gdk-Pango-Interaction: Pango Interaction

Description

Using Pango in GDK

Arguments

Methods and Functions

gdkPangoRendererNew(screen) gdkPangoRendererGetDefault(screen) gdkPangoRendererSetDrawable(object, drawable = NULL) gdkPangoRendererSetGc(object, gc = NULL) gdkPangoRendererSetStipple(object, part, stipple) gdkPangoRendererSetOverrideColor(object, part, color = NULL) gdkPangoContextGet() gdkPangoContextGetForScreen(screen) gdkPangoContextSetColormap(context, colormap) gdkPangoAttrEmbossColorNew(color) gdkPangoAttrEmbossedNew(embossed) gdkPangoAttrStippleNew(stipple) gdkPangoLayoutGetClipRegion(layout, x.origin, index.ranges) gdkPangoLayoutLineGetClipRegion(line, x.origin, index.ranges) gdkPangoRenderer(screen)

Hierarchy

GObject +----PangoRenderer +----GdkPangoRenderer

Detailed Description

Pango is the text layout system used by GDK and GTK+. The functions and types in this section are used to render Pango objects to GDK. drawables, and also extend the set of Pango attributes to include stippling and embossing. Creating a PangoLayout object is the first step in rendering text, and requires getting a handle to a PangoContext. For GTK+ programs, you'll usually want to use gtkWidgetGetPangoContext, or gtkWidgetCreatePangoLayout, rather than using the lowlevel gdkPangoContextGetForScreen. Once you have a PangoLayout, you can set the text and attributes of it with Pango functions like pangoLayoutSetText and get its size with pangoLayoutGetSize. (Note that Pango uses a fixed point system internally, so converting between Pango units and pixels using PANGO_SCALE or the pangoPixels() function.) Rendering a Pango layout is done most simply with gdkDrawLayout; you can also draw pieces of the layout with gdkDrawLayout or gdkDrawGlyphs. GdkPangoRenderer is a subclass of PangoRenderer that is used internally to implement these functions. Using it directly or subclassing it can be useful in some cases. See the GdkPangoRenderer documentation for details. Using GdkPangoRenderer to draw transformed text window <- NULL

RADIUS <- 150 N.WORDS <- 10 FONT <- "Sans Bold 27"

rotated.text.expose.event <- function(widget, event, data) {

## matrix describing font transformation, initialize to identity matrix <- pangoMatrixInit() width <- widget[["allocation"]][["width"]] height <- widget[["allocation"]][["height"]]

## Get the default renderer for the screen, and set it up for drawing renderer <- gdkPangoRendererGetDefault(widget$getScreen()) renderer$setDrawable(widget[["window"]]) renderer$setGc(widget[["style"]][["blackGc"]])

## Set up a transformation matrix so that the user space coordinates for ## the centered square where we draw are [-RADIUS, RADIUS], [-RADIUS, RADIUS] ## We first center, then change the scale device.radius <- min(width, height) / 2. matrix$translate(device.radius + (width - 2 * device.radius) / 2, device.radius + (height - 2 * device.radius) / 2) matrix$scale(device.radius / RADIUS, device.radius / RADIUS)

## Create a PangoLayout, set the font and text context <- widget$createPangoContext() layout <- pangoLayoutNew(context) layout$setText("Text") desc <- pangoFontDescriptionFromString(FONT) layout$setFontDescription(desc)

# Draw the layout N.WORDS times in a circle for (i in 1:N.WORDS) { rotated.matrix <- matrix$copy() angle <- (360 * i) / N.WORDS color <- list() ## Gradient from red at angle 60 to blue at angle 300 color$red <- 65535 * (1 + cos((angle - 60) * pi / 180)) / 2 color$green <- 0 color$blue <- 65535 - color$red renderer$setOverrideColor("foreground", color) rotated.matrix$rotate(angle) context$setMatrix(rotated.matrix) ## Inform Pango to re-layout the text with the new transformation matrix layout$contextChanged() size <- layout$getSize() renderer$drawLayout(layout, - size$width / 2, - RADIUS * 1024) } ## Clean up default renderer, since it is shared renderer$setOverrideColor("foreground", NULL) renderer$setDrawable(NULL) renderer$setGc(NULL)

return(FALSE) }

white <- c( 0, "0xffff", "0xffff", "0xffff" )

window <- gtkWindowNew("toplevel") window$setTitle("Rotated Text") drawing.area <- gtkDrawingAreaNew() window$add(drawing.area)

# This overrides the background color from the theme drawing.area$modifyBg("normal", white)

gSignalConnect(drawing.area, "expose-event", rotated.text.expose.event)

window$setDefaultSize(2 * RADIUS, 2 * RADIUS)

window$showAll()

Convenient Construction

gdkPangoRenderer is the equivalent of gdkPangoRendererNew.

References

http://developer.gnome.org/doc/API/2.0/gdk/gdk-Pango-Interaction.html