From ae85c31176728d1b3944844572bf6c7c690b9698 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Sat, 1 Mar 2025 12:43:08 +0100
Subject: [PATCH] render/vulkan: add luminance multiplier for texture shader

---
 include/render/vulkan.h            |  1 +
 render/vulkan/pass.c               | 10 ++++++++++
 render/vulkan/shaders/texture.frag |  3 +++
 3 files changed, 14 insertions(+)

diff --git a/include/render/vulkan.h b/include/render/vulkan.h
index 1ed69d6e4..deff0eac3 100644
--- a/include/render/vulkan.h
+++ b/include/render/vulkan.h
@@ -343,6 +343,7 @@ struct wlr_vk_vert_pcr_data {
 struct wlr_vk_frag_texture_pcr_data {
 	float matrix[4][4]; // only a 3x3 subset is used
 	float alpha;
+	float luminance_multiplier;
 };
 
 struct wlr_vk_frag_output_pcr_data {
diff --git a/render/vulkan/pass.c b/render/vulkan/pass.c
index 0ff4f52c6..4fd357113 100644
--- a/render/vulkan/pass.c
+++ b/render/vulkan/pass.c
@@ -849,8 +849,18 @@ static void render_pass_add_texture(struct wlr_render_pass *wlr_pass,
 		wlr_matrix_identity(color_matrix);
 	}
 
+	float luminance_multiplier = 1;
+	if (tf != WLR_COLOR_TRANSFER_FUNCTION_SRGB) {
+		struct wlr_color_luminances src_lum, srgb_lum;
+		wlr_color_transfer_function_get_default_luminance(tf, &src_lum);
+		wlr_color_transfer_function_get_default_luminance(
+			WLR_COLOR_TRANSFER_FUNCTION_SRGB, &srgb_lum);
+		luminance_multiplier = get_luminance_multiplier(&src_lum, &srgb_lum);
+	}
+
 	struct wlr_vk_frag_texture_pcr_data frag_pcr_data = {
 		.alpha = alpha,
+		.luminance_multiplier = luminance_multiplier,
 	};
 	encode_color_matrix(color_matrix, frag_pcr_data.matrix);
 
diff --git a/render/vulkan/shaders/texture.frag b/render/vulkan/shaders/texture.frag
index e1467023b..2a7e2c517 100644
--- a/render/vulkan/shaders/texture.frag
+++ b/render/vulkan/shaders/texture.frag
@@ -9,6 +9,7 @@ layout(location = 0) out vec4 out_color;
 layout(push_constant, row_major) uniform UBO {
 	layout(offset = 80) mat4 matrix;
 	float alpha;
+	float luminance_multiplier;
 } data;
 
 layout (constant_id = 0) const int TEXTURE_TRANSFORM = 0;
@@ -61,6 +62,8 @@ void main() {
 		rgb = pq_color_to_linear(rgb);
 	}
 
+	rgb *= data.luminance_multiplier;
+
 	rgb = mat3(data.matrix) * rgb;
 
 	// Back to pre-multiplied alpha