Added no-op fallback for unsupported EXT_texture_filter_anisotropic.

This extension is ubiquitous, but to make users' life even easier we
now provide no-op fallback for both Sampler::maxAnisotropy() and
Texture::setMaxAnisotropy().

src/AbstractTexture.cpp

@@ -45,6 +45,8 @@ AbstractTexture::ParameterfImplementation AbstractTexture::parameterfImplementat
     &AbstractTexture::parameterImplementationDefault;
 AbstractTexture::ParameterfvImplementation AbstractTexture::parameterfvImplementation =
     &AbstractTexture::parameterImplementationDefault;
+AbstractTexture::SetMaxAnisotropyImplementation AbstractTexture::setMaxAnisotropyImplementation =
+    &AbstractTexture::setMaxAnisotropyImplementationNoOp;
 #ifndef MAGNUM_TARGET_GLES
 AbstractTexture::GetLevelParameterivImplementation AbstractTexture::getLevelParameterivImplementation =
     &AbstractTexture::getLevelParameterImplementationDefault;
@@ -270,9 +272,13 @@ void AbstractTexture::initializeContextBasedFunctionality(Context& context) {
             storage3DImplementation = &AbstractTexture::storageImplementationDefault;
         }
     }
-    #else
-    static_cast<void>(context);
     #endif
+
+    if(context.isExtensionSupported<Extensions::GL::EXT::texture_filter_anisotropic>()) {
+        Debug() << "AbstractTexture: using" << Extensions::GL::EXT::texture_filter_anisotropic::string() << "features";
+
+        setMaxAnisotropyImplementation = &AbstractTexture::setMaxAnisotropyImplementationExt;
+    }
 }
 
 ColorFormat AbstractTexture::imageFormatForInternalFormat(const TextureFormat internalFormat) {
@@ -677,6 +683,12 @@ void AbstractTexture::parameterImplementationDSA(GLenum parameter, const GLfloat
 }
 #endif
 
+void AbstractTexture::setMaxAnisotropyImplementationNoOp(GLfloat) {}
+
+void AbstractTexture::setMaxAnisotropyImplementationExt(GLfloat anisotropy) {
+    (this->*parameterfImplementation)(GL_TEXTURE_MAX_ANISOTROPY_EXT, anisotropy);
+}
+
 #ifndef MAGNUM_TARGET_GLES
 void AbstractTexture::getLevelParameterImplementationDefault(GLenum target, GLint level, GLenum parameter, GLint* values) {
     bindInternal();

src/AbstractTexture.h

@@ -273,18 +273,18 @@ class MAGNUM_EXPORT AbstractTexture: public AbstractObject {
          * @return Reference to self (for method chaining)
          *
          * Default value is `1.0f`, which means no anisotropy. Set to value
-         * greater than `1.0f` for anisotropic filtering. If
-         * @extension{EXT,direct_state_access} is not available, the texture
-         * is bound to some layer before the operation.
+         * greater than `1.0f` for anisotropic filtering. If extension
+         * @extension{EXT,texture_filter_anisotropic} (desktop or ES) is not
+         * available, this function does nothing. If
+         * @extension{EXT,direct_state_access} is not available, the texture is
+         * bound to some layer before the operation.
          * @see @ref Sampler::maxAnisotropy(), @fn_gl{ActiveTexture},
          *      @fn_gl{BindTexture} and @fn_gl{TexParameter} or
          *      @fn_gl_extension{TextureParameter,EXT,direct_state_access} with
          *      @def_gl{TEXTURE_MAX_ANISOTROPY_EXT}
-         * @requires_extension %Extension @extension{EXT,texture_filter_anisotropic}
-         * @requires_es_extension %Extension @es_extension2{EXT,texture_filter_anisotropic,texture_filter_anisotropic}
          */
         AbstractTexture& setMaxAnisotropy(Float anisotropy) {
-            (this->*parameterfImplementation)(GL_TEXTURE_MAX_ANISOTROPY_EXT, anisotropy);
+            (this->*setMaxAnisotropyImplementation)(anisotropy);
             return *this;
         }
 
@@ -380,6 +380,11 @@ class MAGNUM_EXPORT AbstractTexture: public AbstractObject {
         #endif
         static ParameterfvImplementation parameterfvImplementation;
 
+        typedef void(AbstractTexture::*SetMaxAnisotropyImplementation)(GLfloat);
+        void MAGNUM_LOCAL setMaxAnisotropyImplementationNoOp(GLfloat);
+        void MAGNUM_LOCAL setMaxAnisotropyImplementationExt(GLfloat anisotropy);
+        static SetMaxAnisotropyImplementation setMaxAnisotropyImplementation;
+
         #ifndef MAGNUM_TARGET_GLES
         typedef void(AbstractTexture::*GetLevelParameterivImplementation)(GLenum, GLint, GLenum, GLint*);
         void MAGNUM_LOCAL getLevelParameterImplementationDefault(GLenum target, GLint level, GLenum parameter, GLint* values);

src/Sampler.cpp

@@ -29,6 +29,7 @@
 #include "Context.h"
 #include "Implementation/State.h"
 #include "Implementation/TextureState.h"
+#include "Extensions.h"
 
 namespace Magnum {
 
@@ -46,6 +47,9 @@ static_assert((filter_or(Nearest, Base) == GL_NEAREST) &&
 #undef filter_or
 
 Float Sampler::maxAnisotropy() {
+    if(!Context::current()->isExtensionSupported<Extensions::GL::EXT::texture_filter_anisotropic>())
+        return 0.0f;
+
     GLfloat& value = Context::current()->state().texture->maxAnisotropy;
 
     /** @todo Re-enable when extension header is available */

src/Sampler.h

@@ -136,10 +136,9 @@ class MAGNUM_EXPORT Sampler {
          * @brief Max supported anisotropy
          *
          * The result is cached, repeated queries don't result in repeated
-         * OpenGL calls.
+         * OpenGL calls. If extension @extension{EXT,texture_filter_anisotropic}
+         * (desktop or ES) is not available, returns `0.0f`.
          * @see setMaxAnisotropy(), @fn_gl{Get} with @def_gl{MAX_TEXTURE_MAX_ANISOTROPY_EXT}
-         * @requires_extension %Extension @extension{EXT,texture_filter_anisotropic}
-         * @requires_es_extension %Extension @es_extension2{EXT,texture_filter_anisotropic,texture_filter_anisotropic}
          */
         static Float maxAnisotropy();