Graphics.UI.Gtk.Cairo

Gtk specific functions to for redering with Cairo.

Cairo is a graphics library that supports vector graphics and image compositing that can be used with Gdk. The Cairo API is an addition to Gdk/Gtk (rather than a replacement). Cairo rendering can be performed on any Drawable by calling renderWithDrawable. The functions in this module provide ways of drawing Gtk specific elements, such as Pixbufs or text laid out with Pango.

All functions in this module are only available in Gtk 2.8 or higher.

Global Cairo settings.

cairoFontMapGetDefault :: IO FontMap

Retrieve the default FontMap that contains a list of available fonts.

• One purpose of creating an explicit FontMap is to set a different scaling factor between font sizes (in points, pt) and Cairo units (in pixels). The default is 96dpi (dots per inch) which corresponds to an average screen as output medium. A 10pt font will therefore scale to 10pt * (1/72 pt/inch) * (96 pixel/inch) = 13.3 pixel.

cairoFontMapSetResolution :: FontMap -> Double -> IO ()

Set the scaling factor between font size and Cairo units.

• Value is in dots per inch (dpi). See cairoFontMapGetDefault.

cairoFontMapGetResolution :: FontMap -> IO Double

Ask for the scaling factor between font size and Cairo units.

• Value is in dots per inch (dpi). See cairoFontMapGetDefault.

cairoCreateContext :: Maybe FontMap -> IO PangoContext

Create a PangoContext.

• If no FontMap is specified, it uses the default FontMap that has a scaling factor of 96 dpi. See cairoFontMapGetDefault.

cairoContextSetResolution :: PangoContext -> Double -> IO ()

Set the scaling factor of the PangoContext.

• Supplying zero or a negative value will result in the resolution value of the underlying FontMap to be used. See also cairoFontMapGetDefault.

cairoContextGetResolution :: PangoContext -> IO Double

Ask for the scaling factor of the PangoContext.

• A negative value will be returned if no resolution has been set. See cairoContextSetResolution.

cairoContextSetFontOptions :: PangoContext -> FontOptions -> IO ()

Set Cairo font options.

• Apply the given font options to the context. Values set through this functions override those that are set by updateContext.

cairoContextGetFontOptions :: PangoContext -> IO FontOptions

Retrieve Cairo font options.

Functions for the Render monad.

getClipRectangle :: Render (Maybe Rectangle)

Compute a bounding box in user coordinates covering the area inside the current clip. It rounds the bounding box to integer coordinates. Returns Nothing indicating if a clip area doesn't exist.

renderWithDrawWindow

Arguments

:: DrawWindowClass drawWindow

=> drawWindow

drawWindow - a DrawWindow

-> Render a

A newly created Cairo context.

-> IO a

Creates a Cairo context for drawing to a DrawWindow.

setSourceColor :: Color -> Render ()

Sets the specified Color as the source color of the Render context.

setSourcePixbuf

Arguments

:: Pixbuf

-> Double

x

-> Double

y

-> Render ()

Sets the given pixbuf as the source pattern for the Cairo context. The pattern has an extend mode of ExtendNone and is aligned so that the origin of pixbuf is (x, y).

rectangle :: Rectangle -> Render ()

Adds the given region to the current path of the Render context.

updateContext :: PangoContext -> Render ()

Update a PangoContext with respect to changes in a Render environment.

• The PangoContext must have been created with cairoCreateContext. Any PangoLayouts that have been previously created with this context have to be update using layoutContextChanged.

createLayout :: GlibString string => string -> Render PangoLayout

Create a PangoLayout within a Render context.

• This is a convenience function that creates a new PangoContext within this Render context and creates a new PangoLayout. If the transformation or target surface of the Render context change, updateLayout has to be called on this layout.

updateLayout :: PangoLayout -> Render ()

Propagate changed to the Render context to a PangoLayout.

• This is a convenience function that calls updateContext on the (private) PangoContext of the given layout to propagate changes from the Render context to the PangoContext and then calls layoutContextChanged on the layout. This function is necessary for createLayout since a private PangoContext is created that is not visible to the user.

showGlyphString :: GlyphItem -> Render ()

Draw a glyph string.

• The origin of the glyphs (the left edge of the baseline) will be drawn at the current point of the cairo context.

showLayoutLine :: LayoutLine -> Render ()

Draw a LayoutLine.

• The origin of the glyphs (the left edge of the baseline) will be drawn at the current point of the cairo context.

showLayout :: PangoLayout -> Render ()

Draw a PangoLayout.

• The top-left corner of the PangoLayout will be drawn at the current point of the cairo context.

glyphStringPath :: GlyphItem -> Render ()

Add the extent of a glyph string to the current path.

• The origin of the glyphs (the left edge of the line) will be at the current point of the cairo context.

layoutLinePath :: LayoutLine -> Render ()

Add the extent of a layout line to the current path.

• The origin of the glyphs (the left edge of the line) will be at the current point of the cairo context.

layoutPath :: PangoLayout -> Render ()

Add the layout to the current path.

• Adds the top-left corner of the text to the current path. Afterwards, the path position is at the bottom-right corner of the PangoLayout.