From 96e13fc706ba4e1702ff90eb999ee0660278cb0d Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 31 May 2020 12:43:03 +0300
Subject: [PATCH] Add a texunit statement which automatically determines the
 unit number

---
 source/renderpass.cpp | 11 +++++++++++
 source/renderpass.h   |  2 ++
 source/texturing.cpp  | 18 ++++++++++++++++++
 source/texturing.h    |  1 +
 4 files changed, 32 insertions(+)

diff --git a/source/renderpass.cpp b/source/renderpass.cpp
index 4e3b1f13..d2ce1652 100644
--- a/source/renderpass.cpp
+++ b/source/renderpass.cpp
@@ -131,6 +131,7 @@ void RenderPass::Loader::init()
 	add("material_slot", &RenderPass::material_slot);
 	add("back_faces",&RenderPass::back_faces);
 	add("texunit",  &Loader::texunit);
+	add("texunit",  &Loader::texunit_auto);
 	add("texunit",  &Loader::texunit_named);
 	add("uniforms", &Loader::uniforms);
 	add("uniform_slot", &Loader::uniform_slot);
@@ -160,6 +161,16 @@ void RenderPass::Loader::texunit(unsigned i)
 	load_sub_with(ldr);
 }
 
+void RenderPass::Loader::texunit_auto(const string &n)
+{
+	if(!obj.texturing)
+		obj.texturing = new Texturing;
+	int i = obj.texturing->find_free_unit(n);
+	if(i<0)
+		throw runtime_error("no free texunit");
+	texunit_named(i, n);
+}
+
 void RenderPass::Loader::texunit_named(unsigned i, const string &n)
 {
 	texunit(i);
diff --git a/source/renderpass.h b/source/renderpass.h
index 66768772..d4f7a34d 100644
--- a/source/renderpass.h
+++ b/source/renderpass.h
@@ -31,9 +31,11 @@ public:
 
 	private:
 		void init();
+
 		void material_inline();
 		void material(const std::string &);
 		void texunit(unsigned);
+		void texunit_auto(const std::string &);
 		void texunit_named(unsigned, const std::string &);
 		void uniforms();
 		void uniform_slot(const std::string &);
diff --git a/source/texturing.cpp b/source/texturing.cpp
index d8d178b3..c30216f1 100644
--- a/source/texturing.cpp
+++ b/source/texturing.cpp
@@ -1,3 +1,4 @@
+#include <msp/core/hash.h>
 #include "texture.h"
 #include "texturing.h"
 #include "texunit.h"
@@ -13,6 +14,23 @@ Texturing::~Texturing()
 		unbind();
 }
 
+int Texturing::find_free_unit(const string &name_hint) const
+{
+	unsigned max_unit = TexUnit::get_n_units();
+	// Leave some space for effect textures
+	max_unit -= min(max_unit/4, 8U);
+	unsigned initial_unit = (name_hint.empty() ? 0 : hash32(name_hint)%max_unit);
+	unsigned unit = initial_unit;
+	while(get_attached_texture(unit))
+	{
+		unit = (unit+1)%max_unit;
+		if(unit==initial_unit)
+			return -1;
+	}
+
+	return unit;
+}
+
 void Texturing::attach(unsigned attch, const Texture &tex)
 {
 	set_attachment(attch, &tex);
diff --git a/source/texturing.h b/source/texturing.h
index 79647f1d..cba77e3f 100644
--- a/source/texturing.h
+++ b/source/texturing.h
@@ -25,6 +25,7 @@ private:
 public:
 	~Texturing();
 
+	int find_free_unit(const std::string & = std::string()) const;
 	void attach(unsigned, const Texture &);
 	void detach(unsigned);
 private:
-- 
2.45.2