pyglet.text.layout

Render simple text and formatted documents efficiently.

Three layout classes are provided:

TextLayout

The entire document is laid out before it is rendered. The layout will be grouped with other layouts in the same batch (allowing for efficient rendering of multiple layouts).

Any change to the layout or document, and even querying some properties, will cause the entire document to be laid out again.

ScrollableTextLayout

Based on TextLayout().

A separate group is used for layout which crops the contents of the layout to the layout rectangle. Additionally, the contents of the layout can be “scrolled” within that rectangle with the view_x and view_y properties.

IncrementalTextLayout

Based on ScrollableTextLayout.

When the layout or document are modified, only the affected regions are laid out again. This permits efficient interactive editing and styling of text.

Only the visible portion of the layout is actually rendered; as the viewport is scrolled additional sections are rendered and discarded as required. This permits efficient viewing and editing of large documents.

Additionally, this class provides methods for locating the position of a caret in the document, and for displaying interactive text selections.

All three layout classes can be used with either UnformattedDocument or FormattedDocument, and can be either single-line or multiline. The combinations of these options effectively provides 12 different text display possibilities.

Style attributes

The following character style attribute names are recognised by the layout classes. Data types and units are as specified.

Where an attribute is marked “as a distance” the value is assumed to be in pixels if given as an int or float, otherwise a string of the form "0u" is required, where 0 is the distance and u is the unit; one of "px" (pixels), "pt" (points), "pc" (picas), "cm" (centimeters), "mm" (millimeters) or "in" (inches). For example, "14pt" is the distance covering 14 points, which at the default DPI of 96 is 18 pixels.

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, as a distance. Defaults to 0.
baseline: Offset of glyph baseline from line baseline, as a distance. 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. 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 glyph of the first line of a paragraph, as a distance.
leading: Additional space to insert between consecutive lines within a paragraph, as a distance. Defaults to 0.
line_spacing: Distance between consecutive baselines in a paragraph, as a distance. 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, as a distance.
margin_right: Right paragraph margin, as a distance.
margin_top: Margin above paragraph, as a distance.
margin_bottom: Margin below paragraph, as a distance. Adjacent margins do not collapse.
tab_stops: List of horizontal tab stops, as distances, 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: char, word, True (default) or False. The boundaries at which to wrap text to prevent it overflowing a line. With char, the line wraps anywhere in the text; with word or True, the line wraps at appropriate boundaries between words; with False the line does not wrap, and may overflow the layout width.

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

class IncrementalTextDecorationGroup

scissor_area: ClassVar[tuple[int, int, int, int]] = (0, 0, 0, 0)

class IncrementalTextLayout

Displayed text suitable for interactive editing and/or scrolling large documents.

Unlike TextLayout() and ScrollableTextLayout, this class generates vertex lists only for lines of text that are visible. As the document is scrolled, vertex lists are deleted and created as appropriate to keep video memory usage to a minimum and improve rendering speed.

Changes to the document are quickly reflected in this layout, as only the affected line(s) are reflowed. Use begin_update() and end_update() to further reduce the amount of processing required.

The layout can also display a text selection (text with a different background color). The Caret class implements a visible text cursor and provides event handlers for scrolling, selecting and editing text in an incremental text layout.

Class Variables:

group_class (ClassVar[type[IncrementalTextLayoutGroup]]) – Default group used to set the state for all glyphs.
decoration_class (ClassVar[type[IncrementalTextDecorationGroup]]) – Default group used to set the state for all decorations including background colors and underlines.

property anchor_x: Literal['left', 'center', 'right']

Horizontal anchor alignment.

This property determines the meaning of the x coordinate.

The following values are supported:

"left" (default): The X coordinate gives the position of the left edge of the layout.
"center": The X coordinate gives the position of the center of the layout.
"right": The X coordinate gives the position of the right edge of the layout.

For the purposes of calculating the position resulting from this alignment, the width of the layout is taken to be width if multiline is True and wrap_lines is True, otherwise content_width.

property anchor_y: Literal['top', 'bottom', 'center', 'baseline']

Vertical anchor alignment.

This property determines the meaning of the y coordinate.

The following values are supported:

"top": The Y coordinate gives the position of the top edge of the layout.
"center": The Y coordinate gives the position of the center of the layout.
"baseline": The Y coordinate gives the position of the baseline of the first line of text in the layout.
"bottom" (default): The Y coordinate gives the position of the bottom edge of the layout.

For the purposes of calculating the position resulting from this alignment, the height of the layout is taken to be the smallest of height and content_height.