camera: Reworked to operate with a driver interface, like other subsystems.

include/SDL3/SDL_hints.h

@@ -355,6 +355,22 @@ extern "C" {
  */
 #define SDL_HINT_BMP_SAVE_LEGACY_FORMAT "SDL_BMP_SAVE_LEGACY_FORMAT"
 
+/**
+ *  A variable that decides what camera backend to use.
+ *
+ *  By default, SDL will try all available camera backends in a reasonable
+ *  order until it finds one that can work, but this hint allows the app
+ *  or user to force a specific target, such as "directshow" if, say, you are
+ *  on Windows Media Foundations but want to try DirectShow instead.
+ *
+ *  The default value is unset, in which case SDL will try to figure out
+ *  the best camera backend on your behalf. This hint needs to be set
+ *  before SDL_Init() is called to be useful.
+ *
+ *  This hint is available since SDL 3.0.0.
+ */
+#define SDL_HINT_CAMERA_DRIVER "SDL_CAMERA_DRIVER"
+
 /**
  * A variable controlling whether DirectInput should be used for controllers
  *
@@ -2478,7 +2494,6 @@ extern "C" {
  */
 #define SDL_HINT_XINPUT_ENABLED "SDL_XINPUT_ENABLED"
 
-
 /**
  *  An enumeration of hint priorities
  */