Add multiline braille support.

chrome/browser/extensions/api/braille_display_private/braille_controller_brlapi.cc

 // Copyright 2013 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.
 
 #include "chrome/browser/extensions/api/braille_display_private/braille_controller_brlapi.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <algorithm>
 #include <cerrno>
@@ skipping 69 matching lines @@
       return;
   }
   LOG(WARNING) << "Couldn't load libbrlapi: " << strerror(errno);
 }
 
 std::unique_ptr<DisplayState> BrailleControllerImpl::GetDisplayState() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   StartConnecting();
   std::unique_ptr<DisplayState> display_state(new DisplayState);
   if (connection_.get() && connection_->Connected()) {
-    size_t size;
-    if (!connection_->GetDisplaySize(&size)) {
+    unsigned int columns, rows;
+    if (!connection_->GetDisplaySize(&columns, &rows)) {
       Disconnect();
-    } else if (size > 0) {  // size == 0 means no display present.
+    } else if (rows * columns > 0) {
+      // rows * columns == 0 means no display present.
       display_state->available = true;
-      display_state->text_cell_count.reset(new int(size));
+      display_state->text_column_count.reset(new int(columns));
+      display_state->text_row_count.reset(new int(rows));
     }
   }
   return display_state;
 }
 
-void BrailleControllerImpl::WriteDots(const std::vector<char>& cells) {
+void BrailleControllerImpl::WriteDots(const std::vector<char>& cells,
+                                      unsigned int cells_cols,
+                                      unsigned int cells_rows) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (connection_ && connection_->Connected()) {
-    size_t size;
-    if (!connection_->GetDisplaySize(&size)) {
+    // Row count and column count of current display.
+    unsigned int rows, columns;
+    if (!connection_->GetDisplaySize(&columns, &rows)) {
       Disconnect();
     }
-    std::vector<unsigned char> sizedCells(size);
-    std::memcpy(&sizedCells[0], cells.data(), std::min(cells.size(), size));
-    if (size > cells.size())
-      std::fill(sizedCells.begin() + cells.size(), sizedCells.end(), 0);
-    if (!connection_->WriteDots(&sizedCells[0]))
+    std::vector<unsigned char> sized_cells(rows * columns);
+    for (unsigned int i = 0; i < rows; i++) {
+      for (unsigned int j = 0; j < columns; j++) {
+        // If we go out of the bounds of cell's size, pad with 0.
+        sized_cells[i * columns + j] = (i >= cells_rows || j >= cells_cols)
+                                           ? 0
+                                           : cells[i * cells_cols + j];

[Devlin, 2016/10/18 23:01:28]

nit: why not init the vector to all zeros (std::vector<unsigned char>
sized_cells(rows * columns, 0);) and then just iterate from 0 ->
cells_[rows|cols]?

[ultimatedbz, 2016/10/20 18:27:45]

That's a great suggestion! As I was thinking about it though, I thought of the
case where cells_[row|cols] is bigger than [rows|columns]. With your suggestion,
wouldn't I still need to do some bounds checking and iterate from 0 ->
min(cells_rows, rows)?

[Devlin, 2016/10/21 15:41:39]

Ah, didn't realize that cells_rows could be bigger than rows.  Slightly-tweaked
suggestion:
std::vector<unsigned char> sized_cells(rows * columns, 0);
unsigned int row_limit = std::min(rows, cells_rows);
unisgned int col_limit = std::min(cols, cells_cols);
for (unsigned int row = 0; row < row_limit; ++row) {
  for (unsinged int col = 0; col < col_limit; ++col) {
    sized_cells[row * columns + col] = cells[row * cells_cols + col];
}

[ultimatedbz, 2016/10/25 19:24:41]

Looks good. Thanks!

+      }
+    }
+
+    if (!connection_->WriteDots(sized_cells))
       Disconnect();
   }
 }
 
 void BrailleControllerImpl::AddObserver(BrailleObserver* observer) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   if (!BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
                                base::Bind(
                                    &BrailleControllerImpl::StartConnecting,
                                    base::Unretained(this)))) {
@@ skipping 195 matching lines @@
     }
     return;
   }
   FOR_EACH_OBSERVER(BrailleObserver, observers_,
                     OnBrailleDisplayStateChanged(*new_state));
 }
 
 }  // namespace braille_display_private
 }  // namespace api
 }  // namespace extensions