Add multiline braille support.

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

Index: chrome/browser/extensions/api/braille_display_private/brlapi_connection.cc
diff --git a/chrome/browser/extensions/api/braille_display_private/brlapi_connection.cc b/chrome/browser/extensions/api/braille_display_private/brlapi_connection.cc
index 10dd503680c12a4222d94654bb78b948d292018d..b68d83a2653615af0953e83dff984b2e4f4a20b6 100644
--- a/chrome/browser/extensions/api/braille_display_private/brlapi_connection.cc
+++ b/chrome/browser/extensions/api/braille_display_private/brlapi_connection.cc
@@ -41,8 +41,8 @@ class BrlapiConnectionImpl : public BrlapiConnection {
   bool Connected() override { return handle_ != nullptr; }
   brlapi_error_t* BrlapiError() override;
   std::string BrlapiStrError() override;
-  bool GetDisplaySize(size_t* size) override;
-  bool WriteDots(const unsigned char* cells) override;
+  bool GetDisplaySize(unsigned int* rows, unsigned int* columns) override;
+  bool WriteDots(const std::vector<unsigned char> cells) override;
   int ReadKey(brlapi_keyCode_t* keyCode) override;
 
  private:
@@ -93,9 +93,10 @@ BrlapiConnection::ConnectResult BrlapiConnectionImpl::Connect(
     Disconnect();
     return CONNECT_ERROR_RETRY;
   }
+  unsigned int rows = 0;
+  unsigned int columns = 0;
 
-  size_t size;
-  if (!GetDisplaySize(&size)) {
+  if (!GetDisplaySize(&rows, &columns)) {
     // Error already logged.
     Disconnect();
     return CONNECT_ERROR_RETRY;
@@ -104,7 +105,7 @@ BrlapiConnection::ConnectResult BrlapiConnectionImpl::Connect(
   // A display size of 0 means no display connected.  We can't reliably
   // detect when a display gets connected, so fail and let the caller
   // retry connecting.
-  if (size == 0) {
+  if (rows * columns == 0) {
     VLOG(1) << "No braille display connected";
     Disconnect();
     return CONNECT_ERROR_RETRY;
@@ -148,24 +149,24 @@ std::string BrlapiConnectionImpl::BrlapiStrError() {
   return libbrlapi_loader_->brlapi_strerror(BrlapiError());
 }
 
-bool BrlapiConnectionImpl::GetDisplaySize(size_t* size) {
+bool BrlapiConnectionImpl::GetDisplaySize(unsigned int* columns,
+                                          unsigned int* rows) {
   if (!CheckConnected()) {
     return false;
   }
-  unsigned int columns, rows;
-  if (libbrlapi_loader_->brlapi__getDisplaySize(
-          handle_.get(), &columns, &rows) < 0) {
+  if (libbrlapi_loader_->brlapi__getDisplaySize(handle_.get(), columns, rows) <
+      0) {
     LOG(ERROR) << "Couldn't get braille display size " << BrlapiStrError();
     return false;
   }
-  *size = columns * rows;
   return true;
 }
 
-bool BrlapiConnectionImpl::WriteDots(const unsigned char* cells) {
+bool BrlapiConnectionImpl::WriteDots(const std::vector<unsigned char> cells) {
+  // Cells is a 2D vector, compressed into 1D.
   if (!CheckConnected())
     return false;
-  if (libbrlapi_loader_->brlapi__writeDots(handle_.get(), cells) < 0) {
+  if (libbrlapi_loader_->brlapi__writeDots(handle_.get(), &cells[0]) < 0) {

[Devlin, 2016/10/25 22:36:54]

Do we need to check if cells is empty?

Also, prefer cells.data() to access the pointer to the beginning of the array,
rather than &cells[0].

[ultimatedbz, 2016/10/27 03:16:58]

Cool! I did not know vectors had a data() function! And I can't say for sure
what would happen if cells was empty, but I think nothing would be drawn on the
braille display, or brlapi__writeDots(...) would return a negative number.

[Devlin, 2016/10/27 14:59:28]

Reason I asked about checking emptiness before was because it would otherwise
crash on cells[0].  Using data() should be safe as long as writeDots doesn't try
to write anything with the passed data.

     VLOG(1) << "Couldn't write to brlapi: " << BrlapiStrError();
     return false;
   }