LIS650 lecture 2 Major CSS

1
LIS650 lecture 2Major CSS

• Thomas Krichel
• 2006-02-17

2
today

• Introduction to style sheets
• How to give style sheet data
• Basic CSS selectors
• Some important properties
• Some less important properties

3
style sheets

• Style sheets are the officially sanctioned way to
  add style to your document
• We will cover Cascading Style Sheets CSS.
• This is the default style sheet language.
• We are discussing version 2.1. This is not yet a
  W3C recommendation, but it is in last call.
• You can read all about it at http//www.w3.org/TR/
  CSS21/

4
what is in a style sheet?

• A style sheet is a sequence of style rules.
• In the sheet, one rule follows the other. There
  is no nesting of rules.
• Therefore the way rules are written in a style
  sheet is much simpler than the way elements are
  written in XML.
• Remember that in XML we have nesting of elements.

5
what is a style rule about?

• It is about two or three things
• Where to find what to style? --gt selector
• How style it?
• Which property to set? --gt property name
• Which value to give to the property? --gt
  property value
• In this lecture I will use the following syntax
• Write property names as property-name
• Write property values as value

6
why are they cascading?

• You can have many style sheet in different
  places. Style sheets comes in the form of rules
  at this place, do that.
• Where there are many rules, there is potential
  for conflict. We do not learn the exact rules
  here but note
• Some rules are read after others other. Later
  rules override earlier rules.
• Some rules concern more specific locations than
  others. The specific rules override general
  rules.

7
in-element style

• You can add a style attribute to any element
  that admits the core attributes as in
• ltelement style"style"gt .. ltelementgt
• where style is a style sheet. There is no
  selector.
• Example
• lth1 style"color blue"gtI am so bluelt/h1gt
• Such a declaration only takes effect for the
  element concerned.
• I do not recommend this.

8
document level style

• You can add a ltstylegt element as child of the
  ltheadgt. The style sheet is the contents of
  ltstylegt
• ltheadgtltstylegt stylesheet lt/stylegtlt/headgt
• ltstylegt takes the core attributes.
• It takes a type attribute, "text/css" is the
  default value.
• It takes the media attribute for the intended
  media. This attribute allows you to set write
  different styles for different media. See later
  slide.

9
linking to an external style sheet

• This is the best way! Use the same style sheet
  file for all the pages in your site, by adding to
  every pages something like
• ltlink rel"stylesheet" type"text/css"
• href"URI"/gt
• where URI is a URI where the style sheet is to
  be downloaded from. On wotan, this can just be
  the file name.
• type and href are required attributes here.
• Example
• ltlink rel"stylesheet" type"text/css"
  href"http//openlib.org/home/krichel/krichel.css"
  gt

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in our situation

• ltlink rel"stylesheet" type"text/css"
• href"main.css"/gt
• Then create a file main.css with a simple test
  rule such as
• h1 color blue
• main.css is just an example filename, any file
  name will do.
• Try it out!

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basic style syntax

• selector property1 value1 property2 value2
  
• selector is a selector (see following slides)
• property is the name of a property
• value is the value of a property
• note colon and semicolon use!
• all names and values are case-insensitive
• Examples
• h1 color grey text-align center
• .blue color blue / yes, with a dot /

12
comments in the style sheet

• You can add comments is the style sheet by
  enclosing the comment between / and /.
• This comment syntax comes from the C programming
  language.
• This technique is especially useful if you want
  to remove code from your style sheet temporarily.

13
some selectors

• The most elementary selector is the name of an
  HTML element, e.g.
• h1 text-align center
• will center all lth1gt element contents.
• But the selectors can be more precise, we are
  only look at one alternative here, class
  selectors.

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class selectors

• The is the standard way to style up a class
• .class property1 value1 property2 value2
  
• will give all the properties and values to
  any element in the class class.
• Recall that in HTML, you can say
• ltelement class"class"gt ... lt/elementgt
• to place the element element into the class
  class. Note that you can place an element into
  several classes. Use blanks to separate the
  different class names.

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id selectors

• The standard way to style up a single element is
  to use its id
• id property1 value1 property2 value2
• will give all the properties and values to
  the element with the identifier id attribute set
  to id.
• Recall that in HTML, you can identify an
  individual element element by giving it an id
• ltelement id"id"gt ... lt/elementgt

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visual style sheets

• In this class we ignore aural style sheets and
  work only on visual ones.
• We have two important concepts.
• The canvas is the support of the rendering. There
  may be several canvases on a document. On screen,
  each canvas is flat and of infinite dimensions.
• The viewport is the part of the canvas that is
  currently visible. There is only one viewport per
  canvas.
• We will now examine some important property
  values in visual style sheet regarding
• colors
• distances

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property values colors

• they follow the RGB color model.
• expressed as three hex numbers 00 to FF.
• The following standard color names are defined
• Black 000000 Green 00FF00
• Silver C0C0C0 Lime 008000
• Gray 808080 Olive 808000
• White FFFFFF Yellow FFFF00
• Maroon 800000 Navy 000080
• Red FF0000 Blue 0000FF
• Purple 800080 Teal 008080
• Fuchsia FF00FF Aqua 00FFFF
• other names may be supported by browsers.

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values measures

• relatively
• em the font-size of the relevant font
• ex the x-height of the relevant font
• px pixels, relative to the viewing device
• absolutely
• in inches 1 inch is equal to 2.54 centimeters.
  
• cm centimeters
• mm millimeters
• pt points 1 point is equal to 1/72th of an
  inch
• pc picas 1 pica is equal to 12 points
• percentage, depending on other values. That other
  value may be
• some property for other element
• same property of an ancestor element
• the value used in a formating context.

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the default style sheet (extract)

• blockquote, body, dd, div, dl, dt, h1, h2, h3,
  h4, h5, h6, ol, p, ul, hr, pre display block
• li display list-item
• head display none
• body margin 8px line-height 1.12
• h1 font-size 2em margin .67em 0
• h2 font-size 1.5em margin .75em 0
• h3 font-size 1.17em margin .83em 0
• h4, p, blockquote, ul, ol, dl, margin 1.12em 0
  
• h5 font-size .83em margin 1.5em 0
• h6 font-size .75em margin 1.67em 0

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the default style sheet (extract)

• h1, h2, h3, h4, h5, h6, b, strong font-weight
  bolder
• blockquote margin-left 40px margin-right
  40px
• i, cite, em, var, address font-style italic
• pre, tt, code, kbd, samp font-family monospace
  
• pre white-space pre
• big font-size 1.17em
• small, sub, sup font-size .83em
• sub vertical-align sub
• sup vertical-align super
• del text-decoration line-through
• hr border 1px inset
• ol, ul, dd margin-left 40px
• ol list-style-type decimal

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important properties

• We will now look at the properties as defined by
  CSS. These are the things that you can set using
  CSS.
• We group properties into six groups
• colors, and background
• boxes and layout
• fonts
• text
• lists
• element classification

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color background properties

• color sets the foreground color of an
  element.
• background-color gives the color of the
  background
• background-image url(URI) places a picture
  found at a URI URI.
• background-repeat can take the value repeat
  (default), repeat-x, repeat-y, and
  no-repeat.
• background-attachment can take the value of
  fixed or scroll (default) to say if the image
  scrolls with the viewport.

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color background properties II

• background-position property places the
  background image. It can take values
• '0 0' to '100 100'
• 'length length' to put length of offset from top
  left
• mixing both is allowed
• top, center,bottom and left, right,
  center can be used too

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normal flow

• In general, every piece of HTML is placed into a
  conceptual thingy called a box.
• In visual formatting, we can think about the box
  as a rectangle that fills the material that is
  being visualized.
• For text-level elements, boxes are set
  horizontally next to each other.
• For block-level elements, boxes are set
  vertically next to each other.

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the box model

• The total width that the box occupies is the sum
  of
• the left and right margin
• the left and right border width
• the left and right padding
• the width of the boxs contents
• The margin concept here is the same as the
  spacing in the tables.
• A similar reasoning holds for the height that the
  box occupies.

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box border properties

• border-style border-top-style
  border-right-style border-bottom-style
  border-left-style take the following values
• none No border. border-width becomes zero.
  This is the default.
• hidden Same as 'none', except in terms of border
  conflict resolution
• dotted The border is a series of dots.
• dashed The border is a series of short line
  segments.
• solid The border is a single line segment.
• double The border is two solid lines.
• groove The border looks as though it were carved
  into the canvas.
• ridge The border looks as though it were coming
  out of the canvas.
• inset The border makes the box look like
  embedded in the canvas.
• outset The border makes the box look like coming
  out of the canvas.

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box properties I

• border-color can hold up to four colors,
  separated by blanks
• one value means all borders have the same color
• two values mean first number for top and bottom,
  second for left and right
• three values mean first sets top, second left
  and right, third bottom
• four values mean first sets top, second sets
  right etc.
• border-width can hold up to four widths, as
  well as the words 'thin', 'thick' and 'medium'.

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box properties II

• border-top-width , border-bottom-width ,
  border-left-width and border-right-width
  also exist.
• same properties exists for margin-top ,
  margin-bottom etc and padding-top ,
  padding-bottom etc.
• width sets the total width of the box and
  height sets the total height of the box, both
  take a dimension or the word 'auto' e.g. img
  width 100px height auto

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box properties III

• clear tells the user agent whether to place
  the current element next to a floating element or
  on the next line below it.
• value 'none' tells the user agent to put contents
  on either side of the floating element
• value 'left' means that the left side has to stay
  clear
• value 'right' means that the right side has to
  stay clear
• value 'all' means that both sides have to stay
  clear

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position

• 'static' The box is a normal box, laid out
  according to the normal flow.
• 'relative' The box's position is calculated
  according to the normal flow. Then it is offset
  relative to its normal position. The position of
  the following box is not affected.
• 'absolute' The box's position is specified by
  offsets with respect to the box's containing
  element. There is no effect on sibling boxes.
• 'fixed' The box's position is calculated
  according to the 'absolute' model, but the
  reference is not the containing element but
• For continuous media, the box is fixed with
  respect to the viewport
• For paged media, the box is fixed with respect to
  the page

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properties with position

• top, right, bottom, left set offsets
  if positioning is relative, absolute or fixed.
• They can take length values, percentages, and
  'auto'.
• the effect of 'auto' depends on which other
  properties have been set to 'auto
• Now check the examples page.

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box properties V

• z-index let you set an integer value for a
  layer on the canvas where the element will
  appear.
• If element 1 has z-index value 1 and element 2
  has z-index value number 2, element 2 lies on top
  of element 1.
• A negative value means that the element contents
  is behind its containing block.
• the initial value is 'auto'.
• browser support for this property is limited.

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general background to foreground order

• For an element, the order is approximately
• background and borders of element
• children of the element with negative z-index
• non-inline in-flow children
• children that are floats
• children that are in-line in-flow
• children with z-index 0 or better
• not worth remembering for quiz

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box properties VI

• The visibility property sets the visibility
  of a tag. It takes values
• 'visible' The generated box is visible.
• 'hidden' The generated box is invisible (fully
  transparent), but still affects layout.
• 'collapse' The element collapses in the table.
  Only useful if applied to table elements.
  Otherwise, 'collapse' has the same meaning as
  'hidden'.
• With this you can do sophisticated alignments.

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box properties VII

• We now look at overflow and clipping. When a box
  contents is larger than the containing box, it
  overflows.
• overflow can take the values
• visible contents is allowed to overflow
• hidden contents is hidden
• scroll UA displays a scroll device at the edge
  of the box
• auto leave to the user agent to decide what
  to do

36
list properties

• list-style-position can take the value
  inside or outside. The latter is the default,
  the property refers to the position of the list
  item start marker
• list-style-property
• takes the values disc, circle, square,
  none with an unordered list
• takes the value decimal, lower-roman,
  upper-roman, lower-alpha, upper-alpha with
  ordered list, and some others
• list-style-image define the bullet point of a
  list as a graphic, use url(URL) to give the
  location of the graphic.

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classification properties I

• display sets the display type of an element,
  it take the following values
• 'block' displays the contents as a block
• 'inline' displays the contents as inline
  contents
• 'list-item' makes contents an item of a list. You
  can
• then attach list properties to
  it.
• 'none' does not display the contents.
• 'run-in' (see later)
• 'compact' (see later)

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classification properties II

• display also takes the following values
• table table-footer-group
• table-row table-row-group
• table-cell table-column
• table-caption table-column-group
• inline-table table-header-group
• These means that they behave like the table
  elements that we already discussed.

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run-in box

• If a block box (that does not float and is not
  absolutely positioned) follows the run-in box,
  the run-in box becomes the first inline box of
  the block box.
• Otherwise, the run-in box becomes a block box.
• Example on next page

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example for run-in box

• ltheadgtlttitlegta run-in box examplelt/titlegt
• ltstyle type"text/css"gt
• h3 display run-in
• lt/stylegt lt/headgt ltbodygt
• lth3gta run-in heading lt/h3gtltpgtand a paragraph
  of text that follows it and it continues on the
  line of the h3lt/pgt
• lt/bodygt

41
compact box

• If a block-level box follows the compact box, the
  compact box is formatted like a one-line inline
  box. The resulting box width is compared to one
  of the side margins of the block box,
• left margin if direction is left-to-right
• right margin if direction is right-to-left
• If the inline box width is less than or equal to
  the margin, the inline box is given a position in
  the margin as described immediately below.
• Otherwise, the compact box becomes a block box.

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compact box example

• ltdiv style"dt display compact
• dd margin-left 4em gt
• ltdlgtltdtgtshort lt/dtgtltddgtdescription is herelt/ddgt
• ltdtgttoo long for the marginlt/dtgt
• ltddgtdescription goes
  herelt/ddgt
• lt/divgt

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classification properties III

• The whitespace property controls the display
  of white space in a block level tag.
• 'normal' collapses white space
• 'pre' value similar to ltpregt tag
• 'nowrap' ignores carriage returns only
• It seemed not to work in firefox last time I
  tried.

44
text properties I

• letter-spacing set the spacing between
  letters, takes a length value or the word
  'normal'
• word-spacing same as for letter-spacing
• line-height sets the distance between several
  lines of an element's contents,
• in pt or pixel numbers
• age (referring to a percentage of current font
  size)
• with a number (referring to a multiplicity of
  the size of the text)
• 'normal'

45
text properties II

• text-align can take the values left right
  center and justify.
• text-decoration can take the values
  underline, overline, line-through and
  blink.
• text-indent , margin-left take length
  units but are best expressed in the relative "em"
  unit.
• vertical-align can take the values
  baseline, middle, sub, super, text-top,
  text-bottom, top, bottom, as well as
  percentages.
• text-transform can take the value
  uppercase, lowercase, capitalize and
  none.

46
font properties I

• font-family accepts a comma-separated list of
  font names
• there are five generic names, one should be
  quoted last as a fall-back
• serif sans-serif cursive
• fantasy monospace
• example
• lang(ja-jp) font-family "Heisei Mincho
  W9", serif

47
font properties II

• font-size accepts sizes as npt, n, npt,
  -npt where n is a number, or some sizes like
• xx-small x-small small medium
• large x-large xx-large larger
  smaller
• incremental font sizes may not be handled
  properly by the browser.
• font-style can be either italic, oblique
  or normal

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font properties III

• font-variant can be either normal or small
  caps
• font-weight can be
• a number between 100 for the thinnest and 900 for
  the boldest. 400 is normal.
• normal bold bolder lighter
• font-stretch can be any of
• ultra-condensed extra-condensed
  condensed
• semi-condensed normal semi-expanded
• expanded extra-expanded
  ultra-expanded

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other font properties

• There is a whole bunch of other properties
• unicode-range stemv stroke
• units-per-em stemh bbox
• definitions-src ascent dscent
• baseline widths mathline
• centerline topine panose1
• There also is a font property that allows you
  to put several of the previous properties
  together.
• But all that is not worth learning. Keep fonts
  simple.

50
table properties I

• caption-side says where the caption should go,
  either 'top' or 'bottom'
• border-collapse allows to choose the
  fundamental table model. It can take two values
• 'separate' implies that each cell has its own
  box.
• 'collapse' implies that adjacent cells share the
  same border

51
table properties II

• The properties on this slide are only useful if
  you choose the separated border model.
• You can set the distance between adjacent cells
  using the border-spacing property. Set it to
  two distances to specify different horizontal and
  vertical values
• empty-cells can be set to
• 'show' shows empty cells with their border
• 'hide' does not show the border around an empty
  cell
• there are some other table properties

52
Lesk in HTML/CSS

• I have struggled to reproduce the Lesk tables in
  the examples area.
• It is at doc/examples after the directory of the
  course home page.
• You can see a version with CSS and a version
  without CSS.

53
advice for cheaters

• Within a style sheet, for example the contents of
  a ltstylegt element, you can import another file
  using the _at_import command
• _at_import url(http//www.art.org/kitsch.css)
• or
• _at_import "http//www.art.org/kitsch.css"
• these two ways appear to be equivalent

54
style sheet media types

• Different media, different style.
• CSS has a controlled vocabulary lof media
• projection handheld
• print braille
• screen (default) tty
• embossed aural
• all
• Note that style sheet media are not the same as
  the MIME types. MIME types are a controlled
  vocabulary for file types.

55
media dependent styles

• Remember the media CSS knows about ?
• Using _at_import, you can import different types for
  different media
• _at_import "URI" medialist
• where medialist is a list of one or more
  media, separated by comma
• Example
• _at_import challenged.css" braille, handheld

56
advice about spacing

• Traditionally only use horizontally, the em
  nowadays is the height of the font, and should be
  used vertically as well, as in div.menu padding
  1.5em margin 1.5em
• For body, use ages, as in body margin-left
  15 margin-right 0
• To create a menu, do something like div.menu
  float left width 15em

57
the 'inherit' value

• Each property can have the 'inherit' value. In
  this case, the value of the property for the
  element is determined by the containing element.
• Sometimes, 'inherit' is the default value.

58
validating CSS

• It is at http//jigsaw.w3.org/css-validator/
• Check your style sheet there when you wonder why
  the damn thing does not work.
• Note that checking the style sheet will not be
  part of the assessment of the web site.

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http//openlib.org/home/krichel

• Thank you for your attention!