feat: add DSR response handling for nushell compatibility (#82)

Author: sreya

lib/ghostty.ts

@@ -609,6 +609,40 @@ export class GhosttyTerminal {
     return null; // TODO: Add hyperlink support
   }
 
+  /**
+   * Check if there are pending responses from the terminal.
+   * Responses are generated by escape sequences like DSR (Device Status Report).
+   */
+  hasResponse(): boolean {
+    return this.exports.ghostty_terminal_has_response(this.handle);
+  }
+
+  /**
+   * Read pending responses from the terminal.
+   * Returns the response string, or null if no responses pending.
+   *
+   * Responses are generated by escape sequences that require replies:
+   * - DSR 6 (cursor position): Returns \x1b[row;colR
+   * - DSR 5 (operating status): Returns \x1b[0n
+   */
+  readResponse(): string | null {
+    if (!this.hasResponse()) return null;
+
+    const bufSize = 256; // Most responses are small
+    const bufPtr = this.exports.ghostty_wasm_alloc_u8_array(bufSize);
+
+    try {
+      const bytesRead = this.exports.ghostty_terminal_read_response(this.handle, bufPtr, bufSize);
+
+      if (bytesRead <= 0) return null;
+
+      const bytes = new Uint8Array(this.memory.buffer, bufPtr, bytesRead);
+      return new TextDecoder().decode(bytes.slice());
+    } finally {
+      this.exports.ghostty_wasm_free_u8_array(bufPtr, bufSize);
+    }
+  }
+
   /**
    * Query arbitrary terminal mode by number
    * @param mode Mode number (e.g., 25 for cursor visibility, 2004 for bracketed paste)

lib/terminal.ts

@@ -539,6 +539,10 @@ export class Terminal implements ITerminalCore {
     // Write directly to WASM terminal (handles VT parsing internally)
     this.wasmTerm!.write(data);
 
+    // Process any responses generated by the terminal (e.g., DSR cursor position)
+    // These need to be sent back to the PTY via onData
+    this.processTerminalResponses();
+
     // Check for bell character (BEL, \x07)
     // WASM doesn't expose bell events, so we detect it in the data stream
     if (typeof data === 'string' && data.includes('\x07')) {
@@ -1721,6 +1725,29 @@ export class Terminal implements ITerminalCore {
     animate();
   }
 
+  /**
+   * Process any pending terminal responses and emit them via onData.
+   *
+   * This handles escape sequences that require the terminal to send a response
+   * back to the PTY, such as:
+   * - DSR 6 (cursor position): Shell sends \x1b[6n, terminal responds with \x1b[row;colR
+   * - DSR 5 (operating status): Shell sends \x1b[5n, terminal responds with \x1b[0n
+   *
+   * Without this, shells like nushell that rely on cursor position queries
+   * will hang waiting for a response that never comes.
+   */
+  private processTerminalResponses(): void {
+    if (!this.wasmTerm) return;
+
+    // Read any pending responses from the WASM terminal
+    const response = this.wasmTerm.readResponse();
+    if (response) {
+      // Send response back to the PTY via onData
+      // This is the same path as user keyboard input
+      this.dataEmitter.fire(response);
+    }
+  }
+
   /**
    * Check for title changes in written data (OSC sequences)
    * Simplified implementation - looks for OSC 0, 1, 2

lib/types.ts

@@ -445,6 +445,10 @@ export interface GhosttyWasmExports extends WebAssembly.Exports {
     bufLen: number
   ): number; // Returns cells written or -1 on error
   ghostty_terminal_is_row_wrapped(terminal: TerminalHandle, row: number): number;
+
+  // Response API (for DSR and other terminal queries)
+  ghostty_terminal_has_response(terminal: TerminalHandle): boolean;
+  ghostty_terminal_read_response(terminal: TerminalHandle, bufPtr: number, bufLen: number): number; // Returns bytes written, 0 if no response, -1 on error
 }
 
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