Added *Texture::unbind().

Will be used in fallback implementation of multi-bind.

src/Magnum/AbstractTexture.cpp

@@ -91,6 +91,42 @@ Int AbstractTexture::maxIntegerSamples() {
 }
 #endif
 
+void AbstractTexture::unbind(const Int textureUnit) {
+    Implementation::TextureState* const textureState = Context::current()->state().texture;
+
+    /* If given texture unit is already unbound, nothing to do */
+    if(textureState->bindings[textureUnit].second == 0) return;
+
+    /* Unbind the texture, reset state tracker */
+    Context::current()->state().texture->unbindImplementation(textureUnit);
+    textureState->bindings[textureUnit] = {};
+}
+
+void AbstractTexture::unbindImplementationDefault(const GLint textureUnit) {
+    Implementation::TextureState* const textureState = Context::current()->state().texture;
+
+    /* Activate given texture unit if not already active, update state tracker */
+    if(textureState->currentTextureUnit != textureUnit)
+        glActiveTexture(GL_TEXTURE0 + (textureState->currentTextureUnit = textureUnit));
+
+    CORRADE_INTERNAL_ASSERT(textureState->bindings[textureUnit].first != 0);
+    glBindTexture(textureState->bindings[textureUnit].first, 0);
+}
+
+#ifndef MAGNUM_TARGET_GLES
+void AbstractTexture::unbindImplementationMulti(const GLint textureUnit) {
+    constexpr static const GLuint zero = 0;
+    glBindTextures(textureUnit, 1, &zero);
+}
+
+void AbstractTexture::unbindImplementationDSA(const GLint textureUnit) {
+    Implementation::TextureState* const textureState = Context::current()->state().texture;
+
+    CORRADE_INTERNAL_ASSERT(textureState->bindings[textureUnit].first != 0);
+    glBindMultiTextureEXT(GL_TEXTURE0 + textureUnit, textureState->bindings[textureUnit].first, 0);
+}
+#endif
+
 AbstractTexture::AbstractTexture(GLenum target): _target(target) {
     glGenTextures(1, &_id);
 }

src/Magnum/AbstractTexture.h

@@ -157,6 +157,21 @@ class MAGNUM_EXPORT AbstractTexture: public AbstractObject {
         static Int maxIntegerSamples();
         #endif
 
+        /**
+         * @brief Unbind any texture from given texture unit
+         *
+         * If @extension{ARB,multi_bind} (part of OpenGL 4.4) or
+         * @extension{EXT,direct_state_access} is not available, the texture
+         * unit is made active before binding the texture.
+         * @note This function is meant to be used only internally from
+         *      @ref AbstractShaderProgram subclasses. See its documentation
+         *      for more information.
+         * @see @ref bind(), @ref Shader::maxCombinedTextureImageUnits(),
+         *      @fn_gl{ActiveTexture}, @fn_gl{BindTexture}, @fn_gl{BindTextures}
+         *      or @fn_gl_extension{BindMultiTexture,EXT,direct_state_access}
+         */
+        static void unbind(Int textureUnit);
+
         /** @brief Copying is not allowed */
         AbstractTexture(const AbstractTexture&) = delete;
 
@@ -215,7 +230,7 @@ class MAGNUM_EXPORT AbstractTexture: public AbstractObject {
          * @note This function is meant to be used only internally from
          *      @ref AbstractShaderProgram subclasses. See its documentation
          *      for more information.
-         * @see @ref Shader::maxCombinedTextureImageUnits(),
+         * @see @ref unbind(), @ref Shader::maxCombinedTextureImageUnits(),
          *      @fn_gl{ActiveTexture}, @fn_gl{BindTexture}, @fn_gl{BindTextures}
          *      or @fn_gl_extension{BindMultiTexture,EXT,direct_state_access}
          */
@@ -254,6 +269,12 @@ class MAGNUM_EXPORT AbstractTexture: public AbstractObject {
         GLenum _target;
 
     private:
+        static void MAGNUM_LOCAL unbindImplementationDefault(GLint textureUnit);
+        #ifndef MAGNUM_TARGET_GLES
+        static void MAGNUM_LOCAL unbindImplementationMulti(GLint textureUnit);
+        static void MAGNUM_LOCAL unbindImplementationDSA(GLint textureUnit);
+        #endif
+
         void MAGNUM_LOCAL bindImplementationDefault(GLint textureUnit);
         #ifndef MAGNUM_TARGET_GLES
         void MAGNUM_LOCAL bindImplementationMulti(GLint textureUnit);

src/Magnum/Implementation/TextureState.cpp

@@ -45,13 +45,20 @@ TextureState::TextureState(Context& context, std::vector<std::string>& extension
     #ifndef MAGNUM_TARGET_GLES
     if(context.isExtensionSupported<Extensions::GL::ARB::multi_bind>()) {
         extensions.push_back(Extensions::GL::ARB::multi_bind::string());
+
+        unbindImplementation = &AbstractTexture::unbindImplementationMulti;
         bindImplementation = &AbstractTexture::bindImplementationMulti;
+
     } else if(context.isExtensionSupported<Extensions::GL::EXT::direct_state_access>()) {
         /* Extension name added below */
+
+        unbindImplementation = &AbstractTexture::unbindImplementationDSA;
         bindImplementation = &AbstractTexture::bindImplementationDSA;
+
     } else
     #endif
     {
+        unbindImplementation = &AbstractTexture::unbindImplementationDefault;
         bindImplementation = &AbstractTexture::bindImplementationDefault;
     }
 

src/Magnum/Implementation/TextureState.h

@@ -37,6 +37,7 @@ struct TextureState {
     explicit TextureState(Context& context, std::vector<std::string>& extensions);
     ~TextureState();
 
+    void(*unbindImplementation)(GLint);
     void(AbstractTexture::*bindImplementation)(GLint);
     void(AbstractTexture::*parameteriImplementation)(GLenum, GLint);
     void(AbstractTexture::*parameterfImplementation)(GLenum, GLfloat);

src/Magnum/Test/BufferTextureGLTest.cpp

@@ -70,6 +70,10 @@ void BufferTextureGLTest::bind() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void BufferTextureGLTest::setBuffer() {

src/Magnum/Test/CubeMapTextureArrayGLTest.cpp

@@ -97,6 +97,10 @@ void CubeMapTextureArrayGLTest::bind() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void CubeMapTextureArrayGLTest::sampling() {

src/Magnum/Test/CubeMapTextureGLTest.cpp

@@ -117,6 +117,10 @@ void CubeMapTextureGLTest::bind() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void CubeMapTextureGLTest::sampling() {

src/Magnum/Test/MultisampleTextureGLTest.cpp

@@ -123,6 +123,10 @@ void MultisampleTextureGLTest::bind2D() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void MultisampleTextureGLTest::bind2DArray() {
@@ -133,6 +137,10 @@ void MultisampleTextureGLTest::bind2DArray() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void MultisampleTextureGLTest::storage2D() {

src/Magnum/Test/RectangleTextureGLTest.cpp

@@ -98,6 +98,10 @@ void RectangleTextureGLTest::bind() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void RectangleTextureGLTest::sampling() {

src/Magnum/Test/TextureArrayGLTest.cpp

@@ -208,6 +208,10 @@ void TextureArrayGLTest::bind1D() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 #endif
 
@@ -221,6 +225,10 @@ void TextureArrayGLTest::bind2D() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 #ifndef MAGNUM_TARGET_GLES

src/Magnum/Test/TextureGLTest.cpp

@@ -257,6 +257,10 @@ void TextureGLTest::bind1D() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 #endif
 
@@ -265,6 +269,10 @@ void TextureGLTest::bind2D() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void TextureGLTest::bind3D() {
@@ -277,6 +285,10 @@ void TextureGLTest::bind3D() {
     texture.bind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::unbind(15);
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 #ifndef MAGNUM_TARGET_GLES