Support ARB_multi_bind for textures.

doc/opengl-support.dox

@@ -201,7 +201,7 @@ following:
 @extension{ARB,buffer_storage}               | |
 @extension{ARB,clear_texture}                | |
 @extension{ARB,enhanced_layouts}             | done (shading language only)
-@extension{ARB,multi_bind}                   | only single texture binding
+@extension{ARB,multi_bind}                   | only texture binding
 @extension{ARB,query_buffer_object}          | |
 @extension{ARB,texture_mirror_clamp_to_edge} | done
 @extension{ARB,texture_stencil8}             | done

src/Magnum/AbstractTexture.cpp

@@ -127,6 +127,36 @@ void AbstractTexture::unbindImplementationDSA(const GLint textureUnit) {
 }
 #endif
 
+void AbstractTexture::bind(const Int firstTextureUnit, std::initializer_list<AbstractTexture*> textures) {
+    /* State tracker is updated in the implementations */
+    Context::current()->state().texture->bindMultiImplementation(firstTextureUnit, textures);
+}
+
+void AbstractTexture::bindImplementationFallback(const GLint firstTextureUnit, std::initializer_list<AbstractTexture*> textures) {
+    Int unit = firstTextureUnit;
+    for(AbstractTexture* const texture: textures) {
+        if(texture) texture->bind(unit);
+        else unbind(unit);
+        ++unit;
+    }
+}
+
+#ifndef MAGNUM_TARGET_GLES
+void AbstractTexture::bindImplementationMulti(const GLint firstTextureUnit, std::initializer_list<AbstractTexture*> textures) {
+    Implementation::TextureState* const textureState = Context::current()->state().texture;
+
+    /* Create array of IDs and also update bindings in state tracker */
+    Containers::Array<GLuint> ids{textures.size()};
+    Int i{};
+    for(const AbstractTexture* const texture: textures) {
+        textureState->bindings[firstTextureUnit + i].second = ids[i] = texture ? texture->id() : 0;
+        ++i;
+    }
+
+    glBindTextures(firstTextureUnit, ids.size(), ids);
+}
+#endif
+
 AbstractTexture::AbstractTexture(GLenum target): _target(target) {
     glGenTextures(1, &_id);
 }

src/Magnum/AbstractTexture.h

@@ -172,6 +172,19 @@ class MAGNUM_EXPORT AbstractTexture: public AbstractObject {
          */
         static void unbind(Int textureUnit);
 
+        /**
+         * @brief Bind textures to given range of texture units
+         *
+         * Binds first texture in the list to @p firstTextureUnit, second to
+         * `firstTextureUnit + 1` etc. If any texture is `nullptr`, given
+         * texture unit is unbound. If @extension{ARB,multi_bind} (part of
+         * OpenGL 4.4) is not available, the feature is emulated with sequence
+         * of @ref bind(Int) / @ref unbind() calls.
+         * @see @fn_gl{BindTextures}, eventually @fn_gl{ActiveTexture},
+         *      @fn_gl{BindTexture} or @fn_gl_extension{BindMultiTexture,EXT,direct_state_access}
+         */
+        static void bind(Int firstTextureUnit, std::initializer_list<AbstractTexture*> textures);
+
         /** @brief Copying is not allowed */
         AbstractTexture(const AbstractTexture&) = delete;
 
@@ -230,7 +243,8 @@ 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 unbind(), @ref Shader::maxCombinedTextureImageUnits(),
+         * @see @ref bind(Int, std::initializer_list<AbstractTexture*>),
+         *      @ref unbind(), @ref Shader::maxCombinedTextureImageUnits(),
          *      @fn_gl{ActiveTexture}, @fn_gl{BindTexture}, @fn_gl{BindTextures}
          *      or @fn_gl_extension{BindMultiTexture,EXT,direct_state_access}
          */
@@ -275,6 +289,11 @@ class MAGNUM_EXPORT AbstractTexture: public AbstractObject {
         static void MAGNUM_LOCAL unbindImplementationDSA(GLint textureUnit);
         #endif
 
+        static void MAGNUM_LOCAL bindImplementationFallback(GLint firstTextureUnit, std::initializer_list<AbstractTexture*> textures);
+        #ifndef MAGNUM_TARGET_GLES
+        static void MAGNUM_LOCAL bindImplementationMulti(GLint firstTextureUnit, std::initializer_list<AbstractTexture*> textures);
+        #endif
+
         void MAGNUM_LOCAL bindImplementationDefault(GLint textureUnit);
         #ifndef MAGNUM_TARGET_GLES
         void MAGNUM_LOCAL bindImplementationMulti(GLint textureUnit);

src/Magnum/Implementation/TextureState.cpp

@@ -47,18 +47,21 @@ TextureState::TextureState(Context& context, std::vector<std::string>& extension
         extensions.push_back(Extensions::GL::ARB::multi_bind::string());
 
         unbindImplementation = &AbstractTexture::unbindImplementationMulti;
+        bindMultiImplementation = &AbstractTexture::bindImplementationMulti;
         bindImplementation = &AbstractTexture::bindImplementationMulti;
 
     } else if(context.isExtensionSupported<Extensions::GL::EXT::direct_state_access>()) {
         /* Extension name added below */
 
         unbindImplementation = &AbstractTexture::unbindImplementationDSA;
+        bindMultiImplementation = &AbstractTexture::bindImplementationFallback;
         bindImplementation = &AbstractTexture::bindImplementationDSA;
 
     } else
     #endif
     {
         unbindImplementation = &AbstractTexture::unbindImplementationDefault;
+        bindMultiImplementation = &AbstractTexture::bindImplementationFallback;
         bindImplementation = &AbstractTexture::bindImplementationDefault;
     }
 

src/Magnum/Implementation/TextureState.h

@@ -38,6 +38,7 @@ struct TextureState {
     ~TextureState();
 
     void(*unbindImplementation)(GLint);
+    void(*bindMultiImplementation)(GLint, std::initializer_list<AbstractTexture*>);
     void(AbstractTexture::*bindImplementation)(GLint);
     void(AbstractTexture::*parameteriImplementation)(GLenum, GLint);
     void(AbstractTexture::*parameterfImplementation)(GLenum, GLfloat);

src/Magnum/Test/BufferTextureGLTest.cpp

@@ -74,6 +74,10 @@ void BufferTextureGLTest::bind() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void BufferTextureGLTest::setBuffer() {

src/Magnum/Test/CubeMapTextureArrayGLTest.cpp

@@ -101,6 +101,10 @@ void CubeMapTextureArrayGLTest::bind() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void CubeMapTextureArrayGLTest::sampling() {

src/Magnum/Test/CubeMapTextureGLTest.cpp

@@ -121,6 +121,10 @@ void CubeMapTextureGLTest::bind() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void CubeMapTextureGLTest::sampling() {

src/Magnum/Test/MultisampleTextureGLTest.cpp

@@ -127,6 +127,10 @@ void MultisampleTextureGLTest::bind2D() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void MultisampleTextureGLTest::bind2DArray() {
@@ -141,6 +145,10 @@ void MultisampleTextureGLTest::bind2DArray() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void MultisampleTextureGLTest::storage2D() {

src/Magnum/Test/RectangleTextureGLTest.cpp

@@ -102,6 +102,10 @@ void RectangleTextureGLTest::bind() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void RectangleTextureGLTest::sampling() {

src/Magnum/Test/TextureArrayGLTest.cpp

@@ -212,6 +212,10 @@ void TextureArrayGLTest::bind1D() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 #endif
 
@@ -229,6 +233,10 @@ void TextureArrayGLTest::bind2D() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 #ifndef MAGNUM_TARGET_GLES

src/Magnum/Test/TextureGLTest.cpp

@@ -261,6 +261,10 @@ void TextureGLTest::bind1D() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 #endif
 
@@ -273,6 +277,10 @@ void TextureGLTest::bind2D() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 void TextureGLTest::bind3D() {
@@ -289,6 +297,10 @@ void TextureGLTest::bind3D() {
     AbstractTexture::unbind(15);
 
     MAGNUM_VERIFY_NO_ERROR();
+
+    AbstractTexture::bind(7, {&texture, nullptr, &texture});
+
+    MAGNUM_VERIFY_NO_ERROR();
 }
 
 #ifndef MAGNUM_TARGET_GLES