| text-space-collapse 'collapse' This value Since Jan 2008, some CSS modules useinstead of in the first column of a table.propdef. These rules handle both. As of Jan 2008, http://www.w3.org/Style/spec-mark-up still only documents text-space-collapse 'collapse' This value directs user agents to collapse sequences of white space into a single character (or in some cases, no character). 'preserve' This value prevents user agents from collapsing sequences of white space. Line feeds are preserved as forced line breaks. 'preserve-breaks' This value collapses white space as for 'collapse', but preserves line feeds as forced line breaks. 'discard' This value directs user agents to "discard" all white space in the element. 'trim-inner' For block containers this value directs UAs to discard all whitespace at the beginning of the element up to and including the last line feed before the first non-white-space character in the element as well as to discard all white space at the end of the element starting with the first line feed after the last non-white-space character in the element. For other elements this value directs UAs to discard all whitespace at the beginning and end of the element. 'consume-before' This value directs the UA to collapse all collapsible whitespace immediately before the start of the element. 'consume-after' This value directs the UA to collapse all collapsible whitespace immediately after the end of the element. 8. Alignment and Justification 8.1. Text Alignment: the 'text-align' property Name: text-align Value: [ start | ]? [ start | end | left | right | center | justify | match-parent ] Initial: start Applies to: block containers Inherited: yes Percentages: N/A Media: visual Computed value: specified value, except for 'match-parent' (see prose) This property describes how inline contents of a block are horizontally aligned if the contents do not completely fill the line box. Values have the following meanings: ( http://www.w3.org/ ) start The inline contents are aligned to the start edge of the line box. end The inline contents are aligned to the end edge of the line box. left The inline contents are aligned to the left edge of the line box. In vertical text, 'left' aligns to the edge of the line box that would be the start edge for left-to-right text. right The inline contents are aligned to the right edge of the line box. In vertical text, 'right' aligns to the edge of the line box that would be the end edge for left-to-right text. center The inline contents are centered within the line box. justify The text is justified according to the method specified by the 'text-justify' property. The string must be a single character; otherwise the declaration must be ignored. When applied to a table cell, specifies the alignment character around which the cell's contents will align. See below for further details. match-parent This value behaves the same as 'inherit' except that an inherited 'start' or 'end' keyword is calculated against its parent's 'direction' value and results in a computed value of either 'left' or 'right'. If two keywords are given in combination, then the first value specifies the alignment of the first line and any line immediately after a forced line break; and the second value specifies the alignment of any remaining lines. A block of text is a stack of line boxes. In the case of 'start', 'end', 'left', 'right' and 'center', this property specifies how the inline-level boxes within each line box align with respect to the start and end sides of the line box: alignment is not with respect to the viewport or containing block. In the case of 'justify', the UA may stretch or shrink any inline boxes by adjusting their text in addition to shifting their positions. (See also 'text-justify', 'letter-spacing', and 'word-spacing'.) If an element's white space is set to be collapsible, then the UA is not required to adjust its text for the purpose of justification and may instead treat the text as having no expansion opportunities. If the UA chooses to adjust the text, then it must ensure that tab stops continue to line up as required by the white space processing rules. 3.2. Tab Character Size: the 'tab-size' property Name: tab-size Value: | Initial: 8 Applies to: block containers Inherited: yes Percentages: N/A Media: visual Computed value: specified value This property determines the measure of the tab character (U+0009) when rendered. Integers represent the measure in space characters (U+0020). Negative integers are not allowed. 3.3. The White Space Processing Rules White space processing affects only spaces (U+0020), tabs (U+0009), and (post-normalization) line feeds (U+00A0). For each inline (including anonymous inlines) within an inline formatting context, white space characters are handled as follows, ignoring bidi formatting characters as if they were not there: If 'text-space-collapse' is set to 'collapse' or 'preserve-breaks', white space characters are considered collapsible and are processed by performing the following steps: All spaces and tabs immediately preceding or following a line feed character are removed. If 'text-space-collapse' is not 'preserve-breaks', line feed characters are transformed for rendering according to the line feed transformation rules. Every tab is converted to a space (U+0020). Any space immediately following another collapsible space -even one outside the boundary of the inline-is removed. However, if removing this space would eliminate a line breaking opportunity in the text, that opportunity is still considered to exist. A collapsible space immediately preceding an element with 'consume-before' is removed. Such removed spaces do not indicate a line breaking opportunity in the text. Any collapsible spaces after the end of an element with 'consume-after' are removed. Such removed spaces do not indicate a line breaking opportunity in the text. If 'text-space-collapse' is set to 'preserve', any sequence of spaces unbroken by an element boundary is treated as a sequence of non-breaking spaces. However, a line breaking opportunity exists at the end of the sequence. If 'text-space-collapse' is set to 'discard', the first white space character in every white space sequence is converted to a zero width non-joiner (U+200C) and the rest of the sequence is removed. Then, the entire block is rendered. Inlines are laid out, taking bidi reordering into account, and wrapping as specified by the 'text-wrap' property. As each line is laid out, A sequence of collapsible spaces at the beginning of a line is removed. Each tab is rendered as a horizontal shift that lines up the start edge of the next glyph with the next tab stop. Tab stops occur at points that are multiples of the width of a space (U+0020) rendered in the block's font from the block's starting content edge. How many spaces is given by the 'tab-size' property. A sequence of collapsible spaces at the end of a line is removed. If spaces or tabs at the end of a line are non-collapsible but have 'text-wrap' set to 'normal' or 'avoid' the UA may visually collapse their character advance widths. White space that was not removed during the white space processing steps is called preserved white space. 3.3.1. Example of bidirectionality with white space collapsing Consider the following markup fragment, taking special note of spaces (with varied backgrounds and borders for emphasis and identification): A B C where the element represents a left-to-right embedding and the element represents a right-to-left embedding. If the 'text-space-collapse' property is set to 'collapse', the above processing model would result in the following: The space before the B ( ) would collapse with the space after the A ( ). The space before the C ( ) would collapse with the space after the B ( ). This would leave two spaces, one after the A in the left-to-right embedding level, and one after the B in the right-to-left embedding level. This is then ordered according to the Unicode bidirectional algorithm, with the end result being: A BC Note that there are two spaces between A and B, and none between B and C. This is best avoided by putting spaces outside the element instead of just inside the opening and closing tags and, where practical, by relying on implicit bidirectionality instead of explicit embedding levels. **************** CSS Text Level 3 **************** --------------------------- Editor's Draft 29 July 2011 --------------------------- This version A B C **************** CSS Text Level 3 **************** --------------------------- Editor's Draft 29 July 2011 --------------------------- This version A B C New Lines Spaces and Tabs Text Wrapping normal Collapse Collapse Wrap pre Preserve Preserve No wrap nowrap Collapse Collapse No wrap pre-wrap Preserve Preserve Wrap pre-line Preserve Collapse Wrap New Lines Spaces and Tabs Text Wrapping normal Collapse Collapse Wrap pre Preserve Preserve No wrap nowrap Collapse Collapse No wrap pre-wrap Preserve Preserve Wrap pre-line Preserve Collapse Wrap |
