Advanced Rich Text Processing Rich Text Processing APIs

Supported HTML Subset

Qt's text widgets are able to display rich text, specified using a subset of HTML 4 markup. Widgets that use QTextDocument, such as QLabel and QTextEdit, are able to display rich text specified in this way.

Using HTML Markup in Text Widgets

Widgets automatically detect HTML markup and display rich text accordingly. For example, setting a label's text property with the string "Hello Qt!" will result in the label displaying text like this: Hello Qt!

When HTML markup is used for text, Qt follows the rules defined by the HTML 4 specification. This includes default properties for text layout, such as the direction of the text flow (left-to-right) which can be changed by applying the dir attribute to blocks of text.

Supported Tags

The following table lists the HTML tags supported by Qt's rich text engine.

Note: The functionality implemented for tags listed below is a subset of the full HTML 4 specification. Not all attributes are supported, see comments for each tag.

Tag	Description	Comment
`a`	Anchor or link	Supports the `href` and `name` attributes.
`address`	Address
`b`	Bold
`big`	Larger font
`blockquote`	Indented paragraph
`body`	Document body	Supports the `bgcolor` attribute, which can be a Qt color name or a `#RRGGBB` color specification.
`br`	Line break
`center`	Centered paragraph
`cite`	Inline citation	Same as `i`.
`code`	Code	Same as `tt`.
`dd`	Definition data
`dfn`	Definition	Same as `i`.
`div`	Document division	Supports the standard block attributes.
`dl`	Definition list	Supports the standard block attributes.
`dt`	Definition term	Supports the standard block attributes.
`em`	Emphasized	Same as `i`.
`font`	Font size, family, and/or color	Supports the following attributes: `size`, `face`, and `color` (Qt color names or `#RRGGBB`).
`h1`	Level 1 heading	Supports the standard block attributes.
`h2`	Level 2 heading	Supports the standard block attributes.
`h3`	Level 3 heading	Supports the standard block attributes.
`h4`	Level 4 heading	Supports the standard block attributes.
`h5`	Level 5 heading	Supports the standard block attributes.
`h6`	Level 6 heading	Supports the standard block attributes.
`head`	Document header
`hr`	Horizontal line	Supports the `width` attribute, which can be specified as an absolute or relative (`%`) value.
`html`	HTML document
`i`	Italic
`img`	Image	Supports the `src`, `source` (for Qt 3 compatibility), `width`, and `height` attributes.
`kbd`	User-entered text
`meta`	Meta-information	If a text encoding is specified using the `meta` tag, it is picked up by Qt::codecForHtml(). Likewise, if an encoding is specified to QTextDocument::toHtml(), the encoding is stored using a `meta` tag, for example: `<meta http-equiv="Content-Type" content="text/html; charset=EUC-JP" />`
`li`	List item
`nobr`	Non-breakable text
`ol`	Ordered list	Supports the standard list attributes.
`p`	Paragraph	Left-aligned by default. Supports the standard block attributes.
`pre`	Preformated text
`qt`	Qt rich-text document	Synonym for `html`. Provided for compatibility with earlier versions of Qt.
`s`	Strikethrough
`samp`	Sample code	Same as `tt`.
`small`	Small font
`span`	Grouped elements
`strong`	Strong	Same as `b`.
`sub`	Subscript
`sup`	Superscript
`table`	Table	Supports the following attributes: `border`, `bgcolor` (Qt color names or `#RRGGBB`), `cellspacing`, `cellpadding`, `width` (absolute or relative), and `height`.
`tbody`	Table body	Does nothing.
`td`	Table data cell	Supports the standard table cell attributes.
`tfoot`	Table footer	Does nothing.
`th`	Table header cell	Supports the standard table cell attributes.
`thead`	Table header	If the `thead` tag is specified, it is used when printing tables that span multiple pages.
`title`	Document title	The value specified using the `title` tag is available through QTextDocument::metaInformation().
`tr`	Table row	Supports the `bgcolor` attribute, which can be a Qt color name or a `#RRGGBB` color specification.
`tt`	Typewrite font
`u`	Underlined
`ul`	Unordered list	Supports the standard list attributes.
`var`	Variable	Same as `i`.

Block Attributes

The following attributes are supported by the div, dl, dt, h1, h2, h3, h4, h5, h6, p tags:

align (left, right, center, justify)
dir (ltr, rtl)

List Attributes

The following attribute is supported by the ol and ul tags:

type (1, a, A, square, disc, circle)

Table Cell Attributes

The following attributes are supported by the td and th tags:

width (absolute, relative, or no-value)
bgcolor (Qt color names or #RRGGBB)
colspan
rowspan
align (left, right, center, justify)
valign (top, middle, bottom)

CSS Properties

The following table lists the CSS properties supported by Qt's rich text engine:

Property	Values	Description
`background-color`	<color>	Background color for elements
`background-image`	<uri>	Background image for elements
`color`	<color>	Text foreground color
`font-family`	<family name>	Font family name
`font-size`	[ small \| medium \| large \| x-large \| xx-large ] \| <size>pt \| <size>px	Font size relative to the document font, or specified in points or pixels
`font-style`	[ normal \| italic \| oblique ]
`font-weight`	[ normal \| bold \| 100 \| 200 \| 300 \| 400 \| 500 \| 600 \| 700 \| 800 \| 900 ]	Specifies the font weight used for text, where `normal` and `bold` are mapped to the corresponding QFont weights. Numeric values are 8 times the equivalent QFont weight values.
`text-decoration`	none \| [ underline \|\| overline \|\| line-through ]	Additional text effects
`font`	[ [ <'font-style'> \|\| <'font-weight'> ]? <'font-size'> <'font-family'> ]	Font shorthand property
`text-indent`	<length>px	First line text indentation in pixels
`white-space`	normal \| pre \| nowrap \| pre-wrap	Declares how whitespace in HTML is handled.
`margin-top`	<length>px	Top paragraph margin in pixels
`margin-bottom`	<length>px	Bottom paragraph margin in pixels
`margin-left`	<length>px	Left paragraph margin in pixels
`margin-right`	<length>px	Right paragraph margin in pixels
`padding-top`	<length>px	Top table cell padding in pixels
`padding-bottom`	<length>px	Bottom table cell padding in pixels
`padding-left`	<length>px	Left table cell padding in pixels
`padding-right`	<length>px	Right table cell padding in pixels
`padding`	<length>px	Shorthand for setting all the padding properties at once.
`vertical-align`	baseline \| sub \| super \| middle \| top \| bottom	Vertical text alignment. For vertical alignment in text table cells only middle, top, and bottom apply.
`border-collapse`	collapse \| separate	Border Collapse mode for text tables. If set to collapse, cell-spacing will not be applied.
`border-color`	<color>	Border color for text tables and table cells.
`border-top-color`	<color>	Top border color for table cells.
`border-bottom-color`	<color>	Bottom border color for table cells.
`border-left-color`	<color>	Left border color for table cells.
`border-right-color`	<color>	Right border color for table cells.
`border-style`	none \| dotted \| dashed \| dot-dash \| dot-dot-dash \| solid \| double \| groove \| ridge \| inset \| outset	Border style for text tables and table cells.
`border-top-style`	<border-style>	Top border style for table cells.
`border-bottom-style`	<border-style>	Bottom border style for table cells.
`border-left-style`	<border-style>	Left border style for table cells.
`border-right-style`	<border-style>	Right border style for table cells.
`border-width`	<width>px	Width of table or cell border
`border-top-width`	<length>px	Top border width for table cells.
`border-bottom-width`	<length>px	Bottom border width for table cells.
`border-left-width`	<length>px	Left border width for table cells.
`border-right-width`	<length>px	Right border width for table cells.
`border-top`	<width>px <border-style> <border-color>	Shorthand for setting top border width, style and color
`border-bottom`	<width>px <border-style> <border-color>	Shorthand for setting bottom border width, style and color
`border-left`	<width>px <border-style> <border-color>	Shorthand for setting left border width, style and color
`border-right`	<width>px <border-style> <border-color>	Shorthand for setting right border width, style and color
`border-top`	<width>px <border-style> <border-color>	Shorthand for setting top border width, style and color
`border-bottom`	<width>px <border-style> <border-color>	Shorthand for setting bottom border width, style and color
`border`	<width>px <border-style> <border-color>	Shorthand for setting all four border's width, style and color
`background`	[ <'background-color'> \|\| <'background-image'> ]	Background shorthand property
`page-break-before`	[ auto \| always ]	Make it possible to enforce a page break before the paragraph/table
`page-break-after`	[ auto \| always ]	Make it possible to enforce a page break after the paragraph/table
`float`	[ left \| right \| none ]	Specifies where an image or a text will be placed in another element. Note that the `float` property is only supported for tables and images.
`text-transform`	[ uppercase \| lowercase ]	Select the transformation that will be performed on the text prior to displaying it.
`font-kerning`	[ normal \| none ]	Enables or disables kerning between text characters.
`font-variant`	small-caps	Perform the smallcaps transformation on the text prior to displaying it.
`word-spacing`	<width>px	Specifies an alternate spacing between each word.
`line-height`	<number>[% \| px \| pt \| cm]	Specifies the height of a line. It can be one of the following: fixed line height in pixels, points, or centimeters. a percentage of the current font size.

Note: Certain CSS properties are only supported when applied to a block tag, such as . Setting these properties on a , for instance, will have no effect. The margin is one example of such a property. See QTextBlockFormat and QTextCharFormat for an overview of the formatting options available on blocks and spans in QTextDocument.

Qt-specific CSS properties

Besides the standard CSS properties listed earlier, the following Qt-specific properties can also be used to style a text block:

Property	Values	Description
`-qt-block-indent`	`<number>`	Indents the text block by the specified no. spaces.
`-qt-list-indent`	`<number>`	Indents the list items by the specified no. of spaces.
`-qt-list-number-prefix`	`<string>`	Prefixes the given string to list number in an HTML ordered list.
`-qt-list-number-suffix`	<string>	Suffixes the given string to list number in an HTML ordered list.
`-qt-paragraph-type`	`empty`	Hides the text block.
`-qt-table-type`	`root \| frame`	`root` renders the text blocks inline without borders and indentation, whereas `frame` renders them on a new line with a frame around.
`-qt-user-state`	`<number>`	Adds it as user data for the text block.

Supported CSS Selectors

All CSS 2.1 selector classes are supported except pseudo-class selectors such as :first-child, :visited and :hover.

Advanced Rich Text Processing Rich Text Processing APIs

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