From 5d15a41b0fbd1c72a852918ff67a61dc9df283f9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kacper=20Michaj=C5=82ow?= <kasper93@gmail.com>
Date: Sun, 14 Jun 2026 05:21:10 +0200
Subject: [PATCH] vo/win32/d3d11_helpers: add
 mp_dxgi_sdr_white_level_from_hwnd()

---
 video/out/gpu/d3d11_helpers.c | 35 +++++++++++++++++++++++++++++++++++
 video/out/gpu/d3d11_helpers.h |  7 +++++++
 2 files changed, 42 insertions(+)

diff --git a/video/out/gpu/d3d11_helpers.c b/video/out/gpu/d3d11_helpers.c
index 92f412542c..93510d705b 100644
--- a/video/out/gpu/d3d11_helpers.c
+++ b/video/out/gpu/d3d11_helpers.c
@@ -26,6 +26,7 @@
 #include "osdep/io.h"
 #include "osdep/threads.h"
 #include "osdep/windows_utils.h"
+#include "video/out/win32/displayconfig.h"
 
 #include "d3d11_helpers.h"
 
@@ -992,6 +993,8 @@ void mp_dxgi_factory_uninit(struct mp_dxgi_factory_ctx *ctx)
 
     SAFE_RELEASE(ctx->factory);
     SAFE_RELEASE(ctx->last_matched_output);
+    ctx->white_level_monitor = NULL;
+    ctx->sdr_white_level = 0;
 }
 
 bool mp_dxgi_output_desc_from_hwnd(struct mp_dxgi_factory_ctx *ctx,
@@ -1006,6 +1009,10 @@ bool mp_dxgi_output_desc_from_hwnd(struct mp_dxgi_factory_ctx *ctx,
         return false;
 
     if (!ctx->factory || !IDXGIFactory1_IsCurrent(ctx->factory)) {
+        // This also clears `white_level_monitor`, to invalidate cached value.
+        // While we are using displayconfig API to get reference luminance,
+        // DXGI IsCurrent() is actually tracking reference luminance changes in
+        // settings. There is no window message sent on this change.
         mp_dxgi_factory_uninit(ctx);
         PFN_CREATE_DXGI_FACTORY pCreateDXGIFactory1 = get_CreateDXGIFactory1();
         if (FAILED(pCreateDXGIFactory1(&IID_IDXGIFactory1, (void **)&ctx->factory)))
@@ -1067,6 +1074,34 @@ bool mp_dxgi_output_desc_from_swapchain(struct mp_dxgi_factory_ctx *ctx,
     return false;
 }
 
+float mp_dxgi_sdr_white_level_from_hwnd(struct mp_dxgi_factory_ctx *ctx,
+                                        HWND hwnd)
+{
+#if HAVE_WIN32_DESKTOP
+    DXGI_OUTPUT_DESC1 desc;
+    if (!mp_dxgi_output_desc_from_hwnd(ctx, hwnd, &desc))
+        return 0;
+
+    if (ctx && ctx->white_level_monitor == desc.Monitor)
+        return ctx->sdr_white_level;
+
+    MONITORINFOEXW mi = { .cbSize = sizeof(mi) };
+    if (!GetMonitorInfoW(desc.Monitor, (MONITORINFO*)&mi))
+        return 0;
+
+    float white_level = mp_w32_displayconfig_get_sdr_white_level(mi.szDevice);
+
+    if (ctx) {
+        ctx->white_level_monitor = desc.Monitor;
+        ctx->sdr_white_level = white_level;
+    }
+
+    return white_level;
+#else
+    return 0;
+#endif
+}
+
 struct pl_color_space mp_dxgi_desc_to_color_space(const DXGI_OUTPUT_DESC1 *desc)
 {
     struct pl_color_space ret = {0};
diff --git a/video/out/gpu/d3d11_helpers.h b/video/out/gpu/d3d11_helpers.h
index 669348df1b..f3d4908a17 100644
--- a/video/out/gpu/d3d11_helpers.h
+++ b/video/out/gpu/d3d11_helpers.h
@@ -65,6 +65,8 @@ struct d3d11_device_opts {
 struct mp_dxgi_factory_ctx {
     IDXGIFactory1 *factory;
     IDXGIOutput6 *last_matched_output;
+    HMONITOR white_level_monitor;
+    float sdr_white_level;
 };
 
 void mp_dxgi_factory_uninit(struct mp_dxgi_factory_ctx *ctx);
@@ -79,6 +81,11 @@ bool mp_dxgi_output_desc_from_swapchain(struct mp_dxgi_factory_ctx *ctx,
                                         IDXGISwapChain *swapchain,
                                         DXGI_OUTPUT_DESC1 *desc);
 
+// Returns the system SDR white level for the monitor the window is on, in nits,
+// or 0 if unknown.
+float mp_dxgi_sdr_white_level_from_hwnd(struct mp_dxgi_factory_ctx *ctx,
+                                        HWND hwnd);
+
 struct pl_color_space mp_dxgi_desc_to_color_space(const DXGI_OUTPUT_DESC1 *desc);
 
 OPT_STRING_VALIDATE_FUNC(mp_dxgi_validate_adapter);