class Pango::Layout

Overview

A Pango::Layout 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. Pango::Layout 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 Pango::Layout is initialized with a Pango::Context, 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 Pango::Layout. The following image shows adjustable parameters (on the left) and font metrics (on the right):

Pango Layout Parameters

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 Pango::Layout as a list of lines.

Defined in:

lib/gi-crystal/src/auto/pango-1.0/layout.cr
lib/pango/src/bindings/pango/layout.cr

Constructors

Class Method Summary

Instance Method Summary

Instance methods inherited from class GObject::Object

==(other : self) ==, bind_property(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags) : GObject::Binding bind_property, bind_property_full(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags, transform_to : GObject::Closure, transform_from : GObject::Closure) : GObject::Binding bind_property_full, data(key : String) : Pointer(Void) | Nil data, finalize finalize, freeze_notify : Nil freeze_notify, getv(names : Enumerable(String), values : Enumerable(_)) : Nil getv, hash(hasher) hash, notify(property_name : String) : Nil notify, notify_by_pspec(pspec : GObject::ParamSpec) : Nil notify_by_pspec, notify_signal notify_signal, property(property_name : String, value : _) : Nil property, qdata(quark : UInt32) : Pointer(Void) | Nil qdata, ref_count : UInt32 ref_count, run_dispose : Nil run_dispose, set_data(key : String, data : Pointer(Void) | Nil) : Nil set_data, set_property(property_name : String, value : _) : Nil set_property, steal_data(key : String) : Pointer(Void) | Nil steal_data, steal_qdata(quark : UInt32) : Pointer(Void) | Nil steal_qdata, thaw_notify : Nil thaw_notify, to_unsafe : Pointer(Void) to_unsafe, watch_closure(closure : GObject::Closure) : Nil watch_closure

Constructor methods inherited from class GObject::Object

cast(obj : GObject::Object) : self cast, new(pointer : Pointer(Void), transfer : GICrystal::Transfer)
new
new
, newv(object_type : UInt64, parameters : Enumerable(GObject::Parameter)) : self newv

Class methods inherited from class GObject::Object

cast?(obj : GObject::Object) : self | Nil cast?, compat_control(what : UInt64, data : Pointer(Void) | Nil) : UInt64 compat_control, g_type : UInt64 g_type, interface_find_property(g_iface : GObject::TypeInterface, property_name : String) : GObject::ParamSpec interface_find_property, interface_list_properties(g_iface : GObject::TypeInterface) : Enumerable(GObject::ParamSpec) interface_list_properties

Constructor Detail

def self.new(context : Pango::Context) : self #

Create a new Pango::Layout object with attributes initialized to default values for a particular Pango::Context.


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def self.new #

Initialize a new Layout.


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Class Method Detail

def self.g_type : UInt64 #

Returns the type id (GType) registered in GLib type system.


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Instance Method Detail

def ==(other : self) #
Description copied from class Reference

Returns true if this reference is the same as other. Invokes same?.


def alignment : Pango::Alignment #

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


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def alignment=(alignment : Pango::Alignment) : Nil #

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

The default alignment is %PANGO_ALIGN_LEFT.


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def attributes : Pango::AttrList | Nil #

Gets the attribute list for the layout, if any.


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def attributes=(attrs : Pango::AttrList | Nil) : Nil #

Sets the text attributes for a layout object.

References attrs, so the caller can unref its reference.


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def auto_dir : Bool #

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

See Pango::Layout#auto_dir=.


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def auto_dir=(auto_dir : Bool) : Nil #

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 Pango::Context. (See Pango::Context#base_dir=).

When the auto-computed direction of a paragraph differs from the base direction of the context, the interpretation of %PANGO_ALIGN_LEFT and %PANGO_ALIGN_RIGHT are swapped.


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def baseline : Int32 #

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


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def caret_pos(index_ : Int32) : Pango::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 Pango::Layout#cursor_pos that applies font metric information about caret slope and offset to the positions it returns.

Caret metrics

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def character_count : Int32 #

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


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def context : Pango::Context #

Retrieves the Pango::Context used for this layout.


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def context_changed : Nil #

Forces recomputation of any state in the Pango::Layout 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.


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def copy : Pango::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.


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def cursor_pos(index_ : Int32) : Pango::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.

Cursor positions

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.

Strong and weak cursors

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.


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def deserialize(context : Pango::Context, bytes : GLib::Bytes, flags : Pango::LayoutDeserializeFlags) : Pango::Layout | Nil #

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def direction(index : Int32) : Pango::Direction #

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


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def ellipsize : Pango::EllipsizeMode #

Gets the type of ellipsization being performed for layout.

See Pango::Layout#ellipsize=.

Use Pango::Layout#is_ellipsized? to query whether any paragraphs were actually ellipsized.


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def ellipsize=(ellipsize : Pango::EllipsizeMode) : Nil #

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 Pango::Layout#width= and Pango::Layout#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 %PANGO_ELLIPSIZE_NONE.

See Pango::Layout#height= for details.


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def extents : Pango::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.


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def font_description : Pango::FontDescription | Nil #

Gets the font description for the layout, if any.


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def font_description=(desc : Pango::FontDescription | Nil) : Nil #

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.


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def hash(hasher) #
Description copied from class Reference

See Object#hash(hasher)


def height : Int32 #

Gets the height of layout used for ellipsization.

See Pango::Layout#height= for details.


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def height=(height : Int32) : Nil #

Sets the height to which the Pango::Layout 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 %PANGO_ELLIPSIZE_NONE. The behavior is undefined if a height other than -1 is set and ellipsization mode is set to %PANGO_ELLIPSIZE_NONE, and may change in the future.


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def indent : Int32 #

Gets the paragraph indent width in Pango units.

A negative value indicates a hanging indentation.


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def indent=(indent : Int32) : Nil #

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 %PANGO_ALIGN_CENTER.

The default value is 0.


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def index_to_line_x(index_ : Int32, trailing : Bool) : Nil #

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

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


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def index_to_pos(index_ : Int32) : Pango::Rectangle #

Converts from an index within a Pango::Layout to the onscreen position corresponding to the grapheme at that index.

The return value 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.


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def is_ellipsized : Bool #

Queries whether the layout had to ellipsize any paragraphs.

This returns true if the ellipsization mode for layout is not %PANGO_ELLIPSIZE_NONE, a positive width is set on layout, and there are paragraphs exceeding that width that have to be ellipsized.


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def 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 %PANGO_ELLIPSIZE_NONE, and there are paragraphs exceeding the layout width that have to be wrapped.


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def iter : Pango::LayoutIter #

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


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def justify : Bool #

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


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def justify=(justify : Bool) : Nil #

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 Pango::Layout#justify_last_line=.


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def justify_last_line : Bool #

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


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def justify_last_line=(justify : Bool) : Nil #

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

This only has an effect if Pango::Layout#justify= has been called as well.

The default value is false.


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def line(line : Int32) : Pango::LayoutLine | Nil #

Retrieves a particular line from a Pango::Layout.

Use the faster Pango::Layout#line_readonly if you do not plan to modify the contents of the line (glyphs, glyph widths, etc.).


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def line_count : Int32 #

Retrieves the count of lines for the layout.


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def line_readonly(line : Int32) : Pango::LayoutLine | Nil #

Retrieves a particular line from a Pango::Layout.

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


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def line_spacing : Float32 #

Gets the line spacing factor of layout.

See Pango::Layout#line_spacing=.


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def line_spacing=(factor : Float32) : Nil #

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 Pango::Layout#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 Pango::attr_line_height_new.


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def lines : GLib::SList #

Returns the lines of the layout as a list.

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


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def lines_readonly : GLib::SList #

Returns the lines of the layout as a list.

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


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def log_attrs(attrs : Enumerable(Pango::LogAttr)) : Nil #

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


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def log_attrs(*attrs : Pango::LogAttr) #

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def log_attrs_readonly : Enumerable(Pango::LogAttr) #

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

This is a faster alternative to Pango::Layout#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.


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def move_cursor_visually(strong : Bool, old_index : Int32, old_trailing : Int32, direction : Int32, new_index : Int32, new_trailing : Int32) : Nil #

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.


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def pixel_extents : Pango::Rectangle #

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

This function just calls Pango::Layout#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 Pango::extents_to_pixels).


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def pixel_size : Nil #

Determines the logical width and height of a Pango::Layout in device units.

Pango::Layout#size returns the width and height scaled by %PANGO_SCALE. This is simply a convenience function around Pango::Layout#pixel_extents.


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def serial : UInt32 #

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 Pango::Context 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 Pango::Layout, and is useful for example to decide whether a layout needs redrawing. To force the serial to be increased, use Pango::Layout#context_changed.


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def serialize(flags : Pango::LayoutSerializeFlags) : GLib::Bytes #

Serializes the layout for later deserialization via Pango::Layout#deserialize.

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


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def set_markup(markup : String, length : Int32) : Nil #

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 Pango::Layout#markup_with_accel=, but the markup text isn't scanned for accelerators.


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def set_markup_with_accel(markup : String, length : Int32, accel_marker : Char) : Char #

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 %PANGO_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.


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def set_text(text : String, length : Int32) : Nil #

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 Pango::Layout#markup= or Pango::Layout#markup_with_accel= on layout before, you may want to call Pango::Layout#attributes= to clear the attributes set on the layout from the markup as this function does not clear attributes.


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def single_paragraph_mode : Bool #

Obtains whether layout is in single paragraph mode.

See Pango::Layout#single_paragraph_mode=.


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def single_paragraph_mode=(setting : Bool) : Nil #

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.


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def size : Nil #

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

This is simply a convenience function around Pango::Layout#extents.


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def spacing : Int32 #

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


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def spacing=(spacing : Int32) : Nil #

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 Pango::Layout#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 Pango::attr_line_height_new.


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def tabs : Pango::TabArray | Nil #

Gets the current Pango::TabArray used by this layout.

If no Pango::TabArray has been set, then the default tabs are in use and nil is returned. Default tabs are every 8 spaces.

The return value should be freed with Pango::TabArray#free.


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def tabs=(tabs : Pango::TabArray | Nil) : Nil #

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

Pango::Layout 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 nil, 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 %PANGO_ALIGN_LEFT.


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def text : String #

Gets the text in the layout.

The returned text should not be freed or modified.


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def unknown_glyphs_count : Int32 #

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 %PANGO_ATTR_FALLBACK, to check if a certain font supports all the characters in the string.


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def width : Int32 #

Gets the width to which the lines of the Pango::Layout should wrap.


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def width=(width : Int32) : Nil #

Sets the width to which the lines of the Pango::Layout should wrap or ellipsized.

The default value is -1: no width set.


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def wrap : Pango::WrapMode #

Gets the wrap mode for the layout.

Use Pango::Layout#is_wrapped? to query whether any paragraphs were actually wrapped.


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def wrap=(wrap : Pango::WrapMode) : Nil #

Sets the wrap mode.

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

The default value is %PANGO_WRAP_WORD.


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def write_to_file(flags : Pango::LayoutSerializeFlags, filename : String) : Bool #

A convenience method to serialize a layout to a file.

It is equivalent to calling Pango::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.


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def xy_to_index(x : Int32, y : Int32, index_ : Int32, trailing : Int32) : Bool #

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 Pango::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.


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