Gnome::Canvas::Canvas Class Reference

Canvas functions usually operate in either World coordinates (units for the entire canvas), or Canvas coordinates (pixels starting at 0,0 in the top left). More...

#include <canvas.h>

Inheritance diagram for Gnome::Canvas::Canvas:

Layout Gnome::Canvas::CanvasAA

List of all members.

Public Member Functions

virtual ~Canvas ()
GnomeCanvas * gobj ()
 Provides access to the underlying C GtkObject.
const GnomeCanvas * gobj () const
 Provides access to the underlying C GtkObject.
 Canvas ()
Grouproot () const
 Queries the root group of a canvas.
void set_scroll_region (double x1, double y1, double x2, double y2)
 Sets the scrolling region of a canvas to the specified rectangle.
void get_scroll_region (double &x1, double &y1, double &x2, double &y2) const
 Queries the scrolling region of a canvas.
void set_center_scroll_region (bool center)
 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.
bool get_center_scroll_region () const
 Returns whether the canvas is set to center the scrolling region in the window if the former is smaller than the canvas' allocation.
void set_pixels_per_unit (double n=1.0)
 Sets the zooming factor of a canvas by specifying the number of pixels that correspond to one canvas unit.
void scroll_to (int x, int y)
 Makes a canvas scroll to the specified offsets, given in canvas pixel units.
void get_scroll_offsets (int &cx, int &cy) const
 Queries the scrolling offsets of a canvas.
void update_now ()
 Forces an immediate update and redraw of a canvas.
Itemget_item_at (double x, double y) const
 Looks for the item that is under the specified position, which must be specified in world coordinates.
void request_redraw (int x1, int y1, int x2, int y2)
 Convenience function that informs a canvas that the specified rectangle needs to be repainted.
void request_redraw (ArtUta *uta)
 Informs a canvas that the specified area, given as a microtile array, needs to be repainted.
Art::AffineTrans w2c_affine () const
void w2c (double wx, double wy, int &cx, int &cy) const
 Converts world coordinates into canvas pixel coordinates.
void w2c (double wx, double wy, double &cx, double &cy) const
 Converts world coordinates into canvas pixel coordinates.
void c2w (int cx, int cy, double &wx, double &wy) const
 Converts canvas pixel coordinates to world coordinates.
void window_to_world (double winx, double winy, double &worldx, double &worldy) const
 Converts window-relative coordinates into world coordinates.
void world_to_window (double worldx, double worldy, double &winx, double &winy) const
 Converts world coordinates into window-relative coordinates.
bool get_color (const Glib::ustring &spec, Gdk::Color &color) const
gulong get_color_pixel (guint rgba) const
 Allocates a color from the RGBA value passed into this function.
void set_stipple_origin (const Glib::RefPtr< Gdk::GC > &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.
void set_dither (Gdk::RgbDither dither)
 Controls dithered rendering for antialiased canvases.
Gdk::RgbDither get_dither () const
 Returns the type of dithering used to render an antialiased canvas.
void update_svp (ArtSVP **p_svp, ArtSVP *new_svp)
 Sets the svp to the new value, requesting repaint on what's changed.
void update_svp_clip (ArtSVP **p_svp, ArtSVP *new_svp, ArtSVP *clip_svp)
 Sets the svp to the new value, clipping if necessary, and requesting repaint on what's changed.
double get_pixels_per_unit () const
Glib::SignalProxy5< void,
const Glib::RefPtr
< Gdk::Drawable > &, int, int,
int, int > 
signal_draw_background ()
Glib::SignalProxy1< void,
GnomeCanvasBuf * > 
signal_render_background ()
virtual void request_update_vfunc ()
Glib::PropertyProxy_ReadOnly
< bool > 
property_aa () const
 The antialiasing mode of the canvas.

Protected Member Functions

virtual void on_draw_background (const Glib::RefPtr< Gdk::Drawable > &drawable, int x, int y, int width, int height)
virtual void on_render_background (GnomeCanvasBuf *buf)

Related Functions

(Note that these are not member functions.)

Gnome::Canvas::Canvaswrap (GnomeCanvas *object, bool take_copy=false)
 A Glib::wrap() method for this object.


Detailed Description

Canvas functions usually operate in either World coordinates (units for the entire canvas), or Canvas coordinates (pixels starting at 0,0 in the top left).

There are functions to transform from one to the other.


Constructor & Destructor Documentation

virtual Gnome::Canvas::Canvas::~Canvas (  )  [virtual]

Gnome::Canvas::Canvas::Canvas (  ) 


Member Function Documentation

void Gnome::Canvas::Canvas::c2w ( int  cx,
int  cy,
double &  wx,
double &  wy 
) const

Converts canvas pixel coordinates to world coordinates.

Parameters:
cx Canvas pixel X coordinate.
cy Canvas pixel Y coordinate.
wx X world coordinate (return value).
wy Y world coordinate (return value).

bool Gnome::Canvas::Canvas::get_center_scroll_region (  )  const

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

Returns:
Whether the scroll region is being centered in the canvas window.

bool Gnome::Canvas::Canvas::get_color ( const Glib::ustring &  spec,
Gdk::Color &  color 
) const

gulong Gnome::Canvas::Canvas::get_color_pixel ( guint  rgba  )  const

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.

Parameters:
rgba RGBA color specification.
Returns:
Allocated pixel value corresponding to the specified color.

Gdk::RgbDither Gnome::Canvas::Canvas::get_dither (  )  const

Returns the type of dithering used to render an antialiased canvas.

Returns:
The dither setting.

Item* Gnome::Canvas::Canvas::get_item_at ( double  x,
double  y 
) const

Looks for the item that is under the specified position, which must be specified in world coordinates.

Parameters:
x X position in world coordinates.
y Y position in world coordinates.
Returns:
The sought item, or 0 if no item is at the specified coordinates.

double Gnome::Canvas::Canvas::get_pixels_per_unit (  )  const

void Gnome::Canvas::Canvas::get_scroll_offsets ( int &  cx,
int &  cy 
) const

Queries the scrolling offsets of a canvas.

The values are returned in canvas pixel units.

Parameters:
cx Horizontal scrolling offset (return value).
cy Vertical scrolling offset (return value).

void Gnome::Canvas::Canvas::get_scroll_region ( double &  x1,
double &  y1,
double &  x2,
double &  y2 
) const

Queries the scrolling region of a canvas.

Parameters:
x1 Leftmost limit of the scrolling region (return value).
y1 Upper limit of the scrolling region (return value).
x2 Rightmost limit of the scrolling region (return value).
y2 Lower limit of the scrolling region (return value).

const GnomeCanvas* Gnome::Canvas::Canvas::gobj (  )  const [inline]

Provides access to the underlying C GtkObject.

GnomeCanvas* Gnome::Canvas::Canvas::gobj (  )  [inline]

Provides access to the underlying C GtkObject.

virtual void Gnome::Canvas::Canvas::on_draw_background ( const Glib::RefPtr< Gdk::Drawable > &  drawable,
int  x,
int  y,
int  width,
int  height 
) [protected, virtual]

virtual void Gnome::Canvas::Canvas::on_render_background ( GnomeCanvasBuf *  buf  )  [protected, virtual]

Glib::PropertyProxy_ReadOnly<bool> Gnome::Canvas::Canvas::property_aa (  )  const

The antialiasing mode of the canvas.

You rarely need to use properties because there are get_ and set_ methods for almost all of them.

Returns:
A PropertyProxy that allows you to get or set the property of the value, or receive notification when the value of the property changes.

void Gnome::Canvas::Canvas::request_redraw ( ArtUta *  uta  ) 

Informs a canvas that the specified area, given as a microtile array, needs to be repainted.

To be used only by item implementations.

Parameters:
uta Microtile array that specifies the area to be redrawn. It will be freed by this function, so the argument you pass will be invalid after you call this function.

void Gnome::Canvas::Canvas::request_redraw ( int  x1,
int  y1,
int  x2,
int  y2 
)

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 request_redraw_uta(). The rectangle includes x1 and y1, but not x2 and y2. To be used only by item implementations.

Parameters:
x1 Leftmost coordinate of the rectangle to be redrawn.
y1 Upper coordinate of the rectangle to be redrawn.
x2 Rightmost coordinate of the rectangle to be redrawn, plus 1.
y2 Lower coordinate of the rectangle to be redrawn, plus 1.

virtual void Gnome::Canvas::Canvas::request_update_vfunc (  )  [virtual]

Group* Gnome::Canvas::Canvas::root (  )  const

Queries the root group of a canvas.

Returns:
The root group of the specified canvas.

void Gnome::Canvas::Canvas::scroll_to ( int  x,
int  y 
)

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.

Parameters:
cx Horizontal scrolling offset in canvas pixel units.
cy Vertical scrolling offset in canvas pixel units.

void Gnome::Canvas::Canvas::set_center_scroll_region ( bool  center  ) 

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.

This function lets you configure this property.

Parameters:
center_scroll_region Whether to center the scrolling region in the canvas window when it is smaller than the canvas' allocation.

void Gnome::Canvas::Canvas::set_dither ( Gdk::RgbDither  dither  ) 

Controls dithered rendering for antialiased canvases.

The value of dither should be Gdk::RGB_DITHER_NONE, Gdk::RGB_DITHER_NORMAL, or Gdk::RGB_DITHER_MAX. The default canvas setting is Gdk::RGB_DITHER_NORMAL.

Parameters:
dither Type of dithering used to render an antialiased canvas.

void Gnome::Canvas::Canvas::set_pixels_per_unit ( double  n = 1.0  ) 

Sets the zooming factor of a canvas by specifying the number of pixels that correspond to one canvas unit.

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 set_center_scroll_region() 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.

Parameters:
n The number of pixels that correspond to one canvas unit.

void Gnome::Canvas::Canvas::set_scroll_region ( double  x1,
double  y1,
double  x2,
double  y2 
)

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

The canvas will then be able to scroll only within this region. The view of the canvas is adjusted as appropriate to display as much of the new region as possible.

Parameters:
x1 Leftmost limit of the scrolling region.
y1 Upper limit of the scrolling region.
x2 Rightmost limit of the scrolling region.
y2 Lower limit of the scrolling region.

void Gnome::Canvas::Canvas::set_stipple_origin ( const Glib::RefPtr< Gdk::GC > &  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.

Parameters:
gc GC on which to set the stipple origin.

Glib::SignalProxy5< void,const Glib::RefPtr<Gdk::Drawable>&,int,int,int,int > Gnome::Canvas::Canvas::signal_draw_background (  ) 

Prototype:
void on_my_draw_background(const Glib::RefPtr<Gdk::Drawable>& drawable, int x, int y, int width, int height)

Glib::SignalProxy1< void,GnomeCanvasBuf* > Gnome::Canvas::Canvas::signal_render_background (  ) 

Prototype:
void on_my_render_background(GnomeCanvasBuf* buf)

void Gnome::Canvas::Canvas::update_now (  ) 

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.

void Gnome::Canvas::Canvas::update_svp ( ArtSVP **  p_svp,
ArtSVP *  new_svp 
)

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

This function takes responsibility for freeing new_svp.

Parameters:
p_svp A pointer to the existing svp.
new_svp The new svp.

void Gnome::Canvas::Canvas::update_svp_clip ( ArtSVP **  p_svp,
ArtSVP *  new_svp,
ArtSVP *  clip_svp 
)

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

This function takes responsibility for freeing new_svp.

Parameters:
p_svp A pointer to the existing svp.
new_svp The new svp.
clip_svp A clip path, if non-null.

void Gnome::Canvas::Canvas::w2c ( double  wx,
double  wy,
double &  cx,
double &  cy 
) const

Converts world coordinates into canvas pixel coordinates.

This version

Parameters:
wx World X coordinate.
wy World Y coordinate.
cx X pixel coordinate (return value).
cy Y pixel coordinate (return value).
Returns:
Coordinates in floating point coordinates, for greater precision.

void Gnome::Canvas::Canvas::w2c ( double  wx,
double  wy,
int &  cx,
int &  cy 
) const

Converts world coordinates into canvas pixel coordinates.

Parameters:
wx World X coordinate.
wy World Y coordinate.
cx X pixel coordinate (return value).
cy Y pixel coordinate (return value).

Art::AffineTrans Gnome::Canvas::Canvas::w2c_affine (  )  const

void Gnome::Canvas::Canvas::window_to_world ( double  winx,
double  winy,
double &  worldx,
double &  worldy 
) const

Converts window-relative coordinates into world coordinates.

You can use this when you need to convert mouse coordinates into world coordinates, for example.

Parameters:
winx Window-relative X coordinate.
winy Window-relative Y coordinate.
worldx X world coordinate (return value).
worldy Y world coordinate (return value).

void Gnome::Canvas::Canvas::world_to_window ( double  worldx,
double  worldy,
double &  winx,
double &  winy 
) const

Converts world coordinates into window-relative coordinates.

Parameters:
worldx World X coordinate.
worldy World Y coordinate.
winx X window-relative coordinate.
winy Y window-relative coordinate.


Friends And Related Function Documentation

Gnome::Canvas::Canvas * wrap ( GnomeCanvas *  object,
bool  take_copy = false 
) [related]

A Glib::wrap() method for this object.

Parameters:
object The C instance.
take_copy False if the result should take ownership of the C instance. True if it should take a new copy or ref.
Returns:
A C++ instance that wraps this C instance.


The documentation for this class was generated from the following file:

Generated on Wed Sep 2 16:27:12 2009 for libgnomecanvasmm by  doxygen 1.5.9