goldfishterm: Don’t hard-code std::cout/STDOUT_FILENOHEADmain

Make terminal-handling code purer by requiring the user pass TERM, a
termios struct, and an appropriate ostream rather than querying them
from the environment. This eliminates some error-handling code and
makes duplicate syscalls less likely.

4 files changed, 26 insertions, 44 deletions

diff --git a/goldfishterm/internal/emit.cc b/goldfishterm/internal/emit.cc
index 2cc7609..608aa3c 100644
--- a/goldfishterm/internal/emit.cc
+++ b/goldfishterm/internal/emit.cc
@@ -14,15 +14,9 @@
 
 #include "goldfishterm/internal/emit.h"
 
-#include <errno.h>
-#include <stdint.h>
-#include <unistd.h>
-
 #include <memory>
-#include <system_error>
-#include <vector>
+#include <ostream>
 
-#include "third_party/abseil/absl/strings/string_view.h"
 #include "third_party/abseil/absl/time/clock.h"
 #include "third_party/abseil/absl/types/span.h"
 
diff --git a/goldfishterm/simple.cc b/goldfishterm/simple.cc
index 88ceef0..0afa08f 100644
--- a/goldfishterm/simple.cc
+++ b/goldfishterm/simple.cc
@@ -14,9 +14,7 @@
 
 #include "goldfishterm/simple.h"
 
-#include <stdlib.h>
 #include <termios.h>
-#include <unistd.h>
 
 #include <stdexcept>
 #include <vector>
@@ -33,22 +31,6 @@ namespace {
 using ::goldfishterm_internal::InterpretStringCapability;
 using ::goldfishterm_internal::InterpretStringCapabilityInput;
 
-termios StdoutTermios() {
-  termios tty;
-  if (tcgetattr(STDOUT_FILENO, &tty) < 0) {
-    throw std::system_error(errno, std::system_category(), "tcgetattr");
-  }
-  return tty;
-}
-
-absl::string_view TerminalNameFromEnvironment() {
-  const char* name = getenv("TERM");
-  if (name == nullptr) {
-    throw std::runtime_error("TERM unset");
-  }
-  return name;
-}
-
 StringCapability CursorVisibilityCapability(CursorVisibility v) {
   switch (v) {
     case CursorVisibility::kInvisible:
@@ -64,14 +46,12 @@ StringCapability CursorVisibilityCapability(CursorVisibility v) {
 
 }  // namespace
 
-SimpleTerminalOutput::SimpleTerminalOutput()
-    : SimpleTerminalOutput(StdoutTermios()) {}
-
-SimpleTerminalOutput::SimpleTerminalOutput(const termios& tty)
-    : terminfo_(
-          TerminfoEntry::FromSystemDatabase(TerminalNameFromEnvironment())) {
-  baud_ = cfgetospeed(&tty);
-}
+SimpleTerminalOutput::SimpleTerminalOutput(absl::string_view terminal_name,
+                                           const termios& tty,
+                                           std::ostream& out)
+    : terminfo_(TerminfoEntry::FromSystemDatabase(terminal_name)),
+      baud_(cfgetospeed(&tty)),
+      out_(out) {}
 
 void SimpleTerminalOutput::SetCursorVisibility(CursorVisibility v) {
   return Emit(CursorVisibilityCapability(v));
@@ -86,7 +66,7 @@ void SimpleTerminalOutput::Emit(
                                          std::move(parameters), /*baud=*/baud_,
                                          /*lines_affected=*/1))
           .terms,
-      std::cout);
+      out_);
 }
 
 }  // namespace goldfishterm
diff --git a/goldfishterm/simple.h b/goldfishterm/simple.h
index 48a7789..0228749 100644
--- a/goldfishterm/simple.h
+++ b/goldfishterm/simple.h
@@ -17,7 +17,7 @@
 
 #include <termios.h>
 
-#include <iostream>
+#include <ostream>
 #include <vector>
 
 #include "goldfishterm/internal/string_capability.h"
@@ -33,15 +33,14 @@ enum class CursorVisibility {
   kVeryVisible,
 };
 
-// Looks up escape sequences for the terminal described in the TERM environment
-// variable, and allows sending those escape sequences to standard output.
+// Looks up escape sequences for the specified terminal and allows sending those
+// escape sequences to the specified ostream.
 //
-// This class is thread-safe, provided you don't mutate the TERM environment
-// variable while its constructor is running.
+// This class is thread-safe.
 class SimpleTerminalOutput final {
  public:
-  explicit SimpleTerminalOutput();
-  explicit SimpleTerminalOutput(const termios&);
+  explicit SimpleTerminalOutput(absl::string_view terminal_name, const termios&,
+                                std::ostream&);
 
   SimpleTerminalOutput(const SimpleTerminalOutput&) noexcept = default;
   SimpleTerminalOutput& operator=(const SimpleTerminalOutput&) noexcept =
@@ -49,9 +48,9 @@ class SimpleTerminalOutput final {
   SimpleTerminalOutput(SimpleTerminalOutput&&) noexcept = default;
   SimpleTerminalOutput& operator=(SimpleTerminalOutput&&) noexcept = default;
 
-  void Write(absl::string_view s) { std::cout.write(s.data(), s.size()); }
+  void Write(absl::string_view s) { out_.write(s.data(), s.size()); }
 
-  void Flush() { std::cout.flush(); }
+  void Flush() { out_.flush(); }
 
   // Rings the bell. On some terminals, this may flash the screen instead.
   void Beep() { Emit(StringCapability::kBell); }
@@ -74,6 +73,7 @@ class SimpleTerminalOutput final {
 
   TerminfoEntry terminfo_;
   int baud_;
+  std::ostream& out_;
 };
 
 }  // namespace goldfishterm
diff --git a/src/ui/terminal/line.cc b/src/ui/terminal/line.cc
index 962b692..e668b28 100644
--- a/src/ui/terminal/line.cc
+++ b/src/ui/terminal/line.cc
@@ -16,6 +16,7 @@
 
 #include <errno.h>
 #include <signal.h>
+#include <stdlib.h>
 #include <sys/ioctl.h>
 #include <termios.h>
 #include <unistd.h>
@@ -78,7 +79,14 @@ TerminalLine::TerminalLine() {
   }
 
   EnterRawMode();
-  tty_ = std::make_unique<goldfishterm::SimpleTerminalOutput>(current_termios_);
+
+  const char* terminal_name = getenv("TERM");
+  if (terminal_name == nullptr) {
+    // Fall back to a minimal subset of the ANSI capabilities.
+    terminal_name = "ansi-mini";
+  }
+  tty_ = std::make_unique<goldfishterm::SimpleTerminalOutput>(
+      terminal_name, current_termios_, std::cout);
 
   sigwinch_watcher_ = std::thread([this] {
     sigset_t sigwinch = SigsetContaining(SIGWINCH);