# Gdk::GC Class Reference

All drawing operations in GDK take a graphics context (GC) argument. More...

Inheritance diagram for Gdk::GC:
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Collaboration diagram for Gdk::GC:
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List of all members.

## Public Member Functions

virtual | ~GC ()
GdkGC* | gobj ()
| Provides access to the underlying C GObject.
const GdkGC* | gobj () const
| Provides access to the underlying C GObject.
GdkGC* | gobj_copy ()
| Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.
void | set_foreground (const Color& color)
| Sets the foreground color for a graphics context.
void | set_background (const Color& color)
| Sets the background color for a graphics context.
void | set_function (Function function)
| Determines how the current pixel values and the pixel values being drawn are combined to produce the final pixel values.
void | set_fill (Fill fill)
| Set the fill mode for a graphics context.
void | set_tile (const Glib::RefPtr< Pixmap >& tile)
| Set a tile pixmap for a graphics context.
void | set_stipple (const Glib::RefPtr< Pixmap >& stipple)
| Set the stipple bitmap for a graphics context.
void | set_ts_origin (int x, int y)
| Set the origin when using tiles or stipples with the GC.
void | set_clip_origin (int x, int y)
| Sets the origin of the clip mask.
void | set_clip_mask (const Glib::RefPtr< Bitmap >& mask)
| Sets the clip mask for a graphics context from a bitmap.
void | set_clip_rectangle (Rectangle& rectangle)
| Sets the clip mask for a graphics context from a rectangle.
void | set_clip_rectangle (const Rectangle& rectangle)
| Sets the clip mask for a graphics context from a rectangle.
void | set_clip_region (const Region& region)
| Sets the clip mask for a graphics context from a region structure.
void | set_subwindow (SubwindowMode mode)
| Sets how drawing with this GC on a window will affect child windows of that window.
void | set_exposures (bool exposures)
| Sets whether copying non-visible portions of a drawable using this graphics context generate exposure events for the corresponding regions of the destination drawable.
void | set_line_attributes (int line_width, LineStyle line_style, CapStyle cap_style, JoinStyle join_style)
| Sets various attributes of how lines are drawn.
void | set_dashes (int dash_offset, gint8* dash_list, int n)
| Sets the way dashed-lines are drawn.
void | offset (int x_offset, int y_offset)
| Offset attributes such as the clip and tile-stipple origins of the GC so that drawing at x - x_offset, y - y_offset with the offset GC has the same effect as drawing at x, y with the original GC.
void | set_colormap (const Glib::RefPtr< Colormap >& colormap)
| Sets the colormap for the GC to the given colormap.
Glib::RefPtr< Colormap > | get_colormap ()
| Retrieves the colormap for a given GC, if it exists.
void | set_rgb_fg_color (const Color& color)
| Set the foreground color of a GC using an unallocated color.
void | set_rgb_bg_color (const Color& color)
| Set the background color of a GC using an unallocated color.
Glib::RefPtr< Screen > | get_screen ()
| Gets the Gdk::Screen for which gc was created.
Glib::RefPtr< const Screen > | get_screen () const
| Gets the Gdk::Screen for which gc was created.

## Static Public Member Functions

static Glib::RefPtr< GC > | create ()
static Glib::RefPtr< GC > | create (const Glib::RefPtr< Drawable >& drawable)

## Protected Member Functions

| GC ()
| GC (const Glib::RefPtr< Drawable >& drawable)

## Related Functions

(Note that these are not member functions.)
Glib::RefPtr< Gdk::GC > | wrap (GdkGC* object, bool take_copy=false)
| A Glib::wrap() method for this object.

## Detailed Description

All drawing operations in GDK take a graphics context (GC) argument.

A graphics context encapsulates information about the way things are drawn, such as the foreground color or line width. By using graphics contexts, the number of arguments to each drawing call is greatly reduced, and communication overhead is minimized, since identical arguments do not need to be passed repeatedly.

## Constructor & Destructor Documentation

virtual Gdk::GC::~GC | ( |  | ) | `[virtual]`

Gdk::GC::GC | ( |  | ) | `[protected]`

Gdk::GC::GC | ( | const Glib::RefPtr< Drawable >& | drawable | ) | `[explicit, protected]`

## Member Function Documentation

static Glib::RefPtr<GC> Gdk::GC::create | ( |  | ) | `[static]`

static Glib::RefPtr<GC> Gdk::GC::create | ( | const Glib::RefPtr< Drawable >& | drawable | ) | `[static]`

Glib::RefPtr<Colormap> Gdk::GC::get_colormap | ( |  | ) |

Retrieves the colormap for a given GC, if it exists.

A GC will have a colormap if the drawable for which it was created has a colormap, or if a colormap was set explicitely with gdk_gc_set_colormap.

Deprecated: 2.22: There is no replacement. Cairo handles colormaps automatically, so there is no need to care about them.

Returns:
  The colormap of gc, or `0` if gc doesn't have one.

Glib::RefPtr<Screen> Gdk::GC::get_screen | ( |  | ) |

Gets the Gdk::Screen for which gc was created.

Since gtkmm 2.2:

Returns:
  The Gdk::Screen for gc.

Glib::RefPtr<const Screen> Gdk::GC::get_screen | ( |  | ) | const

Gets the Gdk::Screen for which gc was created.

Since gtkmm 2.2:

Returns:
  The Gdk::Screen for gc.

const GdkGC* Gdk::GC::gobj | ( |  | ) | const`[inline]`

Provides access to the underlying C GObject.

Reimplemented from Glib::ObjectBase.

GdkGC* Gdk::GC::gobj | ( |  | ) | `[inline]`

Provides access to the underlying C GObject.

Reimplemented from Glib::ObjectBase.

GdkGC* Gdk::GC::gobj_copy | ( |  | ) |

Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.

void Gdk::GC::offset | ( | int | x_offset,
|  | int | y_offset
| ) |  |

Offset attributes such as the clip and tile-stipple origins of the GC so that drawing at x - x_offset, y - y_offset with the offset GC has the same effect as drawing at x, y with the original GC.

Deprecated: 2.22: There is no direct replacement, as this is just a convenience function for gdk_gc_set_ts_origin and set_clip_origin().

Parameters:

  x_offset | Amount by which to offset the GC in the X direction.
  y_offset | Amount by which to offset the GC in the Y direction.

void Gdk::GC::set_background | ( | const Color& | color | ) |

Sets the background color for a graphics context.

Note that this function uses color->pixel, use set_rgb_bg_color() to specify the background color as red, green, blue components.

Deprecated: 2.22: Use gdk_cairo_set_source_color() to use a Gdk::Color as the source in Cairo. Note that if you want to draw a background and a foreground in Cairo, you need to call drawing functions (like cairo_fill()) twice.

Parameters:

  color | The new background color.

void Gdk::GC::set_clip_mask | ( | const Glib::RefPtr< Bitmap >& | mask | ) |

Sets the clip mask for a graphics context from a bitmap.

The clip mask is interpreted relative to the clip origin. (See set_clip_origin()).

Deprecated: 2.22: Use cairo_mask() instead.

Parameters:

  mask | A bitmap.

void Gdk::GC::set_clip_origin | ( | int | x,
|  | int | y
| ) |  |

Sets the origin of the clip mask.

The coordinates are interpreted relative to the upper-left corner of the destination drawable of the current operation.

Deprecated: 2.22: Use cairo_translate() before applying the clip path in Cairo.

Parameters:

  x | The x-coordinate of the origin.
  y | The y-coordinate of the origin.

void Gdk::GC::set_clip_rectangle | ( | const Rectangle& | rectangle | ) |

Sets the clip mask for a graphics context from a rectangle.

The clip mask is interpreted relative to the clip origin. (See set_clip_origin()).

Deprecated: 2.22: Use cairo_rectangle() and cairo_clip() in Cairo.

Parameters:

  rectangle | The rectangle to clip to.

void Gdk::GC::set_clip_rectangle | ( | Rectangle& | rectangle | ) |

Sets the clip mask for a graphics context from a rectangle.

The clip mask is interpreted relative to the clip origin. (See set_clip_origin()).

Deprecated: 2.22: Use cairo_rectangle() and cairo_clip() in Cairo.

Deprecated:
  Use set_clip_rectangle(const Rectangle& rectangle) instead.

Parameters:

  rectangle | The rectangle to clip to.

void Gdk::GC::set_clip_region | ( | const Region& | region | ) |

Sets the clip mask for a graphics context from a region structure.

The clip mask is interpreted relative to the clip origin. (See set_clip_origin()).

Deprecated: 2.22: Use gdk_cairo_region() and cairo_clip() in Cairo.

Parameters:

  region | The Gdk::Region.

void Gdk::GC::set_colormap | ( | const Glib::RefPtr< Colormap >& | colormap | ) |

Sets the colormap for the GC to the given colormap.

The depth of the colormap's visual must match the depth of the drawable for which the GC was created.

Deprecated: 2.22: There is no replacement. Cairo handles colormaps automatically, so there is no need to care about them.

Parameters:

  colormap | A Gdk::Colormap.

void Gdk::GC::set_dashes | ( | int | dash_offset,
|  | gint8 * | dash_list,
|  | int | n
| ) |  |

Sets the way dashed-lines are drawn.

Lines will be drawn with alternating on and off segments of the lengths specified in dash_list. The manner in which the on and off segments are drawn is determined by the line_style value of the GC. (This can be changed with set_line_attributes().)

The dash_offset defines the phase of the pattern, specifying how many pixels into the dash-list the pattern should actually begin.

Deprecated: 2.22: Use cairo_set_dash() to set the dash in Cairo.

Parameters:

  dash_offset | The phase of the dash pattern.
  dash_list | An array of dash lengths.
  n | The number of elements in dash_list.

void Gdk::GC::set_exposures | ( | bool | exposures | ) |

Sets whether copying non-visible portions of a drawable using this graphics context generate exposure events for the corresponding regions of the destination drawable.

(See gdk_draw_drawable()).

Deprecated: 2.22: There is no replacement. If you need to control exposures, you must use drawing operations of the underlying window system or use Gdk::Window::invalidate_rect(). Cairo will never generate exposures.

Parameters:

  exposures | If `true`, exposure events will be generated.

void Gdk::GC::set_fill | ( | Fill | fill | ) |

Set the fill mode for a graphics context.

Deprecated: 2.22: You can achieve tiling in Cairo by using cairo_pattern_set_extend() on the source. For stippling, see the deprecation comments on set_stipple().

Parameters:

  fill | The new fill mode.

void Gdk::GC::set_foreground | ( | const Color& | color | ) |

Sets the foreground color for a graphics context.

Note that this function uses color->pixel, use set_rgb_fg_color() to specify the foreground color as red, green, blue components.

Deprecated: 2.22: Use gdk_cairo_set_source_color() to use a Gdk::Color as the source in Cairo.

Parameters:

  color | The new foreground color.

void Gdk::GC::set_function | ( | Function | function | ) |

Determines how the current pixel values and the pixel values being drawn are combined to produce the final pixel values.

Deprecated: 2.22: Use cairo_set_operator() with Cairo.

Parameters:

  function | The Gdk::Function to use.

void Gdk::GC::set_line_attributes | ( | int | line_width,
|  | LineStyle | line_style,
|  | CapStyle | cap_style,
|  | JoinStyle | join_style
| ) |  |

Sets various attributes of how lines are drawn.

See the corresponding members of Gdk::GCValues for full explanations of the arguments.

Deprecated: 2.22: Use the Cairo functions cairo_set_line_width(), cairo_set_line_join(), cairo_set_line_cap() and cairo_set_dash() to affect the stroking behavior in Cairo. Keep in mind that the default attributes of a #cairo_t are different from the default attributes of a Gdk::GC.

Parameters:

  line_width | The width of lines.
  line_style | The dash-style for lines.
  cap_style | The manner in which the ends of lines are drawn.
  join_style | The in which lines are joined together.

void Gdk::GC::set_rgb_bg_color | ( | const Color& | color | ) |

Set the background color of a GC using an unallocated color.

The pixel value for the color will be determined using GdkRGB. If the colormap for the GC has not previously been initialized for GdkRGB, then for pseudo-color colormaps (colormaps with a small modifiable number of colors), a colorcube will be allocated in the colormap.

Calling this function for a GC without a colormap is an error.

Deprecated: 2.22: Use gdk_cairo_set_source_color() instead.

Parameters:

  color | An unallocated Gdk::Color.

void Gdk::GC::set_rgb_fg_color | ( | const Color& | color | ) |

Set the foreground color of a GC using an unallocated color.

The pixel value for the color will be determined using GdkRGB. If the colormap for the GC has not previously been initialized for GdkRGB, then for pseudo-color colormaps (colormaps with a small modifiable number of colors), a colorcube will be allocated in the colormap.

Calling this function for a GC without a colormap is an error.

Deprecated: 2.22: Use gdk_cairo_set_source_color() instead.

Parameters:

  color | An unallocated Gdk::Color.

void Gdk::GC::set_stipple | ( | const Glib::RefPtr< Pixmap >& | stipple | ) |

Set the stipple bitmap for a graphics context.

The stipple will only be used if the fill mode is Gdk::STIPPLED or Gdk::OPAQUE_STIPPLED.

Deprecated: 2.22: Stippling has no direct replacement in Cairo. If you want to achieve an identical look, you can use the stipple bitmap as a mask. Most likely, this involves rendering the source to an intermediate surface using cairo_push_group() first, so that you can then use cairo_mask() to achieve the stippled look.

Parameters:

  stipple | The new stipple bitmap.

void Gdk::GC::set_subwindow | ( | SubwindowMode | mode | ) |

Sets how drawing with this GC on a window will affect child windows of that window.

Deprecated: 2.22: There is no replacement. If you need to control subwindows, you must use drawing operations of the underlying window system manually. Cairo will always use Gdk::INCLUDE_INFERIORS on sources and masks and Gdk::CLIP_BY_CHILDREN on targets.

Parameters:

  mode | The subwindow mode.

void Gdk::GC::set_tile | ( | const Glib::RefPtr< Pixmap >& | tile | ) |

Set a tile pixmap for a graphics context.

This will only be used if the fill mode is Gdk::TILED.

Deprecated: 2.22: The following code snippet sets a tiling Gdk::Pixmap as the source in Cairo: |[gdk_cairo_set_source_pixmap (cr, tile, ts_origin_x, ts_origin_y); cairo_pattern_set_extend (cairo_get_source (cr), CAIRO_EXTEND_REPEAT);]|

Parameters:

  tile | The new tile pixmap.

void Gdk::GC::set_ts_origin | ( | int | x,
|  | int | y
| ) |  |

Set the origin when using tiles or stipples with the GC.

The tile or stipple will be aligned such that the upper left corner of the tile or stipple will coincide with this point.

Deprecated: 2.22: You can set the origin for tiles and stipples in Cairo by changing the source's matrix using cairo_pattern_set_matrix(). Or you can specify it with gdk_cairo_set_source_pixmap() as shown in the example for set_tile().

Parameters:

  x | The x-coordinate of the origin.
  y | The y-coordinate of the origin.

## Friends And Related Function Documentation

Glib::RefPtr< Gdk::GC > wrap | ( | GdkGC * | 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:

- gdkmm/gc.h