gi-pango-1.0.22: Pango bindings
Copyright Will Thompson Iñaki García Etxebarria and Jonas Platte LGPL-2.1 Iñaki García Etxebarria None Haskell2010

GI.Pango.Objects.Layout

Description

The Layout structure represents an entire paragraph of text. It is initialized with a 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 also a number of parameters to adjust the formatting of a Layout, which are illustrated in <xref linkend="parameters"/>. It is possible, as well, to ignore the 2-D setup, and simply treat the results of a Layout as a list of lines.

<figure id="parameters"> <title>Adjustable parameters for a PangoLayout</title> <graphic fileref="layout.gif" format="GIF"></graphic> </figure>

The Layout structure is opaque, and has no user-visible fields.

Synopsis

# Exported types

newtype Layout Source #

Memory-managed wrapper type.

Constructors

 Layout (ManagedPtr Layout)

#### Instances

Instances details
 Source # Instance detailsDefined in GI.Pango.Objects.Layout Methods(==) :: Layout -> Layout -> Bool #(/=) :: Layout -> Layout -> Bool # Source # Instance detailsDefined in GI.Pango.Objects.Layout Methods Source # Convert Layout to and from GValue with toGValue and fromGValue. Instance detailsDefined in GI.Pango.Objects.Layout Methods Source # Instance detailsDefined in GI.Pango.Objects.Layout Source # Instance detailsDefined in GI.Pango.Objects.Layout type ParentTypes Layout = '[Object]

class (GObject o, IsDescendantOf Layout o) => IsLayout o Source #

Type class for types which can be safely cast to Layout, for instance with toLayout.

#### Instances

Instances details
 (GObject o, IsDescendantOf Layout o) => IsLayout o Source # Instance detailsDefined in GI.Pango.Objects.Layout

toLayout :: (MonadIO m, IsLayout o) => o -> m Layout Source #

Cast to Layout, for types for which this is known to be safe. For general casts, use castTo.

A convenience alias for Nothing :: Maybe Layout.

# Methods

## contextChanged

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m ()

Forces recomputation of any state in the 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.

## copy

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a src: a Layout -> m Layout Returns: the newly allocated Layout, with a reference count of one, which should be freed with objectUnref.

Does a deep copy-by-value of the src layout. The attribute list, tab array, and text from the original layout are all copied by value.

## getAlignment

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Alignment Returns: the alignment.

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

## getAttributes

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m AttrList Returns: a AttrList.

Gets the attribute list for the layout, if any.

## getAutoDir

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Bool Returns: True if the bidirectional base direction is computed from the layout's contents, False otherwise.

Gets whether to calculate the bidirectional base direction for the layout according to the contents of the layout. See layoutSetAutoDir.

Since: 1.4

## getBaseline

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Int32 Returns: baseline of first line, from top of layout.

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

Since: 1.22

## getCharacterCount

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Int32 Returns: the number of Unicode characters in the text of layout

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

Since: 1.30

## getContext

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Context Returns: the Context for the layout. This does not have an additional refcount added, so if you want to keep a copy of this around, you must reference it yourself.

Retrieves the Context used for this layout.

## getCursorPos

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Int32 index_: the byte index of the cursor -> m (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. 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.

## getEllipsize

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m EllipsizeMode Returns: the current ellipsization mode for layout.Use layoutIsEllipsized to query whether any paragraphs were actually ellipsized.

Gets the type of ellipsization being performed for layout. See layoutSetEllipsize

Since: 1.6

## getExtents

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m (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.

## getFontDescription

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m (Maybe FontDescription) Returns: a pointer to the layout's font description, or Nothing if the font description from the layout's context is inherited. This value is owned by the layout and must not be modified or freed.

Gets the font description for the layout, if any.

Since: 1.8

## getHeight

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Int32 Returns: the height, in Pango units if positive, or number of lines if negative.

Gets the height of layout used for ellipsization. See layoutSetHeight for details.

Since: 1.20

## getIndent

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Int32 Returns: the indent in Pango units.

Gets the paragraph indent width in Pango units. A negative value indicates a hanging indentation.

## getIter

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m LayoutIter Returns: the new LayoutIter that should be freed using layoutIterFree.

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

## getJustify

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Bool Returns: the justify.

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

## getLine

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Int32 line: the index of a line, which must be between 0 and pango_layout_get_line_count(layout) - 1, inclusive. -> m (Maybe LayoutLine) Returns: the requested LayoutLine, or Nothing if the index is out of range. This layout line can be ref'ed and retained, but will become invalid if changes are made to the Layout.

Retrieves a particular line from a Layout.

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

## getLineCount

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: Layout -> m Int32 Returns: the line count.

Retrieves the count of lines for the layout.

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Int32 line: the index of a line, which must be between 0 and pango_layout_get_line_count(layout) - 1, inclusive. -> m (Maybe LayoutLine) Returns: the requested LayoutLine, or Nothing if the index is out of range. This layout line can be ref'ed and retained, but will become invalid if changes are made to the Layout. No changes should be made to the line.

Retrieves a particular line from a Layout.

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

Since: 1.16

## getLines

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m [LayoutLine] Returns: a SList containing the lines in the layout. This points to internal data of the Layout and must be used with care. It will become invalid on any change to the layout's text or properties.

Returns the lines of the layout as a list.

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

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m [LayoutLine] Returns: a SList containing the lines in the layout. This points to internal data of the Layout and must be used with care. It will become invalid on any change to the layout's text or properties. No changes should be made to the lines.

Returns the lines of the layout as a list.

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

Since: 1.16

## getLogAttrs

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m [LogAttr]

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

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m [LogAttr] Returns: an array of logical attributes

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

This is a faster alternative to layoutGetLogAttrs. 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 nAttrs 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.

Since: 1.30

## getPixelExtents

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m (Rectangle, Rectangle)

Computes the logical and ink extents of layout in device units. This function just calls layoutGetExtents followed by two extentsToPixels calls, rounding inkRect and logicalRect such that the rounded rectangles fully contain the unrounded one (that is, passes them as first argument to extentsToPixels).

## getPixelSize

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m (Int32, Int32)

Determines the logical width and height of a Layout in device units. (layoutGetSize returns the width and height scaled by SCALE.) This is simply a convenience function around layoutGetPixelExtents.

## getSerial

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Word32 Returns: The current serial number of layout.

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 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 Layout, and is useful for example to decide whether a layout needs redrawing. To force the serial to be increased, use layoutContextChanged.

Since: 1.32.4

## getSingleParagraphMode

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Bool Returns: True if the layout does not break paragraphs at paragraph separator characters, False otherwise.

Obtains the value set by layoutSetSingleParagraphMode.

## getSize

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m (Int32, Int32)

Determines the logical width and height of a Layout in Pango units (device units scaled by SCALE). This is simply a convenience function around layoutGetExtents.

## getSpacing

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Int32 Returns: the spacing in Pango units.

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

## getTabs

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m (Maybe TabArray) Returns: a copy of the tabs for this layout, or Nothing.

Gets the current TabArray used by this layout. If no TabArray has been set, then the default tabs are in use and Nothing is returned. Default tabs are every 8 spaces. The return value should be freed with tabArrayFree.

## getText

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Text Returns: the text in the layout.

Gets the text in the layout. The returned text should not be freed or modified.

## getUnknownGlyphsCount

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Int32 Returns: The number of unknown glyphs in layout.

Counts the number unknown glyphs in layout. That is, zero if glyphs for all characters in the layout text were found, or more than zero otherwise.

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

Since: 1.16

## getWidth

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Int32 Returns: the width in Pango units, or -1 if no width set.

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

## getWrap

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m WrapMode Returns: active wrap mode.

Gets the wrap mode for the layout.

Use layoutIsWrapped to query whether any paragraphs were actually wrapped.

## indexToLineX

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Int32 index_: the byte index of a grapheme within the layout. -> Bool 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. -> m (Int32, Int32)

Converts from byte index_ within the layout to line and X position. (X position is measured from the left edge of the line)

## indexToPos

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Int32 index_: byte index within layout -> m Rectangle

Converts from an index within a Layout to the onscreen position corresponding to the grapheme at that index, which is represented as rectangle. Note that <literal>pos->x</literal> is always the leading edge of the grapheme and <literal>pos->x + pos->width</literal> the trailing edge of the grapheme. If the directionality of the grapheme is right-to-left, then <literal>pos->width</literal> will be negative.

## isEllipsized

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Bool Returns: True if any paragraphs had to be ellipsized, False otherwise.

Queries whether the layout had to ellipsize any paragraphs.

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

Since: 1.16

## isWrapped

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> m Bool Returns: True if any paragraphs had to be wrapped, False otherwise.

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 EllipsizeModeNone, and there are paragraphs exceeding the layout width that have to be wrapped.

Since: 1.16

## moveCursorVisually

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout. -> Bool 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. -> Int32 oldIndex: the byte index of the grapheme for the old index -> Int32 oldTrailing: if 0, the cursor was at the leading edge of the grapheme indicated by oldIndex, if > 0, the cursor was at the trailing edge. -> Int32 direction: direction to move cursor. A negative value indicates motion to the left. -> m (Int32, Int32)

Computes a new cursor position from an old position and a count of positions to move visually. If direction is positive, then the new strong cursor position will be one position to the right of the old cursor position. If direction is negative, then the new strong cursor position will be one position to the left of the old cursor position.

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 layoutMoveCursorVisually may move the cursor over multiple characters when multiple characters combine to form a single grapheme.

## new

Arguments

 :: (HasCallStack, MonadIO m, IsContext a) => a context: a Context -> m Layout Returns: the newly allocated Layout, with a reference count of one, which should be freed with objectUnref.

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

## setAlignment

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Alignment alignment: the alignment -> m ()

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

## setAttributes

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Maybe AttrList attrs: a AttrList, can be Nothing -> m ()

Sets the text attributes for a layout object. References attrs, so the caller can unref its reference.

## setAutoDir

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Bool autoDir: if True, compute the bidirectional base direction from the layout's contents. -> m ()

Sets whether to calculate the bidirectional base direction for the layout according to the contents of the layout; 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 Context. (See contextSetBaseDir).

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

Since: 1.4

## setEllipsize

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> EllipsizeMode ellipsize: the new ellipsization mode for layout -> m ()

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 layoutSetWidth and layoutSetHeight.

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. See layoutSetHeight for details.

Since: 1.6

## setFontDescription

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Maybe FontDescription desc: the new FontDescription, or Nothing to unset the current font description -> m ()

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.

## setHeight

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout. -> Int32 height: the desired height of the layout in Pango units if positive, or desired number of lines if negative. -> m ()

Sets the height to which the 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 first line of each paragraph is ellipsized. This behvaior may be changed in the future to act per layout instead of per paragraph. File a bug against pango at <ulink url="http://bugzilla.gnome.org/">http://bugzilla.gnome.org/</ulink> 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 EllipsizeModeNone. The behavior is undefined if a height other than -1 is set and ellipsization mode is set to EllipsizeModeNone, and may change in the future.

Since: 1.20

## setIndent

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout. -> Int32 indent: the amount by which to indent. -> m ()

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 AlignmentCenter.

## setJustify

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Bool justify: whether the lines in the layout should be justified. -> m ()

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

## setMarkup

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Text markup: marked-up text -> Int32 length: length of marked-up text in bytes, or -1 if markup is null-terminated -> m ()

Same as layoutSetMarkupWithAccel, but the markup text isn't scanned for accelerators.

## setSingleParagraphMode

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Bool setting: new setting -> m ()

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.

## setSpacing

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout. -> Int32 spacing: the amount of spacing -> m ()

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

## setTabs

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Maybe TabArray tabs: a TabArray, or Nothing -> m ()

Sets the tabs to use for layout, overriding the default tabs (by default, tabs are every 8 spaces). If tabs is Nothing, the default tabs are reinstated. tabs is copied into the layout; you must free your copy of tabs yourself.

## setText

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Text text: a valid UTF-8 string -> Int32 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. -> m ()

Sets the text of the layout.

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

## setWidth

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout. -> Int32 width: the desired width in Pango units, or -1 to indicate that no wrapping or ellipsization should be performed. -> m ()

Sets the width to which the lines of the Layout should wrap or ellipsized. The default value is -1: no width set.

## setWrap

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> WrapMode wrap: the wrap mode -> m ()

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

## xyToIndex

Arguments

 :: (HasCallStack, MonadIO m, IsLayout a) => a layout: a Layout -> Int32 x: the X offset (in Pango units) from the left edge of the layout. -> Int32 y: the Y offset (in Pango units) from the top edge of the layout -> m (Bool, Int32, Int32) Returns: True if the coordinates were inside text, False otherwise.

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 layoutLineXToIndex. If either the X or Y positions were not inside the layout, then the function returns False; on an exact hit, it returns True.