Description
These functions provide support for drawing points, lines, arcs and text
onto what are called 'drawables'. Drawables, as the name suggests, are things
which support drawing onto them, and are either GdkWindow or GdkPixmap
objects.
Many of the drawing operations take a GdkGC argument, which represents a
graphics context. This GdkGC contains a number of drawing attributes such
as foreground color, background color and line width, and is used to reduce
the number of arguments needed for each drawing operation. See the
Graphics Contexts section for
more information.
Details
struct GdkDrawable
struct GdkDrawable
{
gpointer user_data;
}; |
An opaque structure representing an object that can be
drawn onto. This can be a GdkPixmap, a GdkBitmap,
or a GdkWindow.
gdk_drawable_ref ()
Warning |
gdk_drawable_ref is deprecated and should not be used in newly-written code. |
Deprecated equivalent of calling g_object_ref() on drawable.
(Drawables were not objects in previous versions of GDK.)
gdk_drawable_unref ()
Warning |
gdk_drawable_unref is deprecated and should not be used in newly-written code. |
Deprecated equivalent of calling g_object_unref() on drawable.
gdk_drawable_set_data ()
Warning |
gdk_drawable_set_data is deprecated and should not be used in newly-written code. |
This function is equivalent to g_object_set_data(),
the GObject variant should be used instead.
gdk_drawable_get_data ()
Warning |
gdk_drawable_get_data is deprecated and should not be used in newly-written code. |
Equivalent to g_object_get_data(); the GObject variant should be
used instead.
gdk_drawable_get_visual ()
Gets the GdkVisual describing the pixel format of drawable.
gdk_drawable_set_colormap ()
Sets the colormap associated with drawable. Normally this will
happen automatically when the drawable is created; you only need to
use this function if the drawable-creating function did not have a
way to determine the colormap, and you then use drawable operations
that require a colormap. The colormap for all drawables and
graphics contexts you intend to use together should match. i.e.
when using a GdkGC to draw to a drawable, or copying one drawable
to another, the colormaps should match.
gdk_drawable_get_colormap ()
Gets the colormap for drawable, if one is set; returns
NULL otherwise.
gdk_drawable_get_depth ()
Obtains the bit depth of the drawable, that is, the number of bits
that make up a pixel in the drawable's visual. Examples are 8 bits
per pixel, 24 bits per pixel, etc.
gdk_drawable_get_size ()
Fills *width and *height with the size of drawable.
width or height can be NULL if you only want the other one.
On the X11 platform, if drawable is a GdkWindow, the returned
size is the size reported in the most-recently-processed configure
event, rather than the current size on the X server.
gdk_drawable_get_clip_region ()
Computes the region of a drawable that potentially can be written
to by drawing primitives. This region will not take into account
the clip region for the GC, and may also not take into account
other factors such as if the window is obscured by other windows,
but no area outside of this region will be affected by drawing
primitives.
gdk_drawable_get_visible_region ()
Computes the region of a drawable that is potentially visible.
This does not necessarily take into account if the window is
obscured by other windows, but no area outside of this region
is visible.
gdk_draw_point ()
Draws a point, using the foreground color and other attributes of the GdkGC.
gdk_draw_points ()
Draws a number of points, using the foreground color and other attributes of
the GdkGC.
gdk_draw_line ()
Draws a line, using the foreground color and other attributes of the GdkGC.
gdk_draw_lines ()
Draws a series of lines connecting the given points.
The way in which joins between lines are draw is determined by the
GdkCapStyle value in the GdkGC. This can be set with
gdk_gc_set_line_attributes().
gdk_draw_segments ()
Draws a number of unconnected lines.
struct GdkSegment
struct GdkSegment
{
gint x1;
gint y1;
gint x2;
gint y2;
}; |
Specifies the start and end point of a line for use by the gdk_draw_segments()
function.
gdk_draw_rectangle ()
Draws a rectangular outline or filled rectangle, using the foreground color
and other attributes of the GdkGC.
Note: A rectangle drawn filled is 1 pixel smaller in both dimensions than a rectangle
outlined. Calling gdk_draw_rectangle (window, gc, TRUE, 0, 0, 20, 20) results
in a filled rectangle 20 pixels wide and 20 pixels high. Calling
gdk_draw_rectangle (window, gc, FALSE, 0, 0, 20, 20) results in an outlined
rectangle with corners at (0, 0), (0, 20), (20, 20), and (20, 0), which
makes it 21 pixels wide and 21 pixels high.
gdk_draw_arc ()
Draws an arc or a filled 'pie slice'. The arc is defined by the bounding
rectangle of the entire ellipse, and the start and end angles of the part of
the ellipse to be drawn.
gdk_draw_polygon ()
Draws an outlined or filled polygon.
gdk_draw_glyphs ()
This is a low-level function; 99% of text rendering should be done
using gdk_draw_layout() instead.
A glyph is a character in a font. This function draws a sequence of
glyphs. To obtain a sequence of glyphs you have to understand a
lot about internationalized text handling, which you don't want to
understand; thus, use gdk_draw_layout() instead of this function,
gdk_draw_layout() handles the details.
gdk_draw_layout_line_with_colors ()
Render a PangoLayoutLine onto a GdkDrawable, overriding the
layout's normal colors with foreground and/or background.
foreground and background need not be allocated.
gdk_draw_layout ()
Render a PangoLayout onto a GDK drawable
gdk_draw_layout_with_colors ()
Render a PangoLayout onto a GdkDrawable, overriding the
layout's normal colors with foreground and/or background.
foreground and background need not be allocated.
gdk_draw_string ()
Warning |
gdk_draw_string is deprecated and should not be used in newly-written code. |
Draws a string of characters in the given font or fontset.
gdk_draw_text ()
Warning |
gdk_draw_text is deprecated and should not be used in newly-written code. |
Draws a number of characters in the given font or fontset.
gdk_draw_text_wc ()
Warning |
gdk_draw_text_wc is deprecated and should not be used in newly-written code. |
Draws a number of wide characters using the given font of fontset.
If the font is a 1-byte font, the string is converted into 1-byte characters
(discarding the high bytes) before output.
gdk_draw_pixmap
#define gdk_draw_pixmap gdk_draw_drawable |
Warning |
gdk_draw_pixmap is deprecated and should not be used in newly-written code. |
Draws a pixmap, or a part of a pixmap, onto another drawable.
gdk_draw_drawable ()
Copies the width x height region of src at coordinates (xsrc,
ysrc) to coordinates (xdest, ydest) in drawable.
width and/or height may be given as -1, in which case the entire
src drawable will be copied.
Most fields in gc are not used for this operation, but notably the
clip mask or clip region will be honored.
The source and destination drawables must have the same visual and
colormap, or errors will result. (On X11, failure to match
visual/colormap results in a BadMatch error from the X server.)
A common cause of this problem is an attempt to draw a bitmap to
a color drawable. The way to draw a bitmap is to set the
bitmap as a clip mask on your GdkGC, then use gdk_draw_rectangle()
to draw a rectangle clipped to the bitmap.
gdk_drawable_get_image ()
A GdkImage stores client-side image data (pixels). In contrast,
GdkPixmap and GdkWindow are server-side
objects. gdk_drawable_get_image() obtains the pixels from a
server-side drawable as a client-side GdkImage. The format of a
GdkImage depends on the GdkVisual of the current display, which
makes manipulating GdkImage extremely difficult; therefore, in
most cases you should use gdk_pixbuf_get_from_drawable() instead of
this lower-level function. A GdkPixbuf contains image data in a
canonicalized RGB format, rather than a display-dependent format.
Of course, there's a convenience vs. speed tradeoff here, so you'll
want to think about what makes sense for your application.
x, y, width, and height define the region of drawable to
obtain as an image.
You would usually copy image data to the client side if you intend
to examine the values of individual pixels, for example to darken
an image or add a red tint. It would be prohibitively slow to
make a round-trip request to the windowing system for each pixel,
so instead you get all of them at once, modify them, then copy
them all back at once.
If the X server or other windowing system backend is on the local
machine, this function may use shared memory to avoid copying
the image data.
If the source drawable is a GdkWindow and partially offscreen
or obscured, then the obscured portions of the returned image
will contain undefined data.