Use shared memory images when shared pixmaps are not available.

Modern graphics drivers tend to disable shared memory pixmaps,
since rendering operations often can't be accelerated by the
GPU when the pixmap data is pinned in system RAM.

Use XShmPutImage() to flush the window surface when this is case,
instead of falling back to the slower XPutImage() method.

Merge-request: 1684
Reviewed-by: Samuel Rødal <sroedal@trolltech.com>

4 files changed, 21 insertions, 10 deletions

diff --git a/src/gui/image/qnativeimage.cpp b/src/gui/image/qnativeimage.cpp
index 88faea8..e4ea2e9 100644
--- a/src/gui/image/qnativeimage.cpp
+++ b/src/gui/image/qnativeimage.cpp
@@ -199,10 +199,12 @@ QNativeImage::QNativeImage(int width, int height, QImage::Format format,bool /*
             shmctl(xshminfo.shmid, IPC_RMID, 0);
         return;
     }
-    xshmpm = XShmCreatePixmap(X11->display, DefaultRootWindow(X11->display), xshmimg->data,
-                              &xshminfo, width, height, dd);
-    if (!xshmpm) {
-        qWarning() << "QNativeImage: Unable to create shared Pixmap.";
+    if (X11->use_mitshm_pixmaps) {
+        xshmpm = XShmCreatePixmap(X11->display, DefaultRootWindow(X11->display), xshmimg->data,
+                                  &xshminfo, width, height, dd);
+        if (!xshmpm) {
+            qWarning() << "QNativeImage: Unable to create shared Pixmap.";
+        }
     }
 }
 
diff --git a/src/gui/kernel/qapplication_x11.cpp b/src/gui/kernel/qapplication_x11.cpp
index bf95684..7f11faa 100644
--- a/src/gui/kernel/qapplication_x11.cpp
+++ b/src/gui/kernel/qapplication_x11.cpp
@@ -1625,6 +1625,7 @@ void qt_init(QApplicationPrivate *priv, int,
 
     // MIT-SHM
     X11->use_mitshm = false;
+    X11->use_mitshm_pixmaps = false;
     X11->mitshm_major = 0;
 
     X11->sip_serial = 0;
@@ -1918,12 +1919,13 @@ void qt_init(QApplicationPrivate *priv, int,
             bool local = displayName.isEmpty() || displayName.lastIndexOf(QLatin1Char(':')) == 0;
             if (local && (qgetenv("QT_X11_NO_MITSHM").toInt() == 0)) {
                 Visual *defaultVisual = DefaultVisual(X11->display, DefaultScreen(X11->display));
-                X11->use_mitshm = mitshm_pixmaps && ((defaultVisual->red_mask == 0xff0000
-                                                      || defaultVisual->red_mask == 0xf800)
-                                                     && (defaultVisual->green_mask == 0xff00
-                                                         || defaultVisual->green_mask == 0x7e0)
-                                                     && (defaultVisual->blue_mask == 0xff
-                                                         || defaultVisual->blue_mask == 0x1f));
+                X11->use_mitshm = ((defaultVisual->red_mask == 0xff0000
+                                    || defaultVisual->red_mask == 0xf800)
+                                   && (defaultVisual->green_mask == 0xff00
+                                       || defaultVisual->green_mask == 0x7e0)
+                                   && (defaultVisual->blue_mask == 0xff
+                                       || defaultVisual->blue_mask == 0x1f));
+                X11->use_mitshm_pixmaps = X11->use_mitshm && mitshm_pixmaps;
             }
         }
 #endif // QT_NO_MITSHM
diff --git a/src/gui/kernel/qt_x11_p.h b/src/gui/kernel/qt_x11_p.h
index 61acbac..9f08dc6 100644
--- a/src/gui/kernel/qt_x11_p.h
+++ b/src/gui/kernel/qt_x11_p.h
@@ -428,6 +428,7 @@ struct QX11Data
 
     // true if Qt is compiled w/ MIT-SHM support and MIT-SHM is supported on the connected Display
     bool use_mitshm;
+    bool use_mitshm_pixmaps;
     int mitshm_major;
 
     // true if Qt is compiled w/ Tablet support and we have a tablet.
diff --git a/src/gui/painting/qwindowsurface_raster.cpp b/src/gui/painting/qwindowsurface_raster.cpp
index 3a118bd..d412040 100644
--- a/src/gui/painting/qwindowsurface_raster.cpp
+++ b/src/gui/painting/qwindowsurface_raster.cpp
@@ -215,6 +215,12 @@ void QRasterWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoi
         XCopyArea(X11->display, d_ptr->image->xshmpm, widget->handle(), d_ptr->gc,
                   br.x(), br.y(), br.width(), br.height(), wbr.x(), wbr.y());
         XSync(X11->display, False);
+    } else if (d_ptr->image->xshmimg) {
+        const QImage &src = d->image->image;
+        br = br.intersected(src.rect());
+        XShmPutImage(X11->display, widget->handle(), d_ptr->gc, d_ptr->image->xshmimg,
+                     br.x(), br.y(), wbr.x(), wbr.y(), br.width(), br.height(), False);
+        XSync(X11->display, False);
     } else
 #endif
     {