[gpu.graph] added graph_info.on_execute so that the user has a CPU ca…

…llback function when the graph is executed. this is pretty pointless right now, but will be useful for the imgui render backend and also for when subgraphs are implemented

include/tz/gpu/graph.hpp

@@ -29,6 +29,7 @@ namespace tz::gpu
 		return static_cast<int>(lhs) & static_cast<int>(rhs);
 	}
 
+	using graph_handle = tz::handle<pass_handle>;
 
 	/**
 	 * @ingroup tz_gpu_graph
@@ -45,9 +46,10 @@ namespace tz::gpu
 		std::span<std::span<const pass_handle>> dependencies = {};
 		/// Specifies extra optional behaviour for the graph.
 		graph_flag flags = static_cast<graph_flag>(0);
+		/// Optional. Executed when the graph is executed.
+		void(*on_execute)(graph_handle graph) = nullptr;
 	};
 
-	using graph_handle = tz::handle<pass_handle>;
 	/**
 	 * @ingroup tz_gpu_graph
 	 * @brief Helper struct for creating a new graph. Follows the builder pattern.

include/tz/imgui.hpp

@@ -1,7 +1,10 @@
 #include "imgui.h"
+#include "tz/gpu/graph.hpp"
 
 namespace tz::detail
 {
 	void imgui_initialise();
 	void imgui_terminate();
+
+	tz::gpu::graph_handle imgui_render_graph();
 }

src/tz/gpu/rhi_vulkan.cpp

@@ -1614,16 +1614,20 @@ namespace tz::gpu
 
 	void execute(graph_handle graphh)
 	{
+		const auto& graph = graphs[graphh.peek()];
+		if(graph.info.on_execute != nullptr)
+		{
+			graph.info.on_execute(graphh);
+		}
+
 		impl_check_for_resize();
 		if(swapchain_width == 0 || swapchain_height == 0)
 		{
 			return;
 		}
 		const auto& frame = frames[current_frame];
-		const auto& graph = graphs[graphh.peek()];
 		auto present_pass_iter = std::find(graph.timeline.begin(), graph.timeline.end(), tz::gpu::present_pass);
 		const bool will_present = present_pass_iter != graph.timeline.end();
-
 
 		std::uint32_t image_index;
 		if(will_present)

src/tz/imgui.cpp

@@ -24,10 +24,12 @@ namespace tz::detail
 		tz::gpu::shader_handle shader = tz::nullhand;
 
 		std::vector<tz::gpu::pass_handle> passes = {};
+		tz::gpu::graph_handle graph = tz::nullhand;
 	} render;
 
 	void impl_write_vertices_and_indices(ImDrawData* draw);
 	void impl_add_new_pass();
+	void impl_on_render(tz::gpu::graph_handle graph);
 
 	void imgui_initialise()
 	{
@@ -76,6 +78,8 @@ namespace tz::detail
 			ImportedShaderSource(imgui, fragment)
 		));
 
+		// empty graph for now, because we dont know what imgui wants to draw until we end the frame.
+		render.graph = tz_must(tz::gpu::create_graph(tz::gpu::graph_info{.on_execute = impl_on_render}));
 	}
 
 	void imgui_terminate()
@@ -90,9 +94,22 @@ namespace tz::detail
 		tz::gpu::destroy_shader(render.shader);
 		ImGui::DestroyContext();
 	}
+
+	tz::gpu::graph_handle imgui_render_graph()
+	{
+		return render.graph;
+	}
 
 	// impl bits
 
+	void impl_on_render(gpu::graph_handle graph)
+	{
+		(void)graph;
+		// we have a graph that could be completely wrong.
+		ImDrawData* draws = ImGui::GetDrawData();
+		(void)draws;
+	}
+
 	void impl_write_vertices_and_indices(ImDrawData* draw)
 	{
 		const auto req_idx_size = static_cast<std::size_t>(draw->TotalIdxCount) * sizeof(ImDrawIdx);