windows: emit SIGWINCH when the console size changes

include/uv-private/uv-win.h

@@ -65,6 +65,7 @@ typedef intptr_t ssize_t;
  */
 #define SIGHUP                1
 #define SIGKILL               9
+#define SIGWINCH             28
 
 /*
  * Guids and typedefs for winsock extension functions

include/uv.h

@@ -1608,6 +1608,13 @@ UV_EXTERN int uv_fs_poll_stop(uv_fs_poll_t* handle);
  *   program is given approximately 10 seconds to perform cleanup. After that
  *   Windows will unconditionally terminate it.
  *
+ *   SIGWINCH is raised whenever libuv detects that the console has been
+ *   resized. SIGWINCH is emulated by libuv when the program uses an uv_tty_t
+ *   handle to write to the console. SIGWINCH may not always be delivered in a
+ *   timely manner; libuv will only detect size changes when the cursor is
+ *   being moved. When a readable uv_tty_handle is used in raw mode, resizing
+ *   the console buffer will also trigger a SIGWINCH signal.
+ *
  * Watchers for other signals can be successfully created, but these signals
  * are never generated. These signals are: SIGILL, SIGABRT, SIGFPE, SIGSEGV,
  * SIGTERM and SIGKILL.

src/win/signal.c

@@ -169,6 +169,10 @@ static uv_err_t uv__signal_register(int signum) {
     case SIGHUP:
       return uv__signal_register_control_handler();
 
+    case SIGWINCH:
+      /* SIGWINCH is generated in tty.c. No need to register anything. */
+      return uv_ok_;
+
     case SIGILL:
     case SIGABRT_COMPAT:
     case SIGFPE:
@@ -193,6 +197,10 @@ static void uv__signal_unregister(int signum) {
       uv__signal_unregister_control_handler();
       return;
 
+    case SIGWINCH:
+      /* SIGWINCH is generated in tty.c. No need to unregister anything. */
+      return;
+
     case SIGILL:
     case SIGABRT_COMPAT:
     case SIGFPE:

src/win/tty.c

@@ -82,6 +82,8 @@ static int uv_tty_virtual_width = -1;
 
 static CRITICAL_SECTION uv_tty_output_lock;
 
+static HANDLE uv_tty_output_handle = INVALID_HANDLE_VALUE;
+
 
 void uv_console_init() {
   InitializeCriticalSection(&uv_tty_output_lock);
@@ -113,10 +115,17 @@ int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, uv_file fd, int readable) {
       return -1;
     }
 
-    /* Update the virtual window. We must hold the tty_output_lock because the */
-    /* virtual window state is shared between all uv_tty handles. */
+    /* Obtain the the tty_output_lock because the virtual window state is */
+    /* shared between all uv_tty_t handles. */
     EnterCriticalSection(&uv_tty_output_lock);
+
+    /* Store the global tty output handle. This handle is used by TTY read */
+    /* streams to update the virtual window when a CONSOLE_BUFFER_SIZE_EVENT */
+    /* is received. */
+    uv_tty_output_handle = handle;
+
     uv_tty_update_virtual_window(&screen_buffer_info);
+
     LeaveCriticalSection(&uv_tty_output_lock);
   }
 
@@ -513,7 +522,20 @@ void uv_process_tty_read_raw_req(uv_loop_t* loop, uv_tty_t* handle,
       }
       records_left--;
 
-      /* Ignore events that are not keyboard events */
+      /* If the window was resized, recompute the virtual window size. This */
+      /* will trigger a SIGWINCH signal if the window size changed in an */
+      /* way that matters to libuv. */
+      if (handle->last_input_record.EventType == WINDOW_BUFFER_SIZE_EVENT) {
+        CONSOLE_SCREEN_BUFFER_INFO info;
+        if (uv_tty_output_handle == INVALID_HANDLE_VALUE)
+          continue;
+        if (!GetConsoleScreenBufferInfo(uv_tty_output_handle, &info))
+          continue;
+        uv_tty_update_virtual_window(&info);
+        continue;
+      }
+
+      /* Ignore other events that are not key or resize events. */
       if (handle->last_input_record.EventType != KEY_EVENT) {
         continue;
       }
@@ -835,8 +857,11 @@ int uv_tty_read_stop(uv_tty_t* handle) {
 
 
 static void uv_tty_update_virtual_window(CONSOLE_SCREEN_BUFFER_INFO* info) {
-  uv_tty_virtual_height = info->srWindow.Bottom - info->srWindow.Top + 1;
+  int old_virtual_width = uv_tty_virtual_width;
+  int old_virtual_height = uv_tty_virtual_height;
+
   uv_tty_virtual_width = info->dwSize.X;
+  uv_tty_virtual_height = info->srWindow.Bottom - info->srWindow.Top + 1;
 
   /* Recompute virtual window offset row. */
   if (uv_tty_virtual_offset == -1) {
@@ -854,6 +879,14 @@ static void uv_tty_update_virtual_window(CONSOLE_SCREEN_BUFFER_INFO* info) {
   if (uv_tty_virtual_offset < 0) {
     uv_tty_virtual_offset = 0;
   }
+
+  /* If the virtual window size changed, emit a SIGWINCH signal. Don't emit */
+  /* if this was the first time the virtual window size was computed. */
+  if (old_virtual_width != -1 && old_virtual_height != -1 &&
+      (uv_tty_virtual_width != old_virtual_width ||
+       uv_tty_virtual_height != old_virtual_height)) {
+    uv__signal_dispatch(SIGWINCH);
+  }
 }