From fb5143d34d7a187e6bd9cdb1ce47806db18bbd27 Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Tue, 13 Oct 2020 21:46:42 +0300
Subject: [PATCH] qpa: Query various properties of the platform OpenGL context

Qt checks OpenGL version to determine if some features can be enabled.
This change ensures that the format EGLPlatformContext returns has
properly initialized the OpenGL version, the context profile and the
format options (e.g. whether it's a debug context, etc).
---
 plugins/qpa/eglplatformcontext.cpp | 79 ++++++++++++++++++++++++++++++
 plugins/qpa/eglplatformcontext.h   |  1 +
 2 files changed, 80 insertions(+)

diff --git a/plugins/qpa/eglplatformcontext.cpp b/plugins/qpa/eglplatformcontext.cpp
index 70c8ee5dab..d65faf4234 100644
--- a/plugins/qpa/eglplatformcontext.cpp
+++ b/plugins/qpa/eglplatformcontext.cpp
@@ -262,6 +262,85 @@ void EGLPlatformContext::create(const QSurfaceFormat &format, EGLContext shareCo
         return;
     }
     m_context = context;
+    updateFormatFromContext();
+}
+
+static EGLSurface createDummyPbufferSurface(EGLDisplay display, const QSurfaceFormat &format)
+{
+    const EGLConfig config = configFromFormat(display, format, EGL_PBUFFER_BIT);
+    if (config == EGL_NO_CONFIG_KHR) {
+        return EGL_NO_SURFACE;
+    }
+
+    const EGLint attribs[] = {
+        EGL_WIDTH, 16,
+        EGL_HEIGHT, 16,
+        EGL_NONE
+    };
+
+    return eglCreatePbufferSurface(display, config, attribs);
+}
+
+void EGLPlatformContext::updateFormatFromContext()
+{
+    const EGLSurface oldDrawSurface = eglGetCurrentSurface(EGL_DRAW);
+    const EGLSurface oldReadSurface = eglGetCurrentSurface(EGL_READ);
+    const EGLContext oldContext = eglGetCurrentContext();
+
+    EGLSurface dummySurface;
+    if (!kwinApp()->platform()->supportsSurfacelessContext()) {
+        dummySurface = createDummyPbufferSurface(m_eglDisplay, m_format);
+        if (dummySurface == EGL_NO_SURFACE) {
+            qCWarning(KWIN_QPA, "Failed to create dummy surface: 0x%x", eglGetError());
+            return;
+        }
+    } else {
+        dummySurface = EGL_NO_SURFACE;
+    }
+
+    eglMakeCurrent(m_eglDisplay, dummySurface, dummySurface, m_context);
+
+    const char *version = reinterpret_cast<const char *>(glGetString(GL_VERSION));
+    int major, minor;
+    if (parseOpenGLVersion(version, major, minor)) {
+        m_format.setMajorVersion(major);
+        m_format.setMinorVersion(minor);
+    } else {
+        qCWarning(KWIN_QPA) << "Unrecognized OpenGL version:" << version;
+    }
+
+    GLint value;
+
+    if (m_format.version() >= qMakePair(3, 0)) {
+        glGetIntegerv(GL_CONTEXT_FLAGS, &value);
+        if (value & GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT) {
+            m_format.setOption(QSurfaceFormat::DeprecatedFunctions);
+        }
+        if (value & GL_CONTEXT_FLAG_DEBUG_BIT) {
+            m_format.setOption(QSurfaceFormat::DebugContext);
+        }
+    } else {
+        m_format.setOption(QSurfaceFormat::DeprecatedFunctions);
+    }
+
+    if (m_format.version() >= qMakePair(3, 2)) {
+        glGetIntegerv(GL_CONTEXT_PROFILE_MASK, &value);
+        if (value & GL_CONTEXT_CORE_PROFILE_BIT) {
+            m_format.setProfile(QSurfaceFormat::CoreProfile);
+        } else if (value & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT) {
+            m_format.setProfile(QSurfaceFormat::CompatibilityProfile);
+        } else {
+            m_format.setProfile(QSurfaceFormat::NoProfile);
+        }
+    } else {
+        m_format.setProfile(QSurfaceFormat::NoProfile);
+    }
+
+    eglMakeCurrent(m_eglDisplay, oldDrawSurface, oldReadSurface, oldContext);
+
+    if (dummySurface != EGL_NO_SURFACE) {
+        eglDestroySurface(m_eglDisplay, dummySurface);
+    }
 }
 
 } // namespace QPA
diff --git a/plugins/qpa/eglplatformcontext.h b/plugins/qpa/eglplatformcontext.h
index b582d84866..07ae3e3a36 100644
--- a/plugins/qpa/eglplatformcontext.h
+++ b/plugins/qpa/eglplatformcontext.h
@@ -40,6 +40,7 @@ public:
 
 private:
     void create(const QSurfaceFormat &format, EGLContext shareContext);
+    void updateFormatFromContext();
 
     EGLDisplay m_eglDisplay;
     EGLConfig m_config = EGL_NO_CONFIG_KHR;