Make swap buffer call non-blocking for subsurfaces

Allows clients that use subsurfaces in synchronized mode to continue
processing the event loop even in cases where a frame callback is not
delivered from the compositor pending a parent surface commit

Change-Id: I7df38afc4080546b60184dacecde321ba8062fac
Reviewed-by: Giulio Camuffo <giulio.camuffo@jollamobile.com>

2 files changed, 30 insertions, 1 deletions

diff --git a/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp b/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp
index 18ed1d61e..b8ba4c631 100644
--- a/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp
+++ b/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp
@@ -35,6 +35,7 @@
 
 #include <QtWaylandClient/private/qwaylanddisplay_p.h>
 #include <QtWaylandClient/private/qwaylandwindow_p.h>
+#include <QtWaylandClient/private/qwaylandsubsurface_p.h>
 #include <QtWaylandClient/private/qwaylandabstractdecoration_p.h>
 #include <QtWaylandClient/private/qwaylandintegration_p.h>
 #include "qwaylandeglwindow.h"
@@ -50,6 +51,8 @@
 #include <QtGui/QOpenGLShaderProgram>
 #include <QtGui/QOpenGLFunctions>
 
+#include <QtCore/qmutex.h>
+
 // Constants from EGL_KHR_create_context
 #ifndef EGL_CONTEXT_MINOR_VERSION_KHR
 #define EGL_CONTEXT_MINOR_VERSION_KHR 0x30FB
@@ -220,6 +223,7 @@ QWaylandGLContext::QWaylandGLContext(EGLDisplay eglDisplay, QWaylandDisplay *dis
     , m_display(display)
     , m_blitter(0)
     , mUseNativeDefaultFbo(false)
+    , mSupportNonBlockingSwap(true)
 {
     QSurfaceFormat fmt = format;
     if (static_cast<QWaylandIntegration *>(QGuiApplicationPrivate::platformIntegration())->display()->supportsWindowDecoration())
@@ -290,6 +294,17 @@ QWaylandGLContext::QWaylandGLContext(EGLDisplay eglDisplay, QWaylandDisplay *dis
         return;
     }
 
+    EGLint a = EGL_MIN_SWAP_INTERVAL;
+    EGLint b = EGL_MAX_SWAP_INTERVAL;
+    if (!eglGetConfigAttrib(m_eglDisplay, m_config, a, &a) ||
+        !eglGetConfigAttrib(m_eglDisplay, m_config, b, &b) ||
+        a > 0) {
+       mSupportNonBlockingSwap = false;
+    }
+    if (!mSupportNonBlockingSwap) {
+        qWarning() << "Non-blocking swap buffers not supported. Subsurface rendering can be affected.";
+    }
+
     updateGLFormat();
 }
 
@@ -518,7 +533,20 @@ void QWaylandGLContext::swapBuffers(QPlatformSurface *surface)
         m_blitter->blit(window);
     }
 
-    eglSwapBuffers(m_eglDisplay, eglSurface);
+
+    QWaylandSubSurface *sub = window->subSurfaceWindow();
+    if (sub) {
+        QMutexLocker l(sub->syncMutex());
+
+        int si = (sub->isSync() && mSupportNonBlockingSwap) ? 0 : m_format.swapInterval();
+
+        eglSwapInterval(m_eglDisplay, si);
+        eglSwapBuffers(m_eglDisplay, eglSurface);
+    } else {
+        eglSwapInterval(m_eglDisplay, m_format.swapInterval());
+        eglSwapBuffers(m_eglDisplay, eglSurface);
+    }
+
 
     window->setCanResize(true);
 }
diff --git a/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.h b/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.h
index bc92c9501..42236c643 100644
--- a/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.h
+++ b/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.h
@@ -86,6 +86,7 @@ private:
     DecorationsBlitter *m_blitter;
     bool mUseNativeDefaultFbo;
     uint m_api;
+    bool mSupportNonBlockingSwap;
 
     friend class DecorationsBlitter;
 };