Win32: warn if the console font doesn't support Unicode

Unicode console output won't display correctly with default settings
because the default console font ("Terminal") only supports the system's
OEM charset. Unfortunately, this is a user specific setting, so it cannot
be easily fixed by e.g. some registry tricks in the setup program.

This change prints a warning on exit if console output contained non-ascii
characters and the console font is supposedly not a TrueType font (which
usually have decent Unicode support).

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Stepan Kasal <kasal@ucw.cz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/winansi.c

@@ -2,8 +2,11 @@
  * Copyright 2008 Peter Harris <git@peter.is-a-geek.org>
  */
 
+#undef NOGDI
 #include "../git-compat-util.h"
 #include <malloc.h>
+#include <wingdi.h>
+#include <winreg.h>
 
 /*
  Functions to be wrapped:
@@ -27,6 +30,62 @@ static WORD attr;
 static int negative;
 static FILE *last_stream = NULL;
 
+#ifdef __MINGW32__
+typedef struct _CONSOLE_FONT_INFOEX {
+	ULONG cbSize;
+	DWORD nFont;
+	COORD dwFontSize;
+	UINT FontFamily;
+	UINT FontWeight;
+	WCHAR FaceName[LF_FACESIZE];
+} CONSOLE_FONT_INFOEX, *PCONSOLE_FONT_INFOEX;
+#endif
+
+typedef BOOL (WINAPI *PGETCURRENTCONSOLEFONTEX)(HANDLE, BOOL,
+		PCONSOLE_FONT_INFOEX);
+
+static void print_font_warning(void)
+{
+	warning("Your console font probably doesn\'t support Unicode. If "
+		"you experience strange characters in the output, consider "
+		"switching to a TrueType font such as Lucida Console!");
+}
+
+static void check_truetype_font(void)
+{
+	static int truetype_font_checked;
+	DWORD fontFamily = 0;
+	PGETCURRENTCONSOLEFONTEX pGetCurrentConsoleFontEx;
+
+	/* don't do this twice */
+	if (truetype_font_checked)
+		return;
+	truetype_font_checked = 1;
+
+	/* GetCurrentConsoleFontEx is available since Vista */
+	pGetCurrentConsoleFontEx = (PGETCURRENTCONSOLEFONTEX) GetProcAddress(
+			GetModuleHandle("kernel32.dll"), "GetCurrentConsoleFontEx");
+	if (pGetCurrentConsoleFontEx) {
+		CONSOLE_FONT_INFOEX cfi;
+		cfi.cbSize = sizeof(cfi);
+		if (pGetCurrentConsoleFontEx(console, 0, &cfi))
+			fontFamily = cfi.FontFamily;
+	} else {
+		/* pre-Vista: check default console font in registry */
+		HKEY hkey;
+		if (ERROR_SUCCESS == RegOpenKeyExA(HKEY_CURRENT_USER, "Console", 0,
+				KEY_READ, &hkey)) {
+			DWORD size = sizeof(fontFamily);
+			RegQueryValueExA(hkey, "FontFamily", NULL, NULL,
+					(LPVOID) &fontFamily, &size);
+			RegCloseKey(hkey);
+		}
+	}
+
+	if (!(fontFamily & TMPF_TRUETYPE))
+		atexit(print_font_warning);
+}
+
 static int is_console(FILE *stream)
 {
 	CONSOLE_SCREEN_BUFFER_INFO sbi;
@@ -69,6 +128,13 @@ static int write_console(const char *str, size_t len)
 
 	WriteConsoleW(console, wbuf, wlen, NULL, NULL);
 
+	/*
+	 * if non-ascii characters are printed, check that the current console
+	 * font supports this
+	 */
+	if (wlen != len)
+		check_truetype_font();
+
 	/* return original (utf-8 encoded) length */
 	return len;
 }