gnome-sharp 2.8.0.0 Gtk# is thread aware, but not thread safe; See the Gtk# Thread Programming for details.

Main canvas widget

The is an engine for structured graphics that offers a rich imaging model, high performance rendering, and a powerful, high level API. It offers a choice of two rendering back-ends, one based on Xlib for extremely fast display, and another based on Libart, a sophisticated, antialiased, alpha-compositing engine. This widget can be used for flexible display of graphics and for creating interactive user interface elements. To create a new GnomeCanvas widget call or for an anti-aliased mode canvas. A widget contains one or more objects. Items consist of graphing elements like lines, ellipses, polygons, images, text, and curves. These items are organized using objects, which are themselves derived from . Since a group is an item it can be contained within other groups, forming a tree of canvas items. Certain operations, like translating and scaling, can be performed on all items in a group. There is a special root group created by a GnomeCanvas. This is the top level group under which all items in a canvas are contained. To get the root group from a canvas, use property. There are several different coordinate systems used by widgets. The primary system is a logical, abstract coordinate space called world coordinates. World coordinates are expressed as unbounded double floating point numbers. When it comes to rendering to a screen the canvas pixel coordinate system (also referred to as just canvas coordinates) is used. This system uses integers to specify screen pixel positions. A user defined scaling factor and offset are used to convert between world coordinates and canvas coordinates. Each item in a canvas has its own coordinate system called item coordinates. This system is specified in world coordinates but they are relative to an item (0.0, 0.0 would be the top left corner of the item). The final coordinate system of interest is window coordinates. These are like canvas coordinates but are offsets from within a window a canvas is displayed in. This last system is rarely used, but is useful when manually handling GDK events (such as drag and drop) which are specified in window coordinates (the events processed by the canvas are already converted for you). Along with different coordinate systems comes functions to convert between them. converts world to canvas pixel coordinates and from canvas to world. is like but returns the pixel coordinates as doubles which is useful to avoid precision loss from integer rounding. To get the affine transform matrix for converting from world coordinates to canvas coordinates call . converts from window to world coordinates and converts in the other direction. There are no functions for converting between canvas and window coordinates, since this is just a matter of subtracting the canvas scrolling offset. To convert to/from item coordinates use the functions defined for objects. To set the canvas zoom factor (canvas pixels per world unit, the scaling factor) use the property, setting this to 1.0 will cause the two coordinate systems to correspond (e.g., [5, 6] in pixel units would be [5.0, 6.0] in world units). Defining the scrollable area of a canvas widget is done by calling and to get the current region can be used. If the window is larger than the canvas scrolling region it can optionally be centered in the window. Use the property to enable or disable this behavior. To scroll to a particular canvas pixel coordinate use (typically not used since scrollbars are usually set up to handle the scrolling), and to get the current canvas pixel scroll offset call . Gtk.Layout Method System.Void

Sets the bounding box to the new value, requesting full repaint.

The canvas item needing update Left coordinate of the new bounding box Top coordinate of the new bounding box Right coordinate of the new bounding box Bottom coordinate of the new bounding box Method System.Void

Computes the butt points of a line segment.

X coordinate of first point in the line Y cooordinate of first point in the line X coordinate of second point (endpoint) of the line Y coordinate of second point (endpoint) of the line Width of the line Whether the butt points should project out by width/2 distance Return value of the X coordinate of first butt point Return value of the Y coordinate of first butt point Return value of the X coordinate of second butt point Return value of the Y coordinate of second butt point Method System.Boolean

Given three points forming an angle, computes the coordinates of the inside and outside points of the mitered corner formed by a line of a given width at that angle.

X coordinate of the first point Y coordinate of the first point X coordinate of the second (angle) point Y coordinate of the second (angle) point X coordinate of the third point Y coordinate of the third point Width of the line The return value of the X coordinate of the first miter point The return value of the Y coordinate of the first miter point The return value of the X coordinate of the second miter point The return value of the Y coordinate of the second miter point if the angle is less than 11 degrees (this is the same threshold as X uses. If this occurs, the return points are not modified. Otherwise, returns . Method Art.PathStrokeJoinType

Convert from GDK line join specifier to libart.

a join type, represented in GDK format The line join specifier in libart format. Method System.Void

Render the over the .

the canvas buffer to render over the vector path to render the rgba color to render Method Art.PathStrokeCapType

Convert from GDK line cap specifier to the libart format.

a cap type, represented in GDK format The line cap specifier in libart format. Method Gnome.Canvas

Creates a new empty canvas in antialiased mode. You should push the visual and colormap before calling this functions, and they can be popped afterwards.

A newly-created antialiased canvas. Method System.Boolean

Allocates a color based on the specified X color specification.

X color specification, or for"transparent". Return value the allocated color. if spec is non-NULL and the color is allocated. If spec is , then returns . To be added Method System.Void

Sets the svp to the new value, requesting repaint on what has changed.

The existing svp The new svp Method Gnome.CanvasItem

Looks for the item that is under the specified position.

X position in world coordinates. Y position in world coordinates. The requested item, or if no item is at the specified coordinates. Method Gnome.CanvasGroup

Queries the root group of a canvas.

The root group of the specified canvas. Method System.Void

Sets the svp to the new value, clipping if necessary, and requesting repaint on what has changed.

the existing svp the new svp a clip path Method System.Void

Convenience function that informs a canvas that the specified rectangle needs to be repainted.

Leftmost coordinate of the rectangle to be redrawn. Upper coordinate of the rectangle to be redrawn. Rightmost coordinate of the rectangle to be redrawn, plus 1. Lower coordinate of the rectangle to be redrawn, plus 1. Convenience function that informs a canvas that the specified rectangle needs to be repainted. This function converts the rectangle to a microtile array and feeds it to . The rectangle includes and , but not and . To be used only by item implementations. Method System.Void

Queries the scrolling offsets of a canvas. The values are returned in canvas pixel units.

Return value for the horizontal scrolling offset Return value for the vertical scrolling offset Method System.Void

Forces an immediate update and redraw of a canvas.

Forces an immediate update and redraw of a canvas. If the canvas does not have any pending update or redraw requests, then no action is taken. This is typically only used by applications that need explicit control of when the display is updated, like games. It is not needed by normal applications. Method System.Void

Converts world coordinates into canvas pixel coordinates. This version returns coordinates in floating point coordinates, for greater precision.

World X coordinate. World Y coordinate. Return value for the X pixel coordinate Return value for the Y pixel coordinate Method System.Void

Sets the scrolling region of a canvas to the specified rectangle.

Leftmost limit of the scrolling region. Upper limit of the scrolling region. Rightmost limit of the scrolling region. Lower limit of the scrolling region. To be added Method System.Void

Informs a canvas that the specified area, given as a microtile array, needs to be repainted. To be used only by item implementations.

Microtile array that specifies the area to be redrawn. Method System.Void

Converts world coordinates into window-relative coordinates.

World X coordinate. World Y coordinate. Return value for the X window-relative coordinate. Return value for the Y window-relative coordinate. Method System.Void

Converts world coordinates into canvas pixel coordinates.

World X coordinate. World Y coordinate. Return value for the X pixel coordinate Return value for the Y pixel coordinate Method System.Void

Makes a canvas scroll to the specified offsets, given in canvas pixel units.

Horizontal scrolling offset in canvas pixel units. Vertical scrolling offset in canvas pixel units. Makes a canvas scroll to the specified offsets, given in canvas pixel units. The canvas will adjust the view so that it is not outside the scrolling region. This function is typically not used, as it is better to hook scrollbars to the canvas layout's scrolling adjusments. Method System.UInt64

Allocates a color from the RGBA value passed into this function.

RGBA color specification. Allocated pixel value corresponding to the specified color. Allocates a color from , the RGBA value passed into this function. The alpha opacity value is discarded, since normal X colors do not support it. Method System.Void

Converts canvas pixel coordinates to world coordinates.

Canvas pixel X coordinate. Canvas pixel Y coordinate. Return value for the X world coordinate Return value for the Y world coordinate Constructor

Internal constructor

Pointer to the C object. This is an internal constructor, and should not be used by user code. Constructor

Creates a new empty canvas in non-antialiased mode.

Creates a new empty canvas in non-antialiased mode. If you wish to use the item inside this canvas, then you must push the gdk_imlib visual and colormap before calling this function, and they can be popped afterwards. Property Gdk.RgbDither

The type of dithering used to render an antialiased canvas.

The type of dithering used to render an antialiased canvas. Property System.Boolean

Whether the canvas is set to center the scrolling region in the window if the former is smaller than the canvas' allocation.

Whether the scroll region is being centered in the canvas window. When the scrolling region of the canvas is smaller than the canvas window, e.g. the allocation of the canvas, it can be either centered on the window or simply made to be on the upper-left corner on the window. Property Gdk.GC

Sets the stipple origin of the specified GC as is appropriate for the canvas, so that it will be aligned with other stipple patterns used by canvas items.

This is typically only needed by item implementations. To be added. Property System.Boolean

Whether to enable anti-aliasing mode

to enable anti-aliasing Note that this parameter can only be set at the time of object construction. The same effect can be achieved by calling to create new non-aa canvas or for an anti-aliased canvas. GLib.Property(Name="aa") Event Gnome.DrawBackgroundHandler

Emitted to draw the background for non-antialiased mode canvas widgets. The default method uses the canvas widget's style to draw the background.

GLib.Signal(CName="draw_background") Event Gnome.RenderBackgroundHandler

This signal is emitted for antialiased mode canvas widgets to render the background. The buf data structure contains both a pointer to a packed 24-bit RGB array and the coordinates.

GLib.Signal(CName="render_background") Method System.Void

Queries the scrolling region of a canvas.

Return value for the leftmost limit of the scrolling region Return value for the upper limit of the scrolling region Return value for the rightmost limit of the scrolling region Return value for the lower limit of the scrolling region Method System.Void

Converts world coordinates into window-relative coordinates.

World X coordinate. World Y coordinate. Return value for the X window-relative coordinate. Return value for the Y window-relative coordinate. Property GLib.GType

GType Property.

a Returns the native value for . Method System.Void

Default handler for the event.

a a a a a Override this method in a subclass to provide a default handler for the event. Constructor

Protected Constructor.

a Chain to this constructor if you have manually registered a native value for your subclass. System.Obsolete(Message=null, IsError=False) Property System.Double

Gets or Sets the number of pixels that correspond to one canvas unit.

a The anchor point for zooming, i.e. the point that stays fixed and all others zoom inwards or outwards from it, depends on whether the canvas is set to center the scrolling region or not. You can control this using the function. If the canvas is set to center the scroll region, then the center of the canvas window is used as the anchor point for zooming. Otherwise, the upper-left corner of the canvas window is used as the anchor point. Method System.Void To be added.

To be added.

To be added. Method System.Void To be added.

Default handler for the event.

Override this method in a subclass to provide a default handler for the event. Constructor if an antialiased canvas should be created.

Constructs a canvas with or without antialiasing.