pyglet.text.document

Formatted and unformatted document interfaces used by text layout.

Abstract representation

Styled text in pyglet is represented by one of the AbstractDocument classes, which manage the state representation of text and style independently of how it is loaded or rendered.

A document consists of the document text (a Unicode string) and a set of named style ranges. For example, consider the following (artificial) example:

0    5   10   15   20
The cat sat on the mat.
+++++++        +++++++    "weight"
            ++++++      "italic"

If this example were to be rendered, “The cat” and “the mat” would have a weight set (“bold”, “thin”, etc.), and “on the” would be in italics. Note that the second “the” is both weighted and italic.

The document styles recorded for this example would be a specific "weight" over ranges (0-7) & (15-22) and "italic" over range (12-18). Overlapping styles are permitted; unlike HTML and other structured markup, the ranges need not be nested.

The document has no knowledge of the semantics of "weight" names or "italic", it stores only the style names. The pyglet layout classes give meaning to these style names in the way they are rendered; but you are also free to invent your own style names (which will be ignored by the layout classes). This can be useful to tag areas of interest in a document, or maintain references back to the source material.

As well as text, the document can contain arbitrary elements represented by InlineElement. An inline element behaves like a single character in the document, but can be rendered by the application.

Paragraph breaks

Paragraph breaks are marked with a “newline” character (U+0010). The Unicode paragraph break (U+2029) can also be used.

Line breaks (U+2028) can be used to force a line break within a paragraph.

See Unicode recommendation UTR #13 for more information: https://www.unicode.org/standard/reports/tr13/tr13-5.html.

Document classes

Any class implementing AbstractDocument provides an interface to a document model as described above. In theory a structured document such as HTML or XML could export this model, though the classes provided by pyglet implement only unstructured documents.

The UnformattedDocument class assumes any styles set are set over the entire document. So, regardless of the range specified when setting a "weight" style attribute, for example, the entire document will receive that style.

The FormattedDocument class implements the document model directly, using the RunList class to represent style runs efficiently.

Style attributes

The following character style attribute names are recognised by pyglet:

font_name: Font family name, as given to pyglet.font.load().
font_size: Font size, in points.
weight: String.
italic: Boolean.
underline: 4-tuple of ints in range (0, 255) giving RGBA underline color, or None (default) for no underline.
kerning: Additional space to insert between glyphs, in points. Defaults to 0.
baseline: Offset of glyph baseline from line baseline, in points. Positive values give a superscript, negative values give a subscript. Defaults to 0.
color: 4-tuple of ints in range (0, 255) giving RGBA text color
background_color: 4-tuple of ints in range (0, 255) giving RGBA text background color; or None for no background fill.

The following paragraph style attribute names are recognised by pyglet. Note that paragraph styles are handled no differently from character styles by the document: it is the application’s responsibility to set the style over an entire paragraph, otherwise results are undefined.

align: left (default), center or right.
indent: Additional horizontal space to insert before the first
leading: Additional space to insert between consecutive lines within a paragraph, in points. Defaults to 0.
line_spacing: Distance between consecutive baselines in a paragraph, in points. Defaults to None, which automatically calculates the tightest line spacing for each line based on the font ascent and descent.
margin_left: Left paragraph margin, in pixels.
margin_right: Right paragraph margin, in pixels.
margin_top: Margin above paragraph, in pixels.
margin_bottom: Margin below paragraph, in pixels. Adjacent margins do not collapse.
tab_stops: List of horizontal tab stops, in pixels, measured from the left edge of the text layout. Defaults to the empty list. When the tab stops are exhausted, they implicitly continue at 50 pixel intervals.
wrap: Boolean. If True (the default), text wraps within the width of the layout.

Other attributes can be used to store additional style information within the document; it will be ignored by the built-in text classes.

All style attributes (including those not present in a document) default to None (including the so-called “boolean” styles listed above). The meaning of a None style is style- and application-dependent.

class AbstractDocument

Abstract document interface used by all pyglet.text classes.

This class can be overridden to interface pyglet with a third-party document format. It may be easier to implement the document format in terms of one of the supplied concrete classes FormattedDocument or UnformattedDocument.

event_types: list = ['on_insert_text', 'on_delete_text', 'on_style_text']

property text: str

Document text.

For efficient incremental updates, use the insert_text() and delete_text() methods instead of replacing this property.

class FormattedDocument

Simple implementation of a document that maintains text formatting.

Changes to text style are applied according to the description in AbstractDocument. All styles default to None.

class InlineElement

Arbitrary inline element positioned within a formatted document.

Elements behave like a single glyph in the document. They are measured by their horizontal advance, ascent above the baseline, and descent below the baseline.

The pyglet layout classes reserve space in the layout for elements and call the element’s methods to ensure they are rendered at the appropriate position.

If the size of an element (any of the advance, ascent, or descent variables) is modified it is the application’s responsibility to trigger a reflow of the appropriate area in the affected layouts. This can be done by forcing a style change over the element’s position.

advance: int

ascent: int

descent: int

property position: int | None

Character position within the document.

Determined by the layout it is in. Will return None if it has not been placed.

class UnformattedDocument

A document having uniform style over all text.

Changes to the style of text within the document affects the entire document. For convenience, the position parameters of the style methods may therefore be omitted.

STYLE_INDETERMINATE = 'indeterminate': The style attribute takes on multiple values in the document.