3 files changed, 30 insertions, 22 deletions

diff --git a/src/plugins/platforms/eglfs/qeglfscontext.cpp b/src/plugins/platforms/eglfs/qeglfscontext.cpp
index 06db4e02db..44bc9b2344 100644
--- a/src/plugins/platforms/eglfs/qeglfscontext.cpp
+++ b/src/plugins/platforms/eglfs/qeglfscontext.cpp
@@ -79,6 +79,7 @@ void QEglFSContext::swapBuffers(QPlatformSurface *surface)
             cursor->paintOnScreen();
     }
 
+    hooks->waitForVSync();
     QEGLPlatformContext::swapBuffers(surface);
 }
 
diff --git a/src/plugins/platforms/eglfs/qeglfshooks.h b/src/plugins/platforms/eglfs/qeglfshooks.h
index f3b6a28e70..fc1ee16073 100644
--- a/src/plugins/platforms/eglfs/qeglfshooks.h
+++ b/src/plugins/platforms/eglfs/qeglfshooks.h
@@ -69,6 +69,7 @@ public:
     virtual bool hasCapability(QPlatformIntegration::Capability cap) const;
     virtual QEglFSCursor *createCursor(QEglFSScreen *screen) const;
     virtual bool filterConfig(EGLDisplay display, EGLConfig config) const;
+    virtual void waitForVSync() const;
 
     virtual const char *fbDeviceName() const;
 };
diff --git a/src/plugins/platforms/eglfs/qeglfshooks_stub.cpp b/src/plugins/platforms/eglfs/qeglfshooks_stub.cpp
index a8fa81a6ec..6c036cd680 100644
--- a/src/plugins/platforms/eglfs/qeglfshooks_stub.cpp
+++ b/src/plugins/platforms/eglfs/qeglfshooks_stub.cpp
@@ -47,9 +47,14 @@
 #include <sys/ioctl.h>
 
 #include <private/qmath_p.h>
+#include <private/qcore_unix_p.h>
 
 QT_BEGIN_NAMESPACE
 
+// file descriptor for the frame buffer
+// this is a global static to keep the QEglFSHooks interface as clean as possible
+static int framebuffer = -1;
+
 const char *QEglFSHooks::fbDeviceName() const
 {
     return "/dev/fb0";
@@ -58,10 +63,17 @@ const char *QEglFSHooks::fbDeviceName() const
 void QEglFSHooks::platformInit()
 {
     Q_UNUSED(hooks);
+
+    framebuffer = qt_safe_open(fbDeviceName(), O_RDONLY);
+
+    if (framebuffer == -1)
+        qWarning("EGLFS: Failed to open %s", fbDeviceName());
 }
 
 void QEglFSHooks::platformDestroy()
 {
+    if (framebuffer != -1)
+        close(framebuffer);
 }
 
 EGLNativeDisplayType QEglFSHooks::platformDisplay() const
@@ -86,22 +98,16 @@ QSizeF QEglFSHooks::physicalScreenSize() const
         }
 
         struct fb_var_screeninfo vinfo;
-        int fd = open(fbDeviceName(), O_RDONLY);
-
         int w = -1;
         int h = -1;
 
-        if (fd != -1) {
-            if (ioctl(fd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
+        if (framebuffer != -1) {
+            if (ioctl(framebuffer, FBIOGET_VSCREENINFO, &vinfo) == -1) {
                 qWarning("EGLFS: Could not query variable screen info.");
             } else {
                 w = vinfo.width;
                 h = vinfo.height;
             }
-
-            close(fd);
-        } else {
-            qWarning("EGLFS: Failed to open %s to detect physical screen size.", fbDeviceName());
         }
 
         const int defaultPhysicalDpi = 100;
@@ -140,22 +146,17 @@ QSize QEglFSHooks::screenSize() const
         }
 
         struct fb_var_screeninfo vinfo;
-        int fd = open(fbDeviceName(), O_RDONLY);
 
         int xres = -1;
         int yres = -1;
 
-        if (fd != -1) {
-            if (ioctl(fd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
+        if (framebuffer != -1) {
+            if (ioctl(framebuffer, FBIOGET_VSCREENINFO, &vinfo) == -1) {
                 qWarning("EGLFS: Could not query variable screen info.");
             } else {
                 xres = vinfo.xres;
                 yres = vinfo.yres;
             }
-
-            close(fd);
-        } else {
-            qWarning("EGLFS: Failed to open %s to detect screen resolution.", fbDeviceName());
         }
 
         const int defaultWidth = 800;
@@ -185,17 +186,12 @@ int QEglFSHooks::screenDepth() const
 
     if (depth == 0) {
         struct fb_var_screeninfo vinfo;
-        int fd = open(fbDeviceName(), O_RDONLY);
 
-        if (fd != -1) {
-            if (ioctl(fd, FBIOGET_VSCREENINFO, &vinfo) == -1)
+        if (framebuffer != -1) {
+            if (ioctl(framebuffer, FBIOGET_VSCREENINFO, &vinfo) == -1)
                 qWarning("EGLFS: Could not query variable screen info.");
             else
                 depth = vinfo.bits_per_pixel;
-
-            close(fd);
-        } else {
-            qWarning("EGLFS: Failed to open %s to detect screen depth.", fbDeviceName());
         }
 
         const int defaultDepth = 32;
@@ -250,6 +246,16 @@ QEglFSCursor *QEglFSHooks::createCursor(QEglFSScreen *screen) const
     return 0;
 }
 
+void QEglFSHooks::waitForVSync() const
+{
+    static const bool forceSync = qgetenv("QT_QPA_EGLFS_FORCEVSYNC").toInt();
+    if (forceSync && framebuffer != -1) {
+        int arg = 0;
+        if (ioctl(framebuffer, FBIO_WAITFORVSYNC, &arg) == -1)
+            qWarning("Could not wait for vsync.");
+    }
+}
+
 #ifndef EGLFS_PLATFORM_HOOKS
 QEglFSHooks stubHooks;
 #endif