Color (XForms (Forms Library) - Version 1.2 (Rev. 4) A Graphical User Interface Toolkit for X)

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#### 3.11.1 Color

To change the color of a particular object use the routine

    void fl_set_object_color(FL_OBJECT *obj,
                             FL_COLOR col1, FL_COLOR col2);

`col1` and `col2` are indices into a colormap. Which colors are actually changed depends on the type of the object. For box and text only `col1` is important. It indicates the color of the box or of the box in which the text is placed. For buttons, `col1` is the color of the button when released and `col2` is the color of the button when pushed. (Note that when changing the color of a button the nice property that the color of a button changes when the mouse moves over it disappears.) For light buttons the two colors indicate the color of the light when off and when on. For bitmap buttons, `col1` is the color of the box and `col2` is the color of the bitmap. For sliders `col1` is the color of the background of the slider and `col2` is the color of the slider itself. Finally, for input objects `col1` is the color of the input field when it is not selected and `col2` is the color when it has input focus, i.e., the user can enter text. For all types of objects, the default colors can be found in the file `forms.h`. For example, for input fields the default colors are `FL_INPUT_COL1` and `FL_INPUT_COL2`. Form Designer comes in very handy in familiarizing you with various attributes since you can change all attributes of an object and immediately see the difference by "test"ing the object.

To find out the colors of an object use

    void fl_get_object_color(FL_OBJECT *obj,
                             FL_COLOR *col1, FL_COLOR *col2);

The following pre-defined color symbols can be used in all color change requests. If the workstation does not support this many colors, substitution by the closest color will happen.

Name | RGB triple
--- | ---
`FL_BLACK` | `( 0, 0, 0)` |
`FL_WHITE` | `(255, 255, 255)`, |
`FL_COL1` | `(173, 173, 173)` |
`FL_BOTTOM_BCOL` | `( 89, 89, 89)` |
`FL_RIGHT_BCOL` | `( 41, 41, 41)` |
`FL_MCOL` | `(191, 191, 191)` |
`FL_LEFT_BCOL` | `(222, 222, 222)` |
`FL_LIGHTER_COL1` | `(204, 204, 204)` |
`FL_DARKER_COL1` | `(161, 161, 161)` |
`FL_SLATEBLUE` | `(113, 113, 198)` |
`FL_INDIANRED` | `(198, 113, 113)` |
`FL_RED` | `(255, 0, 0)` |
`FL_BLUE` | `( 0, 0, 255)` |
`FL_GREEN` | `( 0, 255, 0)` |
`FL_YELLOW` | `(255, 255, 0)` |
`FL_MAGENTA` | `(255, 0, 255)` |
`FL_CYAN` | `( 0, 255, 255)` |
`FL_TOMATO` | `255, 99, 71` |
`FL_INACTIVE` | `(110, 110, 110)` |
`FL_TOP_BCOL` | `(204, 204, 204)` |
`FL_PALEGREEN` | `(113, 198, 113)` |
`FL_DARKGOLD` | `(205, 149, 10)` |
`FL_ORCHID` | `(205, 105, 201)` |
`FL_DARKCYAN` | `(40, 170, 175)` |
`FL_DARKTOMATO` | `(139, 54, 38)` |
`FL_WHEAT` | `(255, 231, 155)` |
`FL_DARKORANGE` | `(255, 128, 0)` |
`FL_DEEPPINK` | `(255, 0, 128)` |
`FL_CHARTREUSE` | `(128, 255, 0)` |
`FL_DARKVIOLET` | `(128, 0, 255)` |
`FL_SPRINGGREEN` | `( 0, 255, 128)` |
`FL_DODGERBLUE` | `( 0, 128, 255)` |
`FL_FREE_COL1` | `( ?, ?, ?)`

Of all the colors listed in the table above `FL_FREE_COL1` has the largest numerical value, and all color with indices smaller than that are used (or can potentially be used) by the Forms Library although, if you wish, they can also be changed using the following routine prior to `fl_initialize()`:

    void fl_set_icm_color(FL_COLOR index, int r, int g, int b);

Note that although the color of an object is indicated by a single index, it is not necessarily true that the Forms Library is operating in PseudoColor. Forms Library is capable of operating in all visuals and as a matter of fact the Forms Library will always select TrueColor or DirectColor if the hardware is capable of it.

The actual color is handled by an internal colormap of `FL_MAX_COLORS` entries (default is 1024). To change or query the values of this internal colormap use the call

    void fl_set_icm_color(FL_COLOR index, int r, int g, int b);
    void fl_get_icm_color(FL_COLOR index, int *r, int *g, int *b);

Call `fl_set_icm_color()` before `fl_initialize()` to change XForms’s default colormap. Note that these two routines do not communicate with the X server, they only populate/return information about the internal colormap, which is made known to the X server by the initialization routine `fl_initialize()`.

To change the colormap and make a color index active so that it can be used in various drawing routines after `fl_initialize()` initialization, use the following function

    unsigned long fl_mapcolor(FL_COLOR i,
                              int red, int green, int blue);

This function frees the previous allocated pixel corresponding to color index `i` and re-allocates a pixel with the RGB value specified. The pixel value is returned by the function. It is recommended that you use an index larger than `FL_FREE_COL1` for your remap request to avoid accidentally freeing the colors you have not explicitly allocated. Indices larger than 224 are reserved and should not be used.

Sometimes it may be more convenient to associate an index with a colorname, e.g., "red" etc., which may have been obtained via resources. To this end, the following routine exists

    long fl_mapcolorname(FL_COLOR i, const char *name);

where `name` is the color name2. The function returns -1 if the colorname name is not resolved. You can obtain the RGB values of an index by using the following routine

    unsigned long fl_getmcolor(FL_COLOR i,
                               int *red, int *green, int *blue);

The function returns the pixel value as known by the Xserver. If the requested index, `i`, is never mapped or is freed, the RGB values as well as the pixel value are random. Since this function communicates with the Xserver to obtain the pixel information, it has a two-way traffic overhead. If you’re only interested in the internal colormap of XForms, `fl_get_icm_color()` is more efficient.

Note that the current version only uses the lower byte of the primary color. Thus all primary colors in the above functions should be specified in the range of 0-255 inclusive.

To free any colors that you no longer need, the following routine should be used

    void fl_free_colors(FL_COLOR colors[], int ncolors);

Prior to XForms version 0.76, there is a color "leakage" in the implementation of the internal colormap that prevents the old index from being freed in the call `fl_mapcolor()`, resulting in accelerated colormap overflow and some other undesirable behavior. Since there may still be some applications based on older versions of the Forms Library, a routine is provided to force the library to be compatible with the (buggy) behavior:

    void fl_set_color_leak(int flag);

Due to the use of an internal colormap and the simplified user interface, changing the colormap value for the index may not result in a change of the color for the object. An actual redraw of the object (see below) whose color is changed may be required to have the change take effect. Therefore, a typical sequence of changing the color of a visible object is as follows:

    fl_mapcolor(newcol, red, green, blue);  /* obj uses newcol */
    fl_redraw_object(obj);

#### Footnotes

### (2)

Standard color names are listed in a file named `rgb.txt` and usually resides in `/usr/lib/X11/`

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