# SDL: Use the maximum potential headroom if EDR content isn't currently being displayed.

**URL:** <https://discourse.libsdl.org/t/sdl-use-the-maximum-potential-headroom-if-edr-content-isnt-currently-being-displayed/49434>\
**Category:** SDL Commits\
**Created:** [February 25, 2024, 11:56pm UTC](https://discourse.libsdl.org/t/sdl-use-the-maximum-potential-headroom-if-edr-content-isnt-currently-being-displayed/49434 "2024-02-25T23:56:01Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![SDLPushPostBot](https://discourse.libsdl.org/user_avatar/discourse.libsdl.org/sdlpushpostbot/32/4370_2.png) [@SDLPushPostBot](https://discourse.libsdl.org/u/SDLPushPostBot)\
**Post date:** [February 25, 2024, 11:56pm UTC](https://discourse.libsdl.org/t/sdl-use-the-maximum-potential-headroom-if-edr-content-isnt-currently-being-displayed/49434/1 "2024-02-25T23:56:02Z")

</div>

> <https://github.com/libsdl-org/SDL/commit/be51b7aceaf5e5641915cfb50564b50196005641>
>
> Also document that the HDR properties can change dynamically at runtime.

```diff
From be51b7aceaf5e5641915cfb50564b50196005641 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Sun, 25 Feb 2024 15:46:38 -0800
Subject: [PATCH] Use the maximum potential headroom if EDR content isn't
 currently being displayed.

Also document that the HDR properties can change dynamically at runtime.
---
 include/SDL3/SDL_render.h | 6 +++---
 include/SDL3/SDL_video.h | 8 ++++----
 src/video/cocoa/SDL_cocoamodes.m | 6 +++++-
 src/video/uikit/SDL_uikitmodes.m | 6 +++++-
 4 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/include/SDL3/SDL_render.h b/include/SDL3/SDL_render.h
index d45681b4389a..2d09319b3af5 100644
--- a/include/SDL3/SDL_render.h
+++ b/include/SDL3/SDL_render.h
@@ -344,13 +344,13 @@ extern DECLSPEC int SDLCALL SDL_GetRendererInfo(SDL_Renderer *renderer, SDL_Rend
  * SDL_COLORSPACE_SRGB.
  * - `SDL_PROP_RENDERER_HDR_ENABLED_BOOLEAN`: true if the output colorspace is
  * SDL_COLORSPACE_SRGB_LINEAR and the renderer is showing on a display with
- * HDR enabled.
+ * HDR enabled. This property can change dynamically when SDL_EVENT_DISPLAY_HDR_STATE_CHANGED is sent.
  * - `SDL_PROP_RENDERER_SDR_WHITE_POINT_FLOAT`: the value of SDR white in the
  * SDL_COLORSPACE_SRGB_LINEAR colorspace. When HDR is enabled, this value is
- * automatically multiplied into the color scale.
+ * automatically multiplied into the color scale. This property can change dynamically when SDL_EVENT_DISPLAY_HDR_STATE_CHANGED is sent.
  * - `SDL_PROP_RENDERER_HDR_HEADROOM_FLOAT`: the additional high dynamic range
  * that can be displayed, in terms of the SDR white point. When HDR is not
- * enabled, this will be 1.0.
+ * enabled, this will be 1.0. This property can change dynamically when SDL_EVENT_DISPLAY_HDR_STATE_CHANGED is sent.
  * - `SDL_PROP_RENDERER_D3D9_DEVICE_POINTER`: the IDirect3DDevice9 associated
  * with the renderer
  * - `SDL_PROP_RENDERER_D3D11_DEVICE_POINTER`: the ID3D11Device associated
diff --git a/include/SDL3/SDL_video.h b/include/SDL3/SDL_video.h
index 1cbc4ec82830..77a03cf81d37 100644
--- a/include/SDL3/SDL_video.h
+++ b/include/SDL3/SDL_video.h
@@ -355,15 +355,15 @@ extern DECLSPEC SDL_DisplayID SDLCALL SDL_GetPrimaryDisplay(void);
  *
  * The following read-only properties are provided by SDL:
  *
- * - `SDL_PROP_DISPLAY_HDR_ENABLED_BOOLEAN`: true if the display has HDR
- * headroom above the SDR white point.
+ * - `SDL_PROP_DISPLAY_HDR_ENABLED_BOOLEAN`: true if the display has HDR 
+ * headroom above the SDR white point. This property can change dynamically when SDL_EVENT_DISPLAY_HDR_STATE_CHANGED is sent.
  * - `SDL_PROP_DISPLAY_SDR_WHITE_POINT_FLOAT`: the value of SDR white in the
  * SDL_COLORSPACE_SRGB_LINEAR colorspace. On Windows this corresponds to the
  * SDR white level in scRGB colorspace, and on Apple platforms this is
- * always 1.0 for EDR content.
+ * always 1.0 for EDR content. This property can change dynamically when SDL_EVENT_DISPLAY_HDR_STATE_CHANGED is sent.
  * - `SDL_PROP_DISPLAY_HDR_HEADROOM_FLOAT`: the additional high dynamic range
  * that can be displayed, in terms of the SDR white point. When HDR is not
- * enabled, this will be 1.0.
+ * enabled, this will be 1.0. This property can change dynamically when SDL_EVENT_DISPLAY_HDR_STATE_CHANGED is sent.
  *
  * \param displayID the instance ID of the display to query
  * \returns a valid property ID on success or 0 on failure; call
diff --git a/src/video/cocoa/SDL_cocoamodes.m b/src/video/cocoa/SDL_cocoamodes.m
index 42d54a4bd67e..862bc56b54d5 100644
--- a/src/video/cocoa/SDL_cocoamodes.m
+++ b/src/video/cocoa/SDL_cocoamodes.m
@@ -299,7 +299,11 @@ static void Cocoa_GetHDRProperties(CGDirectDisplayID displayID, SDL_HDRDisplayPr
     if (@available(macOS 10.15, *)) {
         NSScreen *screen = GetNSScreenForDisplayID(displayID);
         if (screen) {
- HDR->HDR_headroom = screen.maximumExtendedDynamicRangeColorComponentValue;
+ if (screen.maximumExtendedDynamicRangeColorComponentValue > 1.0f) {
+ HDR->HDR_headroom = screen.maximumExtendedDynamicRangeColorComponentValue;
+ } else {
+ HDR->HDR_headroom = screen.maximumPotentialExtendedDynamicRangeColorComponentValue;
+ }
         }
     }
 #endif
diff --git a/src/video/uikit/SDL_uikitmodes.m b/src/video/uikit/SDL_uikitmodes.m
index 8da779e0163e..b64a9c3304dc 100644
--- a/src/video/uikit/SDL_uikitmodes.m
+++ b/src/video/uikit/SDL_uikitmodes.m
@@ -247,7 +247,11 @@ int UIKit_AddDisplay(UIScreen *uiscreen, SDL_bool send_event)
 
 #ifndef SDL_PLATFORM_TVOS
     if (@available(iOS 16.0, *)) {
- display.HDR.HDR_headroom = uiscreen.currentEDRHeadroom;
+ if (uiscreen.currentEDRHeadroom > 1.0f) {
+ display.HDR.HDR_headroom = uiscreen.currentEDRHeadroom;
+ } else {
+ display.HDR.HDR_headroom = uiscreen.potentialEDRHeadroom;
+ }
     }
 #endif /* !SDL_PLATFORM_TVOS */
 

```