Added SDL_HINT_AUDIO_DUMMY_TIMESCALE

docs/README-migration.md

@@ -755,6 +755,23 @@ SDL_AddHintCallback() now returns a standard int result instead of void, returni
 
 Calling SDL_GetHint() with the name of the hint being changed from within a hint callback will now return the new value rather than the old value. The old value is still passed as a parameter to the hint callback.
 
+The environment variables SDL_VIDEODRIVER and SDL_AUDIODRIVER have been renamed to SDL_VIDEO_DRIVER and SDL_AUDIO_DRIVER.
+
+The environment variables SDL_VIDEO_X11_WMCLASS and SDL_VIDEO_WAYLAND_WMCLASS have been removed and replaced by either using the appindentifier param to SDL_SetAppMetadata() or setting SDL_PROP_APP_METADATA_IDENTIFIER_STRING with SDL_SetAppMetadataProperty()
+
+The following hints have been renamed:
+* SDL_HINT_VIDEODRIVER => SDL_VIDEO_DRIVER
+* SDL_HINT_AUDIODRIVER => SDL_HINT_AUDIO_DRIVER
+* SDL_HINT_ALLOW_TOPMOST => SDL_HINT_WINDOW_ALLOW_TOPMOST
+* SDL_HINT_DIRECTINPUT_ENABLED => SDL_HINT_JOYSTICK_DIRECTINPUT
+* SDL_HINT_GDK_TEXTINPUT_DEFAULT => SDL_HINT_GDK_TEXTINPUT_DEFAULT_TEXT
+* SDL_HINT_JOYSTICK_GAMECUBE_RUMBLE_BRAKE => SDL_HINT_JOYSTICK_HIDAPI_GAMECUBE_RUMBLE_BRAKE
+* SDL_HINT_LINUX_DIGITAL_HATS => SDL_HINT_JOYSTICK_LINUX_DIGITAL_HATS
+* SDL_HINT_LINUX_HAT_DEADZONES => SDL_HINT_JOYSTICK_LINUX_HAT_DEADZONES
+* SDL_HINT_LINUX_JOYSTICK_CLASSIC => SDL_HINT_JOYSTICK_LINUX_CLASSIC
+* SDL_HINT_LINUX_JOYSTICK_DEADZONES => SDL_HINT_JOYSTICK_LINUX_DEADZONES
+* SDL_HINT_VIDEO_WAYLAND_EMULATE_MOUSE_WARP => SDL_HINT_MOUSE_EMULATE_WARP_WITH_RELATIVE
+
 The following hints have been removed:
 * SDL_HINT_ACCELEROMETER_AS_JOYSTICK
 * SDL_HINT_ANDROID_BLOCK_ON_PAUSE_PAUSEAUDIO - the audio will be paused when the application is paused, and SDL_HINT_ANDROID_BLOCK_ON_PAUSE can be used to control that
@@ -784,20 +801,8 @@ The following hints have been removed:
 * SDL_HINT_XINPUT_USE_OLD_JOYSTICK_MAPPING
 * SDL_HINT_AUDIO_DEVICE_APP_NAME - replaced by either using the appname param to SDL_SetAppMetadata() or setting SDL_PROP_APP_METADATA_NAME_STRING with SDL_SetAppMetadataProperty()
 
-* Renamed hints SDL_HINT_VIDEODRIVER and SDL_HINT_AUDIODRIVER to SDL_HINT_VIDEO_DRIVER and SDL_HINT_AUDIO_DRIVER
-* Renamed environment variables SDL_VIDEODRIVER and SDL_AUDIODRIVER to SDL_VIDEO_DRIVER and SDL_AUDIO_DRIVER
-* The environment variables SDL_VIDEO_X11_WMCLASS and SDL_VIDEO_WAYLAND_WMCLASS have been removed and replaced by either using the appindentifier param to SDL_SetAppMetadata() or setting SDL_PROP_APP_METADATA_IDENTIFIER_STRING with SDL_SetAppMetadataProperty()
-
-The following hints have been renamed:
-* SDL_HINT_ALLOW_TOPMOST => SDL_HINT_WINDOW_ALLOW_TOPMOST
-* SDL_HINT_DIRECTINPUT_ENABLED => SDL_HINT_JOYSTICK_DIRECTINPUT
-* SDL_HINT_GDK_TEXTINPUT_DEFAULT => SDL_HINT_GDK_TEXTINPUT_DEFAULT_TEXT
-* SDL_HINT_JOYSTICK_GAMECUBE_RUMBLE_BRAKE => SDL_HINT_JOYSTICK_HIDAPI_GAMECUBE_RUMBLE_BRAKE
-* SDL_HINT_LINUX_DIGITAL_HATS => SDL_HINT_JOYSTICK_LINUX_DIGITAL_HATS
-* SDL_HINT_LINUX_HAT_DEADZONES => SDL_HINT_JOYSTICK_LINUX_HAT_DEADZONES
-* SDL_HINT_LINUX_JOYSTICK_CLASSIC => SDL_HINT_JOYSTICK_LINUX_CLASSIC
-* SDL_HINT_LINUX_JOYSTICK_DEADZONES => SDL_HINT_JOYSTICK_LINUX_DEADZONES
-* SDL_HINT_VIDEO_WAYLAND_EMULATE_MOUSE_WARP => SDL_HINT_MOUSE_EMULATE_WARP_WITH_RELATIVE
+The following environment variables have been removed:
+* SDL_DUMMYAUDIODELAY - replaced with the hint SDL_HINT_AUDIO_DUMMY_TIMESCALE which allows scaling the audio time rather than specifying an absolute delay.
 
 The following functions have been removed:
 * SDL_ClearHints() - replaced with SDL_ResetHints()

include/SDL3/SDL_hints.h

@@ -338,6 +338,17 @@ extern "C" {
  */
 #define SDL_HINT_AUDIO_DRIVER "SDL_AUDIO_DRIVER"
 
+/**
+ * A variable controlling the audio rate when using the dummy audio driver.
+ *
+ * The dummy audio driver normally simulates real-time for the audio rate that was specified, but you can use this variable to adjust this rate higher or lower down to 0. The default value is "1.0".
+ *
+ * This hint should be set before an audio device is opened.
+ *
+ * \since This hint is available since SDL 3.0.0.
+ */
+#define SDL_HINT_AUDIO_DUMMY_TIMESCALE "SDL_AUDIO_DUMMY_TIMESCALE"
+
 /**
  * A variable controlling the default audio format.
  *

src/audio/dummy/SDL_dummyaudio.c

@@ -25,9 +25,6 @@
 #include "../SDL_sysaudio.h"
 #include "SDL_dummyaudio.h"
 
-// !!! FIXME: this should be an SDL hint, not an environment variable.
-#define DUMMYENVR_IODELAY "SDL_DUMMYAUDIODELAY"
-
 static int DUMMYAUDIO_WaitDevice(SDL_AudioDevice *device)
 {
     SDL_Delay(device->hidden->io_delay);
@@ -36,8 +33,6 @@ static int DUMMYAUDIO_WaitDevice(SDL_AudioDevice *device)
 
 static int DUMMYAUDIO_OpenDevice(SDL_AudioDevice *device)
 {
-    const char *envr = SDL_getenv(DUMMYENVR_IODELAY);
-
     device->hidden = (struct SDL_PrivateAudioData *) SDL_calloc(1, sizeof(*device->hidden));
     if (!device->hidden) {
         return -1;
@@ -50,8 +45,15 @@ static int DUMMYAUDIO_OpenDevice(SDL_AudioDevice *device)
         }
     }
 
-    device->hidden->io_delay = (Uint32) (envr ? SDL_atoi(envr) : ((device->sample_frames * 1000) / device->spec.freq));
+    device->hidden->io_delay = ((device->sample_frames * 1000) / device->spec.freq);
 
+    const char *hint = SDL_GetHint(SDL_HINT_AUDIO_DUMMY_TIMESCALE);
+    if (hint) {
+        double scale = SDL_atof(hint);
+        if (scale >= 0.0) {
+            device->hidden->io_delay = (Uint32)SDL_round(device->hidden->io_delay * scale);
+        }
+    }
     return 0; // we're good; don't change reported device format.
 }