Graphics.UI.Gtk.Display.Label

A widget that displays a small to medium amount of text

Detail

The Label widget displays a small amount of text. As the name implies, most labels are used to label another widget such as a Button, a MenuItem, or a OptionMenu.

Mnemonics

Labels may contain mnemonics. Mnemonics are underlined characters in the label, used for keyboard navigation. Mnemonics are created by providing a string with an underscore before the mnemonic character, such as "_File", to the functions labelNewWithMnemonic or labelSetTextWithMnemonic.

Mnemonics automatically activate any activatable widget the label is inside, such as a Button; if the label is not inside the mnemonic's target widget, you have to tell the label about the target using labelSetMnemonicWidget. Here's a simple example where the label is inside a button: There's a convenience function to create buttons with a mnemonic label already inside: To create a mnemonic for a widget alongside the label, such as a Entry, you have to point the label at the entry with labelSetMnemonicWidget:

 -- Pressing Alt+H will activate this button
 button <- buttonNew
 label <- labelNewWithMnemonic "_Hello"
 containerAdd button label

 -- Pressing Alt+H will activate this button
 button <- buttonNewWithMnemonic "_Hello"

 -- Pressing Alt+H will focus the entry
 entry <- entryNew
 label <- labelNewWithMnemonic "_Hello"
 labelSetMnemonicWidget label entry

Markup (styled text)

To make it easy to format text in a label (changing colors, fonts, etc.), label text can be provided in a simple markup format. Here's how to create a label with a small font: (See complete documentation of available tags in the Pango manual.)

 label <- labelNew Nothing
 labelSetMarkup label "<small>Small text</small>"

The markup passed to labelSetMarkup must be valid; for example, literal </>/& characters must be escaped as "<", ">", and "&". If you pass text obtained from the user, file, or a network to labelSetMarkup, you'll want to escape it with escapeMarkup.

Selectable labels

Labels can be made selectable with labelSetSelectable. Selectable labels allow the user to copy the label contents to the clipboard. Only labels that contain useful-to-copy information - such as error messages - should be made selectable.

Text layout

A label can contain any number of paragraphs, but will have performance problems if it contains more than a small number. Paragraphs are separated by newlines or other paragraph separators understood by Pango.

Labels can automatically wrap text if you call labelSetLineWrap.

labelSetJustify sets how the lines in a label align with one another. If you want to set how the label as a whole aligns in its available space, see miscSetAlignment.

Class Hierarchy

 | GObject
 | +----Object
 | +----Widget
 | +----Misc
 | +----Label
 | +----AccelLabel
 | +----TipsQuery

Types

data Label

Instances

Eq Label

Ord Label

GObjectClass Label

LabelClass Label

MiscClass Label

WidgetClass Label

ObjectClass Label

class MiscClass o => LabelClass o

Instances

LabelClass AccelLabel

LabelClass Label

castToLabel :: GObjectClass obj => obj -> Label

gTypeLabel :: GType

toLabel :: LabelClass o => o -> Label

Constructors

labelNew :: Maybe String -> IO Label

Creates a new label with the given text inside it. You can pass Nothing to get an empty label widget.

labelNewWithMnemonic

Arguments

:: String

str - The text of the label, with an underscore in front of the mnemonic character

-> IO Label

Creates a new Label, containing the text in str.

If characters in str are preceded by an underscore, they are underlined. If you need a literal underscore character in a label, use '__' (two underscores). The first underlined character represents a keyboard accelerator called a mnemonic. The mnemonic key can be used to activate another widget, chosen automatically, or explicitly using labelSetMnemonicWidget.

If labelSetMnemonicWidget is not called, then the first activatable ancestor of the Label will be chosen as the mnemonic widget. For instance, if the label is inside a button or menu item, the button or menu item will automatically become the mnemonic widget and be activated by the mnemonic.

Methods

labelSetText :: LabelClass self => self -> String -> IO ()

Sets the text within the Label widget. It overwrites any text that was there before.

This will also clear any previously set mnemonic accelerators.

labelSetLabel :: LabelClass self => self -> String -> IO ()

Sets the text of the label. The label is interpreted as including embedded underlines and/or Pango markup depending on the markup and underline properties.

labelSetTextWithMnemonic :: LabelClass self => self -> String -> IO ()

Sets the label's text from the given string. If characters in the string are preceded by an underscore, they are underlined indicating that they represent a keyboard accelerator called a mnemonic. The mnemonic key can be used to activate another widget, chosen automatically, or explicitly using labelSetMnemonicWidget.

labelSetMarkup

Arguments

:: LabelClass self

=> self

-> Markup

str - a markup string (see Pango markup format)

-> IO ()

Parses str which is marked up with the Pango text markup language, as defined in Graphics.Rendering.Pango.Markup, setting the label's text and attribute list based on the parse results. If the str is external data, you may need to escape it.

labelSetMarkupWithMnemonic

Arguments

:: LabelClass self

=> self

-> Markup

str - a markup string (see Pango markup format)

-> IO ()

Parses str which is marked up with the Pango text markup language, as defined in Graphics.Rendering.Pango.Markup, setting the label's text and attribute list based on the parse results. If characters in str are preceded by an underscore, they are underlined indicating that they represent a keyboard accelerator called a mnemonic.

The mnemonic key can be used to activate another widget, chosen automatically, or explicitly using labelSetMnemonicWidget.

labelSetMnemonicWidget

Arguments

:: (LabelClass self, WidgetClass widget)

=> self

-> widget

widget - the target Widget

-> IO ()

If the label has been set so that it has an mnemonic key (using i.e. labelSetMarkupWithMnemonic, labelSetTextWithMnemonic, labelNewWithMnemonic or the "use_underline" property) the label can be associated with a widget that is the target of the mnemonic. When the label is inside a widget (like a Button or a Notebook tab) it is automatically associated with the correct widget, but sometimes (i.e. when the target is a Entry next to the label) you need to set it explicitly using this function.

The target widget will be accelerated by emitting "mnemonic_activate" on it. The default handler for this signal will activate the widget if there are no mnemonic collisions and toggle focus between the colliding widgets otherwise.

labelGetMnemonicWidget

Arguments

:: LabelClass self

=> self

-> IO (Maybe Widget)

returns the target of the label's mnemonic, or Nothing if none has been set and the default algorithm will be used.

Retrieves the target of the mnemonic (keyboard shortcut) of this label. See labelSetMnemonicWidget.

type KeyVal = Word32

Key values are the codes which are sent whenever a key is pressed or released.

labelGetMnemonicKeyval :: LabelClass self => self -> IO KeyVal

If the label has been set so that it has an mnemonic key this function returns the keyval used for the mnemonic accelerator.

labelSetUseMarkup

Arguments

:: LabelClass self

=> self

-> Bool

setting - True if the label's text should be parsed for markup.

-> IO ()

Sets whether the text of the label contains markup in Pango's text markup language. See labelSetMarkup.

labelGetUseMarkup

Arguments

:: LabelClass self

=> self

-> IO Bool

returns True if the label's text will be parsed for markup.

Returns whether the label's text is interpreted as marked up with the Pango text markup language. See labelSetUseMarkup.

labelSetUseUnderline :: LabelClass self => self -> Bool -> IO ()

If True, an underline in the text indicates the next character should be used for the mnemonic accelerator key.

labelGetUseUnderline :: LabelClass self => self -> IO Bool

Returns whether an embedded underline in the label indicates a mnemonic. See labelSetUseUnderline.

labelGetText :: LabelClass self => self -> IO String

Gets the text from a label widget, as displayed on the screen. This does not include any embedded underlines indicating mnemonics or Pango markup. (See labelGetLabel)

labelGetLabel :: LabelClass self => self -> IO String

Gets the text from a label widget including any embedded underlines indicating mnemonics and Pango markup. (See labelGetText).

labelSetAttributes

Arguments

:: LabelClass self

=> self

-> [PangoAttribute]

attr PangoAttribute

-> IO ()

Sets a PangoAttrList; the attributes in the list are applied to the label text.

Note: The attributes set with this function will be applied and merged with any other attributes previously effected by way of the labelUseUnderline or labelUseMarkup properties. While it is not recommended to mix markup strings with manually set attributes, if you must; know that the attributes will be applied to the label after the markup string is parsed.

labelGetAttributes

Arguments

:: LabelClass self

=> self

-> IO [PangoAttribute]

return the attribute list, or Emtpy if none was set.

Gets the attribute list that was set on the label using labelSetAttributes, if any. This function does not reflect attributes that come from the labels markup (see labelSetMarkup). If you want to get the effective attributes for the label, use layoutGetAttributes (labelGetLayout (label)).

labelSetPattern :: LabelClass l => l -> [Int] -> IO ()

Underline parts of the text, odd indices of the list represent underlined parts.

data Justification

Justification for label and maybe other widgets (text?)

Constructors

JustifyLeft

JustifyRight

JustifyCenter

JustifyFill

Instances

Enum Justification

Eq Justification

Show Justification

labelSetJustify :: LabelClass self => self -> Justification -> IO ()

Sets the alignment of the lines in the text of the label relative to each other. JustifyLeft is the default value when the widget is first created with labelNew. If you instead want to set the alignment of the label as a whole, use miscSetAlignment instead. labelSetJustify has no effect on labels containing only a single line.

labelGetJustify :: LabelClass self => self -> IO Justification

Returns the justification of the label. See labelSetJustify.

labelGetLayout :: LabelClass self => self -> IO PangoLayout

Gets the PangoLayout used to display the label. The layout is useful to e.g. convert text positions to pixel positions, in combination with labelGetLayoutOffsets.

labelSetLineWrap

Arguments

:: LabelClass self

=> self

-> Bool

wrap - the setting

-> IO ()

Toggles line wrapping within the Label widget. True makes it break lines if text exceeds the widget's size. False lets the text get cut off by the edge of the widget if it exceeds the widget size.

labelGetLineWrap

Arguments

:: LabelClass self

=> self

-> IO Bool

returns True if the lines of the label are automatically wrapped.

Returns whether lines in the label are automatically wrapped. See labelSetLineWrap.

labelSetLineWrapMode

Arguments

:: LabelClass self

=> self

-> LayoutWrapMode

wrapMode - the line wrapping mode

-> IO ()

If line wrapping is on (see labelSetLineWrap) this controls how the line wrapping is done. The default is WrapWholeWords which means wrap on word boundaries.

• Available since Gtk+ version 2.10

labelGetLineWrapMode

Arguments

:: LabelClass self

=> self

-> IO LayoutWrapMode

return the line wrapping mode

Returns line wrap mode used by the label. See labelSetLineWrapMode.

• Available since Gtk+ version 2.10

labelSetSelectable

Arguments

:: LabelClass self

=> self

-> Bool

setting - True to allow selecting text in the label

-> IO ()

Selectable labels allow the user to select text from the label, for copy-and-paste.

labelGetSelectable

Arguments

:: LabelClass self

=> self

-> IO Bool

returns True if the user can copy text from the label

Gets whether the text selectable.

labelSelectRegion

Arguments

:: LabelClass self

=> self

-> Int

startOffset - start offset

-> Int

endOffset - end offset

-> IO ()

Selects a range of characters in the label, if the label is selectable. See labelSetSelectable. If the label is not selectable, this function has no effect. If startOffset or endOffset are -1, then the end of the label will be substituted.

labelGetSelectionBounds :: LabelClass self => self -> IO (Maybe (Int, Int))

Gets the selected range of characters in the label, if any. If there is a range selected the result is the start and end of the selection as character offsets.

labelGetLayoutOffsets :: LabelClass self => self -> IO (Int, Int)

Obtains the coordinates where the label will draw the PangoLayout representing the text in the label; useful to convert mouse events into coordinates inside the PangoLayout, e.g. to take some action if some part of the label is clicked. Of course you will need to create a EventBox to receive the events, and pack the label inside it, since labels are a 'NoWindow' widget.

labelSetEllipsize

Arguments

:: LabelClass self

=> self

-> EllipsizeMode

mode - a EllipsizeMode

-> IO ()

Sets the mode used to ellipsize (add an ellipsis: "...") to the text if there is not enough space to render the entire string.

• Available since Gtk+ version 2.6

labelGetEllipsize

Arguments

:: LabelClass self

=> self

-> IO EllipsizeMode

returns EllipsizeMode

Returns the ellipsizing position of the label. See labelSetEllipsize.

• Available since Gtk+ version 2.6

labelSetWidthChars

Arguments

:: LabelClass self

=> self

-> Int

nChars - the new desired width, in characters.

-> IO ()

Sets the desired width in characters of label to nChars.

• Available since Gtk+ version 2.6

labelGetWidthChars

Arguments

:: LabelClass self

=> self

-> IO Int

returns the width of the label in characters.

Retrieves the desired width of label, in characters. See labelSetWidthChars.

• Available since Gtk+ version 2.6

labelSetMaxWidthChars

Arguments

:: LabelClass self

=> self

-> Int

nChars - the new desired maximum width, in characters.

-> IO ()

Sets the desired maximum width in characters of label to nChars.

• Available since Gtk+ version 2.6

labelGetMaxWidthChars

Arguments

:: LabelClass self

=> self

-> IO Int

returns the maximum width of the label in characters.

Retrieves the desired maximum width of label, in characters. See labelSetWidthChars.

• Available since Gtk+ version 2.6

labelSetSingleLineMode

Arguments

:: LabelClass self

=> self

-> Bool

singleLineMode - True if the label should be in single line mode

-> IO ()

Sets whether the label is in single line mode.

• Available since Gtk+ version 2.6

labelGetSingleLineMode

Arguments

:: LabelClass self

=> self

-> IO Bool

returns True when the label is in single line mode.

Returns whether the label is in single line mode.

• Available since Gtk+ version 2.6

labelSetAngle

Arguments

:: LabelClass self

=> self

-> Double

angle - the angle that the baseline of the label makes with the horizontal, in degrees, measured counterclockwise

-> IO ()

Sets the angle of rotation for the label. An angle of 90 reads from from bottom to top, an angle of 270, from top to bottom. The angle setting for the label is ignored if the label is selectable, wrapped, or ellipsized.

• Available since Gtk+ version 2.6

labelGetAngle

Arguments

:: LabelClass self

=> self

-> IO Double

returns the angle of rotation for the label

Gets the angle of rotation for the label. See gtk_label_set_angle.

• Available since Gtk+ version 2.6

Attributes

labelLabel :: LabelClass self => Attr self String

The text of the label.

labelUseMarkup :: LabelClass self => Attr self Bool

The text of the label includes XML markup. See pango_parse_markup().

Default value: False

labelUseUnderline :: LabelClass self => Attr self Bool

If set, an underline in the text indicates the next character should be used for the mnemonic accelerator key.

Default value: False

labelJustify :: LabelClass self => Attr self Justification

The alignment of the lines in the text of the label relative to each other. This does NOT affect the alignment of the label within its allocation.

Default value: JustifyLeft

labelWrap :: LabelClass self => Attr self Bool

If set, wrap lines if the text becomes too wide.

Default value: False

labelWrapMode :: LabelClass self => Attr self LayoutWrapMode

If line wrapping is on (see the labelWrap property) this controls how the line wrapping is done. The default is WrapWholeWords, which means wrap on word boundaries.

Default value: WrapWholeWords

• Available since Gtk+ version 2.10

labelSelectable :: LabelClass self => Attr self Bool

Whether the label text can be selected with the mouse.

Default value: False

labelMnemonicWidget :: (LabelClass self, WidgetClass widget) => ReadWriteAttr self (Maybe Widget) widget

The widget to be activated when the label's mnemonic key is pressed.

labelMnemonicKeyval :: LabelClass self => ReadAttr self Int

The mnemonic accelerator key for this label.

Default value: 16777215

labelPattern :: LabelClass self => WriteAttr self String

A string with _ characters in positions correspond to characters in the text to underline.

Default value: \

labelCursorPosition :: LabelClass self => ReadAttr self Int

The current position of the insertion cursor in chars.

Allowed values: >= 0

Default value: 0

labelSelectionBound :: LabelClass self => ReadAttr self Int

The position of the opposite end of the selection from the cursor in chars.

Allowed values: >= 0

Default value: 0

labelEllipsize :: LabelClass self => Attr self EllipsizeMode

The preferred place to ellipsize the string, if the label does not have enough room to display the entire string, specified as a EllipsizeMode.

Note that setting this property to a value other than EllipsizeNone has the side-effect that the label requests only enough space to display the ellipsis "...". In particular, this means that ellipsizing labels don't work well in notebook tabs, unless the tab's tab-expand property is set to True. Other means to set a label's width are widgetSetSizeRequest and labelSetWidthChars.

Default value: EllipsizeNone

labelWidthChars :: LabelClass self => Attr self Int

The desired width of the label, in characters. If this property is set to -1, the width will be calculated automatically, otherwise the label will request either 3 characters or the property value, whichever is greater. If the width-chars property is set to a positive value, then the max-width-chars property is ignored.

Allowed values: >= -1

Default value: -1

labelSingleLineMode :: LabelClass self => Attr self Bool

Whether the label is in single line mode. In single line mode, the height of the label does not depend on the actual text, it is always set to ascent + descent of the font. This can be an advantage in situations where resizing the label because of text changes would be distracting, e.g. in a statusbar.

Default value: False

labelAngle :: LabelClass self => Attr self Double

The angle that the baseline of the label makes with the horizontal, in degrees, measured counterclockwise. An angle of 90 reads from from bottom to top, an angle of 270, from top to bottom. Ignored if the label is selectable, wrapped, or ellipsized.

Allowed values: [0,360]

Default value: 0

labelAttributes :: LabelClass self => Attr self [PangoAttribute]

A list of style attributes to apply to the text of the label.

labelMaxWidthChars :: LabelClass self => Attr self Int

The desired maximum width of the label, in characters. If this property is set to -1, the width will be calculated automatically, otherwise the label will request space for no more than the requested number of characters. If the width-chars property is set to a positive value, then the max-width-chars property is ignored.

Allowed values: >= -1

Default value: -1

labelLineWrap :: LabelClass self => Attr self Bool

'lineWrap' property. See labelGetLineWrap and labelSetLineWrap

labelText :: LabelClass self => Attr self String

'text' property. See labelGetText and labelSetText