x11: Use global share context

This is needed to share window thumbnails between kwin's scene graph and
qtquick.

src/libkwineffects/kwineffectquickview.cpp

@@ -29,8 +29,6 @@
 namespace KWin
 {
 
-static std::unique_ptr<QOpenGLContext> s_shareContext;
-
 class Q_DECL_HIDDEN EffectQuickView::Private
 {
 public:
@@ -88,7 +86,7 @@ EffectQuickView::EffectQuickView(QObject *parent, ExportMode exportMode)
         format.setStencilBufferSize(8);
 
         d->m_glcontext.reset(new QOpenGLContext);
-        d->m_glcontext->setShareContext(s_shareContext.get());
+        d->m_glcontext->setShareContext(QOpenGLContext::globalShareContext());
         d->m_glcontext->setFormat(format);
         d->m_glcontext->create();
 
@@ -103,11 +101,6 @@ EffectQuickView::EffectQuickView(QObject *parent, ExportMode exportMode)
 
         if (!d->m_glcontext->shareContext()) {
             qCDebug(LIBKWINEFFECTS) << "Failed to create a shared context, falling back to raster rendering";
-
-            qCDebug(LIBKWINEFFECTS) << "Extra debug:";
-            qCDebug(LIBKWINEFFECTS) << "our context:" << d->m_glcontext.data();
-            qCDebug(LIBKWINEFFECTS) << "share context:" << s_shareContext.get();
-
             // still render via GL, but blit for presentation
             d->m_useBlit = true;
         }
@@ -238,11 +231,6 @@ void EffectQuickView::forwardKeyEvent(QKeyEvent *keyEvent)
     QCoreApplication::sendEvent(d->m_view, keyEvent);
 }
 
-void EffectQuickView::setShareContext(std::unique_ptr<QOpenGLContext> context)
-{
-    s_shareContext = std::move(context);
-}
-
 QRect EffectQuickView::geometry() const
 {
     return d->m_view->geometry();

src/libkwineffects/kwineffectquickview.h

@@ -21,7 +21,6 @@
 
 class QKeyEvent;
 class QMouseEvent;
-class QOpenGLContext;
 
 class QMouseEvent;
 class QKeyEvent;
@@ -49,8 +48,6 @@ class KWINEFFECTS_EXPORT EffectQuickView : public QObject
     Q_OBJECT
 
 public:
-    static void setShareContext(std::unique_ptr<QOpenGLContext> context);
-
     enum class ExportMode {
         /** The contents will be available as a texture in the shared contexts. Image will be blank*/
         Texture,

src/main_x11.cpp

@@ -417,6 +417,15 @@ int main(int argc, char * argv[])
     QCoreApplication::setAttribute(Qt::AA_DisableHighDpiScaling);
     // KSMServer talks to us directly on DBus.
     QCoreApplication::setAttribute(Qt::AA_DisableSessionManager);
+    // For sharing thumbnails between our scene graph and qtquick.
+    QCoreApplication::setAttribute(Qt::AA_ShareOpenGLContexts);
+
+    QSurfaceFormat format = QSurfaceFormat::defaultFormat();
+    // shared opengl contexts must have the same reset notification policy
+    format.setOptions(QSurfaceFormat::ResetNotification);
+    // disables vsync for any QtQuick windows we create (BUG 406180)
+    format.setSwapInterval(0);
+    QSurfaceFormat::setDefaultFormat(format);
 
     KWin::ApplicationX11 a(argc, argv);
     a.setupTranslator();
@@ -424,11 +433,6 @@ int main(int argc, char * argv[])
     KWin::Application::createAboutData();
     KQuickAddons::QtQuickSettings::init();
 
-    // disables vsync for any QtQuick windows we create (BUG 406180)
-    QSurfaceFormat format = QSurfaceFormat::defaultFormat();
-    format.setSwapInterval(0);
-    QSurfaceFormat::setDefaultFormat(format);
-
     QCommandLineOption replaceOption(QStringLiteral("replace"), i18n("Replace already-running ICCCM2.0-compliant window manager"));
 
     QCommandLineParser parser;

src/plugins/platforms/x11/standalone/eglbackend.cpp

@@ -6,6 +6,7 @@
 */
 
 #include "eglbackend.h"
+#include "logging.h"
 #include "options.h"
 #include "overlaywindow.h"
 #include "platform.h"
@@ -16,6 +17,9 @@
 #include "surfaceitem_x11.h"
 #include "x11_platform.h"
 
+#include <QOpenGLContext>
+#include <QtPlatformHeaders/QEGLNativeContext>
+
 namespace KWin
 {
 
@@ -48,6 +52,30 @@ PlatformSurfaceTexture *EglBackend::createPlatformSurfaceTextureX11(SurfacePixma
     return new EglSurfaceTextureX11(this, texture);
 }
 
+void EglBackend::init()
+{
+    QOpenGLContext *qtShareContext = QOpenGLContext::globalShareContext();
+    EGLContext shareContext = EGL_NO_CONTEXT;
+    if (qtShareContext) {
+        qDebug(KWIN_X11STANDALONE) << "Global share context format:" << qtShareContext->format();
+        const QVariant nativeHandle = qtShareContext->nativeHandle();
+        if (!nativeHandle.canConvert<QEGLNativeContext>()) {
+            setFailed(QStringLiteral("Invalid QOpenGLContext::globalShareContext()"));
+            return;
+        } else {
+            QEGLNativeContext handle = qvariant_cast<QEGLNativeContext>(nativeHandle);
+            shareContext = handle.context();
+        }
+    }
+    if (shareContext == EGL_NO_CONTEXT) {
+        setFailed(QStringLiteral("QOpenGLContext::globalShareContext() is required"));
+        return;
+    }
+
+    kwinApp()->platform()->setSceneEglGlobalShareContext(shareContext);
+    EglOnXBackend::init();
+}
+
 void EglBackend::screenGeometryChanged(const QSize &size)
 {
     Q_UNUSED(size)

src/plugins/platforms/x11/standalone/eglbackend.h

@@ -27,6 +27,8 @@ public:
     EglBackend(Display *display, X11StandalonePlatform *platform);
     ~EglBackend() override;
 
+    void init() override;
+
     PlatformSurfaceTexture *createPlatformSurfaceTextureX11(SurfacePixmapX11 *texture) override;
     QRegion beginFrame(int screenId) override;
     void endFrame(int screenId, const QRegion &damage, const QRegion &damagedRegion) override;

src/plugins/platforms/x11/standalone/glxbackend.cpp

@@ -129,7 +129,6 @@ GlxBackend::~GlxBackend()
     // do cleanup after initBuffer()
     cleanupGL();
     doneCurrent();
-    EffectQuickView::setShareContext(nullptr);
 
     if (ctx)
         glXDestroyContext(display(), ctx);
@@ -311,6 +310,24 @@ bool GlxBackend::initRenderingContext()
 {
     const bool direct = true;
 
+    QOpenGLContext *qtGlobalShareContext = QOpenGLContext::globalShareContext();
+    GLXContext globalShareContext = nullptr;
+    if (qtGlobalShareContext) {
+        qDebug(KWIN_X11STANDALONE) << "Global share context format:" << qtGlobalShareContext->format();
+        const QVariant nativeHandle = qtGlobalShareContext->nativeHandle();
+        if (!nativeHandle.canConvert<QGLXNativeContext>()) {
+            qCDebug(KWIN_X11STANDALONE) << "Invalid QOpenGLContext::globalShareContext()";
+            return false;
+        } else {
+            QGLXNativeContext handle = qvariant_cast<QGLXNativeContext>(nativeHandle);
+            globalShareContext = handle.context();
+        }
+    }
+    if (!globalShareContext) {
+        qCWarning(KWIN_X11STANDALONE) << "QOpenGLContext::globalShareContext() is required";
+        return false;
+    }
+
     // Use glXCreateContextAttribsARB() when it's available
     if (hasExtension(QByteArrayLiteral("GLX_ARB_create_context"))) {
         const bool have_robustness = hasExtension(QByteArrayLiteral("GLX_ARB_create_context_robustness"));
@@ -352,7 +369,7 @@ bool GlxBackend::initRenderingContext()
         }
         for (auto it = candidates.begin(); it != candidates.end(); it++) {
             const auto attribs = it->build();
-            ctx = glXCreateContextAttribsARB(display(), fbconfig, nullptr, true, attribs.data());
+            ctx = glXCreateContextAttribsARB(display(), fbconfig, globalShareContext, true, attribs.data());
             if (ctx) {
                 qCDebug(KWIN_X11STANDALONE) << "Created GLX context with attributes:" << &(*it);
                 break;
@@ -361,7 +378,7 @@ bool GlxBackend::initRenderingContext()
     }
 
     if (!ctx)
-        ctx = glXCreateNewContext(display(), fbconfig, GLX_RGBA_TYPE, nullptr, direct);
+        ctx = glXCreateNewContext(display(), fbconfig, GLX_RGBA_TYPE, globalShareContext, direct);
 
     if (!ctx) {
         qCDebug(KWIN_X11STANDALONE) << "Failed to create an OpenGL context.";
@@ -375,12 +392,6 @@ bool GlxBackend::initRenderingContext()
         return false;
     }
 
-    auto qtContext = new QOpenGLContext;
-    QGLXNativeContext native(ctx, display());
-    qtContext->setNativeHandle(QVariant::fromValue(native));
-    qtContext->create();
-    EffectQuickView::setShareContext(std::unique_ptr<QOpenGLContext>(qtContext));
-
     return true;
 }