Linux: server side backing stores

chrome/common/x11_util.cc

Index: chrome/common/x11_util.cc
diff --git a/chrome/common/x11_util.cc b/chrome/common/x11_util.cc
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+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file defines utility functions for X11 (Linux only). This code has been
+// ported from XCB since we can't use XCB on Ubuntu while its 32-bit support
+// remains woefully incomplete.
+
+#include "chrome/common/x11_util.h"
+#include "chrome/common/x11_util_internal.h"
+
+#include <string.h>
+
+#include <gdk/gdk.h>
+#include <gdk/gdkx.h>
+#include <gtk/gtk.h>
+
+#include <sys/ipc.h>
+#include <sys/shm.h>
+
+#include "base/logging.h"
+#include "base/gfx/size.h"
+
+namespace x11_util {
+
+Display* GetXDisplay() {
+  static Display* display = NULL;
+
+  if (!display)
+    display = gdk_x11_get_default_xdisplay();
+
+  return display;
+}
+
+static bool DoQuerySharedMemorySupport(Display* dpy) {
+  int dummy;
+  Bool pixmaps_supported;
+  // Query the server's support for shared memory
+  if (!XShmQueryVersion(dpy, &dummy, &dummy, &pixmaps_supported))
+    return false;
+  // If the server doesn't support shared memory, give up. (Note that if
+  // |shared_pixmaps| is true, it just means that the server /supports/ shared
+  // memory, not that it will work on this connection.)
+  if (!pixmaps_supported)
+    return false;
+
+  // Next we probe to see if shared memory will really work
+  int shmkey = shmget(IPC_PRIVATE, 1, 0666);
+  if (shmkey == -1)
+    return false;
+  void* address = shmat(shmkey, NULL, 0);
+  // Mark the shared memory region for deletion
+  shmctl(shmkey, IPC_RMID, NULL);
+
+  XShmSegmentInfo shminfo;
+  memset(&shminfo, 0, sizeof(shminfo));
+  shminfo.shmid = shmkey;
+
+  gdk_error_trap_push();
+  bool result = XShmAttach(dpy, &shminfo);
+  XSync(dpy, False);
+  if (gdk_error_trap_pop())
+    result = false;
+  shmdt(address);
+  if (!result)
+    return false;
+
+  XShmDetach(dpy, &shminfo);
+  return true;
+}
+
+bool QuerySharedMemorySupport(Display* dpy) {
+  static bool shared_memory_support = false;
+  static bool shared_memory_support_cached = false;
+
+  if (shared_memory_support_cached)
+    return shared_memory_support;
+
+  shared_memory_support = DoQuerySharedMemorySupport(dpy);
+  shared_memory_support_cached = true;
+
+  return shared_memory_support;
+}
+
+XID GetX11WindowFromGtkWidget(GtkWidget* widget) {
+  return GDK_WINDOW_XID(widget->window);
+}
+
+void* GetVisualFromGtkWidget(GtkWidget* widget) {
+  return GDK_VISUAL_XVISUAL(gtk_widget_get_visual(widget));
+}
+
+XRenderPictFormat* GetRenderVisualFormat(Display* dpy, Visual* visual) {
+  static XRenderPictFormat* pictformat = NULL;
+  if (pictformat)
+    return pictformat;
+
+  int dummy;
+  if (!XRenderQueryExtension(dpy, &dummy, &dummy))
+    CHECK(false) << "XRENDER not supported on display";
+
+  pictformat = XRenderFindVisualFormat(dpy, visual);
+  CHECK(pictformat) << "XRENDER does not support default visual";
+
+  return pictformat;
+}
+
+XRenderPictFormat* GetRenderARGB32Format(Display* dpy) {
+  static XRenderPictFormat* pictformat = NULL;
+  if (pictformat)
+    return pictformat;
+
+  // First look for a 32-bit format which ignores the alpha value
+  XRenderPictFormat templ;
+  templ.depth = 32;
+  templ.type = PictTypeDirect;
+  templ.direct.red = 0;
+  templ.direct.green = 8;
+  templ.direct.blue = 16;
+  templ.direct.redMask = 0xff;
+  templ.direct.greenMask = 0xff;
+  templ.direct.blueMask = 0xff;
+  templ.direct.alphaMask = 0;
+
+  static const unsigned long kMask =
+    PictFormatType | PictFormatDepth |
+    PictFormatRed | PictFormatRedMask |
+    PictFormatGreen | PictFormatGreenMask |
+    PictFormatBlue | PictFormatBlueMask |
+    PictFormatAlphaMask;
+
+  pictformat = XRenderFindFormat(dpy, kMask, &templ, 0 /* first result */);
+  CHECK(pictformat) << "XRENDER doesn't not support a Skia compatable format";
+  // TODO(agl): fallback to a picture format with an alpha channel
+
+  return pictformat;
+}
+
+XID AttachSharedMemory(Display* display, int shared_memory_key) {
+  DCHECK(QuerySharedMemorySupport(display));
+
+  XShmSegmentInfo shminfo;
+  memset(&shminfo, 0, sizeof(shminfo));
+  shminfo.shmid = shared_memory_key;
+
+  // This function is only called if QuerySharedMemorySupport returned true. In
+  // which case we've already succeeded in having the X server attach to one of
+  // our shared memory segments.
+  if (!XShmAttach(display, &shminfo))
+    NOTREACHED();
+
+  return shminfo.shmseg;
+}
+
+void DetachSharedMemory(Display* display, XID shmseg) {
+  DCHECK(QuerySharedMemorySupport(display));
+
+  XShmSegmentInfo shminfo;
+  memset(&shminfo, 0, sizeof(shminfo));
+  shminfo.shmseg = shmseg;
+
+  if (!XShmDetach(display, &shminfo))
+    NOTREACHED();
+}
+
+XID CreatePictureFromSkiaPixmap(Display* display, XID pixmap) {
+  XID picture = XRenderCreatePicture(
+      display, pixmap, GetRenderARGB32Format(display), 0, NULL);
+
+  return picture;
+}
+
+void FreePicture(Display* display, XID picture) {
+  XRenderFreePicture(display, picture);
+}
+
+void FreePixmap(Display* display, XID pixmap) {
+  XFreePixmap(display, pixmap);
+}
+
+}  // namespace x11_util