feat: implement cursor position check for terminal input handling

Author: Nelson-numerical-software

modules/terminal/src/cpp/AdvancedTerminal.cpp

@@ -191,38 +191,6 @@ injectNewlineIntoInput()
 #endif
 }
 //=============================================================================
-static void
-writeStdoutUtf8(const std::string& msg)
-{
-#ifdef _WIN32
-    HANDLE handle = GetStdHandle(STD_OUTPUT_HANDLE);
-    if (handle != nullptr && handle != INVALID_HANDLE_VALUE) {
-        std::wstring wide = utf8_to_wstring(msg);
-        DWORD written = 0;
-        WriteConsoleW(handle, wide.c_str(), static_cast<DWORD>(wide.size()), &written, nullptr);
-        return;
-    }
-#endif
-    std::cout << msg;
-    std::cout.flush();
-}
-//=============================================================================
-static void
-writeStderrUtf8(const std::string& msg)
-{
-#ifdef _WIN32
-    HANDLE handle = GetStdHandle(STD_ERROR_HANDLE);
-    if (handle != nullptr && handle != INVALID_HANDLE_VALUE) {
-        std::wstring wide = utf8_to_wstring(msg);
-        DWORD written = 0;
-        WriteConsoleW(handle, wide.c_str(), static_cast<DWORD>(wide.size()), &written, nullptr);
-        return;
-    }
-#endif
-    std::cerr << msg;
-    std::cerr.flush();
-}
-//=============================================================================
 } // namespace
 //=============================================================================
 std::wstring
@@ -239,7 +207,6 @@ AdvancedTerminal::getTextLine(const std::wstring& prompt, bool bIsInput)
         atPrompt = false;
         return L"\n";
     }
-
     const char* line = repl->input(promptUtf8);
     if (line == nullptr || line[0] == 0) {
         atPrompt = false;
@@ -305,19 +272,19 @@ AdvancedTerminal::getTerminalHeight()
 void
 AdvancedTerminal::outputMessage(const std::wstring& msg)
 {
-    std::string _msg = wstring_to_utf8(msg);
-    if (atPrompt) {
-        writeStdoutUtf8("\n");
-        atPrompt = false;
-    }
-
-    outputMessage(_msg);
+    outputMessage(wstring_to_utf8(msg));
 }
 //=============================================================================
 void
 AdvancedTerminal::outputMessage(const std::string& msg)
 {
-    writeStdoutUtf8(msg);
+    if (atPrompt) {
+        std::cout << "\n";
+
+        atPrompt = false;
+    }
+    std::cout << msg;
+    std::cout.flush();
     this->diary.writeMessage(msg);
 }
 //=============================================================================
@@ -331,10 +298,11 @@ void
 AdvancedTerminal::errorMessage(const std::string& msg)
 {
     if (atPrompt) {
-        writeStdoutUtf8("\n");
+        std::cout << "\n";
         atPrompt = false;
     }
-    writeStderrUtf8(msg);
+    std::cerr << msg;
+    std::cerr.flush();
     this->diary.writeMessage(msg);
 }
 //=============================================================================
@@ -348,11 +316,11 @@ void
 AdvancedTerminal::warningMessage(const std::string& msg)
 {
     if (atPrompt) {
-        writeStdoutUtf8("\n");
+        std::cout << "\n";
         atPrompt = false;
     }
-    writeStdoutUtf8(msg);
-    this->diary.writeMessage(msg);
+    std::cout << msg;
+    std::cout.flush();
 }
 //=============================================================================
 void

modules/terminal/src/cpp/replxx/src/replxx_impl.cxx

@@ -856,6 +856,9 @@ Replxx::ReplxxImpl::input(std::string const& prompt)
 
         /// Always render from beginning of current line. It's to prevent garbage inputs during
         /// starting up.
+        if (!_terminal.is_at_beginning_of_the_line()) {
+            dprintf(_out_fd, "\n");
+        }
         _terminal.jump_cursor(0, 0);
         _asyncPrompt.clear();
         _updatePrompt = false;

modules/terminal/src/cpp/replxx/src/terminal.cxx

@@ -901,6 +901,69 @@ Terminal::set_cursor_visible(bool visible_)
     SetConsoleCursorInfo(_consoleOut, &cursorInfo);
     return;
 }
+#if defined(_WIN32)
+bool
+Terminal::is_at_beginning_of_the_line(void)
+{
+    CONSOLE_SCREEN_BUFFER_INFO inf;
+    HANDLE consoleOut(
+        _consoleOut != INVALID_HANDLE_VALUE ? _consoleOut : GetStdHandle(STD_OUTPUT_HANDLE));
+    if (!GetConsoleScreenBufferInfo(consoleOut, &inf)) {
+        return false;
+    }
+    return (inf.dwCursorPosition.X == 0);
+}
+#else
+bool
+Terminal::is_at_beginning_of_the_line(void)
+{
+    // Request cursor position report (DSR) and parse response: ESC [ row ; col R
+    const char request[] = "\033[6n";
+    write8(request, sizeof(request) - 1);
+
+    fd_set rfds;
+    struct timeval tv;
+    tv.tv_sec = 0;
+    tv.tv_usec = 200000; // 200 ms
+
+    std::string resp;
+    int fd = _in_fd;
+    char buf[32];
+
+    while (true) {
+        FD_ZERO(&rfds);
+        FD_SET(fd, &rfds);
+        int ret = select(fd + 1, &rfds, nullptr, nullptr, &tv);
+        if (ret <= 0) {
+            break; // timeout or error
+        }
+        ssize_t n = read(fd, buf, sizeof(buf));
+        if (n <= 0) {
+            break;
+        }
+        resp.append(buf, buf + n);
+        if (resp.find('R') != std::string::npos) {
+            break;
+        }
+        // small additional delay for more data
+        tv.tv_sec = 0;
+        tv.tv_usec = 50000; // 50ms
+    }
+
+    size_t p1 = resp.find('[');
+    size_t p2 = resp.find('R');
+    if (p1 == std::string::npos || p2 == std::string::npos || p2 <= p1) {
+        return false;
+    }
+    std::string inside = resp.substr(p1 + 1, p2 - p1 - 1);
+    size_t sep = inside.find(';');
+    if (sep == std::string::npos) {
+        return false;
+    }
+    int col = atoi(inside.c_str() + sep + 1);
+    return (col == 1); // DSR is 1-based
+}
+#endif
 #else
 void
 Terminal::set_cursor_visible(bool)

modules/terminal/src/cpp/replxx/src/terminal.hxx

@@ -89,6 +89,8 @@ public:
     jump_cursor(int, int);
     void
     set_cursor_visible(bool);
+    bool
+    is_at_beginning_of_the_line(void);
 #ifndef _WIN32
     int
     read_verbatim(char32_t*, int);