Font selection weirdness

["Juanma Barranquero" <lekktu@gmail.com>]

In my setup, there are a few characters in etc/HELLO (four
mathematical symbols and two extended latin chars from vietnamese, at
least) which are not displayed; I mean, they appear as whitespace, not
the "no font available" empty box. However, describe-char says that
there's a font for them:

--------------------------------------------------------------------------------
        character: ∀ (8704, #o21000, #x2200)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x2200
           syntax: . 	which means: punctuation
         category: h:Korean j:Japanese
      buffer code: #xE2 #x88 #x80
        file code: ESC #x24 #x42 #x22 #x4F (encoded by coding system
iso-2022-7bit-dos)
          display: by this font (glyph code)
     -outline-Symbol-normal-normal-normal-decorative-13-*-*-*-p-*-ms-symbol
(#x2200)

Character code properties: customize what to show
  name: FOR ALL
  general-category: Sm (Symbol, Math)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: ON (Other Neutrals)
  mirrored: N

There are text properties here:
  auto-composed        t
  charset              japanese-jisx0208
--------------------------------------------------------------------------------
        character: ∈ (8712, #o21010, #x2208)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x2208
           syntax: . 	which means: punctuation
         category: c:Chinese h:Korean j:Japanese
      buffer code: #xE2 #x88 #x88
        file code: ESC #x24 #x41 #x21 #x4A (encoded by coding system
iso-2022-7bit-dos)
          display: by this font (glyph code)
     -outline-Symbol-normal-normal-normal-decorative-13-*-*-*-p-*-ms-symbol
(#x2208)

Character code properties: customize what to show
  name: ELEMENT OF
  general-category: Sm (Symbol, Math)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: ON (Other Neutrals)
  mirrored: Y

There are text properties here:
  auto-composed        t
  charset              chinese-gb2312
--------------------------------------------------------------------------------
        character: • (8226, #o20042, #x2022)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x2022
           syntax: _ 	which means: symbol
         category: j:Japanese
      buffer code: #xE2 #x80 #xA2
        file code: ESC #x24 #x28 #x4F #x23 #x40 (encoded by coding
system iso-2022-7bit-dos)
          display: by this font (glyph code)
     -outline-Symbol-normal-normal-normal-decorative-13-*-*-*-p-*-ms-symbol
(#x2022)

Character code properties: customize what to show
  name: BULLET
  general-category: Po (Punctuation, Other)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: ON (Other Neutrals)
  mirrored: N

There are text properties here:
  auto-composed        t
  charset              japanese-jisx0213-1
--------------------------------------------------------------------------------
        character: □ (9633, #o22641, #x25a1)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x25A1
           syntax: _ 	which means: symbol
         category: c:Chinese h:Korean j:Japanese
      buffer code: #xE2 #x96 #xA1
        file code: ESC #x24 #x41 #x21 #x75 (encoded by coding system
iso-2022-7bit-dos)
          display: by this font (glyph code)
     -outline-Symbol-normal-normal-normal-decorative-13-*-*-*-p-*-ms-symbol
(#x25A1)

Character code properties: customize what to show
  name: WHITE SQUARE
  general-category: So (Symbol, Other)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: ON (Other Neutrals)
  mirrored: N

There are text properties here:
  auto-composed        t
  charset              chinese-gb2312
--------------------------------------------------------------------------------
        character: ế (7871, #o17277, #x1ebf)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x1EBF
           syntax: w 	which means: word
         category: l:Latin v:Vietnamese
      buffer code: #xE1 #xBA #xBF
        file code: ESC #x2C #x31 #x2A (encoded by coding system
iso-2022-7bit-dos)
          display: by this font (glyph code)
     -outline-DejaVu Sans
Mono-normal-normal-normal-mono-13-*-*-*-m-*-iso8859-5 (#x03)

Character code properties: customize what to show
  name: LATIN SMALL LETTER E WITH CIRCUMFLEX AND ACUTE
  general-category: Ll (Letter, Lowercase)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: L (Left-to-Right)
  decomposition: (234 769) ('ê' '́')
  mirrored: N
  uppercase: 7870 (Ế)
  titlecase: 7870 (Ế)

There are text properties here:
  auto-composed        t
  charset              vietnamese-viscii-lower
--------------------------------------------------------------------------------
        character: ệ (7879, #o17307, #x1ec7)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x1EC7
           syntax: w 	which means: word
         category: l:Latin v:Vietnamese
      buffer code: #xE1 #xBB #x87
        file code: ESC #x2C #x31 #x2E (encoded by coding system
iso-2022-7bit-dos)
          display: by this font (glyph code)
     -outline-DejaVu Sans
Mono-normal-normal-normal-mono-13-*-*-*-m-*-iso8859-5 (#x03)

Character code properties: customize what to show
  name: LATIN SMALL LETTER E WITH CIRCUMFLEX AND DOT BELOW
  general-category: Ll (Letter, Lowercase)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: L (Left-to-Right)
  decomposition: (7865 770) ('ẹ' '̂')
  mirrored: N
  uppercase: 7878 (Ệ)
  titlecase: 7878 (Ệ)

There are text properties here:
  auto-composed        t
  charset              vietnamese-viscii-lower
--------------------------------------------------------------------------------



If I type these characters in *scratch*, via ucs-insert, three of them
are displayed correctly (U+2208, U+2022 and U+25A1), and the other
three appear as empty boxes (though Emacs still thinks it has a font
for them).

This is what describe-char says for the three non-visible characters
in *scratch*:



--------------------------------------------------------------------------------
        character: ∀ (8704, #o21000, #x2200)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x2200
           syntax: . 	which means: punctuation
         category: h:Korean j:Japanese
      buffer code: #xE2 #x88 #x80
        file code: #xE2 #x88 #x80 (encoded by coding system utf-8-unix)
          display: by this font (glyph code)
     -outline-DejaVu Sans
Mono-normal-normal-normal-mono-13-*-*-*-m-*-iso10646-1 (#x2200)

Character code properties: customize what to show
  name: FOR ALL
  general-category: Sm (Symbol, Math)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: ON (Other Neutrals)
  mirrored: N

There are text properties here:
  auto-composed        t
  fontified            t
--------------------------------------------------------------------------------
        character: ∈ (8712, #o21010, #x2208)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x2208
           syntax: . 	which means: punctuation
         category: c:Chinese h:Korean j:Japanese
      buffer code: #xE2 #x88 #x88
        file code: #xE2 #x88 #x88 (encoded by coding system utf-8-unix)
          display: by this font (glyph code)
     -outline-DejaVu Sans
Mono-normal-normal-normal-mono-13-*-*-*-m-*-iso10646-1 (#x2208)

Character code properties: customize what to show
  name: ELEMENT OF
  general-category: Sm (Symbol, Math)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: ON (Other Neutrals)
  mirrored: Y

There are text properties here:
  auto-composed        t
  fontified            t
--------------------------------------------------------------------------------
        character: • (8226, #o20042, #x2022)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x2022
           syntax: _ 	which means: symbol
         category: j:Japanese
      buffer code: #xE2 #x80 #xA2
        file code: #xE2 #x80 #xA2 (encoded by coding system utf-8-unix)
          display: by this font (glyph code)
     -outline-DejaVu Sans
Mono-normal-normal-normal-mono-13-*-*-*-m-*-iso10646-1 (#x2022)

Character code properties: customize what to show
  name: BULLET
  general-category: Po (Punctuation, Other)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: ON (Other Neutrals)
  mirrored: N

There are text properties here:
  auto-composed        t
  fontified            t
--------------------------------------------------------------------------------
        character: □ (9633, #o22641, #x25a1)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x25A1
           syntax: _ 	which means: symbol
         category: c:Chinese h:Korean j:Japanese
      buffer code: #xE2 #x96 #xA1
        file code: #xE2 #x96 #xA1 (encoded by coding system utf-8-unix)
          display: by this font (glyph code)
     -outline-DejaVu Sans
Mono-normal-normal-normal-mono-13-*-*-*-m-*-iso10646-1 (#x25A1)

Character code properties: customize what to show
  name: WHITE SQUARE
  general-category: So (Symbol, Other)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: ON (Other Neutrals)
  mirrored: N

There are text properties here:
  auto-composed        t
  fontified            t
--------------------------------------------------------------------------------
        character: ế (7871, #o17277, #x1ebf)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x1EBF
           syntax: w 	which means: word
         category: l:Latin v:Vietnamese
      buffer code: #xE1 #xBA #xBF
        file code: #xE1 #xBA #xBF (encoded by coding system utf-8-unix)
          display: by this font (glyph code)
     -outline-DejaVu Sans
Mono-normal-normal-normal-mono-13-*-*-*-m-*-iso10646-1 (#x1EBF)

Character code properties: customize what to show
  name: LATIN SMALL LETTER E WITH CIRCUMFLEX AND ACUTE
  general-category: Ll (Letter, Lowercase)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: L (Left-to-Right)
  decomposition: (234 769) ('ê' '́')
  mirrored: N
  uppercase: 7870 (Ế)
  titlecase: 7870 (Ế)

There are text properties here:
  auto-composed        t
  fontified            t
--------------------------------------------------------------------------------
        character: ệ (7879, #o17307, #x1ec7)
preferred charset: unicode (Unicode (ISO10646))
       code point: 0x1EC7
           syntax: w 	which means: word
         category: l:Latin v:Vietnamese
      buffer code: #xE1 #xBB #x87
        file code: #xE1 #xBB #x87 (encoded by coding system utf-8-unix)
          display: by this font (glyph code)
     -outline-DejaVu Sans
Mono-normal-normal-normal-mono-13-*-*-*-m-*-iso10646-1 (#x1EC7)

Character code properties: customize what to show
  name: LATIN SMALL LETTER E WITH CIRCUMFLEX AND DOT BELOW
  general-category: Ll (Letter, Lowercase)
  canonical-combining-class: 0 (Spacing, split, enclosing, reordrant,
and Tibetan subjoined)
  bidi-class: L (Left-to-Right)
  decomposition: (7865 770) ('ẹ' '̂')
  mirrored: N
  uppercase: 7878 (Ệ)
  titlecase: 7878 (Ệ)

There are text properties here:
  auto-composed        t
  fontified            t
--------------------------------------------------------------------------------



 Juanma