GL: new "intel-windows-buggy-dsa-bufferdata-for-index-buffers" workaround.

This is getting ridiculous, heh.

doc/changelog.dox

@@ -71,6 +71,10 @@ See also:
     @ref opengl-workarounds for more information). This pseudo-extension can be
     also explicitly disabled using the usual `--magnum-disable-extensions`
     @ref GL-Context-command-line "command-line option" for testing purposes.
+-   New @cpp "intel-windows-buggy-dsa-bufferdata-for-index-buffers" @ce
+    workaround for a synchronization bug in the Intel Windows drivers when
+    @ref GL::Buffer::setData() is followed by @ref GL::Mesh::setIndexBuffer()
+    when @gl_extension{ARB,direct_state_access} is used
 -   New `--magnum-gpu-validation` @ref GL-Context-command-line "command-line option"
     and a corresponding environment variable to conveniently enable
     @gl_extension{KHR,debug} debug output

src/Magnum/GL/Buffer.cpp

@@ -464,6 +464,18 @@ void Buffer::dataImplementationDefault(GLsizeiptr size, const GLvoid* data, Buff
 void Buffer::dataImplementationDSA(const GLsizeiptr size, const GLvoid* const data, const BufferUsage usage) {
     glNamedBufferData(_id, size, data, GLenum(usage));
 }
+
+#ifdef CORRADE_TARGET_WINDOWS
+void Buffer::dataImplementationDSAIntelWindows(const GLsizeiptr size, const GLvoid* const data, const BufferUsage usage) {
+    glNamedBufferData(_id, size, data, GLenum(usage));
+    /* See the "intel-windows-buggy-dsa-bufferdata-for-index-buffers"
+       workaround for more information */
+    if(_targetHint == TargetHint::ElementArray) {
+        bindInternal(TargetHint::ElementArray, nullptr);
+        bindInternal(TargetHint::ElementArray, this);
+    }
+}
+#endif
 #endif
 
 void Buffer::subDataImplementationDefault(GLintptr offset, GLsizeiptr size, const GLvoid* data) {

src/Magnum/GL/Buffer.h

@@ -1261,6 +1261,7 @@ class MAGNUM_GL_EXPORT Buffer: public AbstractObject {
 
         void MAGNUM_GL_LOCAL dataImplementationDefault(GLsizeiptr size, const GLvoid* data, BufferUsage usage);
         #ifndef MAGNUM_TARGET_GLES
+        void MAGNUM_GL_LOCAL dataImplementationDSAIntelWindows(GLsizeiptr size, const GLvoid* data, BufferUsage usage);
         void MAGNUM_GL_LOCAL dataImplementationDSA(GLsizeiptr size, const GLvoid* data, BufferUsage usage);
         #endif
 

src/Magnum/GL/Implementation/BufferState.cpp

@@ -107,7 +107,6 @@ BufferState::BufferState(Context& context, std::vector<std::string>& extensions)
         copyImplementation = &Buffer::copyImplementationDSA;
         getParameterImplementation = &Buffer::getParameterImplementationDSA;
         getSubDataImplementation = &Buffer::getSubDataImplementationDSA;
-        dataImplementation = &Buffer::dataImplementationDSA;
         subDataImplementation = &Buffer::subDataImplementationDSA;
         mapImplementation = &Buffer::mapImplementationDSA;
         mapRangeImplementation = &Buffer::mapRangeImplementationDSA;
@@ -123,7 +122,6 @@ BufferState::BufferState(Context& context, std::vector<std::string>& extensions)
         #ifndef MAGNUM_TARGET_GLES
         getSubDataImplementation = &Buffer::getSubDataImplementationDefault;
         #endif
-        dataImplementation = &Buffer::dataImplementationDefault;
         subDataImplementation = &Buffer::subDataImplementationDefault;
         #ifndef MAGNUM_TARGET_WEBGL
         mapImplementation = &Buffer::mapImplementationDefault;
@@ -181,6 +179,24 @@ BufferState::BufferState(Context& context, std::vector<std::string>& extensions)
         setTargetHintImplementation = &Buffer::setTargetHintImplementationDefault;
     }
 
+    #ifndef MAGNUM_TARGET_GLES
+    if(context.isExtensionSupported<Extensions::ARB::direct_state_access>()) {
+        #ifdef CORRADE_TARGET_WINDOWS
+        if((context.detectedDriver() & Context::DetectedDriver::IntelWindows) &&
+           !context.isDriverWorkaroundDisabled("intel-windows-buggy-dsa-bufferdata-for-index-buffers"))
+        {
+            dataImplementation = &Buffer::dataImplementationDSAIntelWindows;
+        } else
+        #endif
+        {
+            dataImplementation = &Buffer::dataImplementationDSA;
+        }
+    } else
+    #endif
+    {
+        dataImplementation = &Buffer::dataImplementationDefault;
+    }
+
     #ifdef MAGNUM_TARGET_GLES
     static_cast<void>(context);
     static_cast<void>(extensions);

src/Magnum/GL/Implementation/driverSpecific.cpp

@@ -200,6 +200,18 @@ namespace {
         "intel-windows-implementation-color-read-format-completely-broken",
         #endif
 
+        #if !defined(MAGNUM_TARGET_GLES) && defined(CORRADE_TARGET_WINDOWS)
+        /* Intel drivers on Windows have some synchronization / memory
+           alignment bug in the DSA glNamedBufferData() when the same buffer is
+           set as an index buffer to a mesh right after or repeatedly. Calling
+           glBindBuffer() right before or after the data upload fixes the
+           issue. Note that this workaround is done only for buffers with
+           TargetHint::ElementArray, as the issue was not observed elsewhere.
+           Reproducible with the 2019.01 ImGui example, unfortunately I was not
+           able to create a standalone minimal repro case. */
+        "intel-windows-buggy-dsa-bufferdata-for-index-buffers",
+        #endif
+
         #ifndef MAGNUM_TARGET_GLES
         /* NVidia seems to be returning values for the default framebuffer when
            GL_IMPLEMENTATION_COLOR_READ_FORMAT and _TYPE is queried using

src/Magnum/GL/Mesh.cpp

@@ -678,10 +678,8 @@ void Mesh::attributePointerImplementationVAO(AttributeLayout&& attribute) {
 
 #ifndef MAGNUM_TARGET_GLES
 void Mesh::attributePointerImplementationVAODSA(AttributeLayout&& attribute) {
-    _flags |= ObjectFlag::Created;
     glEnableVertexArrayAttrib(_id, attribute.location);
 
-
     #ifndef MAGNUM_TARGET_GLES2
     if(attribute.kind == DynamicAttribute::Kind::Integral)
         glVertexArrayAttribIFormat(_id, attribute.location, attribute.size, attribute.type, 0);