Proper no-op fallback for *Framebuffer::invalidate*().

The documentation of ARB_invalidate_subdata mentions that all the
functions are really just a hint for the implementation to make some
performance optimizations and they are not affecting behavior at all. So
it's perfectly fine to do nothing if the extension is not supported.

I didn't do this originally as I mistakenly thought that invalidating
depth buffer would somehow behave the same as clearing it, but that's
not the case.

src/Magnum/AbstractFramebuffer.cpp

@@ -211,7 +211,9 @@ void AbstractFramebuffer::read(const Vector2i& offset, const Vector2i& size, Buf
 }
 #endif
 
-void AbstractFramebuffer::invalidateImplementation(GLsizei count, GLenum* attachments) {
+void AbstractFramebuffer::invalidateImplementationNoOp(GLsizei, const GLenum* const) {}
+
+void AbstractFramebuffer::invalidateImplementationDefault(const GLsizei count, const GLenum* const attachments) {
     /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glInvalidateFramebuffer(GLenum(bindInternal()), count, attachments);
@@ -223,7 +225,9 @@ void AbstractFramebuffer::invalidateImplementation(GLsizei count, GLenum* attach
     #endif
 }
 
-void AbstractFramebuffer::invalidateImplementation(GLsizei count, GLenum* attachments, const Range2Di& rectangle) {
+void AbstractFramebuffer::invalidateImplementationNoOp(GLsizei, const GLenum*, const Range2Di&) {}
+
+void AbstractFramebuffer::invalidateImplementationDefault(const GLsizei count, const GLenum* const attachments, const Range2Di& rectangle) {
     /** @todo Re-enable when extension loader is available for ES */
     #ifndef MAGNUM_TARGET_GLES2
     glInvalidateSubFramebuffer(GLenum(bindInternal()), count, attachments, rectangle.left(), rectangle.bottom(), rectangle.sizeX(), rectangle.sizeY());

src/Magnum/AbstractFramebuffer.h

@@ -333,9 +333,6 @@ class MAGNUM_EXPORT AbstractFramebuffer {
         FramebufferTarget MAGNUM_LOCAL bindInternal();
         void MAGNUM_LOCAL setViewportInternal();
 
-        void MAGNUM_LOCAL invalidateImplementation(GLsizei count, GLenum* attachments);
-        void MAGNUM_LOCAL invalidateImplementation(GLsizei count, GLenum* attachments, const Range2Di& rectangle);
-
         GLuint _id;
         Range2Di _viewport;
 
@@ -362,6 +359,12 @@ class MAGNUM_EXPORT AbstractFramebuffer {
 
         static void MAGNUM_LOCAL readImplementationDefault(const Vector2i& offset, const Vector2i& size, ColorFormat format, ColorType type, std::size_t dataSize, GLvoid* data);
         static void MAGNUM_LOCAL readImplementationRobustness(const Vector2i& offset, const Vector2i& size, ColorFormat format, ColorType type, std::size_t dataSize, GLvoid* data);
+
+        void MAGNUM_LOCAL invalidateImplementationNoOp(GLsizei, const GLenum*);
+        void MAGNUM_LOCAL invalidateImplementationDefault(GLsizei count, const GLenum* attachments);
+
+        void MAGNUM_LOCAL invalidateImplementationNoOp(GLsizei, const GLenum*, const Range2Di&);
+        void MAGNUM_LOCAL invalidateImplementationDefault(GLsizei count, const GLenum* attachments, const Range2Di& rectangle);
 };
 
 CORRADE_ENUMSET_OPERATORS(FramebufferClearMask)

src/Magnum/DefaultFramebuffer.cpp

@@ -77,7 +77,7 @@ void DefaultFramebuffer::invalidate(std::initializer_list<InvalidationAttachment
     for(std::size_t i = 0; i != attachments.size(); ++i)
         _attachments[i] = GLenum(*(attachments.begin()+i));
 
-    invalidateImplementation(attachments.size(), _attachments);
+    (this->*Context::current()->state().framebuffer->invalidateImplementation)(attachments.size(), _attachments);
 }
 
 void DefaultFramebuffer::invalidate(std::initializer_list<InvalidationAttachment> attachments, const Range2Di& rectangle) {
@@ -86,7 +86,7 @@ void DefaultFramebuffer::invalidate(std::initializer_list<InvalidationAttachment
     for(std::size_t i = 0; i != attachments.size(); ++i)
         _attachments[i] = GLenum(*(attachments.begin()+i));
 
-    invalidateImplementation(attachments.size(), _attachments, rectangle);
+    (this->*Context::current()->state().framebuffer->invalidateSubImplementation)(attachments.size(), _attachments, rectangle);
 }
 
 void DefaultFramebuffer::initializeContextBasedFunctionality(Context& context) {

src/Magnum/DefaultFramebuffer.h

@@ -388,17 +388,13 @@ class MAGNUM_EXPORT DefaultFramebuffer: public AbstractFramebuffer {
          * @brief Invalidate framebuffer
          * @param attachments       Attachments to invalidate
          *
-         * The framebuffer is bound to some target before the operation, if
+         * If extension @extension{ARB,invalidate_subdata} (part of OpenGL
-         * not already.
+         * 4.3), extension @es_extension{EXT,discard_framebuffer} in OpenGL ES
+         * 2.0 or OpenGL ES 3.0 is not available, this function does nothing.
+         * The framebuffer is bound to some target before the operation, if not
+         * already.
          * @see @fn_gl{InvalidateFramebuffer} or @fn_gles_extension{DiscardFramebuffer,EXT,discard_framebuffer}
          *      on OpenGL ES 2.0
-         * @requires_gl43 %Extension @extension{ARB,invalidate_subdata}. Use
-         *      @ref Magnum::DefaultFramebuffer::clear() "clear()" instead
-         *      where the extension is not supported.
-         * @requires_gles30 %Extension @es_extension{EXT,discard_framebuffer}
-         *      in OpenGL ES 2.0. Use
-         *      @ref Magnum::DefaultFramebuffer::clear() "clear()" instead
-         *      where the extension is not supported.
          */
         void invalidate(std::initializer_list<InvalidationAttachment> attachments);
 
@@ -407,17 +403,13 @@ class MAGNUM_EXPORT DefaultFramebuffer: public AbstractFramebuffer {
          * @param attachments       Attachments to invalidate
          * @param rectangle         %Rectangle to invalidate
          *
-         * The framebuffer is bound to some target before the operation, if
+         * If extension @extension{ARB,invalidate_subdata} (part of OpenGL
-         * not already.
+         * 4.3), extension @es_extension{EXT,discard_framebuffer} in OpenGL ES
+         * 2.0 or OpenGL ES 3.0 is not available, this function does nothing.
+         * The framebuffer is bound to some target before the operation, if not
+         * already.
          * @see @fn_gl{InvalidateSubFramebuffer} or @fn_gles_extension{DiscardSubFramebuffer,EXT,discard_framebuffer}
          *      on OpenGL ES 2.0
-         * @requires_gl43 %Extension @extension{ARB,invalidate_subdata}. Use
-         *      @ref Magnum::DefaultFramebuffer::clear() "clear()" instead
-         *      where the extension is not supported.
-         * @requires_gles30 %Extension @es_extension{EXT,discard_framebuffer}
-         *      in OpenGL ES 2.0. Use
-         *      @ref Magnum::DefaultFramebuffer::clear() "clear()" instead
-         *      where the extension is not supported.
          */
         void invalidate(std::initializer_list<InvalidationAttachment> attachments, const Range2Di& rectangle);
 

src/Magnum/Framebuffer.cpp

@@ -154,7 +154,7 @@ void Framebuffer::invalidate(std::initializer_list<InvalidationAttachment> attac
     for(std::size_t i = 0; i != attachments.size(); ++i)
         _attachments[i] = GLenum(*(attachments.begin()+i));
 
-    invalidateImplementation(attachments.size(), _attachments);
+    (this->*Context::current()->state().framebuffer->invalidateImplementation)(attachments.size(), _attachments);
 }
 
 void Framebuffer::invalidate(std::initializer_list<InvalidationAttachment> attachments, const Range2Di& rectangle) {
@@ -163,7 +163,7 @@ void Framebuffer::invalidate(std::initializer_list<InvalidationAttachment> attac
     for(std::size_t i = 0; i != attachments.size(); ++i)
         _attachments[i] = GLenum(*(attachments.begin()+i));
 
-    invalidateImplementation(attachments.size(), _attachments, rectangle);
+    (this->*Context::current()->state().framebuffer->invalidateSubImplementation)(attachments.size(), _attachments, rectangle);
 }
 
 Framebuffer& Framebuffer::attachRenderbuffer(const BufferAttachment attachment, Renderbuffer& renderbuffer) {

src/Magnum/Framebuffer.h

@@ -457,16 +457,13 @@ class MAGNUM_EXPORT Framebuffer: public AbstractFramebuffer, public AbstractObje
          * @param attachments       Attachments to invalidate
          * @param rectangle         %Rectangle to invalidate
          *
-         * The framebuffer is bound to some target before the operation, if
+         * If extension @extension{ARB,invalidate_subdata} (part of OpenGL
-         * not already.
+         * 4.3), extension @es_extension{EXT,discard_framebuffer} in OpenGL ES
-         * @see @fn_gl{InvalidateSubFramebuffer} or @fn_gles_extension{DiscardSubFramebuffer,EXT,discard_framebuffer}
+         * 2.0 or OpenGL ES 3.0 is not available, this function does nothing.
+         * The framebuffer is bound to some target before the operation, if not
+         * already.
+         * @see @fn_gl{InvalidateFramebuffer} or @fn_gles_extension{DiscardFramebuffer,EXT,discard_framebuffer}
          *      on OpenGL ES 2.0
-         * @requires_gl43 %Extension @extension{ARB,invalidate_subdata}. Use
-         *      @ref Magnum::Framebuffer::clear() "clear()" instead where the
-         *      extension is not supported.
-         * @requires_gles30 %Extension @es_extension{EXT,discard_framebuffer}
-         *      in OpenGL ES 2.0. Use @ref Magnum::Framebuffer::clear() "clear()"
-         *      instead where the extension is not supported.
          */
         void invalidate(std::initializer_list<InvalidationAttachment> attachments, const Range2Di& rectangle);
 
@@ -476,11 +473,13 @@ class MAGNUM_EXPORT Framebuffer: public AbstractFramebuffer, public AbstractObje
          * @param renderbuffer      %Renderbuffer
          * @return Reference to self (for method chaining)
          *
-         * If @extension{EXT,direct_state_access} is not available and the
+         * If extension @extension{ARB,invalidate_subdata} (part of OpenGL
-         * framebufferbuffer is not currently bound, it is bound before the
+         * 4.3), extension @es_extension{EXT,discard_framebuffer} in OpenGL ES
-         * operation.
+         * 2.0 or OpenGL ES 3.0 is not available, this function does nothing.
-         * @see @fn_gl{BindFramebuffer}, @fn_gl{FramebufferRenderbuffer} or
+         * The framebuffer is bound to some target before the operation, if not
-         *      @fn_gl_extension{NamedFramebufferRenderbuffer,EXT,direct_state_access}
+         * already.
+         * @see @fn_gl{InvalidateSubFramebuffer} or @fn_gles_extension{DiscardSubFramebuffer,EXT,discard_framebuffer}
+         *      on OpenGL ES 2.0
          */
         Framebuffer& attachRenderbuffer(BufferAttachment attachment, Renderbuffer& renderbuffer);
 

src/Magnum/Implementation/FramebufferState.cpp

@@ -138,6 +138,36 @@ FramebufferState::FramebufferState(Context& context, std::vector<std::string>& e
         renderbufferStorageMultisampleImplementation = &Renderbuffer::storageMultisampleImplementationDefault;
         #endif
     }
+
+    /* Framebuffer invalidation implementation on desktop GL */
+    #ifndef MAGNUM_TARGET_GLES
+    if(context.isExtensionSupported<Extensions::GL::ARB::invalidate_subdata>()) {
+        extensions.push_back(Extensions::GL::ARB::invalidate_subdata::string());
+
+        invalidateImplementation = &AbstractFramebuffer::invalidateImplementationDefault;
+        invalidateSubImplementation = &AbstractFramebuffer::invalidateImplementationDefault;
+    } else {
+        invalidateImplementation = &AbstractFramebuffer::invalidateImplementationNoOp;
+        invalidateSubImplementation = &AbstractFramebuffer::invalidateImplementationNoOp;
+    }
+
+    /* Framebuffer invalidation implementation on ES2 */
+    #elif defined(MAGNUM_TARGET_GLES2)
+    if(context.isExtensionSupported<Extensions::GL::EXT::discard_framebuffer>()) {
+        extensions.push_back(Extensions::GL::EXT::discard_framebuffer::string());
+
+        invalidateImplementation = &AbstractFramebuffer::invalidateImplementationDefault;
+        invalidateSubImplementation = &AbstractFramebuffer::invalidateImplementationDefault;
+    } else {
+        invalidateImplementation = &AbstractFramebuffer::invalidateImplementationNoOp;
+        invalidateSubImplementation = &AbstractFramebuffer::invalidateImplementationNoOp;
+    }
+
+    /* Always available on ES3 */
+    #else
+    invalidateImplementation = &AbstractFramebuffer::invalidateImplementationDefault;
+    invalidateSubImplementation = &AbstractFramebuffer::invalidateImplementationDefault;
+    #endif
 }
 
 void FramebufferState::reset() {

src/Magnum/Implementation/FramebufferState.h

@@ -41,6 +41,8 @@ struct FramebufferState {
     void(AbstractFramebuffer::*drawBuffersImplementation)(GLsizei, const GLenum*);
     void(AbstractFramebuffer::*drawBufferImplementation)(GLenum);
     void(AbstractFramebuffer::*readBufferImplementation)(GLenum);
+    void(AbstractFramebuffer::*invalidateImplementation)(GLsizei, const GLenum*);
+    void(AbstractFramebuffer::*invalidateSubImplementation)(GLsizei, const GLenum*, const Range2Di&);
 
     void(Framebuffer::*renderbufferImplementation)(Framebuffer::BufferAttachment, Renderbuffer&);
     #ifndef MAGNUM_TARGET_GLES

src/Magnum/Test/FramebufferGLTest.cpp

@@ -643,11 +643,6 @@ void FramebufferGLTest::invalidate() {
     #ifndef MAGNUM_TARGET_GLES
     if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::framebuffer_object>())
         CORRADE_SKIP(Extensions::GL::ARB::framebuffer_object::string() + std::string(" is not available."));
-    if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::invalidate_subdata>())
-        CORRADE_SKIP(Extensions::GL::ARB::invalidate_subdata::string() + std::string(" is not available."));
-    #elif defined(MAGNUM_TARGET_GLES2)
-    if(!Context::current()->isExtensionSupported<Extensions::GL::EXT::discard_framebuffer>())
-        CORRADE_SKIP(Extensions::GL::EXT::discard_framebuffer::string() + std::string(" is not available."));
     #endif
 
     Renderbuffer color;
@@ -675,11 +670,6 @@ void FramebufferGLTest::invalidateSub() {
     #ifndef MAGNUM_TARGET_GLES
     if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::framebuffer_object>())
         CORRADE_SKIP(Extensions::GL::ARB::framebuffer_object::string() + std::string(" is not available."));
-    if(!Context::current()->isExtensionSupported<Extensions::GL::ARB::invalidate_subdata>())
-        CORRADE_SKIP(Extensions::GL::ARB::invalidate_subdata::string() + std::string(" is not available."));
-    #elif defined(MAGNUM_TARGET_GLES2)
-    if(!Context::current()->isExtensionSupported<Extensions::GL::EXT::discard_framebuffer>())
-        CORRADE_SKIP(Extensions::GL::EXT::discard_framebuffer::string() + std::string(" is not available."));
     #endif
 
     Renderbuffer color;