From 4b49b1d0cc23f909d1be89cf8f816f820b343e0a Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbarenblat@gmail.com>
Date: Sun, 26 Dec 2021 13:53:22 -0500
Subject: Don’t hard-code escape sequences
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Instead of hard-coding VT100-compatible escape sequences, parse the
system terminfo database and read escape sequences from it. This is
both more flexible (it should work well on more terminals) and more
efficient (it won’t insert padding on terminals that don’t need it).
---
 src/ui/terminal/line.cc | 47 +++++++++++++++++++----------------------------
 src/ui/terminal/line.h  |  3 +++
 2 files changed, 22 insertions(+), 28 deletions(-)

(limited to 'src/ui')

diff --git a/src/ui/terminal/line.cc b/src/ui/terminal/line.cc
index 8f156cb..0ae2d30 100644
--- a/src/ui/terminal/line.cc
+++ b/src/ui/terminal/line.cc
@@ -22,12 +22,15 @@
 
 #include <algorithm>
 #include <iostream>
+#include <memory>
 #include <stdexcept>
 #include <string>
 #include <system_error>
 #include <thread>
 #include <type_traits>
+#include <utility>
 
+#include "goldfishterm/simple.h"
 #include "third_party/abseil/absl/strings/str_cat.h"
 #include "third_party/abseil/absl/strings/string_view.h"
 #include "third_party/abseil/absl/synchronization/mutex.h"
@@ -65,12 +68,6 @@ int TerminalColumns() {
   return size.ws_col;
 }
 
-absl::string_view ClearToEol() noexcept {
-  static const std::string kSequence =
-      absl::StrCat("\x1b[K", std::string(3, '\0') /* VT100 padding */);
-  return kSequence;
-}
-
 }  // namespace
 
 TerminalLine::TerminalLine() {
@@ -79,6 +76,7 @@ TerminalLine::TerminalLine() {
   }
 
   EnterRawMode();
+  tty_ = std::make_unique<goldfishterm::SimpleTerminalOutput>(current_termios_);
 
   sigwinch_watcher_ = std::thread([this] {
     sigset_t sigwinch = SigsetContaining(SIGWINCH);
@@ -109,16 +107,17 @@ void TerminalLine::SetLine(std::string text) {
 
 void TerminalLine::Refresh() {
   absl::MutexLock lock(&mu_);
+  tty_->BeginningOfLine();
   if (line_.size() < columns_) {
     // We can fit the whole line and the cursor on the screen at once.
-    WriteRaw(absl::StrCat(kBeginningOfLine, line_, ClearToEol()));
+    tty_->Write(line_);
   } else {
     auto to_display = std::min<int>(line_.size(), columns_ - 4);
-    WriteRaw(
-        absl::StrCat(kBeginningOfLine, "...",
-                     absl::string_view(&*line_.end() - to_display, to_display),
-                     ClearToEol()));
+    tty_->Write("...");
+    tty_->Write(absl::string_view(&*line_.end() - to_display, to_display));
   }
+  tty_->ClearToEndOfLine();
+  tty_->Flush();
 }
 
 char TerminalLine::GetChar() {
@@ -139,21 +138,26 @@ char TerminalLine::GetChar() {
 
 void TerminalLine::Beep() {
   absl::MutexLock lock(&mu_);
-  WriteRaw("\a");
+  tty_->Beep();
+  tty_->Flush();
 }
 
 void TerminalLine::PrintLine(absl::string_view message) {
   {
     absl::MutexLock lock(&mu_);
-    WriteRaw(absl::StrCat("\r\n", message, "\r\n"));
+    tty_->BeginningOfLine();
+    tty_->CursorDown();
+    tty_->Write(message);
+    tty_->BeginningOfLine();
+    tty_->CursorDown();
   }
-  Refresh();
+  Refresh();  // includes a flush
 }
 
 void TerminalLine::EnterRawMode() {
   CheckedCall("tcgetattr", tcgetattr(STDIN_FILENO, &original_termios_));
 
-  current_termios_ = original_termios_;
+  termios current_termios_ = original_termios_;
   current_termios_.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
   current_termios_.c_oflag &= ~(OPOST);
   current_termios_.c_cflag |= CS8;
@@ -184,19 +188,6 @@ void TerminalLine::ReportSigwinch() {
   Refresh();
 }
 
-void TerminalLine::WriteRaw(absl::string_view bytes) {
-  while (true) {
-    int r = write(STDOUT_FILENO, bytes.data(), bytes.size());
-    if (r >= 0) {
-      return;
-    } else if (errno == EINTR) {
-      continue;
-    } else {
-      throw std::system_error(errno, std::generic_category(), "write");
-    }
-  }
-}
-
 void BlockSigwinch() {
   sigset_t sigwinch = SigsetContaining(SIGWINCH);
   CheckedCall("pthread_sigmask",
diff --git a/src/ui/terminal/line.h b/src/ui/terminal/line.h
index a90e2b7..dfe86cb 100644
--- a/src/ui/terminal/line.h
+++ b/src/ui/terminal/line.h
@@ -19,8 +19,10 @@
 
 #include <termios.h>
 
+#include <memory>
 #include <thread>
 
+#include "goldfishterm/simple.h"
 #include "third_party/abseil/absl/base/thread_annotations.h"
 #include "third_party/abseil/absl/strings/string_view.h"
 #include "third_party/abseil/absl/synchronization/mutex.h"
@@ -81,6 +83,7 @@ class TerminalLine final {
   void WriteRaw(absl::string_view bytes) ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);
 
   termios original_termios_, current_termios_;
+  std::unique_ptr<goldfishterm::SimpleTerminalOutput> tty_;
 
   std::thread sigwinch_watcher_;
 
-- 
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