'\" '\" Copyright (c) 1990, 1991 The Regents of the University of California. '\" All rights reserved. '\" '\" Permission is hereby granted, without written agreement and without '\" license or royalty fees, to use, copy, modify, and distribute this '\" documentation for any purpose, provided that the above copyright '\" notice and the following two paragraphs appear in all copies. '\" '\" IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY '\" FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES '\" ARISING OUT OF THE USE OF THIS DOCUMENTATION, EVEN IF THE UNIVERSITY OF '\" CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. '\" '\" THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, '\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY '\" AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS '\" ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO '\" PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. '\" '\" $Header: /user6/ouster/wish/man/RCS/GetColor.3,v 1.9 93/04/01 09:41:25 ouster Exp $ SPRITE (Berkeley) '\" .so man.macros .HS Tk_GetColor tkc .BS .SH NAME Tk_GetColor, Tk_GetColorByValue, Tk_NameOfColor Tk_FreeColor \- maintain database of colors .SH SYNOPSIS .nf \fB#include \fR .sp XColor * \fBTk_GetColor\fR(\fIinterp, tkwin, colorMap, nameId\fB)\fR .sp XColor * \fBTk_GetColorByValue\fR(\fIinterp, tkwin, colorMap, prefPtr\fB)\fR .sp char * \fBTk_NameOfColor(\fIcolorPtr\fB)\fR .sp \fBTk_FreeColor(\fIcolorPtr\fB)\fR .SH ARGUMENTS .AS "Tcl_Interp" *colorPtr .AP Tcl_Interp *interp in Interpreter to use for error reporting. .AP Tk_Window tkwin in Token for window in which color will be used. .AP Colormap colormap in Colormap from which to allocate color. If None, then the default colormap for \fItkwin\fR's screen is used. .AP Tk_Uid nameId in Textual description of desired color. .AP XColor *prefPtr in Indicates red, green, and blue intensities of desired color. .AP XColor *colorPtr in Pointer to X color information. Must have been allocated by previous call to \fBTk_GetColor\fR or \fBTk_GetColorByValue\fR, except when passed to \fBTk_NameOfColor\fR. .BE .SH DESCRIPTION .PP The \fBTk_GetColor\fR and \fBTk_GetColorByValue\fR procedures locate pixel values that may be used to render particular colors in the window given by \fItkwin\fR using the colormap given by \fIcolormap\fR. In \fBTk_GetColor\fR the desired color is specified with a Tk_Uid (\fInameId\fR), which may have any of the following forms: .TP 20 \fIcolorname\fR Any of the valid textual names for a color defined in the server's color database file, such as \fBred\fR or \fBPeachPuff\fR. .TP 20 \fB#\fIRGB\fR .TP 20 \fB#\fIRRGGBB\fR .TP 20 \fB#\fIRRRGGGBBB\fR .TP 20 \fB#\fIRRRRGGGGBBBB\fR A numeric specification of the red, green, and blue intensities to use to display the color. Each \fIR\fR, \fIG\fR, or \fIB\fR 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. .LP In \fBTk_GetColorByValue\fR, the desired color is indicated with the \fIred\fR, \fIgreen\fR, and \fIblue\fR fields of the structure pointed to by \fIcolorPtr\fR. .PP If \fBTk_GetColor\fR or \fBTk_GetColorByValue\fR 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 from \fIcolormap\fR that may be used to draw in the color. If an error occurs in allocating a color then NULL is returned and an error message will be stored in \fIinterp->result\fR. .PP \fBTk_GetColor\fR and \fBTk_GetColorByValue\fR maintain a database of all the colors currently in use. If the same \fInameId\fR is requested multiple times from \fBTk_GetColor\fR (e.g. by different windows), or if the same intensities are requested multiple times from \fBTk_GetColorByValue\fR, 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 \fBTk_GetColor\fR or \fBTk_GetColorByValue\fR instead of Xlib procedures like \fBXAllocColor\fR, \fBXAllocNamedColor\fR, or \fBXParseColor\fR. .PP Since different calls to \fBTk_GetColor\fR or \fBTk_GetColorByValue\fR 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 \fBXAllocColorCells\fR to allocate the pixel value for the color. .PP The procedure \fBTk_NameOfColor\fR is roughly the inverse of \fBTk_GetColor\fR. If its \fIcolorPtr\fR argument was created by \fBTk_GetColor\fR, then the return value is the \fInameId\fR string that was passed to \fBTk_GetColor\fR to create the color. If \fIcolorPtr\fR was created by a call to \fBTk_GetColorByValue\fR, or by any other mechanism, then the return value is a string that could be passed to \fBTk_GetColor\fR to return the same color. Note: the string returned by \fBTk_NameOfColor\fR is only guaranteed to persist until the next call to \fBTk_NameOfColor\fR. .PP When a pixel value returned by \fBTk_GetColor\fR or \fBTk_GetColorByValue\fR is no longer needed, \fBTk_FreeColor\fR should be called to release the color. There should be exactly one call to \fBTk_FreeColor\fR for each call to \fBTk_GetColor\fR or \fBTk_GetColorByValue\fR. When a pixel value is no longer in use anywhere (i.e. it has been freed as many times as it has been gotten) \fBTk_FreeColor\fR will release it to the X server and delete it from the database. .SH KEYWORDS color, intensity, pixel value