[plugins/qpa] Support SharingPlatformContext on the existing eglSurface and eglconfig

Summary:
So far SharingPlatformContext was only used if the OpenGL context
supports EGL_KHR_surfaceless_context. If not supported, KWin tried to
create a context through the Wayland API. Unfortunately on hwcomposer
platform this results in a crash as libhybris only supports the init
of EGLDisplay for one native platform.

This change tries to also use the SharingPlatformContext if there is
an OpenGL context in general. It reuses the native EGLSurface created
for the compositing scene and makes its own OpenGL context current on
that surface, too. As KWin creates an FBO, it never renders to it, so
it shouldn't matter at all.

In order to prevent EGL_BAD_MATCH errors when making Qt's OpenGL context
current also the EGLConfig from the scene is used to create the context.

Test Plan: Tested on Nexus5 with qtvirtualkeyboard in KWin

Reviewers: #kwin, #plasma_on_wayland

Subscribers: plasma-devel, kwin

Tags: #plasma_on_wayland, #kwin

Differential Revision: https://phabricator.kde.org/D2231

abstract_egl_backend.h

@@ -39,17 +39,17 @@ public:
     EGLContext context() const {
         return m_context;
     }
-
-    static void unbindWaylandDisplay();
-
-protected:
-    AbstractEglBackend();
     EGLSurface surface() const {
         return m_surface;
     }
     EGLConfig config() const {
         return m_config;
     }
+
+    static void unbindWaylandDisplay();
+
+protected:
+    AbstractEglBackend();
     void setEglDisplay(const EGLDisplay &display);
     void setSurface(const EGLSurface &surface) {
         m_surface = surface;

platform.cpp

@@ -274,6 +274,26 @@ EGLContext Platform::sceneEglContext() const
     return EGL_NO_CONTEXT;
 }
 
+EGLSurface Platform::sceneEglSurface() const
+{
+    if (Compositor *c = Compositor::self()) {
+        if (SceneOpenGL *s = dynamic_cast<SceneOpenGL*>(c->scene())) {
+            return static_cast<AbstractEglBackend*>(s->backend())->surface();
+        }
+    }
+    return EGL_NO_SURFACE;
+}
+
+EGLConfig Platform::sceneEglConfig() const
+{
+    if (Compositor *c = Compositor::self()) {
+        if (SceneOpenGL *s = dynamic_cast<SceneOpenGL*>(c->scene())) {
+            return static_cast<AbstractEglBackend*>(s->backend())->config();
+        }
+    }
+    return nullptr;
+}
+
 QSize Platform::screenSize() const
 {
     return QSize();

platform.h

@@ -71,6 +71,15 @@ public:
      * The EGLContext used by the compositing scene.
      **/
     virtual EGLContext sceneEglContext() const;
+    /**
+     * The first (in case of multiple) EGLSurface used by the compositing scene.
+     **/
+    EGLSurface sceneEglSurface() const;
+
+    /**
+     * The EglConfig used by the compositing scene.
+     **/
+    EGLConfig sceneEglConfig() const;
 
     /**
      * Implementing subclasses should provide a size in case the backend represents

plugins/qpa/abstractplatformcontext.cpp

@@ -93,11 +93,11 @@ static QSurfaceFormat formatFromConfig(EGLDisplay dpy, EGLConfig config)
     return format;
 }
 
-AbstractPlatformContext::AbstractPlatformContext(QOpenGLContext *context, Integration *integration, EGLDisplay display)
+AbstractPlatformContext::AbstractPlatformContext(QOpenGLContext *context, Integration *integration, EGLDisplay display, EGLConfig config)
     : QPlatformOpenGLContext()
     , m_integration(integration)
     , m_eglDisplay(display)
-    , m_config(configFromGLFormat(m_eglDisplay, context->format()))
+    , m_config(config ? config :configFromGLFormat(m_eglDisplay, context->format()))
     , m_format(formatFromConfig(m_eglDisplay, m_config))
 {
 }

plugins/qpa/abstractplatformcontext.h

@@ -33,7 +33,7 @@ class Integration;
 class AbstractPlatformContext : public QPlatformOpenGLContext
 {
 public:
-    explicit AbstractPlatformContext(QOpenGLContext *context, Integration *integration, EGLDisplay display);
+    explicit AbstractPlatformContext(QOpenGLContext *context, Integration *integration, EGLDisplay display, EGLConfig config = nullptr);
     virtual ~AbstractPlatformContext();
 
     void doneCurrent() override;

plugins/qpa/integration.cpp

@@ -180,6 +180,13 @@ QPlatformOpenGLContext *Integration::createPlatformOpenGLContext(QOpenGLContext
     if (kwinApp()->platform()->supportsQpaContext()) {
         return new SharingPlatformContext(context, const_cast<Integration*>(this));
     }
+    if (kwinApp()->platform()->sceneEglDisplay() != EGL_NO_DISPLAY) {
+        auto s = kwinApp()->platform()->sceneEglSurface();
+        if (s != EGL_NO_SURFACE) {
+            // try a SharingPlatformContext with a created surface
+            return new SharingPlatformContext(context, const_cast<Integration*>(this), s, kwinApp()->platform()->sceneEglConfig());
+        }
+    }
     if (m_eglDisplay == EGL_NO_DISPLAY) {
         const_cast<Integration*>(this)->initEgl();
     }

plugins/qpa/sharingplatformcontext.cpp

@@ -34,7 +34,13 @@ namespace QPA
 {
 
 SharingPlatformContext::SharingPlatformContext(QOpenGLContext *context, Integration *integration)
-    : AbstractPlatformContext(context, integration, kwinApp()->platform()->sceneEglDisplay())
+    : SharingPlatformContext(context, integration, EGL_NO_SURFACE)
+{
+}
+
+SharingPlatformContext::SharingPlatformContext(QOpenGLContext *context, Integration *integration, const EGLSurface &surface, EGLConfig config)
+    : AbstractPlatformContext(context, integration, kwinApp()->platform()->sceneEglDisplay(), config)
+    , m_surface(surface)
 {
     create();
 }
@@ -42,7 +48,7 @@ SharingPlatformContext::SharingPlatformContext(QOpenGLContext *context, Integrat
 bool SharingPlatformContext::makeCurrent(QPlatformSurface *surface)
 {
     Window *window = static_cast<Window*>(surface);
-    if (eglMakeCurrent(eglDisplay(), EGL_NO_SURFACE, EGL_NO_SURFACE, context())) {
+    if (eglMakeCurrent(eglDisplay(), m_surface, m_surface, context())) {
         window->bindContentFBO();
         return true;
     }

plugins/qpa/sharingplatformcontext.h

@@ -32,6 +32,7 @@ class SharingPlatformContext : public AbstractPlatformContext
 {
 public:
     explicit SharingPlatformContext(QOpenGLContext *context, Integration *integration);
+    explicit SharingPlatformContext(QOpenGLContext *context, Integration *integration, const EGLSurface &surface, EGLConfig config = nullptr);
 
     void swapBuffers(QPlatformSurface *surface) override;
 
@@ -43,6 +44,8 @@ public:
 
 private:
     void create();
+
+    EGLSurface m_surface;
 };
 
 }