From 8b3eb4535dc0cc7ee7fef73315a8537f0cb915d7 Mon Sep 17 00:00:00 2001
From: AnotherTest <ali.mpfard@gmail.com>
Date: Tue, 26 May 2020 19:52:01 +0430
Subject: [PATCH] LibLine: Use LibC's getline() when the terminal claims no
 support for escape sequences

We just look at $TERM and refuse to emit any escape sequences if it
doesn't start with "xterm".
This could be made much better, at detecting, and at not caling
getline().
---
 Libraries/LibLine/Editor.cpp | 42 ++++++++++++++++++++++++++++++++++++
 Libraries/LibLine/Editor.h   | 22 ++++++-------------
 2 files changed, 49 insertions(+), 15 deletions(-)

diff --git a/Libraries/LibLine/Editor.cpp b/Libraries/LibLine/Editor.cpp
index bb11476717..2b38e7fa11 100644
--- a/Libraries/LibLine/Editor.cpp
+++ b/Libraries/LibLine/Editor.cpp
@@ -226,11 +226,53 @@ void Editor::suggest(size_t invariant_offset, size_t static_offset, Span::Mode o
     m_suggestion_manager.set_suggestion_variants(internal_static_offset, internal_invariant_offset, 0);
 }
 
+void Editor::initialize()
+{
+    if (m_initialized)
+        return;
+
+    struct termios termios;
+    tcgetattr(0, &termios);
+    m_default_termios = termios; // grab a copy to restore
+
+    auto* term = getenv("TERM");
+    if (StringView { term }.starts_with("xterm"))
+        m_configuration.set(Configuration::Full);
+    else
+        m_configuration.set(Configuration::NoEscapeSequences);
+
+    // Because we use our own line discipline which includes echoing,
+    // we disable ICANON and ECHO.
+    if (m_configuration.operation_mode == Configuration::Full) {
+        termios.c_lflag &= ~(ECHO | ICANON);
+        tcsetattr(0, TCSANOW, &termios);
+    }
+
+    m_termios = termios;
+    m_initialized = true;
+}
+
 Result<String, Editor::Error> Editor::get_line(const String& prompt)
 {
     initialize();
     m_is_editing = true;
 
+    if (m_configuration.operation_mode == Configuration::NoEscapeSequences) {
+        // Do not use escape sequences, instead, use LibC's getline.
+        size_t size = 0;
+        char* line = nullptr;
+        fputs(prompt.characters(), stderr);
+        size_t line_length = getline(&line, &size, stdin);
+        restore();
+        if (line) {
+            String result { line, line_length, Chomp };
+            free(line);
+            return result;
+        }
+
+        return Error::ReadFailure;
+    }
+
     set_prompt(prompt);
     reset();
     set_origin();
diff --git a/Libraries/LibLine/Editor.h b/Libraries/LibLine/Editor.h
index 695345fe0e..07fe8f8797 100644
--- a/Libraries/LibLine/Editor.h
+++ b/Libraries/LibLine/Editor.h
@@ -57,6 +57,10 @@ struct Configuration {
         Lazy,
         Eager,
     };
+    enum OperationMode {
+        Full,
+        NoEscapeSequences,
+    };
 
     Configuration()
     {
@@ -71,9 +75,11 @@ struct Configuration {
 
     void set(RefreshBehaviour refresh) { refresh_behaviour = refresh; }
     void set(TokenSplitMechanism split) { split_mechanism = split; }
+    void set(OperationMode mode) { operation_mode = mode; }
 
     RefreshBehaviour refresh_behaviour { RefreshBehaviour::Lazy };
     TokenSplitMechanism split_mechanism { TokenSplitMechanism::Spaces };
+    OperationMode operation_mode { OperationMode::Full };
 };
 
 class Editor {
@@ -89,21 +95,7 @@ public:
 
     Result<String, Error> get_line(const String& prompt);
 
-    void initialize()
-    {
-        if (m_initialized)
-            return;
-
-        struct termios termios;
-        tcgetattr(0, &termios);
-        m_default_termios = termios; // grab a copy to restore
-        // Because we use our own line discipline which includes echoing,
-        // we disable ICANON and ECHO.
-        termios.c_lflag &= ~(ECHO | ICANON);
-        tcsetattr(0, TCSANOW, &termios);
-        m_termios = termios;
-        m_initialized = true;
-    }
+    void initialize();
 
     void add_to_history(const String&);
     const Vector<String>& history() const { return m_history; }