GdkGC

typedef struct _GdkGC GdkGC;

The GdkGC structure represents a graphics context. It is an opaque structure with no user-visible elements.

GdkGCValues

typedef struct {
  GdkColor	    foreground;
  GdkColor	    background;
  GdkFont	   *font;
  GdkFunction	    function;
  GdkFill	    fill;
  GdkPixmap	   *tile;
  GdkPixmap	   *stipple;
  GdkPixmap	   *clip_mask;
  GdkSubwindowMode  subwindow_mode;
  gint		    ts_x_origin;
  gint		    ts_y_origin;
  gint		    clip_x_origin;
  gint		    clip_y_origin;
  gint		    graphics_exposures;
  gint		    line_width;
  GdkLineStyle	    line_style;
  GdkCapStyle	    cap_style;
  GdkJoinStyle	    join_style;
} GdkGCValues;

The GdkGCValues structure holds a set of values used to create or modify a graphics context.

enum GdkGCValuesMask

typedef enum
{
  GDK_GC_FOREGROUND    = 1 << 0,
  GDK_GC_BACKGROUND    = 1 << 1,
  GDK_GC_FONT	       = 1 << 2,
  GDK_GC_FUNCTION      = 1 << 3,
  GDK_GC_FILL	       = 1 << 4,
  GDK_GC_TILE	       = 1 << 5,
  GDK_GC_STIPPLE       = 1 << 6,
  GDK_GC_CLIP_MASK     = 1 << 7,
  GDK_GC_SUBWINDOW     = 1 << 8,
  GDK_GC_TS_X_ORIGIN   = 1 << 9,
  GDK_GC_TS_Y_ORIGIN   = 1 << 10,
  GDK_GC_CLIP_X_ORIGIN = 1 << 11,
  GDK_GC_CLIP_Y_ORIGIN = 1 << 12,
  GDK_GC_EXPOSURES     = 1 << 13,
  GDK_GC_LINE_WIDTH    = 1 << 14,
  GDK_GC_LINE_STYLE    = 1 << 15,
  GDK_GC_CAP_STYLE     = 1 << 16,
  GDK_GC_JOIN_STYLE    = 1 << 17
} GdkGCValuesMask;

A set of bit flags used to indicate which fields GdkGCValues structure are set.

enum GdkFunction

typedef enum
{
  GDK_COPY,
  GDK_INVERT,
  GDK_XOR,
  GDK_CLEAR,
  GDK_AND,
  GDK_AND_REVERSE,
  GDK_AND_INVERT,
  GDK_NOOP,
  GDK_OR,
  GDK_EQUIV,
  GDK_OR_REVERSE,
  GDK_COPY_INVERT,
  GDK_OR_INVERT,
  GDK_NAND,
  GDK_NOR,
  GDK_SET
} GdkFunction;

Determines how the bit values for the source pixels are combined with the bit values for destination pixels to produce the final result. The sixteen values here correspond to the 16 different possible 2x2 truth tables. Only a couple of these values are usually useful; for colored images, only GDK_COPY, GDK_XOR and GDK_INVERT are generally useful. For bitmaps, GDK_AND and GDK_OR are also useful.

gdk_gc_new ()

GdkGC *             gdk_gc_new                          (GdkDrawable *drawable);

Create a new graphics context with default values.

gdk_gc_new_with_values ()

GdkGC *             gdk_gc_new_with_values              (GdkDrawable *drawable,
                                                         GdkGCValues *values,
                                                         GdkGCValuesMask values_mask);

Create a new GC with the given initial values.

gdk_gc_get_screen ()

GdkScreen *         gdk_gc_get_screen                   (GdkGC *gc);

Gets the GdkScreen for which gc was created

Since 2.2

gdk_gc_ref ()

GdkGC *             gdk_gc_ref                          (GdkGC *gc);

Deprecated function; use g_object_ref() instead.

gdk_gc_unref ()

void                gdk_gc_unref                        (GdkGC *gc);

Decrement the reference count of gc.

gdk_gc_destroy

#define gdk_gc_destroy                 g_object_unref

This function is obsolete and should not be used.

gdk_gc_set_values ()

void                gdk_gc_set_values                   (GdkGC *gc,
                                                         GdkGCValues *values,
                                                         GdkGCValuesMask values_mask);

Sets attributes of a graphics context in bulk. For each flag set in values_mask, the corresponding field will be read from values and set as the new value for gc. If you're only setting a few values on gc, calling individual "setter" functions is likely more convenient.

gdk_gc_get_values ()

void                gdk_gc_get_values                   (GdkGC *gc,
                                                         GdkGCValues *values);

Retrieves the current values from a graphics context. Note that only the pixel values of the values->foreground and values->background are filled, use gdk_colormap_query_color() to obtain the rgb values if you need them.

gdk_gc_set_foreground ()

void                gdk_gc_set_foreground               (GdkGC *gc,
                                                         const GdkColor *color);

Sets the foreground color for a graphics context. Note that this function uses color->pixel, use gdk_gc_set_rgb_fg_color() to specify the foreground color as red, green, blue components.

gdk_gc_set_background ()

void                gdk_gc_set_background               (GdkGC *gc,
                                                         const GdkColor *color);

Sets the background color for a graphics context. Note that this function uses color->pixel, use gdk_gc_set_rgb_bg_color() to specify the background color as red, green, blue components.

gdk_gc_set_rgb_fg_color ()

void                gdk_gc_set_rgb_fg_color             (GdkGC *gc,
                                                         const GdkColor *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.

gdk_gc_set_rgb_bg_color ()

void                gdk_gc_set_rgb_bg_color             (GdkGC *gc,
                                                         const GdkColor *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.

gdk_gc_set_font ()

void                gdk_gc_set_font                     (GdkGC *gc,
                                                         GdkFont *font);

Sets the font for a graphics context. (Note that all text-drawing functions in GDK take a font argument; the value set here is used when that argument is NULL.)

gdk_gc_set_function ()

void                gdk_gc_set_function                 (GdkGC *gc,
                                                         GdkFunction function);

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

gdk_gc_set_fill ()

void                gdk_gc_set_fill                     (GdkGC *gc,
                                                         GdkFill fill);

Set the fill mode for a graphics context.

enum GdkFill

typedef enum
{
  GDK_SOLID,
  GDK_TILED,
  GDK_STIPPLED,
  GDK_OPAQUE_STIPPLED
} GdkFill;

Determines how primitives are drawn.

gdk_gc_set_tile ()

void                gdk_gc_set_tile                     (GdkGC *gc,
                                                         GdkPixmap *tile);

1
2

gdk_cairo_set_source_pixmap (cr, tile, ts_origin_x, ts_origin_y);
cairo_pattern_set_extend (cairo_get_source (cr), CAIRO_EXTEND_REPEAT);

Set a tile pixmap for a graphics context. This will only be used if the fill mode is GDK_TILED.

gdk_gc_set_stipple ()

void                gdk_gc_set_stipple                  (GdkGC *gc,
                                                         GdkPixmap *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.

gdk_gc_set_ts_origin ()

void                gdk_gc_set_ts_origin                (GdkGC *gc,
                                                         gint x,
                                                         gint 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.

gdk_gc_set_clip_origin ()

void                gdk_gc_set_clip_origin              (GdkGC *gc,
                                                         gint x,
                                                         gint 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.

gdk_gc_set_clip_mask ()

void                gdk_gc_set_clip_mask                (GdkGC *gc,
                                                         GdkBitmap *mask);

Sets the clip mask for a graphics context from a bitmap. The clip mask is interpreted relative to the clip origin. (See gdk_gc_set_clip_origin()).

gdk_gc_set_clip_rectangle ()

void                gdk_gc_set_clip_rectangle           (GdkGC *gc,
                                                         const GdkRectangle *rectangle);

Sets the clip mask for a graphics context from a rectangle. The clip mask is interpreted relative to the clip origin. (See gdk_gc_set_clip_origin()).

gdk_gc_set_clip_region ()

void                gdk_gc_set_clip_region              (GdkGC *gc,
                                                         const GdkRegion *region);

Sets the clip mask for a graphics context from a region structure. The clip mask is interpreted relative to the clip origin. (See gdk_gc_set_clip_origin()).

gdk_gc_set_subwindow ()

void                gdk_gc_set_subwindow                (GdkGC *gc,
                                                         GdkSubwindowMode mode);

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

enum GdkSubwindowMode

typedef enum
{
  GDK_CLIP_BY_CHILDREN = 0,
  GDK_INCLUDE_INFERIORS = 1
} GdkSubwindowMode;

Determines how drawing onto a window will affect child windows of that window.

gdk_gc_set_exposures ()

void                gdk_gc_set_exposures                (GdkGC *gc,
                                                         gboolean 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()).

gdk_gc_set_line_attributes ()

void                gdk_gc_set_line_attributes          (GdkGC *gc,
                                                         gint line_width,
                                                         GdkLineStyle line_style,
                                                         GdkCapStyle cap_style,
                                                         GdkJoinStyle join_style);

Sets various attributes of how lines are drawn. See the corresponding members of GdkGCValues for full explanations of the arguments.

enum GdkLineStyle

typedef enum
{
  GDK_LINE_SOLID,
  GDK_LINE_ON_OFF_DASH,
  GDK_LINE_DOUBLE_DASH
} GdkLineStyle;

Determines how lines are drawn.

enum GdkCapStyle

typedef enum
{
  GDK_CAP_NOT_LAST,
  GDK_CAP_BUTT,
  GDK_CAP_ROUND,
  GDK_CAP_PROJECTING
} GdkCapStyle;

Determines how the end of lines are drawn.

enum GdkJoinStyle

typedef enum
{
  GDK_JOIN_MITER,
  GDK_JOIN_ROUND,
  GDK_JOIN_BEVEL
} GdkJoinStyle;

Determines how the joins between segments of a polygon are drawn.

gdk_gc_set_dashes ()

void                gdk_gc_set_dashes                   (GdkGC *gc,
                                                         gint dash_offset,
                                                         gint8 dash_list[],
                                                         gint 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 gdk_gc_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.

gdk_gc_copy ()

void                gdk_gc_copy                         (GdkGC *dst_gc,
                                                         GdkGC *src_gc);

Copy the set of values from one graphics context onto another graphics context.

gdk_gc_set_colormap ()

void                gdk_gc_set_colormap                 (GdkGC *gc,
                                                         GdkColormap *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.

gdk_gc_get_colormap ()

GdkColormap *       gdk_gc_get_colormap                 (GdkGC *gc);

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.

gdk_gc_offset ()

void                gdk_gc_offset                       (GdkGC *gc,
                                                         gint x_offset,
                                                         gint 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.