Support adopting an existing EGLContext in eglfs and xcb

Add also a manual test application. For GLX there is an autotest since
that is likely to be run on one of the CIs. For EGL and especially
eglfs this is likely not the case so a manual test is better.

Task-number: QTBUG-37552
Change-Id: Ib09db5d909befb68d16f69abd401a56abe55f28a
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>

4 files changed, 82 insertions, 22 deletions

diff --git a/src/platformsupport/eglconvenience/qeglplatformcontext.cpp b/src/platformsupport/eglconvenience/qeglplatformcontext.cpp
index eec6463c21..9691d12682 100644
--- a/src/platformsupport/eglconvenience/qeglplatformcontext.cpp
+++ b/src/platformsupport/eglconvenience/qeglplatformcontext.cpp
@@ -44,6 +44,7 @@
 #include "qeglpbuffer_p.h"
 #include <qpa/qplatformwindow.h>
 #include <QOpenGLContext>
+#include <QtPlatformHeaders/QEGLNativeContext>
 #include <QDebug>
 
 QT_BEGIN_NAMESPACE
@@ -108,25 +109,21 @@ QT_BEGIN_NAMESPACE
 #define GL_CONTEXT_COMPATIBILITY_PROFILE_BIT 0x00000002
 #endif
 
-QEGLPlatformContext::QEGLPlatformContext(const QSurfaceFormat &format, QPlatformOpenGLContext *share, EGLDisplay display)
-    : m_eglDisplay(display)
-    , m_eglConfig(q_configFromGLFormat(display, format))
-    , m_swapInterval(-1)
-    , m_swapIntervalEnvChecked(false)
-    , m_swapIntervalFromEnv(-1)
-{
-    init(format, share);
-}
-
 QEGLPlatformContext::QEGLPlatformContext(const QSurfaceFormat &format, QPlatformOpenGLContext *share, EGLDisplay display,
-                                         EGLConfig config)
+                                         EGLConfig *config, const QVariant &nativeHandle)
     : m_eglDisplay(display)
-    , m_eglConfig(config)
     , m_swapInterval(-1)
     , m_swapIntervalEnvChecked(false)
     , m_swapIntervalFromEnv(-1)
 {
-    init(format, share);
+    if (nativeHandle.isNull()) {
+        m_eglConfig = config ? *config : q_configFromGLFormat(display, format);
+        m_ownsContext = true;
+        init(format, share);
+    } else {
+        m_ownsContext = false;
+        adopt(nativeHandle, share);
+    }
 }
 
 void QEGLPlatformContext::init(const QSurfaceFormat &format, QPlatformOpenGLContext *share)
@@ -198,6 +195,59 @@ void QEGLPlatformContext::init(const QSurfaceFormat &format, QPlatformOpenGLCont
         q_printEglConfig(m_eglDisplay, m_eglConfig);
     }
 
+    updateFormatFromGL();
+}
+
+void QEGLPlatformContext::adopt(const QVariant &nativeHandle, QPlatformOpenGLContext *share)
+{
+    if (!nativeHandle.canConvert<QEGLNativeContext>()) {
+        qWarning("QEGLPlatformContext: Requires a QEGLNativeContext");
+        return;
+    }
+    QEGLNativeContext handle = nativeHandle.value<QEGLNativeContext>();
+    EGLContext context = handle.context();
+    if (!context) {
+        qWarning("QEGLPlatformContext: No EGLContext given");
+        return;
+    }
+
+    // A context belonging to a given EGLDisplay cannot be used with another one.
+    if (handle.display() != m_eglDisplay) {
+        qWarning("QEGLPlatformContext: Cannot adopt context from different display");
+        return;
+    }
+
+    // Figure out the EGLConfig.
+    EGLint value = 0;
+    eglQueryContext(m_eglDisplay, context, EGL_CONFIG_ID, &value);
+    EGLint n = 0;
+    EGLConfig cfg;
+    const EGLint attribs[] = { EGL_CONFIG_ID, value, EGL_NONE };
+    if (eglChooseConfig(m_eglDisplay, attribs, &cfg, 1, &n) && n == 1) {
+        m_eglConfig = cfg;
+        m_format = q_glFormatFromConfig(m_eglDisplay, m_eglConfig);
+    } else {
+        qWarning("QEGLPlatformContext: Failed to get framebuffer configuration for context");
+    }
+
+    // Fetch client API type.
+    value = 0;
+    eglQueryContext(m_eglDisplay, context, EGL_CONTEXT_CLIENT_TYPE, &value);
+    if (value == EGL_OPENGL_API || value == EGL_OPENGL_ES_API) {
+        m_api = value;
+        eglBindAPI(m_api);
+    } else {
+        qWarning("QEGLPlatformContext: Failed to get client API type");
+        m_api = EGL_OPENGL_ES_API;
+    }
+
+    m_eglContext = context;
+    m_shareContext = share ? static_cast<QEGLPlatformContext *>(share)->m_eglContext : 0;
+    updateFormatFromGL();
+}
+
+void QEGLPlatformContext::updateFormatFromGL()
+{
 #ifndef QT_NO_OPENGL
     // Make the context current to ensure the GL version query works. This needs a surface too.
     const EGLint pbufferAttributes[] = {
@@ -296,10 +346,10 @@ bool QEGLPlatformContext::makeCurrent(QPlatformSurface *surface)
 
 QEGLPlatformContext::~QEGLPlatformContext()
 {
-    if (m_eglContext != EGL_NO_CONTEXT) {
+    if (m_ownsContext && m_eglContext != EGL_NO_CONTEXT)
         eglDestroyContext(m_eglDisplay, m_eglContext);
-        m_eglContext = EGL_NO_CONTEXT;
-    }
+
+    m_eglContext = EGL_NO_CONTEXT;
 }
 
 void QEGLPlatformContext::doneCurrent()
diff --git a/src/platformsupport/eglconvenience/qeglplatformcontext_p.h b/src/platformsupport/eglconvenience/qeglplatformcontext_p.h
index 714633c3bc..82f062c4a4 100644
--- a/src/platformsupport/eglconvenience/qeglplatformcontext_p.h
+++ b/src/platformsupport/eglconvenience/qeglplatformcontext_p.h
@@ -44,6 +44,7 @@
 
 #include <qpa/qplatformwindow.h>
 #include <qpa/qplatformopenglcontext.h>
+#include <QtCore/QVariant>
 #include <EGL/egl.h>
 
 QT_BEGIN_NAMESPACE
@@ -51,9 +52,8 @@ QT_BEGIN_NAMESPACE
 class QEGLPlatformContext : public QPlatformOpenGLContext
 {
 public:
-    QEGLPlatformContext(const QSurfaceFormat &format, QPlatformOpenGLContext *share, EGLDisplay display);
     QEGLPlatformContext(const QSurfaceFormat &format, QPlatformOpenGLContext *share, EGLDisplay display,
-                        EGLConfig config);
+                        EGLConfig *config = 0, const QVariant &nativeHandle = QVariant());
     ~QEGLPlatformContext();
 
     bool makeCurrent(QPlatformSurface *surface);
@@ -74,6 +74,8 @@ protected:
 
 private:
     void init(const QSurfaceFormat &format, QPlatformOpenGLContext *share);
+    void adopt(const QVariant &nativeHandle, QPlatformOpenGLContext *share);
+    void updateFormatFromGL();
 
     EGLContext m_eglContext;
     EGLContext m_shareContext;
@@ -84,6 +86,7 @@ private:
     int m_swapInterval;
     bool m_swapIntervalEnvChecked;
     int m_swapIntervalFromEnv;
+    bool m_ownsContext;
 };
 
 QT_END_NAMESPACE
diff --git a/src/platformsupport/eglconvenience/qeglplatformintegration.cpp b/src/platformsupport/eglconvenience/qeglplatformintegration.cpp
index 3de0642c93..560ff79ef8 100644
--- a/src/platformsupport/eglconvenience/qeglplatformintegration.cpp
+++ b/src/platformsupport/eglconvenience/qeglplatformintegration.cpp
@@ -158,9 +158,14 @@ QPlatformOpenGLContext *QEGLPlatformIntegration::createPlatformOpenGLContext(QOp
     // If there is a "root" window into which raster and QOpenGLWidget content is
     // composited, all other contexts must share with its context.
     QOpenGLContext *compositingContext = screen ? screen->compositingContext() : 0;
-    return createContext(context->format(),
-                         compositingContext ? compositingContext->handle() : context->shareHandle(),
-                         display());
+    QPlatformOpenGLContext *share = compositingContext ? compositingContext->handle() : context->shareHandle();
+    QVariant nativeHandle = context->nativeHandle();
+    QPlatformOpenGLContext *platformContext = createContext(context->format(),
+                                                            share,
+                                                            display(),
+                                                            &nativeHandle);
+    context->setNativeHandle(nativeHandle);
+    return platformContext;
 }
 
 QPlatformOffscreenSurface *QEGLPlatformIntegration::createPlatformOffscreenSurface(QOffscreenSurface *surface) const
diff --git a/src/platformsupport/eglconvenience/qeglplatformintegration_p.h b/src/platformsupport/eglconvenience/qeglplatformintegration_p.h
index 0de8cc9a33..9d4207e005 100644
--- a/src/platformsupport/eglconvenience/qeglplatformintegration_p.h
+++ b/src/platformsupport/eglconvenience/qeglplatformintegration_p.h
@@ -44,6 +44,7 @@
 
 #include <qpa/qplatformintegration.h>
 #include <qpa/qplatformnativeinterface.h>
+#include <QtCore/QVariant>
 #include <EGL/egl.h>
 
 QT_BEGIN_NAMESPACE
@@ -89,7 +90,8 @@ protected:
     virtual QEGLPlatformWindow *createWindow(QWindow *window) const = 0;
     virtual QEGLPlatformContext *createContext(const QSurfaceFormat &format,
                                                QPlatformOpenGLContext *shareContext,
-                                               EGLDisplay display) const = 0;
+                                               EGLDisplay display,
+                                               QVariant *nativeHandle) const = 0;
     virtual QPlatformOffscreenSurface *createOffscreenSurface(EGLDisplay display,
                                                               const QSurfaceFormat &format,
                                                               QOffscreenSurface *surface) const = 0;