From 456affe7844be742d09063b8ae0b68313e5c39f0 Mon Sep 17 00:00:00 2001
From: Emmanuel Benoit <tseeker@nocternity.net>
Date: Mon, 2 Oct 2017 10:42:06 +0200
Subject: [PATCH] Texture sampler abstraction

---
 texture.cc | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 texture.hh |  48 ++++++++++++++++++++
 2 files changed, 178 insertions(+)

diff --git a/texture.cc b/texture.cc
index e27efc8..337570e 100644
--- a/texture.cc
+++ b/texture.cc
@@ -3,6 +3,8 @@
 #include "texture.hh"
 
 
+/*==============================================================================*/
+
 T_Texture::T_Texture(
 		__rd__ const uint32_t width ,
 		__rd__ const uint32_t height ,
@@ -124,6 +126,134 @@ T_Texture& T_Texture::wrap(
 	return *this;
 }
 
+/*==============================================================================*/
+
+T_TextureSampler::T_TextureSampler( )
+{
+	glGenSamplers( 1 , &id_ );
+	GL_CHECK( );
+}
+
+T_TextureSampler::T_TextureSampler(
+		__rw__ T_TextureSampler&& other ) noexcept
+{
+	std::swap( id_ , other.id_ );
+	std::swap( sampling_ , other.sampling_ );
+	std::swap( lodSampling_ , other.lodSampling_ );
+	std::swap( hasLOD_ , other.hasLOD_ );
+	setSamplingMode( );
+}
+
+T_TextureSampler& T_TextureSampler::operator =(
+		__rw__ T_TextureSampler&& other ) noexcept
+{
+	std::swap( id_ , other.id_ );
+	std::swap( sampling_ , other.sampling_ );
+	std::swap( lodSampling_ , other.lodSampling_ );
+	std::swap( hasLOD_ , other.hasLOD_ );
+	return *this;
+}
+
+T_TextureSampler::~T_TextureSampler( )
+{
+	if ( id_ != 0 ) {
+		glDeleteSamplers( 1 , &id_ );
+	}
+}
+
+/*----------------------------------------------------------------------------*/
+
+T_TextureSampler& T_TextureSampler::sampling(
+		__rd__ const E_TexSampling mode )
+{
+	sampling_ = mode;
+	setSamplingMode( );
+	return *this;
+}
+
+T_TextureSampler& T_TextureSampler::noMipmap( )
+{
+	hasLOD_ = false;
+	setSamplingMode( );
+	return *this;
+}
+
+T_TextureSampler& T_TextureSampler::mipmap(
+		__rd__ const E_TexSampling mode )
+{
+	hasLOD_ = true;
+	lodSampling_ = mode;
+	setSamplingMode( );
+	return *this;
+}
+
+T_TextureSampler& T_TextureSampler::wrap(
+		__rd__ const E_TexWrap mode )
+{
+	GLenum gm;
+	switch ( mode ) {
+		case E_TexWrap::REPEAT:
+			gm = GL_REPEAT;
+			break;
+		case E_TexWrap::CLAMP_EDGE:
+			gm = GL_CLAMP_TO_EDGE;
+			break;
+		case E_TexWrap::CLAMP_BORDER:
+			gm = GL_CLAMP_TO_BORDER;
+			break;
+	}
+	glSamplerParameteri( id_ , GL_TEXTURE_WRAP_S , gm );
+	glSamplerParameteri( id_ , GL_TEXTURE_WRAP_T , gm );
+	GL_CHECK( );
+	return *this;
+}
+
+T_TextureSampler& T_TextureSampler::lod(
+		__rd__ const float min ,
+		__rd__ const float max )
+{
+	glSamplerParameterf( id_ , GL_TEXTURE_MIN_LOD , min );
+	glSamplerParameterf( id_ , GL_TEXTURE_MAX_LOD , max );
+	GL_CHECK( );
+	return *this;
+}
+
+/*----------------------------------------------------------------------------*/
+
+void T_TextureSampler::setSamplingMode( ) const
+{
+	GLenum min , max;
+	if ( hasLOD_ ) {
+		switch ( sampling_ ) {
+
+			case E_TexSampling::NEAREST:
+				min = lodSampling_ == E_TexSampling::LINEAR
+					? GL_NEAREST_MIPMAP_LINEAR
+					: GL_NEAREST_MIPMAP_NEAREST;
+				max = GL_NEAREST;
+				break;
+
+			case E_TexSampling::LINEAR:
+				min = lodSampling_ == E_TexSampling::LINEAR
+					? GL_LINEAR_MIPMAP_LINEAR
+					: GL_LINEAR_MIPMAP_NEAREST;
+				max = GL_LINEAR;
+				break;
+
+		}
+	} else {
+		min = ( sampling_ == E_TexSampling::LINEAR )
+			? GL_LINEAR
+			: GL_NEAREST;
+		max = min;
+	}
+
+	glSamplerParameteri( id_ , GL_TEXTURE_MIN_FILTER , min );
+	glSamplerParameteri( id_ , GL_TEXTURE_MAG_FILTER , max );
+	GL_CHECK( );
+}
+
+
 /*============================================================================*/
 
 
diff --git a/texture.hh b/texture.hh
index 03c4e0f..3ef5595 100644
--- a/texture.hh
+++ b/texture.hh
@@ -52,6 +52,54 @@ struct T_Texture
 	uint32_t levels_ , width_ , height_;
 };
 
+
+struct T_TextureSampler
+{
+	T_TextureSampler( T_TextureSampler const& ) = delete;
+
+	// --------------------------------------------------------------------
+	// Initialisation, destruction & move
+
+	T_TextureSampler( );
+	T_TextureSampler(
+			__rw__ T_TextureSampler&& other ) noexcept;
+	T_TextureSampler& operator=(
+			__rw__ T_TextureSampler&& other ) noexcept;
+	~T_TextureSampler( );
+
+	// --------------------------------------------------------------------
+	// Configuration
+
+	T_TextureSampler& sampling(
+			__rd__ const E_TexSampling mode );
+
+	T_TextureSampler& noMipmap( );
+	T_TextureSampler& mipmap(
+			__rd__ const E_TexSampling mode );
+
+	T_TextureSampler& wrap(
+			__rd__ const E_TexWrap mode );
+
+	T_TextureSampler& lod(
+			__rd__ const float min ,
+			__rd__ const float max );
+
+	// --------------------------------------------------------------------
+	// Usage
+
+	void bind( __rd__ const GLuint unit )
+		{ glBindSampler( unit , id_ ); }
+
+    private:
+	void setSamplingMode( ) const;
+
+	GLuint id_ = 0;
+	E_TexSampling sampling_ = E_TexSampling::NEAREST;
+	E_TexSampling lodSampling_ = E_TexSampling::NEAREST;
+	bool hasLOD_ = false;
+};
+
+
 struct T_TextureBinding
 {
 	T_TextureBinding( ) = delete;