gdk-Graphics-Contexts: Graphics Contexts
In RGtk2: R Bindings for Gtk 2.8.0 and Above

Description Methods and Functions Hierarchy Detailed Description Structures Convenient Construction Enums and Flags Author(s) References

Objects to encapsulate drawing properties

gdkGCNew(drawable)
gdkGCNewWithValues(object, values)
gdkGCGetScreen(object)
gdkGCSetValues(object, values)
gdkGCGetValues(object)
gdkGCSetForeground(object, color)
gdkGCSetBackground(object, color)
gdkGCSetRgbFgColor(object, color)
gdkGCSetRgbBgColor(object, color)
gdkGCSetFont(object, font)
gdkGCSetFunction(object, fun)
gdkGCSetFill(object, fill)
gdkGCSetTile(object, tile)
gdkGCSetStipple(object, stipple)
gdkGCSetTsOrigin(object, x, y)
gdkGCSetClipOrigin(object, x, y)
gdkGCSetClipMask(object, mask)
gdkGCSetClipRectangle(object, rectangle)
gdkGCSetClipRegion(object, region)
gdkGCSetSubwindow(object, mode)
gdkGCSetExposures(object, exposures)
gdkGCSetLineAttributes(object, line.width, line.style, cap.style, join.style)
gdkGCSetDashes(object, dash.list)
gdkGCCopy(object, src.gc)
gdkGCSetColormap(object, colormap)
gdkGCGetColormap(object)
gdkGCOffset(object, x.offset, y.offset)
gdkGC(drawable)

1 2	GObject +----GdkGC

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.

Most values of a graphics context can be set at creation time by using gdkGCNewWithValues, or can be set one-by-one using functions such as gdkGCSetForeground. A few of the values in the GC, such as the dash pattern, can only be set by the latter method.

GdkGC

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

GdkGCValues

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

foreground: the foreground color. Note that gdkGCGetValues only sets the pixel value.
background: the background color. Note that gdkGCGetValues only sets the pixel value.
font: the default font.
function: the bitwise operation used when drawing.
fill: the fill style.
tile: the tile pixmap.
stipple: the stipple bitmap.
clip_mask: the clip mask bitmap.
subwindow_mode: the subwindow mode.
ts_x_origin: the x origin of the tile or stipple.
ts_y_origin: the y origin of the tile or stipple.
clip_x_origin: the x origin of the clip mask.
clip_y_origin: the y origin of the clip mask.
graphics_exposures: whether graphics exposures are enabled.
line_width: the line width.
line_style: the way dashed lines are drawn.
cap_style: the way the ends of lines are drawn.
join_style: the way joins between lines are drawn.

gdkGC is the equivalent of gdkGCNew.

GdkGCValuesMask

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

foreground: the foreground is set.
background: the background is set.
font: the font is set.
function: the function is set.
fill: the fill is set.
tile: the tile is set.
stipple: the stipple is set.
clip-mask: the clip.mask is set.
subwindow: the subwindow.mode is set.
ts-x-origin: the ts.x.origin is set.
ts-y-origin: the ts.y.origin is set.
clip-x-origin: the clip.x.origin is set.
clip-y-origin: the clip.y.origin is set.
exposures: the graphics.exposures is set.
line-width: the line.width is set.
line-style: the line.style is set.
cap-style: the cap.style is set.
join-style: the join.style is 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.

copy: dst = src
invert: dst = NOT dst
xor: dst = src XOR dst
clear: dst = 0
and: dst = dst AND src
and-reverse: dst = src AND (NOT dst)
and-invert: dst = (NOT src) AND dst
noop: dst = dst
or: dst = src OR dst
equiv: dst = (NOT src) XOR dst
or-reverse: dst = src OR (NOT dst)
copy-invert: dst = NOT src
or-invert: dst = (NOT src) OR dst
nand: dst = (NOT src) OR (NOT dst)
nor: dst = (NOT src) AND (NOT dst)
set: dst = 1

GdkFill

Determines how primitives are drawn.

solid: draw with the foreground color.
tiled: draw with a tiled pixmap.
stippled: draw using the stipple bitmap. Pixels corresponding to bits in the stipple bitmap that are set will be drawn in the foreground color; pixels corresponding to bits that are not set will be left untouched.
opaque-stippled: draw using the stipple bitmap. Pixels corresponding to bits in the stipple bitmap that are set will be drawn in the foreground color; pixels corresponding to bits that are not set will be drawn with the background color.

GdkSubwindowMode

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

clip-by-children: only draw onto the window itself.
include-inferiors: draw onto the window and child windows.

GdkLineStyle

Determines how lines are drawn.

solid: lines are drawn solid.
on-off-dash: even segments are drawn; odd segments are not drawn.
double-dash: even segments are normally. Odd segments are drawn in the background color if the fill style is GDK_SOLID, or in the background color masked by the stipple if the fill style is GDK_STIPPLED.

GdkCapStyle

Determines how the end of lines are drawn.

not-last: the same as GDK_CAP_BUTT for lines of non-zero width. for zero width lines, the final point on the line will not be drawn.
butt: the ends of the lines are drawn squared off and extending to the coordinates of the end point.
round: the ends of the lines are drawn as semicircles with the diameter equal to the line width and centered at the end point.
projecting: the ends of the lines are drawn squared off and extending half the width of the line beyond the end point.

GdkJoinStyle

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

miter: the sides of each line are extended to meet at an angle.
round: the sides of the two lines are joined by a circular arc.
bevel: the sides of the two lines are joined by a straight line which makes an equal angle with each line.

Derived by RGtkGen from GTK+ documentation

https://developer.gnome.org/gdk2/stable/gdk2-Graphics-Contexts.html

RGtk2 documentation built on Oct. 14, 2021, 5:08 p.m.