa85fba51ebfaf2f5917
Showing with 48 additions and 5 deletions.
  1. +48 −5 include/SDL_hints.h
@@ -439,11 +439,54 @@ extern "C" {
*/
#define SDL_HINT_WINRT_PRIVACY_POLICY_LABEL "SDL_WINRT_PRIVACY_POLICY_LABEL"

/** \brief If set to "1", back button press events on Windows Phone 8+ will be marked as handled.
*
* TODO, WinRT: document SDL_HINT_WINRT_HANDLE_BACK_BUTTON need and use
* For now, more details on why this is needed can be found at the
* beginning of the following web page:
/** \brief Allows back-button-press events on Windows Phone to be marked as handled
*
* Windows Phone devices typically feature a Back button. When pressed,
* the OS will emit back-button-press events, which apps are expected to
* handle in an appropriate manner. If apps do not explicitly mark these
* events as 'Handled', then the OS will invoke its default behavior for
* unhandled back-button-press events, which on Windows Phone 8 and 8.1 is to
* terminate the app (and attempt to switch to the previous app, or to the
* device's home screen).
*
* Setting the SDL_HINT_WINRT_HANDLE_BACK_BUTTON hint to "1" will cause SDL
* to mark back-button-press events as Handled, if and when one is sent to
* the app.
*
* Internally, Windows Phone sends back button events as parameters to
* special back-button-press callback functions. Apps that need to respond
* to back-button-press events are expected to register one or more
* callback functions for such, shortly after being launched (during the
* app's initialization phase). After the back button is pressed, the OS
* will invoke these callbacks. If the app's callback(s) do not explicitly
* mark the event as handled by the time they return, or if the app never
* registers one of these callback, the OS will consider the event
* un-handled, and it will apply its default back button behavior (terminate
* the app).
*
* SDL registers its own back-button-press callback with the Windows Phone
* OS. This callback will emit a pair of SDL key-press events (SDL_KEYDOWN
* and SDL_KEYUP), each with a scancode of SDL_SCANCODE_AC_BACK, after which
* it will check the contents of the hint, SDL_HINT_WINRT_HANDLE_BACK_BUTTON.
* If the hint's value is set to "1", the back button event's Handled
* property will get set to 'true'. If the hint's value is set to something
* else, or if it is unset, SDL will leave the event's Handled property
* alone. (By default, the OS sets this property to 'false', to note.)
*
* SDL apps can either set SDL_HINT_WINRT_HANDLE_BACK_BUTTON well before a
* back button is pressed, or can set it in direct-response to a back button
* being pressed.
*
* In order to get notified when a back button is pressed, SDL apps should
* register a callback function with SDL_AddEventWatch(), and have it listen
* for SDL_KEYDOWN events that have a scancode of SDL_SCANCODE_AC_BACK.
* (Alternatively, SDL_KEYUP events can be listened-for. Listening for
* either event type is suitable.) Any value of SDL_HINT_WINRT_HANDLE_BACK_BUTTON
* set by such a callback, will be applied to the OS' current
* back-button-press event.
*
* More details on back button behavior in Windows Phone apps can be found
* at the following page, on Microsoft's developer site:
* http://msdn.microsoft.com/en-us/library/windowsphone/develop/jj247550(v=vs.105).aspx
*/
#define SDL_HINT_WINRT_HANDLE_BACK_BUTTON "SDL_WINRT_HANDLE_BACK_BUTTON"

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