Pango.Layout¶

class — extends GObject.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:


align=left	align=left, justify
align=center	align=center, justify
align=right	align=right, justify

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¶

new¶

@classmethod
def new(cls, context: Context) -> Layout

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

Parameters:

context — a PangoContext

Methods¶

context_changed¶

def context_changed(self) -> 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.

copy¶

def copy(self) -> Layout

Creates a deep copy-by-value of the layout.

The attribute list, tab array, and text from the original layout are all copied by value.

get_alignment¶

def get_alignment(self) -> Alignment

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

get_attributes¶

def get_attributes(self) -> AttrList | None

Gets the attribute list for the layout, if any.

get_auto_dir¶

def get_auto_dir(self) -> bool

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

See Layout.set_auto_dir.

get_baseline¶

def get_baseline(self) -> int

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

get_caret_pos¶

def get_caret_pos(self, 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 Layout.get_cursor_pos that applies font metric information about caret slope and offset to the positions it returns.

Parameters:

index_ — the byte index of the cursor

get_character_count¶

def get_character_count(self) -> int

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

get_context¶

def get_context(self) -> Context

Retrieves the PangoContext used for this layout.

get_cursor_pos¶

def get_cursor_pos(self, 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¶

def get_direction(self, index: int) -> Direction

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

Parameters:

index — the byte index of the char

get_ellipsize¶

def get_ellipsize(self) -> EllipsizeMode

Gets the type of ellipsization being performed for layout.

See Layout.set_ellipsize.

Use Layout.is_ellipsized to query whether any paragraphs were actually ellipsized.

get_extents¶

def get_extents(self) -> 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¶

def get_font_description(self) -> FontDescription | None

Gets the font description for the layout, if any.

get_height¶

def get_height(self) -> int

Gets the height of layout used for ellipsization.

See Layout.set_height for details.

get_indent¶

def get_indent(self) -> int

Gets the paragraph indent width in Pango units.

A negative value indicates a hanging indentation.

get_iter¶

def get_iter(self) -> LayoutIter

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

get_justify¶

def get_justify(self) -> bool

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

get_justify_last_line¶

def get_justify_last_line(self) -> bool

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

get_line¶

def get_line(self, line: int) -> LayoutLine | None

Retrieves a particular line from a PangoLayout.

Use the faster Layout.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¶

def get_line_count(self) -> int

Retrieves the count of lines for the layout.

get_line_readonly¶

def get_line_readonly(self, line: int) -> LayoutLine | None

Retrieves a particular line from a PangoLayout.

This is a faster alternative to Layout.get_line, but the user is not expected 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_spacing¶

def get_line_spacing(self) -> float

Gets the line spacing factor of layout.

See Layout.set_line_spacing.

get_lines¶

def get_lines(self) -> list[LayoutLine]

Returns the lines of the layout as a list.

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

get_lines_readonly¶

def get_lines_readonly(self) -> list[LayoutLine]

Returns the lines of the layout as a list.

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

get_log_attrs¶

def get_log_attrs(self) -> list[LogAttr]

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

get_log_attrs_readonly¶

def get_log_attrs_readonly(self) -> list[LogAttr]

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

This is a faster alternative to Layout.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.

get_pixel_extents¶

def get_pixel_extents(self) -> tuple[Rectangle, Rectangle]

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

This function just calls Layout.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¶

def get_pixel_size(self) -> tuple[int, int]

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

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

get_serial¶

def get_serial(self) -> 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 Layout.context_changed.

get_single_paragraph_mode¶

def get_single_paragraph_mode(self) -> bool

Obtains whether layout is in single paragraph mode.

See Layout.set_single_paragraph_mode.

get_size¶

def get_size(self) -> tuple[int, int]

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

This is simply a convenience function around Layout.get_extents.

get_spacing¶

def get_spacing(self) -> int

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

get_tabs¶

def get_tabs(self) -> 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 TabArray.free.

get_text¶

def get_text(self) -> str

Gets the text in the layout.

The returned text should not be freed or modified.

get_unknown_glyphs_count¶

def get_unknown_glyphs_count(self) -> 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 AttrType.FALLBACK, to check if a certain font supports all the characters in the string.

get_width¶

def get_width(self) -> int

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

get_wrap¶

def get_wrap(self) -> WrapMode

Gets the wrap mode for the layout.

Use Layout.is_wrapped to query whether any paragraphs were actually wrapped.

index_to_line_x¶

def index_to_line_x(self, 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¶

def index_to_pos(self, 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¶

def is_ellipsized(self) -> bool

Queries whether the layout had to ellipsize any paragraphs.

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

is_wrapped¶

def is_wrapped(self) -> bool

Queries whether the layout had to wrap any paragraphs.

This returns True if a positive width is set on layout, and there are paragraphs exceeding the layout width that have to be wrapped.

move_cursor_visually¶

def move_cursor_visually(self, 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¶

def serialize(self, flags: LayoutSerializeFlags | int) -> bytes

Serializes the layout for later deserialization via Layout.deserialize.

There are no guarantees about the format of the output across different versions of Pango and Layout.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.

Parameters:

flags — PangoLayoutSerializeFlags

set_alignment¶

def set_alignment(self, alignment: Alignment | int) -> None

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

The default alignment is Alignment.LEFT.

Parameters:

alignment — the alignment

set_attributes¶

def set_attributes(self, attrs: AttrList | 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¶

def set_auto_dir(self, 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 Context.set_base_dir).

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

Parameters:

auto_dir — if True, compute the bidirectional base direction from the layout's contents

set_ellipsize¶

def set_ellipsize(self, ellipsize: EllipsizeMode | int) -> 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 Layout.set_width and Layout.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 EllipsizeMode.NONE.

See Layout.set_height for details.

Parameters:

ellipsize — the new ellipsization mode for layout

set_font_description¶

def set_font_description(self, desc: FontDescription | 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¶

def set_height(self, 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 EllipsizeMode.NONE. The behavior is undefined if a height other than -1 is set and ellipsization mode is set to EllipsizeMode.NONE, and may change in the future.

Parameters:

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

set_indent¶

def set_indent(self, 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 Alignment.CENTER.

The default value is 0.

Parameters:

indent — the amount by which to indent

set_justify¶

def set_justify(self, 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 Layout.set_justify_last_line.

Parameters:

justify — whether the lines in the layout should be justified

set_justify_last_line¶

def set_justify_last_line(self, 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 Layout.set_justify has been called as well.

The default value is False.

Parameters:

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

set_line_spacing¶

def set_line_spacing(self, 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 Layout.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.

Parameters:

factor — the new line spacing factor

set_markup¶

def set_markup(self, markup: str, length: int) -> None

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 Layout.set_markup_with_accel, but the markup text isn't scanned for accelerators.

Parameters:

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

set_markup_with_accel¶

def set_markup_with_accel(self, 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 Underline.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¶

def set_single_paragraph_mode(self, 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¶

def set_spacing(self, 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 Layout.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¶

def set_tabs(self, tabs: TabArray | 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 Alignment.LEFT.

Parameters:

tabs — a PangoTabArray

set_text¶

def set_text(self, text: str, length: int) -> None

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 Layout.set_markup or Layout.set_markup_with_accel on layout before, you may want to call Layout.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¶

def set_width(self, width: int) -> None

Sets the width to which the lines of the PangoLayout should wrap or get 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¶

def set_wrap(self, wrap: WrapMode | int) -> None

Sets the wrap mode.

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

The default value is WrapMode.WORD.

Parameters:

wrap — the wrap mode

write_to_file¶

def write_to_file(self, flags: LayoutSerializeFlags | int, filename: str | bytes | os.PathLike[str] | os.PathLike[bytes]) -> bool

A convenience method to serialize a layout to a file.

It is equivalent to calling Layout.serialize followed by GLib.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.

Parameters:

flags — PangoLayoutSerializeFlags
filename — the file to save it to

xy_to_index¶

def xy_to_index(self, 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 LayoutLine.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

Static functions¶

deserialize¶

@staticmethod
def deserialize(context: Context, bytes: bytes, flags: LayoutDeserializeFlags | int) -> Layout | None

Loads data previously created via Layout.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.

Parameters:

context — a PangoContext
bytes — the bytes containing the data
flags — PangoLayoutDeserializeFlags