From c89a633f59d0e393695c10f28c4ba8635eadffba Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 7 Mar 2026 11:42:46 +0000
Subject: Replace glContainer with glAllocator

glContainer is no longer required, as we can use std::vector with a
custom allocator which uses OpenGL buffers for storage. Minor irritation
is that the mapped buffers aren't guaranteed to be flushed in the tests,
so sometimes we're missing bits in a test render.
---
 lib/glAllocator.h | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 lib/glAllocator.h

(limited to 'lib/glAllocator.h')

diff --git a/lib/glAllocator.h b/lib/glAllocator.h
new file mode 100644
index 0000000..a9015da
--- /dev/null
+++ b/lib/glAllocator.h
@@ -0,0 +1,90 @@
+#include <concepts>
+#include <flat_map>
+#include <glad/gl.h>
+#include <memory>
+#include <stream_support.h>
+#include <vector>
+
+namespace Detail {
+	template<typename T> class glAllocator;
+	template<typename C, typename T>
+	concept IsGlBufferAllocated = requires(const C & container) {
+		{ container.get_allocator() } -> std::same_as<glAllocator<T>>;
+	};
+
+	template<typename T> class glAllocator {
+	public:
+		// NOLINTBEGIN(readability-identifier-naming) - STL like
+		using pointer = T *;
+		using const_pointer = const T *;
+		using value_type = T;
+
+		// NOLINTEND(readability-identifier-naming)
+
+		pointer
+		allocate(size_t count)
+		{
+			constexpr static GLbitfield MAPPING_FLAGS
+					= GL_MAP_WRITE_BIT | GL_MAP_READ_BIT | GL_MAP_PERSISTENT_BIT | GL_MAP_COHERENT_BIT;
+			constexpr static GLbitfield STORAGE_FLAGS = GL_DYNAMIC_STORAGE_BIT | MAPPING_FLAGS;
+			GLuint name = 0;
+			glCreateBuffers(1, &name);
+			const auto size = static_cast<GLsizeiptr>(count * sizeof(T));
+			glNamedBufferStorage(name, size, nullptr, STORAGE_FLAGS);
+			const auto data = static_cast<pointer>(glMapNamedBufferRange(name, 0, size, MAPPING_FLAGS));
+			if (!data) {
+				glDeleteBuffers(1, &name);
+				throw std::bad_alloc();
+			}
+			buffers->emplace(data, name);
+			return data;
+		}
+
+		void
+		deallocate(const_pointer ptr, size_t)
+		{
+			const auto itr = buffers->find(ptr);
+			glUnmapNamedBuffer(itr->second);
+			glDeleteBuffers(1, &itr->second);
+			buffers->erase(itr);
+		}
+
+		[[nodiscard]] GLuint
+		getNameFor(const_pointer ptr) const
+		{
+			const auto itr = buffers->find(ptr);
+			if (itr != buffers->end()) {
+				return itr->second;
+			}
+			return 0;
+		}
+
+		template<IsGlBufferAllocated<T> C>
+		[[nodiscard]]
+		GLuint
+		getNameFor(const C & container) const
+		{
+			return getNameFor(container.data());
+		}
+
+		bool operator==(const glAllocator &) const = default;
+
+	private:
+		using BufferMap = std::flat_map<const_pointer, GLuint>;
+		std::shared_ptr<BufferMap> buffers = std::make_shared<BufferMap>();
+	};
+}
+
+template<typename T>
+// NOLINTNEXTLINE(readability-identifier-naming) - OpenGL like
+using glVector = std::vector<T, typename std::allocator_traits<Detail::glAllocator<T>>::allocator_type>;
+
+template<typename C>
+GLuint
+operator*(const C & container)
+	requires Detail::IsGlBufferAllocated<C, typename C::value_type>
+{
+	return container.get_allocator().getNameFor(container);
+}
+
+static_assert(Detail::IsGlBufferAllocated<glVector<int>, int>);
-- 
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