Warn if the Windows 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 <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>

Author: kblees

compat/winansi.c

@@ -4,6 +4,8 @@
 
 #include "../git-compat-util.h"
 #include <malloc.h>
+#include <wingdi.h>
+#include <winreg.h>
 
 /*
  Functions to be wrapped:
@@ -26,6 +28,54 @@ static WORD plain_attr;
 static WORD attr;
 static int negative;
 static FILE *last_stream = NULL;
+static int non_ascii_used = 0;
+
+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;
+
+typedef BOOL (WINAPI *PGETCURRENTCONSOLEFONTEX)(HANDLE, BOOL,
+		PCONSOLE_FONT_INFOEX);
+
+static void warn_if_raster_font(void)
+{
+	DWORD fontFamily = 0;
+	PGETCURRENTCONSOLEFONTEX pGetCurrentConsoleFontEx;
+
+	/* don't bother if output was ascii only */
+	if (!non_ascii_used)
+		return;
+
+	/* GetCurrentConsoleFontEx is available since Vista */
+	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))
+		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 int is_console(FILE *stream)
 {
@@ -54,6 +104,8 @@ static int is_console(FILE *stream)
 		attr = plain_attr = sbi.wAttributes;
 		negative = 0;
 		initialized = 1;
+		/* check console font on exit */
+		atexit(warn_if_raster_font);
 	}
 
 	console = hcon;
@@ -69,6 +121,10 @@ static int write_console(const char *str, size_t len)
 
 	WriteConsoleW(console, wbuf, wlen, NULL, NULL);
 
+	/* remember if non-ascii characters are printed */
+	if (wlen != len)
+		non_ascii_used = 1;
+
 	/* return original (utf-8 encoded) length */
 	return len;
 }