Fix Framebuffer::attachCubeMapTexture() behaving as a layered attachment.

The DSA function does not accept any texture target parameter so the
cube map texture was bound as a whole (and thus behaving as a layered
attachment) instead of just a single face. Thanks to @chpatrick for the
report.

src/Magnum/Framebuffer.cpp

@@ -236,7 +236,7 @@ Framebuffer& Framebuffer::attachTexture(const BufferAttachment attachment, Multi
 #endif
 
 Framebuffer& Framebuffer::attachCubeMapTexture(const BufferAttachment attachment, CubeMapTexture& texture, CubeMapTexture::Coordinate coordinate, const Int level) {
-    (this->*Context::current()->state().framebuffer->texture2DImplementation)(attachment, GLenum(coordinate), texture.id(), level);
+    (this->*Context::current()->state().framebuffer->textureCubeMapImplementation)(attachment, GLenum(coordinate), texture.id(), level);
     return *this;
 }
 
@@ -319,6 +319,10 @@ void Framebuffer::texture2DImplementationDSAEXT(BufferAttachment attachment, GLe
     _flags |= ObjectFlag::Created;
     glNamedFramebufferTexture2DEXT(_id, GLenum(attachment), textureTarget, textureId, mipLevel);
 }
+
+void Framebuffer::textureCubeMapImplementationDSA(const BufferAttachment attachment, const GLenum textureTarget, const GLuint textureId, const GLint mipLevel) {
+    glNamedFramebufferTextureLayer(_id, GLenum(attachment), textureId, mipLevel, textureTarget - GL_TEXTURE_CUBE_MAP_POSITIVE_X);
+}
 #endif
 
 #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))

src/Magnum/Framebuffer.h

@@ -654,7 +654,7 @@ class MAGNUM_EXPORT Framebuffer: public AbstractFramebuffer, public AbstractObje
          * available, the framebuffer is bound before the operation (if not
          * already).
          * @see @ref detach(), @ref attachTexture(),
-         *      @fn_gl2{NamedFramebufferTexture,FramebufferTexture},
+         *      @fn_gl2{NamedFramebufferTextureLayer,FramebufferTextureLayer},
          *      @fn_gl_extension{NamedFramebufferTexture2D,EXT,direct_state_access},
          *      eventually @fn_gl{BindFramebuffer} and @fn_gl2{FramebufferTexture2D,FramebufferTexture}
          */
@@ -776,6 +776,7 @@ class MAGNUM_EXPORT Framebuffer: public AbstractFramebuffer, public AbstractObje
         #ifndef MAGNUM_TARGET_GLES
         void MAGNUM_LOCAL texture2DImplementationDSA(BufferAttachment attachment, GLenum textureTarget, GLuint textureId, GLint level);
         void MAGNUM_LOCAL texture2DImplementationDSAEXT(BufferAttachment attachment, GLenum textureTarget, GLuint textureId, GLint level);
+        void MAGNUM_LOCAL textureCubeMapImplementationDSA(BufferAttachment attachment, GLenum textureTarget, GLuint textureId, GLint level);
         #endif
 
         #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))

src/Magnum/Implementation/FramebufferState.cpp

@@ -74,7 +74,10 @@ FramebufferState::FramebufferState(Context& context, std::vector<std::string>& e
 
         renderbufferImplementation = &Framebuffer::renderbufferImplementationDSA;
         texture1DImplementation = &Framebuffer::texture1DImplementationDSA;
+        /* DSA doesn't have texture target parameter so we need to use different
+           function to specify cube map face */
         texture2DImplementation = &Framebuffer::texture2DImplementationDSA;
+        textureCubeMapImplementation = &Framebuffer::textureCubeMapImplementationDSA;
         textureLayerImplementation = &Framebuffer::textureLayerImplementationDSA;
 
         renderbufferStorageImplementation = &Renderbuffer::storageImplementationDSA;
@@ -89,7 +92,9 @@ FramebufferState::FramebufferState(Context& context, std::vector<std::string>& e
 
         renderbufferImplementation = &Framebuffer::renderbufferImplementationDSAEXT;
         texture1DImplementation = &Framebuffer::texture1DImplementationDSAEXT;
+        /* The EXT_DSA implementation is the same for both 2D and cube map textures */
         texture2DImplementation = &Framebuffer::texture2DImplementationDSAEXT;
+        textureCubeMapImplementation = &Framebuffer::texture2DImplementationDSAEXT;
         textureLayerImplementation = &Framebuffer::textureLayerImplementationDSAEXT;
 
         renderbufferStorageImplementation = &Renderbuffer::storageImplementationDSAEXT;
@@ -111,7 +116,9 @@ FramebufferState::FramebufferState(Context& context, std::vector<std::string>& e
         #ifndef MAGNUM_TARGET_GLES
         texture1DImplementation = &Framebuffer::texture1DImplementationDefault;
         #endif
+        /* The default implementation is the same for both 2D and cube map textures */
         texture2DImplementation = &Framebuffer::texture2DImplementationDefault;
+        textureCubeMapImplementation = &Framebuffer::texture2DImplementationDefault;
         #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
         textureLayerImplementation = &Framebuffer::textureLayerImplementationDefault;
         #endif

src/Magnum/Implementation/FramebufferState.h

@@ -77,6 +77,7 @@ struct FramebufferState {
     void(Framebuffer::*texture1DImplementation)(Framebuffer::BufferAttachment, GLuint, GLint);
     #endif
     void(Framebuffer::*texture2DImplementation)(Framebuffer::BufferAttachment, GLenum, GLuint, GLint);
+    void(Framebuffer::*textureCubeMapImplementation)(Framebuffer::BufferAttachment, GLenum, GLuint, GLint);
     #if !(defined(MAGNUM_TARGET_WEBGL) && defined(MAGNUM_TARGET_GLES2))
     void(Framebuffer::*textureLayerImplementation)(Framebuffer::BufferAttachment, GLuint, GLint, GLint);
     #endif