unix/x0vncserver/PollingManager.cxx

/* Copyright (C) 2004-2007 Constantin Kaplinsky.  All Rights Reserved.
 *    
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this software; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
 * USA.
 */
//
// PollingManager.cxx
//

#include <stdio.h>
#include <string.h>
#include <time.h>
#include <X11/Xlib.h>
#include <rfb/LogWriter.h>
#include <rfb/VNCServer.h>
#include <rfb/Configuration.h>
#include <rfb/ServerCore.h>

#include <x0vncserver/PollingManager.h>

static LogWriter vlog("PollingMgr");

const int PollingManager::m_pollingOrder[32] = {
   0, 16,  8, 24,  4, 20, 12, 28,
  10, 26, 18,  2, 22,  6, 30, 14,
   1, 17,  9, 25,  7, 23, 15, 31,
  19,  3, 27, 11, 29, 13,  5, 21
};

// FIXME: Check that the parameter's value is in the allowed range.
//        This applies to all other parameters as well.
IntParameter PollingManager::m_videoPriority("VideoPriority",
  "Priority of sending updates for video area (0..8)", 2);

//
// Constructor.
//
// Note that dpy and image should remain valid during the object
// lifetime, while factory is used only in the constructor itself.
//
// FIXME: Pass XPixelBuffer* instead of Image*.
//

PollingManager::PollingManager(Display *dpy, Image *image,
                               ImageFactory *factory,
                               int offsetLeft, int offsetTop)
  : m_dpy(dpy),
    m_server(0),
    m_image(image),
    m_bytesPerPixel(image->xim->bits_per_pixel / 8),
    m_offsetLeft(offsetLeft),
    m_offsetTop(offsetTop),
    m_width(image->xim->width),
    m_height(m_image->xim->height),
    m_numVideoPasses(0),
    m_pollingStep(0)
{
  // Save width and height of the screen (and the image).
  m_width = m_image->xim->width;
  m_height = m_image->xim->height;

  // Compute width and height in 32x32 tiles.
  m_widthTiles = (m_width + 31) / 32;
  m_heightTiles = (m_height + 31) / 32;
  m_numTiles = m_widthTiles * m_heightTiles;

  // Get initial screen image.
  m_image->get(DefaultRootWindow(m_dpy), m_offsetLeft, m_offsetTop);

  // Create additional images used in polling algorithm, warn if
  // underlying class names are different from the class name of the
  // primary image.
  m_rowImage = factory->newImage(m_dpy, m_width, 1);
  m_columnImage = factory->newImage(m_dpy, 1, m_height);
  const char *primaryImgClass = m_image->className();
  const char *rowImgClass = m_rowImage->className();
  const char *columnImgClass = m_columnImage->className();
  if (strcmp(rowImgClass, primaryImgClass) != 0 ||
      strcmp(columnImgClass, primaryImgClass) != 0) {
    vlog.error("Image types do not match (%s, %s, %s)",
               primaryImgClass, rowImgClass, columnImgClass);
  }

  m_changeFlags = new bool[m_numTiles];
  m_rateMatrix = new char[m_numTiles];
  m_videoFlags = new char[m_numTiles];
  memset(m_changeFlags, 0, m_numTiles * sizeof(bool));
  memset(m_rateMatrix, 0, m_numTiles);
  memset(m_videoFlags, 0, m_numTiles);
}

PollingManager::~PollingManager()
{
  delete[] m_videoFlags;
  delete[] m_rateMatrix;
  delete[] m_changeFlags;

  delete m_rowImage;
  delete m_columnImage;
}

//
// Register VNCServer object.
//

void PollingManager::setVNCServer(VNCServer *s)
{
  m_server = s;
}

//
// DEBUG: Measuring time spent in the poll() function,
//        as well as time intervals between poll() calls.
//

#ifdef DEBUG
void PollingManager::debugBeforePoll()
{
  TimeMillis timeNow;
  int diff = timeNow.diffFrom(m_timeSaved);
  fprintf(stderr, "[wait%4dms]\t[step %2d]\t", diff, m_pollingStep % 32);
  m_timeSaved = timeNow;
}

void PollingManager::debugAfterPoll()
{
  TimeMillis timeNow;
  int diff = timeNow.diffFrom(m_timeSaved);
  fprintf(stderr, "[poll%4dms]\n", diff);
  m_timeSaved = timeNow;
}

#endif

//
// Search for changed rectangles on the screen.
//

void PollingManager::poll()
{
#ifdef DEBUG
  debugBeforePoll();
#endif

  // Perform polling and try update clients if changes were detected.
  if (pollScreen())
    m_server->tryUpdate();

#ifdef DEBUG
  debugAfterPoll();
#endif
}

#ifdef DEBUG_REPORT_CHANGED_TILES
#define DBG_REPORT_CHANGES(title)  printChanges((title))
#else
#define DBG_REPORT_CHANGES(title)
#endif

bool PollingManager::pollScreen()
{
  if (!m_server)
    return false;

  // If video data should have higher priority, and video area was
  // detected, perform special passes to send video data only. Such
  // "video passes" will be performed between normal polling passes.
  // No actual polling is performed in a video pass since we know that
  // video is changing continuously.
  //
  // FIXME: Should we move this block into a separate function?
  // FIXME: Giving higher priority to video area lengthens video
  //        detection cycles. Should we do something with that?
  if ((int)m_videoPriority > 1 && !m_videoRect.is_empty()) {
    if (m_numVideoPasses > 0) {
      m_numVideoPasses--;
      getScreenRect(m_videoRect);
      return true;              // we've got changes
    } else {
      // Normal pass now, but schedule video passes for next calls.
      m_numVideoPasses = (int)m_videoPriority - 1;
    }
  }

  // Clear the m_changeFlags[] array, indicating that no changes have
  // been detected yet.
  memset(m_changeFlags, 0, m_numTiles * sizeof(bool));

  // First pass over the framebuffer. Here we scan 1/32 part of the
  // framebuffer -- that is, one line in each (32 * m_width) stripe.
  // We compare the pixels of that line with previous framebuffer
  // contents and raise corresponding elements of m_changeFlags[].
  int scanOffset = m_pollingOrder[m_pollingStep++ % 32];
  int nTilesChanged = 0;
  for (int y = scanOffset; y < m_height; y += 32) {
    nTilesChanged += checkRow(0, y, m_width);
  }

  // Do the work related to video area detection, if enabled.
  bool haveVideoRect = false;
  if ((int)m_videoPriority != 0) {
    handleVideo();
    if (!m_videoRect.is_empty()) {
      getScreenRect(m_videoRect);
      haveVideoRect = true;
    }
  }

  DBG_REPORT_CHANGES("After 1st pass");

  // If some changes have been detected:
  if (nTilesChanged) {
    // Try to find more changes around. Before doing that, mark the
    // video area as changed, to skip comparisons of its pixels.
    flagVideoArea(true);
    DBG_REPORT_CHANGES("Before checking neighbors");
    checkNeighbors();
    DBG_REPORT_CHANGES("After checking neighbors");

    // Inform the server about the changes. This time, we mark the
    // video area as NOT changed, to prevent reading its pixels again.
    flagVideoArea(false);
    DBG_REPORT_CHANGES("Before sending");
    nTilesChanged = sendChanges();
  }

#ifdef DEBUG_PRINT_NUM_CHANGED_TILES
  printf("%3d ", nTilesChanged);
  if (m_pollingStep % 32 == 0) {
    printf("\n");
  }
#endif

#ifdef DEBUG
  if (nTilesChanged != 0) {
    fprintf(stderr, "#%d# ", nTilesChanged);
  }
#endif

  return (nTilesChanged != 0 || haveVideoRect);
}

int PollingManager::checkRow(int x, int y, int w)
{
  int bytesPerLine = m_image->xim->bytes_per_line;

  // If necessary, expand the row to the left, to the tile border.
  // In other words, x must be a multiple of 32.
  if (x % 32 != 0) {
    int correction = x % 32;
    x -= correction;
    w += correction;
  }

  // Compute a pointer to the corresponding element of m_changeFlags.
  // FIXME: Provide an inline function for that?
  bool *pChangeFlags = &m_changeFlags[(y / 32) * m_widthTiles + (x / 32)];

  // Read a row from the screen. Note that getFullRow() may be more
  // efficient than getRow() which is more general.
  // FIXME: Move the logic to getRow()?
  if (x == 0 && w == m_width) {
    getFullRow(y);
  } else {
    getRow(x, y, w);
  }

  // Compute pointers to images to be compared.
  // FIXME: Provide an inline function Image::locatePixel(x, y).
  char *ptr_old = m_image->xim->data + y * bytesPerLine + x * m_bytesPerPixel;
  char *ptr_new = m_rowImage->xim->data;

  // Compare pixels, raise corresponding elements of m_changeFlags[].
  int nTilesChanged = 0;
  for (int i = 0; i < w; i += 32) {
    int tile_w = (w - i >= 32) ? 32 : w - i;
    int nBytes = tile_w * m_bytesPerPixel;
    if (memcmp(ptr_old, ptr_new, nBytes)) {
      *pChangeFlags = true;
      nTilesChanged++;
    }
    pChangeFlags++;
    ptr_old += nBytes;
    ptr_new += nBytes;
  }

  return nTilesChanged;
}

int PollingManager::checkColumn(int x, int y, int h, bool *pChangeFlags)
{
  getColumn(x, y, h);

  int nTilesChanged = 0;
  for (int nTile = 0; nTile < (h + 31) / 32; nTile++) {
    if (!*pChangeFlags) {
      int tile_h = (h - nTile * 32 >= 32) ? 32 : h - nTile * 32;
      for (int i = 0; i < tile_h; i++) {
        // FIXME: Provide an inline function Image::locatePixel(x, y).
        // FIXME: Do not compute these pointers in the inner cycle.
        char *ptr_old = (m_image->xim->data +
                         (y + nTile * 32 + i) * m_image->xim->bytes_per_line +
                         x * m_bytesPerPixel);
        char *ptr_new = (m_columnImage->xim->data +
                         (nTile * 32 + i) * m_columnImage->xim->bytes_per_line);
        if (memcmp(ptr_old, ptr_new, m_bytesPerPixel)) {
          *pChangeFlags = true;
          nTilesChanged++;
          break;
        }
      }
    }
    pChangeFlags += m_widthTiles;
  }

  return nTilesChanged;
}

int PollingManager::sendChanges()
{
  const bool *pChangeFlags = m_changeFlags;
  int nTilesChanged = 0;

  Rect rect;
  for (int y = 0; y < m_heightTiles; y++) {
    for (int x = 0; x < m_widthTiles; x++) {
      if (*pChangeFlags++) {
        // Count successive tiles marked as changed.
        int count = 1;
        while (x + count < m_widthTiles && *pChangeFlags++) {
          count++;
        }
        nTilesChanged += count;
        // Compute the coordinates and the size of this band.
        rect.setXYWH(x * 32, y * 32, count * 32, 32);
        if (rect.br.x > m_width)
          rect.br.x = m_width;
        if (rect.br.y > m_height)
          rect.br.y = m_height;
        // Add to the changed region maintained by the server.
        getScreenRect(rect);
        m_server->add_changed(rect);
        // Skip processed tiles.
        x += count;
      }
    }
  }
  return nTilesChanged;
}

void PollingManager::handleVideo()
{
  // Update counters in m_rateMatrix.
  for (int i = 0; i < m_numTiles; i++)
    m_rateMatrix[i] += (m_changeFlags[i] != false);

  // Once per eight calls: detect video rectangle by examining
  // m_rateMatrix[], then reset counters in m_rateMatrix[].
  if (m_pollingStep % 8 == 0) {
    detectVideo();
    memset(m_rateMatrix, 0, m_numTiles);
  }
}

void PollingManager::flagVideoArea(bool value)
{
  if (m_videoRect.is_empty())
    return;

  Rect r(m_videoRect.tl.x / 32, m_videoRect.tl.y / 32,
         m_videoRect.br.x / 32, m_videoRect.br.y / 32);

  for (int y = r.tl.y; y < r.br.y; y++)
    for (int x = r.tl.x; x < r.br.x; x++)
      m_changeFlags[y * m_widthTiles + x] = value;
}

void
PollingManager::checkNeighbors()
{
  int x, y;

  // Check neighboring pixels above and below changed tiles.
  // FIXME: Fast skip to the first changed tile (and to the last, too).
  // FIXME: Check the full-width line above the first changed tile?
  for (y = 0; y < m_heightTiles; y++) {
    bool doneAbove = false;
    bool doneBelow = false;
    for (x = 0; x < m_widthTiles; x++) {
      if (!doneAbove && y > 0 &&
          m_changeFlags[y * m_widthTiles + x] &&
          !m_changeFlags[(y - 1) * m_widthTiles + x]) {
        // FIXME: Check m_changeFlags[] to decrease height of the row.
        checkRow(x * 32, y * 32 - 1, m_width - x * 32);
        doneAbove = true;
      }
      if (!doneBelow && y < m_heightTiles - 1 &&
          m_changeFlags[y * m_widthTiles + x] &&
          !m_changeFlags[(y + 1) * m_widthTiles + x]) {
        // FIXME: Check m_changeFlags[] to decrease height of the row.
        checkRow(x * 32, (y + 1) * 32, m_width - x * 32);
        doneBelow = true;
      }
      if (doneBelow && doneAbove)
        break;
    }
  }

  // Check neighboring pixels at the right side of changed tiles.
  for (x = 0; x < m_widthTiles - 1; x++) {
    for (y = 0; y < m_heightTiles; y++) {
      if (m_changeFlags[y * m_widthTiles + x] &&
          !m_changeFlags[y * m_widthTiles + x + 1]) {
        // FIXME: Check m_changeFlags[] to decrease height of the column.
        checkColumn((x + 1) * 32, y * 32, m_height - y * 32,
                    &m_changeFlags[y * m_widthTiles + x + 1]);
        break;
      }
    }
  }

  // Check neighboring pixels at the left side of changed tiles.
  for (x = m_widthTiles - 1; x > 0; x--) {
    for (y = 0; y < m_heightTiles; y++) {
      if (m_changeFlags[y * m_widthTiles + x] &&
          !m_changeFlags[y * m_widthTiles + x - 1]) {
        // FIXME: Check m_changeFlags[] to decrease height of the column.
        checkColumn(x * 32 - 1, y * 32, m_height - y * 32,
                    &m_changeFlags[y * m_widthTiles + x - 1]);
        break;
      }
    }
  }
}

void
PollingManager::printChanges(const char *header) const
{
  fprintf(stderr, "%s:", header);

  const bool *pChangeFlags = m_changeFlags;

  for (int y = 0; y < m_heightTiles; y++) {
    for (int x = 0; x < m_widthTiles; x++) {
      if (*pChangeFlags++) {
        // Count successive tiles marked as changed.
        int count = 1;
        while (x + count < m_widthTiles && *pChangeFlags++) {
          count++;
        }
        // Print.
        fprintf(stderr, " (%d,%d)*%d", x, y, count);
        // Skip processed tiles.
        x += count;
      }
    }
  }

  fprintf(stderr, "\n");
}

void
PollingManager::detectVideo()
{
  // Configurable parameters.
  const int VIDEO_THRESHOLD_0 = 3;
  const int VIDEO_THRESHOLD_1 = 5;

  // In m_rateMatrix, clear counters corresponding to non-32x32 tiles.
  // This will guarantee that the size of the video area is always a
  // multiple of 32 pixels. This is important for hardware JPEG encoders.
  if (m_width % 32 != 0) {
    for (int n = m_widthTiles - 1; n < m_numTiles; n += m_widthTiles)
      m_rateMatrix[n] = 0;
  }
  if (m_height % 32 != 0) {
    for (int n = m_numTiles - m_widthTiles; n < m_numTiles; n++)
      m_rateMatrix[n] = 0;
  }

  // First, detect candidate region that looks like video. In other
  // words, find a region that consists of continuously changing
  // pixels. Save the result in m_videoFlags[].
  for (int i = 0; i < m_numTiles; i++) {
    if (m_rateMatrix[i] <= VIDEO_THRESHOLD_0) {
      m_videoFlags[i] = 0;
    } else if (m_rateMatrix[i] >= VIDEO_THRESHOLD_1) {
      m_videoFlags[i] = 1;
    }
  }

  // Now, choose the biggest rectangle from that candidate region.
  Rect newRect;
  getVideoAreaRect(&newRect);

  // Does new rectangle differ from the previously detected one?
  // If it does, save new rectangle and inform the server.
  if (!newRect.equals(m_videoRect)) {
    if (newRect.is_empty()) {
      vlog.debug("No video detected");
    } else {
      vlog.debug("Detected video %dx%d at (%d,%d)",
                 newRect.width(), newRect.height(),
                 newRect.tl.x, newRect.tl.y);
    }
    m_videoRect = newRect;
    m_server->set_video_area(newRect);
  }
}

void
PollingManager::getVideoAreaRect(Rect *result)
{
  int *mx_hlen, *mx_vlen;
  constructLengthMatrices(&mx_hlen, &mx_vlen);

  int full_h = m_heightTiles;
  int full_w = m_widthTiles;
  int x, y;
  Rect max_rect(0, 0, 0, 0);
  Rect local_rect;

  for (y = 0; y < full_h; y++) {
    for (x = 0; x < full_w; x++) {
      int max_w = mx_hlen[y * full_w + x];
      int max_h = mx_vlen[y * full_w + x];
      if (max_w > 2 && max_h > 1 && max_h * max_w > (int)max_rect.area()) {
        local_rect.tl.x = x;
        local_rect.tl.y = y;
        findMaxLocalRect(&local_rect, mx_hlen, mx_vlen);
        if (local_rect.area() > max_rect.area()) {
          max_rect = local_rect;
        }
      }
    }
  }

  destroyLengthMatrices(mx_hlen, mx_vlen);

  max_rect.tl.x *= 32;
  max_rect.tl.y *= 32;
  max_rect.br.x *= 32;
  max_rect.br.y *= 32;
  if (max_rect.br.x > m_width)
    max_rect.br.x = m_width;
  if (max_rect.br.y > m_height)
    max_rect.br.y = m_height;
  *result = max_rect;
}

void
PollingManager::constructLengthMatrices(int **pmx_h, int **pmx_v)
{
  // Handy shortcuts.
  int h = m_heightTiles;
  int w = m_widthTiles;

  // Allocate memory.
  int *mx_h = new int[h * w];
  memset(mx_h, 0, h * w * sizeof(int));
  int *mx_v = new int[h * w];
  memset(mx_v, 0, h * w * sizeof(int));

  int x, y, len, i;

  // Fill in horizontal length matrix.
  for (y = 0; y < h; y++) {
    for (x = 0; x < w; x++) {
      len = 0;
      while (x + len < w && m_videoFlags[y * w + x + len]) {
        len++;
      }
      for (i = 0; i < len; i++) {
        mx_h[y * w + x + i] = len - i;
      }
      x += len;
    }
  }

  // Fill in vertical length matrix.
  for (x = 0; x < w; x++) {
    for (y = 0; y < h; y++) {
      len = 0;
      while (y + len < h && m_videoFlags[(y + len) * w + x]) {
        len++;
      }
      for (i = 0; i < len; i++) {
        mx_v[(y + i) * w + x] = len - i;
      }
      y += len;
    }
  }

  *pmx_h = mx_h;
  *pmx_v = mx_v;
}

void
PollingManager::destroyLengthMatrices(int *mx_h, int *mx_v)
{
  delete[] mx_h;
  delete[] mx_v;
}

// NOTE: This function assumes that current tile has non-zero in mx_h[],
//       otherwise we get division by zero.
void
PollingManager::findMaxLocalRect(Rect *r, int mx_h[], int mx_v[])
{
  int idx = r->tl.y * m_widthTiles + r->tl.x;

  // NOTE: Rectangle's maximum width and height are 25 and 18
  //       (in tiles, where each tile is usually 32x32 pixels).
  int max_w = mx_h[idx];
  if (max_w > 25)
    max_w = 25;
  int cur_h = 18;

  int best_w = max_w;
  int best_area = 1 * best_w;

  for (int i = 0; i < max_w; i++) {
    int h = mx_v[idx + i];
    if (h < cur_h) {
      cur_h = h;
      if (cur_h * max_w <= best_area)
        break;
    }
    if (cur_h * (i + 1) > best_area) {
      best_w = i + 1;
      best_area = cur_h * best_w;
    }
  }

  r->br.x = r->tl.x + best_w;
  r->br.y = r->tl.y + best_area / best_w;
}