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.
bold
Boolean.
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. char and word styles are since pyglet 1.2.

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

New in version 1.1.

class IncrementalTextLayout(document, width, height, multiline=False, dpi=None, batch=None, group=None, wrap_lines=True)

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.

delete()
ensure_line_visible(line)

Adjust view_y so that the line with the given index is visible.

Parameters:line (int) – Line index.
ensure_x_visible(x)

Adjust view_x so that the given X coordinate is visible.

The X coordinate is given relative to the current view_x.

Parameters:x (int) – X coordinate
get_line_count()

Get the number of lines in the text layout.

Return type:int
get_line_from_point(x, y)

Get the closest line index to a point.

Parameters:
  • x (int) – X coordinate.
  • y (int) – Y coordinate.
Return type:

int

get_line_from_position(position)

Get the line index of a character position in the document.

Parameters:position (int) – Document position.
Return type:int
get_point_from_line(line)

Get the X, Y coordinates of a line index.

Parameters:line (int) – Line index.
Return type:(int, int)
Returns:(x, y)
get_point_from_position(position, line=None)

Get the X, Y coordinates of a position in the document.

The position that ends a line has an ambiguous point: it can be either the end of the line, or the beginning of the next line. You may optionally specify a line index to disambiguate the case.

The resulting Y coordinate gives the baseline of the line.

Parameters:
  • position (int) – Character position within document.
  • line (int) – Line index.
Return type:

(int, int)

Returns:

(x, y)

get_position_from_line(line)

Get the first document character position of a given line index.

Parameters:line (int) – Line index.
Return type:int
get_position_from_point(x, y)

Get the closest document position to a point.

Parameters:
  • x (int) – X coordinate
  • y (int) – Y coordinate
get_position_on_line(line, x)

Get the closest document position for a given line index and X coordinate.

Parameters:
  • line (int) – Line index.
  • x (int) – X coordinate.
Return type:

int

on_delete_text(start, end)
on_insert_text(start, text)
on_layout_update()

Some or all of the layout text was reflowed.

Text reflow is caused by document edits or changes to the layout’s size. Changes to the layout’s position or active selection, and certain document edits such as text color, do not cause a reflow.

Handle this event to update the position of a graphical element that depends on the laid out position of a glyph or line.

on_style_text(start, end, attributes)
set_selection(start, end)

Set the text selection range.

If start equals end no selection will be visible.

Parameters:
  • start (int) – Starting character position of selection.
  • end (int) – End of selection, exclusive.
event_types = ['on_layout_update']
height
multiline
selection_background_color

Background color of active selection.

The color is an RGBA tuple with components in range [0, 255].

Type:(int, int, int, int)
selection_color

Text color of active selection.

The color is an RGBA tuple with components in range [0, 255].

Type:(int, int, int, int)
selection_end

End position of the active selection (exclusive).

See:set_selection
Type:int
selection_start

Starting position of the active selection.

See:set_selection
Type:int
view_y
width
class ScrollableTextLayout(document, width, height, multiline=False, dpi=None, batch=None, group=None, wrap_lines=True)

Display text in a scrollable viewport.

This class does not display a scrollbar or handle scroll events; it merely clips the text that would be drawn in TextLayout() to the bounds of the layout given by x, y, width and height; and offsets the text by a scroll offset.

Use view_x and view_y to scroll the text within the viewport.

anchor_x
anchor_y
height
view_x

Horizontal scroll offset.

The initial value is 0, and the left edge of the text will touch the left side of the layout bounds. A positive value causes the text to “scroll” to the right. Values are automatically clipped into the range [0, content_width - width]

Type:int
view_y

Vertical scroll offset.

The initial value is 0, and the top of the text will touch the top of the layout bounds (unless the content height is less than the layout height, in which case content_valign is used).

A negative value causes the text to “scroll” upwards. Values outside of the range [height - content_height, 0] are automatically clipped in range.

Type:int
width
x
y
class ScrollableTextLayoutGroup(parent=None)

Top-level rendering group for ScrollableTextLayout.

The group maintains internal state for setting the clipping planes and view transform for scrolling. Because the group has internal state specific to the text layout, the group is never shared.

set_state()
unset_state()
height

Height of the text layout.

Type:int
left

Left edge of the text layout.

Type:int
top

Top edge of the text layout (measured from the bottom of the graphics viewport).

Type:int
translate_x = 0
translate_y = 0
view_x

Horizontal scroll offset.

Type:int
view_y

Vertical scroll offset.

Type:int
width

Width of the text layout.

Type:int
class TextLayout(document, width=None, height=None, multiline=False, dpi=None, batch=None, group=None, wrap_lines=True)

Lay out and display documents.

This class is intended for displaying documents that do not change regularly – any change will cost some time to lay out the complete document again and regenerate all vertex lists.

The benefit of this class is that texture state is shared between all layouts of this class. The time to draw one TextLayout() may be roughly the same as the time to draw one IncrementalTextLayout; but drawing ten TextLayout() objects in one batch is much faster than drawing ten incremental or scrollable text layouts.

Label() and HTMLLabel() provide a convenient interface to this class.

Variables:
  • content_width (int) – Calculated width of the text in the layout. This may overflow the desired width if word-wrapping failed.
  • content_height (int) – Calculated height of the text in the layout.
  • top_group (Group) – Top-level rendering group.
  • background_group (Group) – Rendering group for background color.
  • foreground_group (Group) – Rendering group for glyphs.
  • foreground_decoration_group (Group) – Rendering group for glyph underlines.
begin_update()

Indicate that a number of changes to the layout or document are about to occur.

Changes to the layout or document between calls to begin_update and end_update do not trigger any costly relayout of text. Relayout of all changes is performed when end_update is called.

Note that between the begin_update and end_update calls, values such as content_width and content_height are undefined (i.e., they may or may not be updated to reflect the latest changes).

delete()

Remove this layout from its batch.

draw()

Draw this text layout.

Note that this method performs very badly if a batch was supplied to the constructor. If you add this layout to a batch, you should ideally use only the batch’s draw method.

end_update()

Perform pending layout changes since begin_update.

See begin_update.

on_delete_text(start, end)

Event handler for AbstractDocument.on_delete_text.

The event handler is bound by the text layout; there is no need for applications to interact with this method.

on_insert_text(start, text)

Event handler for AbstractDocument.on_insert_text.

The event handler is bound by the text layout; there is no need for applications to interact with this method.

on_style_text(start, end, attributes)

Event handler for AbstractDocument.on_style_text.

The event handler is bound by the text layout; there is no need for applications to interact with this method.

anchor_x

Horizontal anchor alignment.

This property determines the meaning of the x coordinate. It is one of the enumerants:

"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.

Type:str
anchor_y

Vertical anchor alignment.

This property determines the meaning of the y coordinate. It is one of the enumerants:

"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 smaller of height and content_height.

See also content_valign.

Type:str
background_group = OrderedGroup(0)
batch

The Batch that this Layout is assigned to.

If no Batch is assigned, an internal Batch is created and used.

Type:Batch
content_valign

Vertical alignment of content within larger layout box.

This property determines how content is positioned within the layout box when content_height is less than height. It is one of the enumerants:

top (default)
Content is aligned to the top of the layout box.
center
Content is centered vertically within the layout box.
bottom
Content is aligned to the bottom of the layout box.

This property has no effect when content_height is greater than height (in which case the content is aligned to the top) or when height is None (in which case there is no vertical layout box dimension).

Type:str
document

Document to display.

For IncrementalTextLayout it is far more efficient to modify a document in-place than to replace the document instance on the layout.

Type:AbstractDocument
dpi

Get DPI used by this layout.

Read-only.

Type:float
foreground_decoration_group = TextLayoutForegroundDecorationGroup(2)
foreground_group = TextLayoutForegroundGroup(1)
height

Height of the layout.

Type:int
multiline

Set if multiline layout is enabled.

If multiline is False, newline and paragraph characters are ignored and text is not word-wrapped. If True, the text is word-wrapped only if the wrap_lines is True.

Type:bool
top_group = <pyglet.text.layout.TextLayoutGroup object>
width

Width of the layout.

This property has no effect if multiline is False or wrap_lines is False.

Type:int
x

X coordinate of the layout.

See also anchor_x.

Type:int
y

Y coordinate of the layout.

See also anchor_y.

Type:int
class TextLayoutForegroundDecorationGroup(order, parent=None)

Rendering group for decorative elements (e.g., glyph underlines) in all text layouts.

The group disables GL_TEXTURE_2D.

set_state()
class TextLayoutForegroundGroup(order, parent=None)

Rendering group for foreground elements (glyphs) in all text layouts.

The group enables GL_TEXTURE_2D.

set_state()
class TextLayoutGroup(parent=None)

Top-level rendering group for TextLayout().

The blend function is set for glyph rendering (GL_SRC_ALPHA / GL_ONE_MINUS_SRC_ALPHA). The group is shared by all TextLayout() instances as it has no internal state.

set_state()
unset_state()
class TextLayoutTextureGroup(texture, parent)

Rendering group for a glyph texture in all text layouts.

The group binds its texture to GL_TEXTURE_2D. The group is shared between all other text layout uses of the same texture.

set_state()

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