From bf8aabe830d215f13e690b21a682fc37aeb8752c Mon Sep 17 00:00:00 2001
From: Corinna Vinschen <corinna@vinschen.de>
Date: Wed, 5 Sep 2018 23:39:25 +0200
Subject: [PATCH] Cygwin: console: improve replacement char algorithm

Try various Unicode characters which may be used as a replacement
character in case an invalid character has to be printed.

Current list is 0xfffd "REPLACEMENT CHARACTER", 0x25a1 "WHITE SQUARE",
and 0x2592 "MEDIUM SHADE" in that order.

Additionally workaround a problem with some fonts (namely DejaVu
Sans Mono) which are returned wit ha broken fontname with trailing
stray characters.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
---
 winsup/cygwin/autoload.cc         |  7 +++
 winsup/cygwin/fhandler_console.cc | 95 ++++++++++++++++++++++++++++++-
 2 files changed, 99 insertions(+), 3 deletions(-)

diff --git a/winsup/cygwin/autoload.cc b/winsup/cygwin/autoload.cc
index f71abe802..4fac3e39c 100644
--- a/winsup/cygwin/autoload.cc
+++ b/winsup/cygwin/autoload.cc
@@ -640,6 +640,12 @@ LoadDLLfunc (LsaRegisterLogonProcess, 12, secur32)
 
 LoadDLLfunc (SHGetDesktopFolder, 4, shell32)
 
+LoadDLLfunc (CreateFontW, 56, gdi32)
+LoadDLLfunc (DeleteObject, 4, gdi32)
+LoadDLLfunc (EnumFontFamiliesExW, 20, gdi32)
+LoadDLLfunc (GetGlyphIndicesW, 20, gdi32)
+LoadDLLfunc (SelectObject, 8, gdi32)
+
 LoadDLLfunc (CloseClipboard, 0, user32)
 LoadDLLfunc (CloseDesktop, 4, user32)
 LoadDLLfunc (CloseWindowStation, 4, user32)
@@ -651,6 +657,7 @@ LoadDLLfunc (DispatchMessageW, 4, user32)
 LoadDLLfunc (EmptyClipboard, 0, user32)
 LoadDLLfunc (EnumWindows, 8, user32)
 LoadDLLfunc (GetClipboardData, 4, user32)
+LoadDLLfunc (GetDC, 4, user32)
 LoadDLLfunc (GetForegroundWindow, 0, user32)
 LoadDLLfunc (GetKeyboardLayout, 4, user32)
 LoadDLLfunc (GetMessageW, 16, user32)
diff --git a/winsup/cygwin/fhandler_console.cc b/winsup/cygwin/fhandler_console.cc
index b4674b8be..c654d66a6 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -1971,14 +1971,103 @@ bad_escape:
     }
 }
 
+#define NUM_REPLACEMENT_CHARS	3
+
+static const wchar_t replacement_char[NUM_REPLACEMENT_CHARS] =
+{
+  0xfffd, /* REPLACEMENT CHARACTER */
+  0x25a1, /* WHITE SQUARE */
+  0x2592  /* MEDIUM SHADE */
+};
+/* nFont member is always 0 so we have to use the facename. */
+static WCHAR cons_facename[LF_FACESIZE];
+static int rp_char_idx;
+static HDC cdc;
+
+static int CALLBACK
+enum_proc (const LOGFONTW *lf, const TEXTMETRICW *tm,
+	   DWORD FontType, LPARAM lParam)
+{
+  int *done = (int *) lParam;
+  *done = 1;
+  return 0;
+}
+
+static void
+check_font (HANDLE hdl)
+{
+  CONSOLE_FONT_INFOEX cfi;
+  LOGFONTW lf;
+
+  cfi.cbSize = sizeof cfi;
+  if (!GetCurrentConsoleFontEx (hdl, 0, &cfi))
+    return;
+  /* Switched font? */
+  if (wcscmp (cons_facename, cfi.FaceName) == 0)
+    return;
+  if (!cdc && !(cdc = GetDC (GetConsoleWindow ())))
+    return;
+  /* Some FaceNames like DejaVu Sans Mono are sometimes returned with stray
+     trailing chars.  Fix it. */
+  lf.lfCharSet = ANSI_CHARSET;
+  lf.lfPitchAndFamily = FIXED_PITCH | FF_DONTCARE;
+  wchar_t *cp = wcpcpy (lf.lfFaceName, cfi.FaceName) - 1;
+  int done = 0;
+  do
+    {
+      EnumFontFamiliesExW (cdc, &lf, enum_proc, (LPARAM) &done, 0);
+      if (!done && cp > lf.lfFaceName)
+	*cp-- = L'\0';
+    }
+  while (!done);
+  /* Yes.  Check for the best replacement char. */
+  HFONT f = CreateFontW (0, 0, 0, 0,
+			 cfi.FontWeight, FALSE, FALSE, FALSE,
+			 ANSI_CHARSET, OUT_DEFAULT_PRECIS,
+			 CLIP_DEFAULT_PRECIS, DEFAULT_QUALITY,
+			 FIXED_PITCH | FF_DONTCARE, lf.lfFaceName);
+  if (!f)
+    return;
+
+  HFONT old_f = (HFONT) SelectObject(cdc, f);
+  if (old_f)
+    {
+      WORD glyph_idx[NUM_REPLACEMENT_CHARS];
+
+      if (GetGlyphIndicesW (cdc, replacement_char,
+			    NUM_REPLACEMENT_CHARS, glyph_idx,
+			    GGI_MARK_NONEXISTING_GLYPHS) != GDI_ERROR)
+	{
+	  int i;
+
+	  for (i = 0; i < NUM_REPLACEMENT_CHARS; ++i)
+	    if (glyph_idx[i] != 0xffff)
+	      break;
+	  if (i == NUM_REPLACEMENT_CHARS)
+	    i = 0;
+	  rp_char_idx = i;
+	  /* Note that we copy the original name returned by
+	     GetCurrentConsoleFontEx, even if it was broken.
+	     This allows an early return, rather than to store
+	     the fixed name and then having to enum font families
+	     all over again. */
+	  wcscpy (cons_facename, cfi.FaceName);
+	}
+      SelectObject (cdc, old_f);
+    }
+  DeleteObject (f);
+}
+
 /* This gets called when we found an invalid input character.
-   Print Unicode REPLACEMENT CHARACTER (UTF 0xfffd). */
+   Print one of the above Unicode chars as replacement char. */
 inline void
 fhandler_console::write_replacement_char ()
 {
-  static const wchar_t replacement_char = 0xfffd; /* REPLACEMENT CHARACTER */
+  check_font (get_output_handle ());
+
   DWORD done;
-  WriteConsoleW (get_output_handle (), &replacement_char, 1, &done, 0);
+  WriteConsoleW (get_output_handle (), &replacement_char[rp_char_idx], 1,
+		 &done, 0);
 }
 
 const unsigned char *