From 4e218d3f24466eb25b1173b625f98e81c1f78916 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Wed, 21 Aug 2019 02:33:19 +0200
Subject: [PATCH] Platform: new nv-egl-forward-compatible-context-unhappy
 workaround.

SIGH. WHY CAN'T WE HAVE NICE THINGS.
---
 doc/changelog.dox                                |  5 +++++
 src/Magnum/GL/Implementation/driverSpecific.cpp  |  6 ++++++
 src/Magnum/Platform/WindowlessEglApplication.cpp | 12 ++++++++++--
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/doc/changelog.dox b/doc/changelog.dox
index 23fd67dfd..a53a38635 100644
--- a/doc/changelog.dox
+++ b/doc/changelog.dox
@@ -303,6 +303,11 @@ See also:
     would assume a zero-sized framebuffer. This behavior is no longer silent
     but advertised as a @cpp "apitrace-zero-initial-viewport" @ce workaround.
     See @ref opengl-workarounds for more information.
+-   Added a @cpp "nv-egl-forward-compatible-context-unhappy" @ce workaround
+    that removes @ref Platform::WindowlessEglApplication::Configuration::Flag::ForwardCompatible
+    from flags passed to `eglCreateContext()` as that otherwise causes NVidia
+    to fail with `EGL_BAD_MATCH`. See @ref opengl-workarounds for more
+    information.
 
 @subsubsection changelog-latest-changes-math Math library
 
diff --git a/src/Magnum/GL/Implementation/driverSpecific.cpp b/src/Magnum/GL/Implementation/driverSpecific.cpp
index 8bd9d7025..ee036c895 100644
--- a/src/Magnum/GL/Implementation/driverSpecific.cpp
+++ b/src/Magnum/GL/Implementation/driverSpecific.cpp
@@ -105,6 +105,12 @@ namespace {
    possible to get driver version through EGL, so enabling this unconditionally
    on all EGL NV contexts. */
 "nv-egl-incorrect-gl11-function-pointers",
+
+/* NVidia is unhappy when EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR is
+   present among attributes passed to eglCreateContext(), blowing up with
+   EGL_BAD_MATCH. This flag is enabled by default, wiping it away to make the
+   context creation work. */
+"nv-egl-forward-compatible-context-unhappy",
 #endif
 
 #ifndef MAGNUM_TARGET_GLES
diff --git a/src/Magnum/Platform/WindowlessEglApplication.cpp b/src/Magnum/Platform/WindowlessEglApplication.cpp
index 7cfe81edb..3b3ca5704 100644
--- a/src/Magnum/Platform/WindowlessEglApplication.cpp
+++ b/src/Magnum/Platform/WindowlessEglApplication.cpp
@@ -169,6 +169,16 @@ WindowlessEglContext::WindowlessEglContext(const Configuration& configuration, G
         flags |= Configuration::Flag::Debug;
     #endif
 
+    #ifndef MAGNUM_TARGET_GLES
+    /* NVidia doesn't like EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR for
+       some reason, failing eglCreateContext() with EGL_BAD_MATCH. If this flag
+       is set, wipe it away. */
+    const char* vendor = eglQueryString(_display, EGL_VENDOR);
+    if((flags & Configuration::Flag::ForwardCompatible) && vendor && std::strcmp(vendor, "NVIDIA") == 0 && (!magnumContext || !magnumContext->isDriverWorkaroundDisabled("nv-egl-forward-compatible-context-unhappy"))) {
+        flags &= ~Configuration::Flag::ForwardCompatible;
+    }
+    #endif
+
     #if !defined(MAGNUM_TARGET_GLES) || defined(MAGNUM_TARGET_WEBGL)
     const /* Is modified below to work around a SwiftShader limitation */
     #endif
@@ -197,8 +207,6 @@ WindowlessEglContext::WindowlessEglContext(const Configuration& configuration, G
 
     #ifdef MAGNUM_TARGET_WEBGL
     static_cast<void>(configuration);
-    #endif
-    #if !defined(MAGNUM_TARGET_GLES) || defined(MAGNUM_TARGET_WEBGL)
     static_cast<void>(magnumContext);
     #endif