Tk_GetColor(3Tk) Tk_GetColor(3Tk)
Tk_GetColor, Tk_GetColorByValue, Tk_NameOfColor, Tk_FreeColor - maintain
database of colors
#include <tk.h>
XColor *
Tk_GetColor(interp, tkwin, nameId)
XColor * |
Tk_GetColorByValue(tkwin, prefPtr) |
char *
Tk_NameOfColor(colorPtr)
GC |
Tk_GCForColor(colorPtr, drawable) |
Tk_FreeColor(colorPtr)
Tcl_Interp *interp (in) Interpreter to use for error
reporting.
Tk_Window tkwin (in) Token for window in which color will
be used.
Tk_Uid nameId (in) Textual description of desired color.
XColor *prefPtr (in) Indicates red, green, and blue
intensities of desired color.
XColor *colorPtr (in) Pointer to X color information. Must
have been allocated by previous call
to Tk_GetColor or Tk_GetColorByValue,
except when passed to Tk_NameOfColor.
Drawable drawable (in) Drawable in which the result graphics |
context will be used. Must have same |
screen and depth as the window for |
which the color was allocated.
The Tk_GetColor and Tk_GetColorByValue procedures locate pixel values
that may be used to render particular colors in the window given by
tkwin. In Tk_GetColor the desired color is specified with a Tk_Uid
(nameId), which may have any of the following forms:
Tk_GetColor(3Tk) Tk_GetColor(3Tk)
colorname Any of the valid textual names for a color defined in
the server's color database file, such as red or
PeachPuff.
#RGB
#RRGGBB
#RRRGGGBBB
#RRRRGGGGBBBB A numeric specification of the red, green, and blue
intensities to use to display the color. Each R, G,
or B represents a single hexadecimal digit. The four
forms permit colors to be specified with 4-bit, 8-
bit, 12-bit or 16-bit values. When fewer than 16
bits are provided for each color, they represent the
most significant bits of the color. For example,
#3a7 is the same as #3000a0007000.
In Tk_GetColorByValue, the desired color is indicated with the red,
green, and blue fields of the structure pointed to by colorPtr.
If Tk_GetColor or Tk_GetColorByValue is successful in allocating the
desired color, then it returns a pointer to an XColor structure; the
structure indicates the exact intensities of the allocated color (which
may differ slightly from those requested, depending on the limitations of
the screen) and a pixel value that may be used to draw in the color. If |
the colormap for tkwin is full, Tk_GetColor and Tk_GetColorByValue will |
use the closest existing color in the colormap. If Tk_GetColor |
encounters an error while allocating the color (such as an unknown color |
name) then NULL is returned and an error message is stored in interp- |
>result; Tk_GetColorByValue never returns an error.
Tk_GetColor and Tk_GetColorByValue maintain a database of all the colors
currently in use. If the same nameId is requested multiple times from
Tk_GetColor (e.g. by different windows), or if the same intensities are
requested multiple times from Tk_GetColorByValue, then existing pixel
values will be re-used. Re-using an existing pixel avoids any
interaction with the X server, which makes the allocation much more
efficient. For this reason, you should generally use Tk_GetColor or
Tk_GetColorByValue instead of Xlib procedures like XAllocColor,
XAllocNamedColor, or XParseColor.
Since different calls to Tk_GetColor or Tk_GetColorByValue may return the
same shared pixel value, callers should never change the color of a pixel
returned by the procedures. If you need to change a color value
dynamically, you should use XAllocColorCells to allocate the pixel value
for the color.
The procedure Tk_NameOfColor is roughly the inverse of Tk_GetColor. If
its colorPtr argument was created by Tk_GetColor, then the return value
is the nameId string that was passed to Tk_GetColor to create the color.
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Tk_GetColor(3Tk) Tk_GetColor(3Tk)
If colorPtr was created by a call to Tk_GetColorByValue, or by any other
mechanism, then the return value is a string that could be passed to
Tk_GetColor to return the same color. Note: the string returned by
Tk_NameOfColor is only guaranteed to persist until the next call to
Tk_NameOfColor.
Tk_GCForColor returns a graphics context whose Foreground field is the |
pixel allocated for colorPtr and whose other fields all have default |
values. This provides an easy way to do basic drawing with a color. The|
graphics context is cached with the color and will exist only as long as |
colorPtr exists; it is freed when the last reference to colorPtr is |
freed by calling Tk_FreeColor.
When a pixel value returned by Tk_GetColor or Tk_GetColorByValue is no
longer needed, Tk_FreeColor should be called to release the color. There
should be exactly one call to Tk_FreeColor for each call to Tk_GetColor
or Tk_GetColorByValue. When a pixel value is no longer in use anywhere
(i.e. it has been freed as many times as it has been gotten) Tk_FreeColor
will release it to the X server and delete it from the database.
color, intensity, pixel value
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getcolor(3G) getcolor(3G)
getcolor - returns the current color
long getcolor()
none
FUNCTION RETURN VALUE
Returns an index into the color map.
getcolor returns the current color for the current drawing mode. In
NORMALDRAW, it is an index into the color map, and is meaningful in both
single and double buffer modes. getcolor is ignored in RGB mode. In
OVERDRAW mode, getcolor returns the color that is drawn into the overlay
bitplanes, etc.
color, doublebuffer, drawmode, getmcolor, singlebuffer
This routine is available only in immediate mode.
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