Layout

class Layout(**properties: Any)

Superclasses: Object

A PangoLayout structure represents an entire paragraph of text.

While complete access to the layout capabilities of Pango is provided using the detailed interfaces for itemization and shaping, using that functionality directly involves writing a fairly large amount of code. PangoLayout provides a high-level driver for formatting entire paragraphs of text at once. This includes paragraph-level functionality such as line breaking, justification, alignment and ellipsization.

A PangoLayout is initialized with a PangoContext, UTF-8 string and set of attributes for that string. Once that is done, the set of formatted lines can be extracted from the object, the layout can be rendered, and conversion between logical character positions within the layout’s text, and the physical position of the resulting glyphs can be made.

There are a number of parameters to adjust the formatting of a PangoLayout. The following image shows adjustable parameters (on the left) and font metrics (on the right):

The following images demonstrate the effect of alignment and justification on the layout of text:

It is possible, as well, to ignore the 2-D setup, and simply treat the results of a PangoLayout as a list of lines.

Constructors

class Layout

classmethod new(context: Context) → Layout

Create a new PangoLayout object with attributes initialized to default values for a particular PangoContext.

Parameters:

context – a PangoContext

Methods

class Layout

context_changed() → None

Forces recomputation of any state in the PangoLayout that might depend on the layout’s context.

This function should be called if you make changes to the context subsequent to creating the layout.

deserialize(context: Context, bytes: Bytes, flags: LayoutDeserializeFlags) → Layout | None

Loads data previously created via serialize.

For a discussion of the supported format, see that function.

Note: to verify that the returned layout is identical to the one that was serialized, you can compare bytes to the result of serializing the layout again.

Added in version 1.50.

Parameters:

• context – a PangoContext

• bytes – the bytes containing the data

• flags – PangoLayoutDeserializeFlags

get_alignment() → Alignment

Gets the alignment for the layout: how partial lines are positioned within the horizontal space available.

get_attributes() → AttrList | None

Gets the attribute list for the layout, if any.

get_auto_dir() → bool

Gets whether to calculate the base direction for the layout according to its contents.

See set_auto_dir.

Added in version 1.4.

get_baseline() → int

Gets the Y position of baseline of the first line in layout.

Added in version 1.22.

get_caret_pos(index_: int) → tuple[Rectangle, Rectangle]

Given an index within a layout, determines the positions that of the strong and weak cursors if the insertion point is at that index.

This is a variant of get_cursor_pos that applies font metric information about caret slope and offset to the positions it returns.

Added in version 1.50.

Parameters:

index – the byte index of the cursor

get_character_count() → int

Returns the number of Unicode characters in the the text of layout.

Added in version 1.30.

get_context() → Context

Retrieves the PangoContext used for this layout.

get_cursor_pos(index_: int) → tuple[Rectangle, Rectangle]

Given an index within a layout, determines the positions that of the strong and weak cursors if the insertion point is at that index.

The position of each cursor is stored as a zero-width rectangle with the height of the run extents.

The strong cursor location is the location where characters of the directionality equal to the base direction of the layout are inserted. The weak cursor location is the location where characters of the directionality opposite to the base direction of the layout are inserted.

The following example shows text with both a strong and a weak cursor.

The strong cursor has a little arrow pointing to the right, the weak cursor to the left. Typing a ‘c’ in this situation will insert the character after the ‘b’, and typing another Hebrew character, like ‘ג’, will insert it at the end.

Parameters:

index – the byte index of the cursor

get_direction(index: int) → Direction

Gets the text direction at the given character position in layout.

Added in version 1.46.

Parameters:

index – the byte index of the char

get_ellipsize() → EllipsizeMode

Gets the type of ellipsization being performed for layout.

See set_ellipsize.

Use is_ellipsized to query whether any paragraphs were actually ellipsized.

Added in version 1.6.

get_extents() → tuple[Rectangle, Rectangle]

Computes the logical and ink extents of layout.

Logical extents are usually what you want for positioning things. Note that both extents may have non-zero x and y. You may want to use those to offset where you render the layout. Not doing that is a very typical bug that shows up as right-to-left layouts not being correctly positioned in a layout with a set width.

The extents are given in layout coordinates and in Pango units; layout coordinates begin at the top left corner of the layout.

get_font_description() → FontDescription | None

Gets the font description for the layout, if any.

Added in version 1.8.

get_height() → int

Gets the height of layout used for ellipsization.

See set_height for details.

Added in version 1.20.

get_indent() → int

Gets the paragraph indent width in Pango units.

A negative value indicates a hanging indentation.

get_iter() → LayoutIter

Returns an iterator to iterate over the visual extents of the layout.

get_justify() → bool

Gets whether each complete line should be stretched to fill the entire width of the layout.

get_justify_last_line() → bool

Gets whether the last line should be stretched to fill the entire width of the layout.

Added in version 1.50.

get_line(line: int) → LayoutLine | None

Retrieves a particular line from a PangoLayout.

Use the faster get_line_readonly if you do not plan to modify the contents of the line (glyphs, glyph widths, etc.).

Parameters:

line – the index of a line, which must be between 0 and pango_layout_get_line_count(layout) - 1, inclusive.

get_line_count() → int

Retrieves the count of lines for the layout.

get_line_readonly(line: int) → LayoutLine | None

Retrieves a particular line from a PangoLayout.

This is a faster alternative to get_line, but the user is not expected to modify the contents of the line (glyphs, glyph widths, etc.).

Added in version 1.16.

Parameters:

line – the index of a line, which must be between 0 and pango_layout_get_line_count(layout) - 1, inclusive.

get_line_spacing() → float

Gets the line spacing factor of layout.

See set_line_spacing.

Added in version 1.44.

get_lines() → list[LayoutLine]

Returns the lines of the layout as a list.

Use the faster get_lines_readonly if you do not plan to modify the contents of the lines (glyphs, glyph widths, etc.).

get_lines_readonly() → list[LayoutLine]

Returns the lines of the layout as a list.

This is a faster alternative to get_lines, but the user is not expected to modify the contents of the lines (glyphs, glyph widths, etc.).

Added in version 1.16.

get_log_attrs() → list[LogAttr]

Retrieves an array of logical attributes for each character in the layout.

get_log_attrs_readonly() → list[LogAttr]

Retrieves an array of logical attributes for each character in the layout.

This is a faster alternative to get_log_attrs. The returned array is part of layout and must not be modified. Modifying the layout will invalidate the returned array.

The number of attributes returned in n_attrs will be one more than the total number of characters in the layout, since there need to be attributes corresponding to both the position before the first character and the position after the last character.

Added in version 1.30.

get_pixel_extents() → tuple[Rectangle, Rectangle]

Computes the logical and ink extents of layout in device units.

This function just calls get_extents followed by two extents_to_pixels calls, rounding ink_rect and logical_rect such that the rounded rectangles fully contain the unrounded one (that is, passes them as first argument to extents_to_pixels).

get_pixel_size() → tuple[int, int]

Determines the logical width and height of a PangoLayout in device units.

get_size returns the width and height scaled by SCALE. This is simply a convenience function around get_pixel_extents.

get_serial() → int

Returns the current serial number of layout.

The serial number is initialized to an small number larger than zero when a new layout is created and is increased whenever the layout is changed using any of the setter functions, or the PangoContext it uses has changed. The serial may wrap, but will never have the value 0. Since it can wrap, never compare it with “less than”, always use “not equals”.

This can be used to automatically detect changes to a PangoLayout, and is useful for example to decide whether a layout needs redrawing. To force the serial to be increased, use context_changed.

Added in version 1.32.4.

get_single_paragraph_mode() → bool

Obtains whether layout is in single paragraph mode.

See set_single_paragraph_mode.

get_size() → tuple[int, int]

Determines the logical width and height of a PangoLayout in Pango units.

This is simply a convenience function around get_extents.

get_spacing() → int

Gets the amount of spacing between the lines of the layout.

get_tabs() → TabArray | None

Gets the current PangoTabArray used by this layout.

If no PangoTabArray has been set, then the default tabs are in use and None is returned. Default tabs are every 8 spaces.

The return value should be freed with free.

get_text() → str

Gets the text in the layout.

The returned text should not be freed or modified.

get_unknown_glyphs_count() → int

Counts the number of unknown glyphs in layout.

This function can be used to determine if there are any fonts available to render all characters in a certain string, or when used in combination with FALLBACK, to check if a certain font supports all the characters in the string.

Added in version 1.16.

get_width() → int

Gets the width to which the lines of the PangoLayout should wrap.

get_wrap() → WrapMode

Gets the wrap mode for the layout.

Use is_wrapped to query whether any paragraphs were actually wrapped.

index_to_line_x(index_: int, trailing: bool) → tuple[int, int]

Converts from byte @``index_`` within the layout to line and X position.

The X position is measured from the left edge of the line.

Parameters:

• index – the byte index of a grapheme within the layout

• trailing – an integer indicating the edge of the grapheme to retrieve the position of. If > 0, the trailing edge of the grapheme, if 0, the leading of the grapheme

index_to_pos(index_: int) → Rectangle

Converts from an index within a PangoLayout to the onscreen position corresponding to the grapheme at that index.

The returns is represented as rectangle. Note that pos->x is always the leading edge of the grapheme and pos->x + pos->width the trailing edge of the grapheme. If the directionality of the grapheme is right-to-left, then pos->width will be negative.

Parameters:

index – byte index within layout

is_ellipsized() → bool

Queries whether the layout had to ellipsize any paragraphs.

This returns True if the ellipsization mode for layout is not NONE, a positive width is set on layout, and there are paragraphs exceeding that width that have to be ellipsized.

Added in version 1.16.

is_wrapped() → bool

Queries whether the layout had to wrap any paragraphs.

This returns True if a positive width is set on layout, ellipsization mode of layout is set to NONE, and there are paragraphs exceeding the layout width that have to be wrapped.

Added in version 1.16.

move_cursor_visually(strong: bool, old_index: int, old_trailing: int, direction: int) → tuple[int, int]

Computes a new cursor position from an old position and a direction.

If direction is positive, then the new position will cause the strong or weak cursor to be displayed one position to right of where it was with the old cursor position. If direction is negative, it will be moved to the left.

In the presence of bidirectional text, the correspondence between logical and visual order will depend on the direction of the current run, and there may be jumps when the cursor is moved off of the end of a run.

Motion here is in cursor positions, not in characters, so a single call to this function may move the cursor over multiple characters when multiple characters combine to form a single grapheme.

Parameters:

• strong – whether the moving cursor is the strong cursor or the weak cursor. The strong cursor is the cursor corresponding to text insertion in the base direction for the layout.

• old_index – the byte index of the current cursor position

• old_trailing – if 0, the cursor was at the leading edge of the grapheme indicated by old_index, if > 0, the cursor was at the trailing edge.

• direction – direction to move cursor. A negative value indicates motion to the left

serialize(flags: LayoutSerializeFlags) → Bytes

Serializes the layout for later deserialization via deserialize.

There are no guarantees about the format of the output across different versions of Pango and deserialize will reject data that it cannot parse.

The intended use of this function is testing, benchmarking and debugging. The format is not meant as a permanent storage format.

Added in version 1.50.

Parameters:

flags – PangoLayoutSerializeFlags

set_alignment(alignment: Alignment) → None

Sets the alignment for the layout: how partial lines are positioned within the horizontal space available.

The default alignment is LEFT.

Parameters:

alignment – the alignment

set_attributes(attrs: AttrList | None = None) → None

Sets the text attributes for a layout object.

References attrs, so the caller can unref its reference.

Parameters:

attrs – a PangoAttrList

set_auto_dir(auto_dir: bool) → None

Sets whether to calculate the base direction for the layout according to its contents.

When this flag is on (the default), then paragraphs in layout that begin with strong right-to-left characters (Arabic and Hebrew principally), will have right-to-left layout, paragraphs with letters from other scripts will have left-to-right layout. Paragraphs with only neutral characters get their direction from the surrounding paragraphs.

When False, the choice between left-to-right and right-to-left layout is done according to the base direction of the layout’s PangoContext. (See set_base_dir).

When the auto-computed direction of a paragraph differs from the base direction of the context, the interpretation of LEFT and RIGHT are swapped.

Added in version 1.4.

Parameters:

auto_dir – if True, compute the bidirectional base direction from the layout’s contents

set_ellipsize(ellipsize: EllipsizeMode) → None

Sets the type of ellipsization being performed for layout.

Depending on the ellipsization mode ellipsize text is removed from the start, middle, or end of text so they fit within the width and height of layout set with set_width and set_height.

If the layout contains characters such as newlines that force it to be layed out in multiple paragraphs, then whether each paragraph is ellipsized separately or the entire layout is ellipsized as a whole depends on the set height of the layout.

The default value is NONE.

See set_height for details.

Added in version 1.6.

Parameters:

ellipsize – the new ellipsization mode for layout

set_font_description(desc: FontDescription | None = None) → None

Sets the default font description for the layout.

If no font description is set on the layout, the font description from the layout’s context is used.

Parameters:

desc – the new PangoFontDescription to unset the current font description

set_height(height: int) → None

Sets the height to which the PangoLayout should be ellipsized at.

There are two different behaviors, based on whether height is positive or negative.

If height is positive, it will be the maximum height of the layout. Only lines would be shown that would fit, and if there is any text omitted, an ellipsis added. At least one line is included in each paragraph regardless of how small the height value is. A value of zero will render exactly one line for the entire layout.

If height is negative, it will be the (negative of) maximum number of lines per paragraph. That is, the total number of lines shown may well be more than this value if the layout contains multiple paragraphs of text. The default value of -1 means that the first line of each paragraph is ellipsized. This behavior may be changed in the future to act per layout instead of per paragraph. File a bug against pango at https://gitlab.gnome.org/gnome/pango if your code relies on this behavior.

Height setting only has effect if a positive width is set on layout and ellipsization mode of layout is not NONE. The behavior is undefined if a height other than -1 is set and ellipsization mode is set to NONE, and may change in the future.

Added in version 1.20.

Parameters:

height – the desired height of the layout in Pango units if positive, or desired number of lines if negative.

set_indent(indent: int) → None

Sets the width in Pango units to indent each paragraph.

A negative value of indent will produce a hanging indentation. That is, the first line will have the full width, and subsequent lines will be indented by the absolute value of indent.

The indent setting is ignored if layout alignment is set to CENTER.

The default value is 0.

Parameters:

indent – the amount by which to indent

set_justify(justify: bool) → None

Sets whether each complete line should be stretched to fill the entire width of the layout.

Stretching is typically done by adding whitespace, but for some scripts (such as Arabic), the justification may be done in more complex ways, like extending the characters.

Note that this setting is not implemented and so is ignored in Pango older than 1.18.

Note that tabs and justification conflict with each other: Justification will move content away from its tab-aligned positions.

The default value is False.

Also see set_justify_last_line.

Parameters:

justify – whether the lines in the layout should be justified

set_justify_last_line(justify: bool) → None

Sets whether the last line should be stretched to fill the entire width of the layout.

This only has an effect if set_justify has been called as well.

The default value is False.

Added in version 1.50.

Parameters:

justify – whether the last line in the layout should be justified

set_line_spacing(factor: float) → None

Sets a factor for line spacing.

Typical values are: 0, 1, 1.5, 2. The default values is 0.

If factor is non-zero, lines are placed so that

baseline2 = baseline1 + factor * height2

where height2 is the line height of the second line (as determined by the font(s)). In this case, the spacing set with set_spacing is ignored.

If factor is zero (the default), spacing is applied as before.

Note: for semantics that are closer to the CSS line-height property, see attr_line_height_new.

Added in version 1.44.

Parameters:

factor – the new line spacing factor

set_markup(text, length=-1)

Sets the layout text and attribute list from marked-up text.

See Pango Markup).

Replaces the current text and attribute list.

This is the same as set_markup_with_accel, but the markup text isn’t scanned for accelerators.

Parameters:

• text

• length – length of marked-up text in bytes, or -1 if markup is NUL-terminated

set_markup_with_accel(markup: str, length: int, accel_marker: str) → str

Sets the layout text and attribute list from marked-up text.

See Pango Markup).

Replaces the current text and attribute list.

If accel_marker is nonzero, the given character will mark the character following it as an accelerator. For example, accel_marker might be an ampersand or underscore. All characters marked as an accelerator will receive a LOW attribute, and the first character so marked will be returned in accel_char. Two accel_marker characters following each other produce a single literal accel_marker character.

Parameters:

• markup –

  marked-up text (see Pango Markup)

• length – length of marked-up text in bytes, or -1 if markup is NUL-terminated

• accel_marker – marker for accelerators in the text

set_single_paragraph_mode(setting: bool) → None

Sets the single paragraph mode of layout.

If setting is True, do not treat newlines and similar characters as paragraph separators; instead, keep all text in a single paragraph, and display a glyph for paragraph separator characters. Used when you want to allow editing of newlines on a single text line.

The default value is False.

Parameters:

setting – new setting

set_spacing(spacing: int) → None

Sets the amount of spacing in Pango units between the lines of the layout.

When placing lines with spacing, Pango arranges things so that

line2.top = line1.bottom + spacing

The default value is 0.

Note: Since 1.44, Pango is using the line height (as determined by the font) for placing lines when the line spacing factor is set to a non-zero value with set_line_spacing. In that case, the spacing set with this function is ignored.

Note: for semantics that are closer to the CSS line-height property, see attr_line_height_new.

Parameters:

spacing – the amount of spacing

set_tabs(tabs: TabArray | None = None) → None

Sets the tabs to use for layout, overriding the default tabs.

PangoLayout will place content at the next tab position whenever it meets a Tab character (U+0009).

By default, tabs are every 8 spaces. If tabs is None, the default tabs are reinstated. tabs is copied into the layout; you must free your copy of tabs yourself.

Note that tabs and justification conflict with each other: Justification will move content away from its tab-aligned positions. The same is true for alignments other than LEFT.

Parameters:

tabs – a PangoTabArray

set_text(text, length=-1)

Sets the text of the layout.

This function validates text and renders invalid UTF-8 with a placeholder glyph.

Note that if you have used set_markup or set_markup_with_accel on layout before, you may want to call set_attributes to clear the attributes set on the layout from the markup as this function does not clear attributes.

Parameters:

• text – the text

• length – maximum length of text, in bytes. -1 indicates that the string is nul-terminated and the length should be calculated. The text will also be truncated on encountering a nul-termination even when length is positive.

set_width(width: int) → None

Sets the width to which the lines of the PangoLayout should wrap or ellipsized.

The default value is -1: no width set.

Parameters:

width – the desired width in Pango units, or -1 to indicate that no wrapping or ellipsization should be performed.

set_wrap(wrap: WrapMode) → None

Sets the wrap mode.

The wrap mode only has effect if a width is set on the layout with set_width. To turn off wrapping, set the width to -1.

The default value is WORD.

Parameters:

wrap – the wrap mode

write_to_file(flags: LayoutSerializeFlags, filename: str) → bool

A convenience method to serialize a layout to a file.

It is equivalent to calling serialize followed by file_set_contents.

See those two functions for details on the arguments.

It is mostly intended for use inside a debugger to quickly dump a layout to a file for later inspection.

Added in version 1.50.

Parameters:

• flags – PangoLayoutSerializeFlags

• filename – the file to save it to

xy_to_index(x: int, y: int) → tuple[bool, int, int]

Converts from X and Y position within a layout to the byte index to the character at that logical position.

If the Y position is not inside the layout, the closest position is chosen (the position will be clamped inside the layout). If the X position is not within the layout, then the start or the end of the line is chosen as described for x_to_index. If either the X or Y positions were not inside the layout, then the function returns False; on an exact hit, it returns True.

Parameters:

• x – the X offset (in Pango units) from the left edge of the layout

• y – the Y offset (in Pango units) from the top edge of the layout