From 7383cfcbe8ade4dce057608e971e8cb7d4b1feb7 Mon Sep 17 00:00:00 2001
From: quou <quou@disroot.org>
Date: Sun, 29 Dec 2024 13:40:45 +1100
Subject: allow binding only a portion of a cbuffer

---
 pipeline.cpp | 11 ++++++++++-
 video.cpp    |  4 ++--
 video.hpp    | 12 ++++++++++--
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/pipeline.cpp b/pipeline.cpp
index 8867a8d..8750db0 100644
--- a/pipeline.cpp
+++ b/pipeline.cpp
@@ -185,7 +185,12 @@ void Pipeline_Builder::texture(
 	td->texture = t;
 }
 
-void Pipeline_Builder::cbuffer(int binding, Buffer_Id id) {
+void Pipeline_Builder::cbuffer(
+	int binding,
+	Buffer_Id id,
+	int offset,
+	int size
+) {
 	Descriptor* d;
 	Constant_Buffer_Descriptor* cd;
 	assert(pip->descriptor_count < pipeline_max_descriptors);
@@ -194,6 +199,8 @@ void Pipeline_Builder::cbuffer(int binding, Buffer_Id id) {
 	d->slot = binding;
 	d->type = Descriptor::Type::constant_buffer;
 	cd->buffer = id;
+	cd->offset = offset;
+	cd->size = size;
 }
 
 void Pipeline_Builder::vertex_format(Vertex_Format_Id vf) {
@@ -237,6 +244,8 @@ Pipeline& Pipeline_Builder::build() {
 				case Descriptor::Type::constant_buffer: {
 					auto cd = (Constant_Buffer_Descriptor*)d->payload;
 					h(pip->descriptor_resource_hash, cd->buffer);
+					h(pip->descriptor_resource_hash, cd->size);
+					h(pip->descriptor_resource_hash, cd->offset);
 				} break;
 			}
 		}
diff --git a/video.cpp b/video.cpp
index 5d88d0c..d0720f5 100644
--- a/video.cpp
+++ b/video.cpp
@@ -2760,8 +2760,8 @@ void Descriptor_Set_Vk::init(
 				Buffer_Vk& b = *(Buffer_Vk*)&dev->get_buffer(cd->buffer);
 				assert(cd->buffer);
 				buf.buffer = b.buf;
-				buf.offset = 0;
-				buf.range = b.size;
+				buf.offset = cd->offset;
+				buf.range = cd->size? cd->size: b.size;
 				wd.descriptorType = VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER;
 				wd.pBufferInfo = &buf;
 			} break;
diff --git a/video.hpp b/video.hpp
index fa479f1..1ccc93d 100644
--- a/video.hpp
+++ b/video.hpp
@@ -44,7 +44,7 @@ struct Sampler_Id : public Primitive_Id<uint32_t> {
 	using Primitive_Id<uint32_t>::Primitive_Id;
 };
 
-#define descriptor_payload_size 8
+#define descriptor_payload_size 16
 
 struct Descriptor {
 	enum class Type {
@@ -61,6 +61,7 @@ struct Texture_Descriptor {
 };
 
 struct Constant_Buffer_Descriptor {
+	int offset, size;
 	Buffer_Id buffer;
 };
 
@@ -146,6 +147,8 @@ struct Pipeline {
 					Constant_Buffer_Descriptor* cb =
 						(Constant_Buffer_Descriptor*)b.payload;
 					if (ca->buffer != cb->buffer) return false;
+					if (ca->size != cb->size) return false;
+					if (ca->offset != cb->offset) return false;
 				} break;
 			}
 		}
@@ -254,7 +257,12 @@ struct Pipeline_Builder {
 	void shader(Shader_Id s);
 	void vertex_format(Vertex_Format_Id vf);
 	void texture(int binding, Texture_Id t, Sampler_Id s);
-	void cbuffer(int binding, Buffer_Id id);
+	void cbuffer(
+		int binding,
+		Buffer_Id id,
+		int offset = 0,
+		int size = 0
+	);
 	Pipeline& build();
 	void validate();
 };
-- 
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