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Add notes on fonts, code pages, and East Asian character widths

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Ryan Prichard 2015-10-10 19:25:20 -05:00
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==================================================================
Notes regarding fonts, code pages, and East Asian character widths
==================================================================
Registry settings
=================
* There are console registry settings in `HKCU\Console`. That key has many
default settings (e.g. the default font settings) and also per-app subkeys
for app-specific overrides.
* It is possible to override the code page with an app-specific setting.
* There are registry settings in
`HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Console`. In particular,
the `TrueTypeFont` subkey has a list of suitable font names associated with
various CJK code pages, as well as default font names.
* There are two values in `HKLM\SYSTEM\CurrentControlSet\Control\Nls\CodePage`
that specify the current code pages -- `OEMCP` and `ACP`. Setting the
system locale via the Control Panel's "Region" or "Language" dialogs seems
to change these code page values.
Console fonts
=============
* The `FontFamily` field of `CONSOLE_FONT_INFOEX` has two parts:
- The high four bits can be exactly one of the `FF_xxxx` font families:
FF_DONTCARE(0x00)
FF_ROMAN(0x10)
FF_SWISS(0x20)
FF_MODERN(0x30)
FF_SCRIPT(0x40)
FF_DECORATIVE(0x50)
- The low four bits are a bitmask:
TMPF_FIXED_PITCH(1) -- actually means variable pitch
TMPF_VECTOR(2)
TMPF_TRUETYPE(4)
TMPF_DEVICE(8)
* Each console has its own independent console font table. The current font
is identified with an index into this table. The size of the table is
returned by the undocumented `GetNumberOfConsoleFonts` API. It is apparently
possible to get the table size without this API, by instead calling
`GetConsoleFontSize` on each nonnegative index starting with 0 until the API
fails by returning (0, 0).
* The font table grows dynamically. Each time the console is configured with
a previously-unused (FaceName, Size) combination, two entries are added to
the font table -- one with normal weight and one with bold weight. Fonts
added this way are always TrueType fonts.
* Initially, the font table appears to contain only raster fonts. For
example, on an English Windows 8 installation, here is the initial font
table:
font 0: 4x6
font 1: 6x8
font 2: 8x8
font 3: 16x8
font 4: 5x12
font 5: 7x12
font 6: 8x12 -- the current font
font 7: 16x12
font 8: 12x16
font 9: 10x18
`GetNumberOfConsoleFonts` returns 10, and this table matches the raster font
sizes according to the console properties dialog.
* With a Japanese or Chinese locale, the initial font table appears to contain
the sizes applicable to both the East Asian raster font, as well as the
sizes for the CP437/CP1252 raster font.
* The index passed to `SetCurrentConsoleFontEx` apparently has no effect.
The undocumented `SetConsoleFont` API, however, accepts *only* a font index,
and on Windows 8 English, it switches between all 10 fonts, even font index
#0.
* If the index passed to `SetConsoleFont` identifies a Raster Font
incompatible with the current code page, then another Raster Font is
activated.
* Passing "Terminal" to `SetCurrentConsoleFontEx` seems to have no effect.
Perhaps relatedly, `SetCurrentConsoleFontEx` does not fail if it is given a
bogus `FaceName`. Some font is still chosen and activated. Passing a face
name and height seems to work reliably, modulo the CP936 issue described
below.
Console fonts and code pages
============================
* On an English Windows installation, the default code page is 437, and it
cannot be set to 932 (Shift-JIS). (The API call fails.) Changing the
system locale to "Japanese (Japan)" using the Region/Language dialog
changes the default CP to 932 and permits changing the console CP between
437 and 932.
* A console has both an input code page and an output code page
(`{Get,Set}ConsoleCP` and `{Get,Set}ConsoleOutputCP`). I'm not going to
distinguish between the two for this document; presumably only the output
CP matters. The code page can change while the console is open, e.g.
by running `mode con: cp select={932,437,1252}` or by calling
`SetConsoleOutputCP`.
* The current code page restricts which TrueType fonts and which Raster Font
sizes are available in the console properties dialog. This can change
while the console is open.
* Changing the code page almost(?) always changes the current console font.
So far, I don't know how the new font is chosen.
* With a CP of 932, the only TrueType font available in the console properties
dialog is "MS Gothic", displayed as "ＭＳ ゴシック". It is still possible to
use the English-default TrueType console fonts, Lucida Console and Consolas,
via `SetCurrentConsoleFontEx`.
* When using a Raster Font and CP437 or CP1252, writing a UTF-16 codepoint not
representable in the code page instead writes a question mark ('?') to the
console. This conversion does not apply with a TrueType font, nor with the
Raster Font for CP932 or CP936.
ReadConsoleOutput and double-width characters
==============================================
* With a Raster Font active, when `ReadConsoleOutputW` reads two cells of a
double-width character, it fills only a single `CHAR_INFO` structure. The
unused trailing `CHAR_INFO` structures are zero-filled. With a TrueType
font active, `ReadConsoleOutputW` instead fills two `CHAR_INFO` structures,
the first marked with `COMMON_LVB_LEADING_BYTE` and the second marked with
`COMMON_LVB_TRAILING_BYTE`. The flag is a misnomer--there aren't two
*bytes*, but two cells, and they have equal `CHAR_INFO.Char.UnicodeChar`
values.
* `ReadConsoleOutputA`, on the other hand, reads two `CHAR_INFO` cells, and
if the UTF-16 value can be represented as two bytes in the ANSI/OEM CP, then
the two bytes are placed in the two `CHAR_INFO.Char.AsciiChar` values, and
the `COMMON_LVB_{LEADING,TRAILING}_BYTE` values are also used. If the
codepoint isn't representable, I don't remember what happens -- I think the
`AsciiChar` values take on an invalid marker.
* Reading only one cell of a double-width character reads a space (U+0020)
instead. Raster-vs-TrueType and wide-vs-ANSI do not matter.
- XXX: what about attributes? Can a double-width character have mismatched
color attributes?
- XXX: what happens when writing to just one cell of a double-width
character?
Default Windows fonts for East Asian languages
==============================================
CP932 / Japanese: "ＭＳ ゴシック" (MS Gothic)
CP936 / Chinese Simplified: "新宋体" (SimSun)
Unreliable character width (half-width vs full-width)
=====================================================
The half-width vs full-width status of a codepoint depends on at least these variables:
* OS version (Win10 legacy and new modes are different versions)
* system locale (English vs Japanese vs Chinese Simplified vs Chinese Traditional, etc)
* code page (437 vs 932 vs 936, etc)
* raster vs TrueType (Terminal vs MS Gothic vs SimSun, etc)
* font size
* rendered-vs-model (rendered width can be larger or smaller than model width)
Example 1: U+2014 (EM DASH): East_Asian_Width: Ambiguous
--------------------------------------------------------
rendered modeled
CP932: Win7/8 Raster Fonts half half
CP932: Win7/8 Gothic 14/15px half full
CP932: Win7/8 Consolas 14/15px half full
CP932: Win7/8 Lucida Console 14px half full
CP932: Win7/8 Lucida Console 15px half half
CP932: Win10New Raster Fonts half half
CP932: Win10New Gothic 14/15px half half
CP932: Win10New Consolas 14/15px half half
CP932: Win10New Lucida Console 14/15px half half
CP936: Win7/8 Raster Fonts full full
CP936: Win7/8 SimSun 14px full full
CP936: Win7/8 SimSun 15px full half
CP936: Win7/8 Consolas 14/15px half full
CP936: Win10New Raster Fonts full full
CP936: Win10New SimSum 14/15px full full
CP936: Win10New Consolas 14/15px half half
Example 2: U+3044 (HIRAGANA LETTER I): East_Asian_Width: Wide
-------------------------------------------------------------
rendered modeled
CP932: Win7/8/10N Raster Fonts full full
CP932: Win7/8/10N Gothic 14/15px full full
CP932: Win7/8/10N Consolas 14/15px half(*2) full
CP932: Win7/8/10N Lucida Console 14/15px half(*3) full
CP936: Win7/8/10N Raster Fonts full full
CP936: Win7/8/10N SimSun 14/15px full full
CP936: Win7/8/10N Consolas 14/15px full full
Example 3: U+30FC (KATAKANA-HIRAGANA PROLONGED SOUND MARK): East_Asian_Width: Wide
----------------------------------------------------------------------------------
rendered modeled
CP932: Win7 Raster Fonts full full
CP932: Win7 Gothic 14/15px full full
CP932: Win7 Consolas 14/15px half(*2) full
CP932: Win7 Lucida Console 14px half(*3) full
CP932: Win7 Lucida Console 15px half(*3) half
CP932: Win8 Raster Fonts full full
CP932: Win8 Gothic 14px full half
CP932: Win8 Gothic 15px full full
CP932: Win8 Consolas 14/15px half(*2) full
CP932: Win8 Lucida Console 14px half(*3) full
CP932: Win8 Lucida Console 15px half(*3) half
CP932: Win10New Raster Fonts full full
CP932: Win10New Gothic 14/15px full full
CP932: Win10New Consolas 14/15px half(*2) half
CP932: Win10New Lucida Console 14/15px half(*2) half
CP936: Win7/8 Raster Fonts full full
CP936: Win7/8 SimSun 14px full full
CP936: Win7/8 SimSun 15px full half
CP936: Win7/8 Consolas 14px full full
CP936: Win7/8 Consolas 15px full half
CP936: Win10New Raster Fonts full full
CP936: Win10New SimSum 14/15px full full
CP936: Win10New Consolas 14/15px full full
Example 4: U+4000 (CJK UNIFIED IDEOGRAPH-4000): East_Asian_Width: Wide
----------------------------------------------------------------------
rendered modeled
CP932: Win7 Raster Fonts half(*1) half
CP932: Win7 Gothic 14/15px full full
CP932: Win7 Consolas 14/15px half(*2) full
CP932: Win7 Lucida Console 14px half(*3) full
CP932: Win7 Lucida Console 15px half(*3) half
CP932: Win8 Raster Fonts half(*1) half
CP932: Win8 Gothic 14px full half
CP932: Win8 Gothic 15px full full
CP932: Win8 Consolas 14/15px half(*2) full
CP932: Win8 Lucida Console 14px half(*3) full
CP932: Win8 Lucida Console 15px half(*3) half
CP932: Win10New Raster Fonts half(*1) half
CP932: Win10New Gothic 14/15px full full
CP932: Win10New Consolas 14/15px half(*2) half
CP932: Win10New Lucida Console 14/15px half(*2) half
CP936: Win7/8 Raster Fonts full full
CP936: Win7/8 SimSun 14px full full
CP936: Win7/8 SimSun 15px full half
CP936: Win7/8 Consolas 14px full full
CP936: Win7/8 Consolas 15px full half
CP936: Win10New Raster Fonts full full
CP936: Win10New SimSum 14/15px full full
CP936: Win10New Consolas 14/15px full full
(*1) Rendered as a half-width filled white box
(*2) Rendered as a half-width box with a question mark inside
(*3) Rendered as a half-width empty box
(!!) One of the only places in Win10New where rendered and modeled width disagree
Windows quirk: unreliable font heights with CP936 / Chinese Simplified
======================================================================
When I set the font to 新宋体 17px, using either the properties dialog or
`SetCurrentConsoleFontEx`, the height reported by `GetCurrentConsoleFontEx` is
not 17, but is instead 19. The same problem does not affect Raster Fonts,
nor have I seen the problem in the English or Japanese locales. I observed
this with Windows 7 and Windows 10 new mode.
If I set the font using the facename, width, *and* height, then the
`SetCurrentConsoleFontEx` and `GetCurrentConsoleFontEx` values agree. If I
set the font using *only* the facename and height, then the two values
disagree.
Windows bug: GetCurrentConsoleFontEx is initially invalid
=========================================================
- Assume there is no configured console font name in the registry. In this
case, the console defaults to a raster font.
- Open a new console and call the `GetCurrentConsoleFontEx` API.
- The `FaceName` field of the returned `CONSOLE_FONT_INFOEX` data
structure is incorrect. On Windows 7, 8, and 10, I observed that the
field was blank. On Windows 8, occasionally, it instead contained:
U+AE72 U+75BE U+0001
The other fields of the structure all appeared correct:
nFont=6 dwFontSize=(8,12) FontFamily=0x30 FontWeight=400
- The `FaceName` field becomes initialized easily:
- Open the console properties dialog and click OK. (Cancel is not
sufficient.)
- Call the undocumented `SetConsoleFont` with the current font table
index, which is 6 in the example above.
- It seems that the console uncritically accepts whatever string is
stored in the registry, including a blank string, and passes it on the
the `GetCurrentConsoleFontEx` caller. It is possible to get the console
to *write* a blank setting into the registry -- simply open the console
(default or app-specific) properties and click OK.