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normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600 |
700 | 800 | 900 | inherit
Initial:
normal
Applies to:
all elements
Inherited:
yes
Percentages: N/A
Media:
visual
The ’font-weight’ property selects the weight of the font. The values ’100’ to ’900’
form an ordered sequence, where each number indicates a weight that is at least as
dark as its predecessor. The keyword ’normal’ is synonymous with ’400’, and ’bold’
is synonymous with ’700’. Keywords other than ’normal’ and ’bold’ have been shown
to be often confused with font names and a numerical scale was therefore chosen
for the 9-value list.
p { font-weight: normal } /* 400 */
h1 { font-weight: 700 } /* bold */
The ’bolder’ and ’lighter’ values select font weights that are relative to the weight
inherited from the parent:
strong { font-weight: bolder }
Child elements inherit the resultant weight, not the keyword value.
Fonts (the font data) typically have one or more properties whose values are
names that are descriptive of the "weight" of a font. There is no accepted, universal
meaning to these weight names. Their primary role is to distinguish faces of differing
darkness within a single font family. Usage across font families is quite variant; for
example a font that you might think of as being bold might be described as being
Regular, Roman, Book, Medium, Semi- or DemiBold, Bold, or Black, depending on
how black the "normal" face of the font is within the design. Because there is no
standard usage of names, the weight property values in CSS 2.1 are given on a
numerical scale in which the value ’400’ (or ’normal’) corresponds to the "normal"
text face for that family. The weight name associated with that face will typically be
Book, Regular, Roman, Normal or sometimes Medium.
The association of other weights within a family to the numerical weight values is
intended only to preserve the ordering of darkness within that family. However, the
following heuristics tell how the assignment is done in typical cases:
195
2 Aug 2002 21:33
Fonts
If the font family already uses a numerical scale with nine values (like e.g.
OpenType does), the font weights should be mapped directly.
If there is both a face labeled Medium and one labeled Book, Regular, Roman
or Normal, then the Medium is normally assigned to the ’500’.
The font labeled "Bold" will often correspond to the weight value ’700’.
If there are fewer then 9 weights in the family, the default algorithm for filling the
"holes" is as follows. If ’500’ is unassigned, it will be assigned the same font as
’400’. If any of the values ’600’, ’700’, ’800’ or ’900’ remains unassigned, they
are assigned to the same face as the next darker assigned keyword, if any, or
the next lighter one otherwise. If any of ’300’, ’200’ or ’100’ remains unassigned,
it is assigned to the next lighter assigned keyword, if any, or the next darker
otherwise.
The following two examples show typical mappings.
Assume four weights in the "Rattlesnake" family, from lightest to darkest: Regular,
Medium, Bold, Heavy.
First example of font-weight mapping
Available faces
Assignments
"Rattlesnake Regular" 400
"Rattlesnake Medium" 500
"Rattlesnake Bold"
700
"Rattlesnake Heavy"
800
Filling the holes
100, 200, 300
600
900
Assume six weights in the "Ice Prawn" family: Book, Medium, Bold, Heavy, Black,
ExtraBlack. Note that in this instance the user agent has decided not to assign a
numeric value to "Ice Prawn ExtraBlack".
Second example of font-weight mapping
Available faces
Assignments Filling the holes
"Ice Prawn Book"
400
"Ice Prawn Medium"
500
"Ice Prawn Bold"
700
"Ice Prawn Heavy"
800
"Ice Prawn Black"
900
"Ice Prawn ExtraBlack" (none)
100, 200, 300
600
2 Aug 2002 21:33
196
Fonts
Since the intent of the relative keywords ’bolder’ and ’lighter’ is to darken or lighten
the face within the family and because a family may not have faces aligned with all
the symbolic weight values, the matching of ’bolder’ is to the next darker face avail-
able on the client within the family and the matching of ’lighter’ is to the next lighter
face within the family. To be precise, the meaning of the relative keywords ’bolder’
and ’lighter’ is as follows:
’bolder’ selects the next weight that is assigned to a font that is darker than the [ Pobierz całość w formacie PDF ]
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