widget/nsShmImage.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  *
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "nsShmImage.h"
   8
   9 #ifdef MOZ_HAVE_SHMIMAGE
  10 #  include "mozilla/X11Util.h"
  11 #  include "mozilla/gfx/gfxVars.h"
  12 #  include "mozilla/ipc/SharedMemory.h"
  13 #  include "gfxPlatform.h"
  14 #  include "nsPrintfCString.h"
  15 #  include "nsTArray.h"
  16
  17 #  include <dlfcn.h>
  18 #  include <errno.h>
  19 #  include <string.h>
  20 #  include <sys/ipc.h>
  21 #  include <sys/shm.h>
  22
  23 extern "C" {
  24 #  include <X11/ImUtil.h>
  25 }
  26
  27 using namespace mozilla::ipc;
  28 using namespace mozilla::gfx;
  29
  30 nsShmImage::nsShmImage(Display* aDisplay, Drawable aWindow, Visual* aVisual,
  31                        unsigned int aDepth)
  32     : mDisplay(aDisplay),
  33       mConnection(XGetXCBConnection(aDisplay)),
  34       mWindow(aWindow),
  35       mVisual(aVisual),
  36       mDepth(aDepth),
  37       mFormat(mozilla::gfx::SurfaceFormat::UNKNOWN),
  38       mSize(0, 0),
  39       mStride(0),
  40       mPixmap(XCB_NONE),
  41       mGC(XCB_NONE),
  42       mRequestPending(false),
  43       mShmSeg(XCB_NONE),
  44       mShmId(-1),
  45       mShmAddr(nullptr) {
  46   mozilla::PodZero(&mSyncRequest);
  47 }
  48
  49 nsShmImage::~nsShmImage() { DestroyImage(); }
  50
  51 // If XShm isn't available to our client, we'll try XShm once, fail,
  52 // set this to false and then never try again.
  53 static bool gShmAvailable = true;
  54 bool nsShmImage::UseShm() { return gShmAvailable; }
  55
  56 bool nsShmImage::CreateShmSegment() {
  57   size_t size = SharedMemory::PageAlignedSize(mStride * mSize.height);
  58
  59 #  if defined(__OpenBSD__) && defined(MOZ_SANDBOX)
  60   static mozilla::LazyLogModule sPledgeLog("SandboxPledge");
  61   MOZ_LOG(sPledgeLog, mozilla::LogLevel::Debug,
  62           ("%s called when pledged, returning false\n", __func__));
  63   return false;
  64 #  endif
  65   mShmId = shmget(IPC_PRIVATE, size, IPC_CREAT | 0600);
  66   if (mShmId == -1) {
  67     return false;
  68   }
  69   mShmAddr = (uint8_t*)shmat(mShmId, nullptr, 0);
  70   mShmSeg = xcb_generate_id(mConnection);
  71
  72   // Mark the handle removed so that it will destroy the segment when unmapped.
  73   shmctl(mShmId, IPC_RMID, nullptr);
  74
  75   if (mShmAddr == (void*)-1) {
  76     // Since mapping failed, the segment is already destroyed.
  77     mShmId = -1;
  78
  79     nsPrintfCString warning("shmat(): %s (%d)\n", strerror(errno), errno);
  80     NS_WARNING(warning.get());
  81     return false;
  82   }
  83
  84 #  ifdef DEBUG
  85   struct shmid_ds info;
  86   if (shmctl(mShmId, IPC_STAT, &info) < 0) {
  87     return false;
  88   }
  89
  90   MOZ_ASSERT(size <= info.shm_segsz, "Segment doesn't have enough space!");
  91 #  endif
  92
  93   return true;
  94 }
  95
  96 void nsShmImage::DestroyShmSegment() {
  97   if (mShmId != -1) {
  98     shmdt(mShmAddr);
  99     mShmId = -1;
 100   }
 101 }
 102
 103 static bool gShmInitialized = false;
 104 static bool gUseShmPixmaps = false;
 105
 106 bool nsShmImage::InitExtension() {
 107   if (gShmInitialized) {
 108     return gShmAvailable;
 109   }
 110
 111   gShmInitialized = true;
 112
 113   // Bugs 1397918, 1293474 - race condition in libxcb fixed upstream as of
 114   // version 1.11. Since we can't query libxcb's version directly, the only
 115   // other option is to check for symbols that were added after 1.11.
 116   // xcb_discard_reply64 was added in 1.11.1, so check for existence of
 117   // that to verify we are using a version of libxcb with the bug fixed.
 118   // Otherwise, we can't risk using libxcb due to aforementioned crashes.
 119   if (!dlsym(RTLD_DEFAULT, "xcb_discard_reply64")) {
 120     gShmAvailable = false;
 121     return false;
 122   }
 123
 124   const xcb_query_extension_reply_t* extReply;
 125   extReply = xcb_get_extension_data(mConnection, &xcb_shm_id);
 126   if (!extReply || !extReply->present) {
 127     gShmAvailable = false;
 128     return false;
 129   }
 130
 131   xcb_shm_query_version_reply_t* shmReply = xcb_shm_query_version_reply(
 132       mConnection, xcb_shm_query_version(mConnection), nullptr);
 133
 134   if (!shmReply) {
 135     gShmAvailable = false;
 136     return false;
 137   }
 138
 139   gUseShmPixmaps = shmReply->shared_pixmaps &&
 140                    shmReply->pixmap_format == XCB_IMAGE_FORMAT_Z_PIXMAP;
 141
 142   free(shmReply);
 143
 144   return true;
 145 }
 146
 147 bool nsShmImage::CreateImage(const IntSize& aSize) {
 148   MOZ_ASSERT(mConnection && mVisual);
 149
 150   if (!InitExtension()) {
 151     return false;
 152   }
 153
 154   mSize = aSize;
 155
 156   BackendType backend = gfxVars::ContentBackend();
 157
 158   mFormat = SurfaceFormat::UNKNOWN;
 159   switch (mDepth) {
 160     case 32:
 161       if (mVisual->red_mask == 0xff0000 && mVisual->green_mask == 0xff00 &&
 162           mVisual->blue_mask == 0xff) {
 163         mFormat = SurfaceFormat::B8G8R8A8;
 164       }
 165       break;
 166     case 24:
 167       // Only support the BGRX layout, and report it as BGRA to the compositor.
 168       // The alpha channel will be discarded when we put the image.
 169       // Cairo/pixman lacks some fast paths for compositing BGRX onto BGRA, so
 170       // just report it as BGRX directly in that case.
 171       if (mVisual->red_mask == 0xff0000 && mVisual->green_mask == 0xff00 &&
 172           mVisual->blue_mask == 0xff) {
 173         mFormat = backend == BackendType::CAIRO ? SurfaceFormat::B8G8R8X8
 174                                                 : SurfaceFormat::B8G8R8A8;
 175       }
 176       break;
 177     case 16:
 178       if (mVisual->red_mask == 0xf800 && mVisual->green_mask == 0x07e0 &&
 179           mVisual->blue_mask == 0x1f) {
 180         mFormat = SurfaceFormat::R5G6B5_UINT16;
 181       }
 182       break;
 183   }
 184
 185   if (mFormat == SurfaceFormat::UNKNOWN) {
 186     NS_WARNING("Unsupported XShm Image format!");
 187     gShmAvailable = false;
 188     return false;
 189   }
 190
 191   // Round up stride to the display's scanline pad (in bits) as XShm expects.
 192   int scanlinePad = _XGetScanlinePad(mDisplay, mDepth);
 193   int bitsPerPixel = _XGetBitsPerPixel(mDisplay, mDepth);
 194   int bitsPerLine =
 195       ((bitsPerPixel * aSize.width + scanlinePad - 1) / scanlinePad) *
 196       scanlinePad;
 197   mStride = bitsPerLine / 8;
 198
 199   if (!CreateShmSegment()) {
 200     DestroyImage();
 201     return false;
 202   }
 203
 204   xcb_generic_error_t* error;
 205   xcb_void_cookie_t cookie;
 206
 207   cookie = xcb_shm_attach_checked(mConnection, mShmSeg, mShmId, 0);
 208
 209   if ((error = xcb_request_check(mConnection, cookie))) {
 210     NS_WARNING("Failed to attach MIT-SHM segment.");
 211     DestroyImage();
 212     gShmAvailable = false;
 213     free(error);
 214     return false;
 215   }
 216
 217   if (gUseShmPixmaps) {
 218     mPixmap = xcb_generate_id(mConnection);
 219     cookie = xcb_shm_create_pixmap_checked(mConnection, mPixmap, mWindow,
 220                                            aSize.width, aSize.height, mDepth,
 221                                            mShmSeg, 0);
 222
 223     if ((error = xcb_request_check(mConnection, cookie))) {
 224       // Disable shared pixmaps permanently if creation failed.
 225       mPixmap = XCB_NONE;
 226       gUseShmPixmaps = false;
 227       free(error);
 228     }
 229   }
 230
 231   return true;
 232 }
 233
 234 void nsShmImage::DestroyImage() {
 235   if (mGC) {
 236     xcb_free_gc(mConnection, mGC);
 237     mGC = XCB_NONE;
 238   }
 239   if (mPixmap != XCB_NONE) {
 240     xcb_free_pixmap(mConnection, mPixmap);
 241     mPixmap = XCB_NONE;
 242   }
 243   if (mShmSeg != XCB_NONE) {
 244     xcb_shm_detach_checked(mConnection, mShmSeg);
 245     mShmSeg = XCB_NONE;
 246   }
 247   DestroyShmSegment();
 248   // Avoid leaking any pending reply.  No real need to wait but CentOS 6 build
 249   // machines don't have xcb_discard_reply().
 250   WaitIfPendingReply();
 251 }
 252
 253 // Wait for any in-flight shm-affected requests to complete.
 254 // Typically X clients would wait for a XShmCompletionEvent to be received,
 255 // but this works as it's sent immediately after the request is sent.
 256 void nsShmImage::WaitIfPendingReply() {
 257   if (mRequestPending) {
 258     xcb_get_input_focus_reply_t* reply =
 259         xcb_get_input_focus_reply(mConnection, mSyncRequest, nullptr);
 260     free(reply);
 261     mRequestPending = false;
 262   }
 263 }
 264
 265 already_AddRefed<DrawTarget> nsShmImage::CreateDrawTarget(
 266     const mozilla::LayoutDeviceIntRegion& aRegion) {
 267   WaitIfPendingReply();
 268
 269   // Due to bug 1205045, we must avoid making GTK calls off the main thread to
 270   // query window size. Instead we just track the largest offset within the
 271   // image we are drawing to and grow the image to accomodate it. Since usually
 272   // the entire window is invalidated on the first paint to it, this should grow
 273   // the image to the necessary size quickly without many intermediate
 274   // reallocations.
 275   IntRect bounds = aRegion.GetBounds().ToUnknownRect();
 276   IntSize size(bounds.XMost(), bounds.YMost());
 277   if (size.width > mSize.width || size.height > mSize.height) {
 278     DestroyImage();
 279     if (!CreateImage(size)) {
 280       return nullptr;
 281     }
 282   }
 283
 284   return gfxPlatform::CreateDrawTargetForData(
 285       reinterpret_cast<unsigned char*>(mShmAddr) + bounds.y * mStride +
 286           bounds.x * BytesPerPixel(mFormat),
 287       bounds.Size(), mStride, mFormat);
 288 }
 289
 290 void nsShmImage::Put(const mozilla::LayoutDeviceIntRegion& aRegion) {
 291   AutoTArray<xcb_rectangle_t, 32> xrects;
 292   xrects.SetCapacity(aRegion.GetNumRects());
 293
 294   for (auto iter = aRegion.RectIter(); !iter.Done(); iter.Next()) {
 295     const mozilla::LayoutDeviceIntRect& r = iter.Get();
 296     xcb_rectangle_t xrect = {(short)r.x, (short)r.y, (unsigned short)r.width,
 297                              (unsigned short)r.height};
 298     xrects.AppendElement(xrect);
 299   }
 300
 301   if (!mGC) {
 302     mGC = xcb_generate_id(mConnection);
 303     xcb_create_gc(mConnection, mGC, mWindow, 0, nullptr);
 304   }
 305
 306   xcb_set_clip_rectangles(mConnection, XCB_CLIP_ORDERING_YX_BANDED, mGC, 0, 0,
 307                           xrects.Length(), xrects.Elements());
 308
 309   if (mPixmap != XCB_NONE) {
 310     xcb_copy_area(mConnection, mPixmap, mWindow, mGC, 0, 0, 0, 0, mSize.width,
 311                   mSize.height);
 312   } else {
 313     xcb_shm_put_image(mConnection, mWindow, mGC, mSize.width, mSize.height, 0,
 314                       0, mSize.width, mSize.height, 0, 0, mDepth,
 315                       XCB_IMAGE_FORMAT_Z_PIXMAP, 0, mShmSeg, 0);
 316   }
 317
 318   // Send a request that returns a response so that we don't have to start a
 319   // sync in nsShmImage::CreateDrawTarget.
 320   mSyncRequest = xcb_get_input_focus(mConnection);
 321   mRequestPending = true;
 322
 323   xcb_flush(mConnection);
 324 }
 325
 326 #endif  // MOZ_HAVE_SHMIMAGE