From b819388acc4faa46e296f4e1f173b2cf2be8799f Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbarenblat@gmail.com>
Date: Sun, 26 Dec 2021 14:17:19 -0500
Subject: Hide cursor during redraws

---
 goldfishterm/simple.cc  | 18 ++++++++++++++++++
 goldfishterm/simple.h   | 10 ++++++++++
 src/ui/terminal/line.cc |  9 +++++++++
 3 files changed, 37 insertions(+)

diff --git a/goldfishterm/simple.cc b/goldfishterm/simple.cc
index 9c4c9a9..88ceef0 100644
--- a/goldfishterm/simple.cc
+++ b/goldfishterm/simple.cc
@@ -23,6 +23,7 @@
 
 #include "goldfishterm/internal/emit.h"
 #include "goldfishterm/terminfo.h"
+#include "third_party/abseil/absl/strings/str_cat.h"
 #include "third_party/abseil/absl/strings/string_view.h"
 
 namespace goldfishterm {
@@ -48,6 +49,19 @@ absl::string_view TerminalNameFromEnvironment() {
   return name;
 }
 
+StringCapability CursorVisibilityCapability(CursorVisibility v) {
+  switch (v) {
+    case CursorVisibility::kInvisible:
+      return StringCapability::kCursorInvisible;
+    case CursorVisibility::kNormal:
+      return StringCapability::kCursorNormal;
+    case CursorVisibility::kVeryVisible:
+      return StringCapability::kCursorVisible;
+    default:
+      throw std::invalid_argument(absl::StrCat("invalid CursorVisibility ", v));
+  }
+}
+
 }  // namespace
 
 SimpleTerminalOutput::SimpleTerminalOutput()
@@ -59,6 +73,10 @@ SimpleTerminalOutput::SimpleTerminalOutput(const termios& tty)
   baud_ = cfgetospeed(&tty);
 }
 
+void SimpleTerminalOutput::SetCursorVisibility(CursorVisibility v) {
+  return Emit(CursorVisibilityCapability(v));
+}
+
 void SimpleTerminalOutput::Emit(
     StringCapability cap,
     std::vector<goldfishterm_internal::StringCapabilityParameter> parameters) {
diff --git a/goldfishterm/simple.h b/goldfishterm/simple.h
index 3f5cc9f..48a7789 100644
--- a/goldfishterm/simple.h
+++ b/goldfishterm/simple.h
@@ -26,6 +26,13 @@
 
 namespace goldfishterm {
 
+// The type of cursor in use.
+enum class CursorVisibility {
+  kInvisible,
+  kNormal,
+  kVeryVisible,
+};
+
 // Looks up escape sequences for the terminal described in the TERM environment
 // variable, and allows sending those escape sequences to standard output.
 //
@@ -58,6 +65,9 @@ class SimpleTerminalOutput final {
   // Moves the cursor down one line.
   void CursorDown() { Emit(StringCapability::kCursorDown); }
 
+  // Sets the cursor visibility.
+  void SetCursorVisibility(CursorVisibility);
+
  private:
   void Emit(StringCapability,
             std::vector<goldfishterm_internal::StringCapabilityParameter> = {});
diff --git a/src/ui/terminal/line.cc b/src/ui/terminal/line.cc
index 0ae2d30..0848b22 100644
--- a/src/ui/terminal/line.cc
+++ b/src/ui/terminal/line.cc
@@ -39,6 +39,8 @@ namespace ec {
 
 namespace {
 
+using ::goldfishterm::CursorVisibility;
+
 constexpr absl::string_view kBeginningOfLine = "\r";
 
 int CheckedCall(const char* what_arg, int r) {
@@ -94,6 +96,7 @@ TerminalLine::~TerminalLine() noexcept {
   pthread_cancel(sigwinch_watcher_.native_handle());
   sigwinch_watcher_.join();
 
+  tty_->SetCursorVisibility(CursorVisibility::kNormal);
   ExitRawMode();
 
   // Move the cursor to the start of the next line.
@@ -107,6 +110,8 @@ void TerminalLine::SetLine(std::string text) {
 
 void TerminalLine::Refresh() {
   absl::MutexLock lock(&mu_);
+  tty_->SetCursorVisibility(CursorVisibility::kInvisible);
+  tty_->Flush();
   tty_->BeginningOfLine();
   if (line_.size() < columns_) {
     // We can fit the whole line and the cursor on the screen at once.
@@ -117,6 +122,7 @@ void TerminalLine::Refresh() {
     tty_->Write(absl::string_view(&*line_.end() - to_display, to_display));
   }
   tty_->ClearToEndOfLine();
+  tty_->SetCursorVisibility(CursorVisibility::kNormal);
   tty_->Flush();
 }
 
@@ -145,11 +151,14 @@ void TerminalLine::Beep() {
 void TerminalLine::PrintLine(absl::string_view message) {
   {
     absl::MutexLock lock(&mu_);
+    tty_->SetCursorVisibility(CursorVisibility::kInvisible);
+    tty_->Flush();
     tty_->BeginningOfLine();
     tty_->CursorDown();
     tty_->Write(message);
     tty_->BeginningOfLine();
     tty_->CursorDown();
+    tty_->SetCursorVisibility(CursorVisibility::kNormal);
   }
   Refresh();  // includes a flush
 }
-- 
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