[PATCH 1 of 3 V2] win32: add a method to enable ANSI color code processing on Windows 10

[Matt Harbison]

# HG changeset patch
# User Matt Harbison <matt_harbison at yahoo.com>
# Date 1495504856 14400
#      Mon May 22 22:00:56 2017 -0400
# Node ID 01e230f1d93a0b0e54164fbce14b5a0c093a4fc4
# Parent  ad37c569ec8121a99e4cd9da52365b114b82e744
win32: add a method to enable ANSI color code processing on Windows 10

SetConsoleMode() fails with an invalid parameter error if given this option
prior to Windows 10, so indicate that to the caller instead of doing explicit
version checks.

diff --git a/mercurial/win32.py b/mercurial/win32.py
--- a/mercurial/win32.py
+++ b/mercurial/win32.py
@@ -131,6 +131,7 @@
                 ('srWindow', _SMALL_RECT),
                 ('dwMaximumWindowSize', _COORD)]
 
+_STD_OUTPUT_HANDLE = _DWORD(-11).value
 _STD_ERROR_HANDLE = _DWORD(-12).value
 
 # CreateToolhelp32Snapshot, Process32First, Process32Next
@@ -202,6 +203,12 @@
 _kernel32.SetConsoleCtrlHandler.argtypes = [_SIGNAL_HANDLER, _BOOL]
 _kernel32.SetConsoleCtrlHandler.restype = _BOOL
 
+_kernel32.SetConsoleMode.argtypes = [_HANDLE, _DWORD]
+_kernel32.SetConsoleMode.restype = _BOOL
+
+_kernel32.GetConsoleMode.argtypes = [_HANDLE, ctypes.c_void_p]
+_kernel32.GetConsoleMode.restype = _BOOL
+
 _kernel32.GetStdHandle.argtypes = [_DWORD]
 _kernel32.GetStdHandle.restype = _HANDLE
 
@@ -372,6 +379,29 @@
     height = csbi.srWindow.Bottom - csbi.srWindow.Top + 1
     return width, height
 
+def enablevtmode():
+    '''Enable virtual terminal mode for the associated console.  Return True if
+    enabled, else False.'''
+
+    ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x4
+
+    handle = _kernel32.GetStdHandle(_STD_OUTPUT_HANDLE) # don't close the handle
+    if handle == _INVALID_HANDLE_VALUE:
+        return False
+
+    mode = _DWORD(0)
+
+    if not _kernel32.GetConsoleMode(handle, ctypes.byref(mode)):
+        return False
+
+    if (mode.value & ENABLE_VIRTUAL_TERMINAL_PROCESSING) == 0:
+        mode.value |= ENABLE_VIRTUAL_TERMINAL_PROCESSING
+
+        if not _kernel32.SetConsoleMode(handle, mode):
+            return False
+
+    return True
+
 def _1stchild(pid):
     '''return the 1st found child of the given pid