modules/desktop_capture/linux/x_server_pixel_buffer.cc - src - Git at Google

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "modules/desktop_capture/linux/x_server_pixel_buffer.h"

 #include <X11/Xutil.h>
 #include <stdint.h>
 #include <string.h>
 #include <sys/ipc.h>
 #include <sys/shm.h>

 #include "modules/desktop_capture/desktop_frame.h"
 #include "modules/desktop_capture/linux/window_list_utils.h"
 #include "modules/desktop_capture/linux/x_error_trap.h"
 #include "modules/desktop_capture/linux/x_window_property.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"

 namespace webrtc {

 namespace {

 // Returns the number of bits |mask| has to be shifted left so its last
 // (most-significant) bit set becomes the most-significant bit of the word.
 // When |mask| is 0 the function returns 31.
 uint32_t MaskToShift(uint32_t mask) {
   int shift = 0;
   if ((mask & 0xffff0000u) == 0) {
     mask <<= 16;
     shift += 16;
   }
   if ((mask & 0xff000000u) == 0) {
     mask <<= 8;
     shift += 8;
   }
   if ((mask & 0xf0000000u) == 0) {
     mask <<= 4;
     shift += 4;
   }
   if ((mask & 0xc0000000u) == 0) {
     mask <<= 2;
     shift += 2;
   }
   if ((mask & 0x80000000u) == 0)
     shift += 1;

   return shift;
 }

 // Returns true if |image| is in RGB format.
 bool IsXImageRGBFormat(XImage* image) {
   return image->bits_per_pixel == 32 && image->red_mask == 0xff0000 &&
          image->green_mask == 0xff00 && image->blue_mask == 0xff;
 }

 // We expose two forms of blitting to handle variations in the pixel format.
 // In FastBlit(), the operation is effectively a memcpy.
 void FastBlit(XImage* x_image,
               uint8_t* src_pos,
               const DesktopRect& rect,
               DesktopFrame* frame) {
   RTC_DCHECK_LE(frame->top_left().x(), rect.left());
   RTC_DCHECK_LE(frame->top_left().y(), rect.top());

   int src_stride = x_image->bytes_per_line;
   int dst_x = rect.left() - frame->top_left().x();
   int dst_y = rect.top() - frame->top_left().y();

   uint8_t* dst_pos = frame->data() + frame->stride() * dst_y;
   dst_pos += dst_x * DesktopFrame::kBytesPerPixel;

   int height = rect.height();
   int row_bytes = rect.width() * DesktopFrame::kBytesPerPixel;
   for (int y = 0; y < height; ++y) {
     memcpy(dst_pos, src_pos, row_bytes);
     src_pos += src_stride;
     dst_pos += frame->stride();
   }
 }

 void SlowBlit(XImage* x_image,
               uint8_t* src_pos,
               const DesktopRect& rect,
               DesktopFrame* frame) {
   RTC_DCHECK_LE(frame->top_left().x(), rect.left());
   RTC_DCHECK_LE(frame->top_left().y(), rect.top());

   int src_stride = x_image->bytes_per_line;
   int dst_x = rect.left() - frame->top_left().x();
   int dst_y = rect.top() - frame->top_left().y();
   int width = rect.width(), height = rect.height();

   uint32_t red_mask = x_image->red_mask;
   uint32_t green_mask = x_image->red_mask;
   uint32_t blue_mask = x_image->blue_mask;

   uint32_t red_shift = MaskToShift(red_mask);
   uint32_t green_shift = MaskToShift(green_mask);
   uint32_t blue_shift = MaskToShift(blue_mask);

   int bits_per_pixel = x_image->bits_per_pixel;

   uint8_t* dst_pos = frame->data() + frame->stride() * dst_y;
   dst_pos += dst_x * DesktopFrame::kBytesPerPixel;
   // TODO(hclam): Optimize, perhaps using MMX code or by converting to
   // YUV directly.
   // TODO(sergeyu): This code doesn't handle XImage byte order properly and
   // won't work with 24bpp images. Fix it.
   for (int y = 0; y < height; y++) {
     uint32_t* dst_pos_32 = reinterpret_cast<uint32_t*>(dst_pos);
     uint32_t* src_pos_32 = reinterpret_cast<uint32_t*>(src_pos);
     uint16_t* src_pos_16 = reinterpret_cast<uint16_t*>(src_pos);
     for (int x = 0; x < width; x++) {
       // Dereference through an appropriately-aligned pointer.
       uint32_t pixel;
       if (bits_per_pixel == 32) {
         pixel = src_pos_32[x];
       } else if (bits_per_pixel == 16) {
         pixel = src_pos_16[x];
       } else {
         pixel = src_pos[x];
       }
       uint32_t r = (pixel & red_mask) << red_shift;
       uint32_t g = (pixel & green_mask) << green_shift;
       uint32_t b = (pixel & blue_mask) << blue_shift;
       // Write as 32-bit RGB.
       dst_pos_32[x] =
           ((r >> 8) & 0xff0000) | ((g >> 16) & 0xff00) | ((b >> 24) & 0xff);
     }
     dst_pos += frame->stride();
     src_pos += src_stride;
   }
 }

 }  // namespace

 XServerPixelBuffer::XServerPixelBuffer() {}

 XServerPixelBuffer::~XServerPixelBuffer() {
   Release();
 }

 void XServerPixelBuffer::Release() {
   if (x_image_) {
     XDestroyImage(x_image_);
     x_image_ = nullptr;
   }
   if (x_shm_image_) {
     XDestroyImage(x_shm_image_);
     x_shm_image_ = nullptr;
   }
   if (shm_pixmap_) {
     XFreePixmap(display_, shm_pixmap_);
     shm_pixmap_ = 0;
   }
   if (shm_gc_) {
     XFreeGC(display_, shm_gc_);
     shm_gc_ = nullptr;
   }

   ReleaseSharedMemorySegment();

   window_ = 0;
 }

 void XServerPixelBuffer::ReleaseSharedMemorySegment() {
   if (!shm_segment_info_)
     return;
   if (shm_segment_info_->shmaddr != nullptr)
     shmdt(shm_segment_info_->shmaddr);
   if (shm_segment_info_->shmid != -1)
     shmctl(shm_segment_info_->shmid, IPC_RMID, 0);
   delete shm_segment_info_;
   shm_segment_info_ = nullptr;
 }

 bool XServerPixelBuffer::Init(XAtomCache* cache, Window window) {
   Release();
   display_ = cache->display();

   XWindowAttributes attributes;
   if (!GetWindowRect(display_, window, &window_rect_, &attributes)) {
     return false;
   }

   if (cache->IccProfile() != None) {
     // |window| is the root window when doing screen capture.
     XWindowProperty<uint8_t> icc_profile_property(cache->display(), window,
                                                   cache->IccProfile());
     if (icc_profile_property.is_valid() && icc_profile_property.size() > 0) {
       icc_profile_ = std::vector<uint8_t>(
           icc_profile_property.data(),
           icc_profile_property.data() + icc_profile_property.size());
     } else {
       RTC_LOG(LS_WARNING) << "Failed to get icc profile";
     }
   }

   window_ = window;
   InitShm(attributes);

   return true;
 }

 void XServerPixelBuffer::InitShm(const XWindowAttributes& attributes) {
   Visual* default_visual = attributes.visual;
   int default_depth = attributes.depth;

   int major, minor;
   Bool have_pixmaps;
   if (!XShmQueryVersion(display_, &major, &minor, &have_pixmaps)) {
     // Shared memory not supported. CaptureRect will use the XImage API instead.
     return;
   }

   bool using_shm = false;
   shm_segment_info_ = new XShmSegmentInfo;
   shm_segment_info_->shmid = -1;
   shm_segment_info_->shmaddr = nullptr;
   shm_segment_info_->readOnly = False;
   x_shm_image_ = XShmCreateImage(display_, default_visual, default_depth,
                                  ZPixmap, 0, shm_segment_info_,
                                  window_rect_.width(), window_rect_.height());
   if (x_shm_image_) {
     shm_segment_info_->shmid =
         shmget(IPC_PRIVATE, x_shm_image_->bytes_per_line * x_shm_image_->height,
                IPC_CREAT | 0600);
     if (shm_segment_info_->shmid != -1) {
       void* shmat_result = shmat(shm_segment_info_->shmid, 0, 0);
       if (shmat_result != reinterpret_cast<void*>(-1)) {
         shm_segment_info_->shmaddr = reinterpret_cast<char*>(shmat_result);
         x_shm_image_->data = shm_segment_info_->shmaddr;

         XErrorTrap error_trap(display_);
         using_shm = XShmAttach(display_, shm_segment_info_);
         XSync(display_, False);
         if (error_trap.GetLastErrorAndDisable() != 0)
           using_shm = false;
         if (using_shm) {
           RTC_LOG(LS_VERBOSE)
               << "Using X shared memory segment " << shm_segment_info_->shmid;
         }
       }
     } else {
       RTC_LOG(LS_WARNING) << "Failed to get shared memory segment. "
                              "Performance may be degraded.";
     }
   }

   if (!using_shm) {
     RTC_LOG(LS_WARNING)
         << "Not using shared memory. Performance may be degraded.";
     ReleaseSharedMemorySegment();
     return;
   }

   if (have_pixmaps)
     have_pixmaps = InitPixmaps(default_depth);

   shmctl(shm_segment_info_->shmid, IPC_RMID, 0);
   shm_segment_info_->shmid = -1;

   RTC_LOG(LS_VERBOSE) << "Using X shared memory extension v" << major << "."
                       << minor << " with" << (have_pixmaps ? "" : "out")
                       << " pixmaps.";
 }

 bool XServerPixelBuffer::InitPixmaps(int depth) {
   if (XShmPixmapFormat(display_) != ZPixmap)
     return false;

   {
     XErrorTrap error_trap(display_);
     shm_pixmap_ = XShmCreatePixmap(
         display_, window_, shm_segment_info_->shmaddr, shm_segment_info_,
         window_rect_.width(), window_rect_.height(), depth);
     XSync(display_, False);
     if (error_trap.GetLastErrorAndDisable() != 0) {
       // |shm_pixmap_| is not not valid because the request was not processed
       // by the X Server, so zero it.
       shm_pixmap_ = 0;
       return false;
     }
   }

   {
     XErrorTrap error_trap(display_);
     XGCValues shm_gc_values;
     shm_gc_values.subwindow_mode = IncludeInferiors;
     shm_gc_values.graphics_exposures = False;
     shm_gc_ = XCreateGC(display_, window_,
                         GCSubwindowMode | GCGraphicsExposures, &shm_gc_values);
     XSync(display_, False);
     if (error_trap.GetLastErrorAndDisable() != 0) {
       XFreePixmap(display_, shm_pixmap_);
       shm_pixmap_ = 0;
       shm_gc_ = 0;  // See shm_pixmap_ comment above.
       return false;
     }
   }

   return true;
 }

 bool XServerPixelBuffer::IsWindowValid() const {
   XWindowAttributes attributes;
   {
     XErrorTrap error_trap(display_);
     if (!XGetWindowAttributes(display_, window_, &attributes) ||
         error_trap.GetLastErrorAndDisable() != 0) {
       return false;
     }
   }
   return true;
 }

 void XServerPixelBuffer::Synchronize() {
   if (shm_segment_info_ && !shm_pixmap_) {
     // XShmGetImage can fail if the display is being reconfigured.
     XErrorTrap error_trap(display_);
     // XShmGetImage fails if the window is partially out of screen.
     xshm_get_image_succeeded_ =
         XShmGetImage(display_, window_, x_shm_image_, 0, 0, AllPlanes);
   }
 }

 bool XServerPixelBuffer::CaptureRect(const DesktopRect& rect,
                                      DesktopFrame* frame) {
   RTC_DCHECK_LE(rect.right(), window_rect_.width());
   RTC_DCHECK_LE(rect.bottom(), window_rect_.height());

   XImage* image;
   uint8_t* data;

   if (shm_segment_info_ && (shm_pixmap_ || xshm_get_image_succeeded_)) {
     if (shm_pixmap_) {
       XCopyArea(display_, window_, shm_pixmap_, shm_gc_, rect.left(),
                 rect.top(), rect.width(), rect.height(), rect.left(),
                 rect.top());
       XSync(display_, False);
     }

     image = x_shm_image_;
     data = reinterpret_cast<uint8_t*>(image->data) +
            rect.top() * image->bytes_per_line +
            rect.left() * image->bits_per_pixel / 8;

   } else {
     if (x_image_)
       XDestroyImage(x_image_);
     x_image_ = XGetImage(display_, window_, rect.left(), rect.top(),
                          rect.width(), rect.height(), AllPlanes, ZPixmap);
     if (!x_image_)
       return false;

     image = x_image_;
     data = reinterpret_cast<uint8_t*>(image->data);
   }

   if (IsXImageRGBFormat(image)) {
     FastBlit(image, data, rect, frame);
   } else {
     SlowBlit(image, data, rect, frame);
   }

   if (!icc_profile_.empty())
     frame->set_icc_profile(icc_profile_);

   return true;
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "modules/desktop_capture/linux/x_server_pixel_buffer.h"

	#include <X11/Xutil.h>
	#include <stdint.h>
	#include <string.h>
	#include <sys/ipc.h>
	#include <sys/shm.h>

	#include "modules/desktop_capture/desktop_frame.h"
	#include "modules/desktop_capture/linux/window_list_utils.h"
	#include "modules/desktop_capture/linux/x_error_trap.h"
	#include "modules/desktop_capture/linux/x_window_property.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/logging.h"

	namespace webrtc {

	namespace {

	// Returns the number of bits \|mask\| has to be shifted left so its last
	// (most-significant) bit set becomes the most-significant bit of the word.
	// When \|mask\| is 0 the function returns 31.
	uint32_t MaskToShift(uint32_t mask) {
	int shift = 0;
	if ((mask & 0xffff0000u) == 0) {
	mask <<= 16;
	shift += 16;
	}
	if ((mask & 0xff000000u) == 0) {
	mask <<= 8;
	shift += 8;
	}
	if ((mask & 0xf0000000u) == 0) {
	mask <<= 4;
	shift += 4;
	}
	if ((mask & 0xc0000000u) == 0) {
	mask <<= 2;
	shift += 2;
	}
	if ((mask & 0x80000000u) == 0)
	shift += 1;

	return shift;
	}

	// Returns true if \|image\| is in RGB format.
	bool IsXImageRGBFormat(XImage* image) {
	return image->bits_per_pixel == 32 && image->red_mask == 0xff0000 &&
	image->green_mask == 0xff00 && image->blue_mask == 0xff;
	}

	// We expose two forms of blitting to handle variations in the pixel format.
	// In FastBlit(), the operation is effectively a memcpy.
	void FastBlit(XImage* x_image,
	uint8_t* src_pos,
	const DesktopRect& rect,
	DesktopFrame* frame) {
	RTC_DCHECK_LE(frame->top_left().x(), rect.left());
	RTC_DCHECK_LE(frame->top_left().y(), rect.top());

	int src_stride = x_image->bytes_per_line;
	int dst_x = rect.left() - frame->top_left().x();
	int dst_y = rect.top() - frame->top_left().y();

	uint8_t* dst_pos = frame->data() + frame->stride() * dst_y;
	dst_pos += dst_x * DesktopFrame::kBytesPerPixel;

	int height = rect.height();
	int row_bytes = rect.width() * DesktopFrame::kBytesPerPixel;
	for (int y = 0; y < height; ++y) {
	memcpy(dst_pos, src_pos, row_bytes);
	src_pos += src_stride;
	dst_pos += frame->stride();
	}
	}

	void SlowBlit(XImage* x_image,
	uint8_t* src_pos,
	const DesktopRect& rect,
	DesktopFrame* frame) {
	RTC_DCHECK_LE(frame->top_left().x(), rect.left());
	RTC_DCHECK_LE(frame->top_left().y(), rect.top());

	int src_stride = x_image->bytes_per_line;
	int dst_x = rect.left() - frame->top_left().x();
	int dst_y = rect.top() - frame->top_left().y();
	int width = rect.width(), height = rect.height();

	uint32_t red_mask = x_image->red_mask;
	uint32_t green_mask = x_image->red_mask;
	uint32_t blue_mask = x_image->blue_mask;

	uint32_t red_shift = MaskToShift(red_mask);
	uint32_t green_shift = MaskToShift(green_mask);
	uint32_t blue_shift = MaskToShift(blue_mask);

	int bits_per_pixel = x_image->bits_per_pixel;

	uint8_t* dst_pos = frame->data() + frame->stride() * dst_y;
	dst_pos += dst_x * DesktopFrame::kBytesPerPixel;
	// TODO(hclam): Optimize, perhaps using MMX code or by converting to
	// YUV directly.
	// TODO(sergeyu): This code doesn't handle XImage byte order properly and
	// won't work with 24bpp images. Fix it.
	for (int y = 0; y < height; y++) {
	uint32_t* dst_pos_32 = reinterpret_cast<uint32_t*>(dst_pos);
	uint32_t* src_pos_32 = reinterpret_cast<uint32_t*>(src_pos);
	uint16_t* src_pos_16 = reinterpret_cast<uint16_t*>(src_pos);
	for (int x = 0; x < width; x++) {
	// Dereference through an appropriately-aligned pointer.
	uint32_t pixel;
	if (bits_per_pixel == 32) {
	pixel = src_pos_32[x];
	} else if (bits_per_pixel == 16) {
	pixel = src_pos_16[x];
	} else {
	pixel = src_pos[x];
	}
	uint32_t r = (pixel & red_mask) << red_shift;
	uint32_t g = (pixel & green_mask) << green_shift;
	uint32_t b = (pixel & blue_mask) << blue_shift;
	// Write as 32-bit RGB.
	dst_pos_32[x] =
	((r >> 8) & 0xff0000) \| ((g >> 16) & 0xff00) \| ((b >> 24) & 0xff);
	}
	dst_pos += frame->stride();
	src_pos += src_stride;
	}
	}

	} // namespace

	XServerPixelBuffer::XServerPixelBuffer() {}

	XServerPixelBuffer::~XServerPixelBuffer() {
	Release();
	}

	void XServerPixelBuffer::Release() {
	if (x_image_) {
	XDestroyImage(x_image_);
	x_image_ = nullptr;
	}
	if (x_shm_image_) {
	XDestroyImage(x_shm_image_);
	x_shm_image_ = nullptr;
	}
	if (shm_pixmap_) {
	XFreePixmap(display_, shm_pixmap_);
	shm_pixmap_ = 0;
	}
	if (shm_gc_) {
	XFreeGC(display_, shm_gc_);
	shm_gc_ = nullptr;
	}

	ReleaseSharedMemorySegment();

	window_ = 0;
	}

	void XServerPixelBuffer::ReleaseSharedMemorySegment() {
	if (!shm_segment_info_)
	return;
	if (shm_segment_info_->shmaddr != nullptr)
	shmdt(shm_segment_info_->shmaddr);
	if (shm_segment_info_->shmid != -1)
	shmctl(shm_segment_info_->shmid, IPC_RMID, 0);
	delete shm_segment_info_;
	shm_segment_info_ = nullptr;
	}

	bool XServerPixelBuffer::Init(XAtomCache* cache, Window window) {
	Release();
	display_ = cache->display();

	XWindowAttributes attributes;
	if (!GetWindowRect(display_, window, &window_rect_, &attributes)) {
	return false;
	}

	if (cache->IccProfile() != None) {
	// \|window\| is the root window when doing screen capture.
	XWindowProperty<uint8_t> icc_profile_property(cache->display(), window,
	cache->IccProfile());
	if (icc_profile_property.is_valid() && icc_profile_property.size() > 0) {
	icc_profile_ = std::vector<uint8_t>(
	icc_profile_property.data(),
	icc_profile_property.data() + icc_profile_property.size());
	} else {
	RTC_LOG(LS_WARNING) << "Failed to get icc profile";
	}
	}

	window_ = window;
	InitShm(attributes);

	return true;
	}

	void XServerPixelBuffer::InitShm(const XWindowAttributes& attributes) {
	Visual* default_visual = attributes.visual;
	int default_depth = attributes.depth;

	int major, minor;
	Bool have_pixmaps;
	if (!XShmQueryVersion(display_, &major, &minor, &have_pixmaps)) {
	// Shared memory not supported. CaptureRect will use the XImage API instead.
	return;
	}

	bool using_shm = false;
	shm_segment_info_ = new XShmSegmentInfo;
	shm_segment_info_->shmid = -1;
	shm_segment_info_->shmaddr = nullptr;
	shm_segment_info_->readOnly = False;
	x_shm_image_ = XShmCreateImage(display_, default_visual, default_depth,
	ZPixmap, 0, shm_segment_info_,
	window_rect_.width(), window_rect_.height());
	if (x_shm_image_) {
	shm_segment_info_->shmid =
	shmget(IPC_PRIVATE, x_shm_image_->bytes_per_line * x_shm_image_->height,
	IPC_CREAT \| 0600);
	if (shm_segment_info_->shmid != -1) {
	void* shmat_result = shmat(shm_segment_info_->shmid, 0, 0);
	if (shmat_result != reinterpret_cast<void*>(-1)) {
	shm_segment_info_->shmaddr = reinterpret_cast<char*>(shmat_result);
	x_shm_image_->data = shm_segment_info_->shmaddr;

	XErrorTrap error_trap(display_);
	using_shm = XShmAttach(display_, shm_segment_info_);
	XSync(display_, False);
	if (error_trap.GetLastErrorAndDisable() != 0)
	using_shm = false;
	if (using_shm) {
	RTC_LOG(LS_VERBOSE)
	<< "Using X shared memory segment " << shm_segment_info_->shmid;
	}
	}
	} else {
	RTC_LOG(LS_WARNING) << "Failed to get shared memory segment. "
	"Performance may be degraded.";
	}
	}

	if (!using_shm) {
	RTC_LOG(LS_WARNING)
	<< "Not using shared memory. Performance may be degraded.";
	ReleaseSharedMemorySegment();
	return;
	}

	if (have_pixmaps)
	have_pixmaps = InitPixmaps(default_depth);

	shmctl(shm_segment_info_->shmid, IPC_RMID, 0);
	shm_segment_info_->shmid = -1;

	RTC_LOG(LS_VERBOSE) << "Using X shared memory extension v" << major << "."
	<< minor << " with" << (have_pixmaps ? "" : "out")
	<< " pixmaps.";
	}

	bool XServerPixelBuffer::InitPixmaps(int depth) {
	if (XShmPixmapFormat(display_) != ZPixmap)
	return false;

	{
	XErrorTrap error_trap(display_);
	shm_pixmap_ = XShmCreatePixmap(
	display_, window_, shm_segment_info_->shmaddr, shm_segment_info_,
	window_rect_.width(), window_rect_.height(), depth);
	XSync(display_, False);
	if (error_trap.GetLastErrorAndDisable() != 0) {
	// \|shm_pixmap_\| is not not valid because the request was not processed
	// by the X Server, so zero it.
	shm_pixmap_ = 0;
	return false;
	}
	}

	{
	XErrorTrap error_trap(display_);
	XGCValues shm_gc_values;
	shm_gc_values.subwindow_mode = IncludeInferiors;
	shm_gc_values.graphics_exposures = False;
	shm_gc_ = XCreateGC(display_, window_,
	GCSubwindowMode \| GCGraphicsExposures, &shm_gc_values);
	XSync(display_, False);
	if (error_trap.GetLastErrorAndDisable() != 0) {
	XFreePixmap(display_, shm_pixmap_);
	shm_pixmap_ = 0;
	shm_gc_ = 0; // See shm_pixmap_ comment above.
	return false;
	}
	}

	return true;
	}

	bool XServerPixelBuffer::IsWindowValid() const {
	XWindowAttributes attributes;
	{
	XErrorTrap error_trap(display_);
	if (!XGetWindowAttributes(display_, window_, &attributes) \|\|
	error_trap.GetLastErrorAndDisable() != 0) {
	return false;
	}
	}
	return true;
	}

	void XServerPixelBuffer::Synchronize() {
	if (shm_segment_info_ && !shm_pixmap_) {
	// XShmGetImage can fail if the display is being reconfigured.
	XErrorTrap error_trap(display_);
	// XShmGetImage fails if the window is partially out of screen.
	xshm_get_image_succeeded_ =
	XShmGetImage(display_, window_, x_shm_image_, 0, 0, AllPlanes);
	}
	}

	bool XServerPixelBuffer::CaptureRect(const DesktopRect& rect,
	DesktopFrame* frame) {
	RTC_DCHECK_LE(rect.right(), window_rect_.width());
	RTC_DCHECK_LE(rect.bottom(), window_rect_.height());

	XImage* image;
	uint8_t* data;

	if (shm_segment_info_ && (shm_pixmap_ \|\| xshm_get_image_succeeded_)) {
	if (shm_pixmap_) {
	XCopyArea(display_, window_, shm_pixmap_, shm_gc_, rect.left(),
	rect.top(), rect.width(), rect.height(), rect.left(),
	rect.top());
	XSync(display_, False);
	}

	image = x_shm_image_;
	data = reinterpret_cast<uint8_t*>(image->data) +
	rect.top() * image->bytes_per_line +
	rect.left() * image->bits_per_pixel / 8;

	} else {
	if (x_image_)
	XDestroyImage(x_image_);
	x_image_ = XGetImage(display_, window_, rect.left(), rect.top(),
	rect.width(), rect.height(), AllPlanes, ZPixmap);
	if (!x_image_)
	return false;

	image = x_image_;
	data = reinterpret_cast<uint8_t*>(image->data);
	}

	if (IsXImageRGBFormat(image)) {
	FastBlit(image, data, rect, frame);
	} else {
	SlowBlit(image, data, rect, frame);
	}

	if (!icc_profile_.empty())
	frame->set_icc_profile(icc_profile_);

	return true;
	}

	} // namespace webrtc