GtkAda Reference Manual - Package Gdk.Color

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# Package Gdk.Color

This package provides an interface to the color handling facilities in gtk+. It is able to handle any kind of visual (monochrome, greyscale, color with different depths, ...), but provides a common and easy interface for all of them. Some of these functions expect a Colormap. There are two ways you can get such a colormap, either a system default colormap or a per-widget colormap. It is recommended, unless you are writing your own new widget, to always use the system default Colormap. All the functions to get these colormaps are found in Gtk.Widget.

Getting the Red/Green/Blue components can be done through Parse, and is actually recommended, since the exact color generally depends on the visual your application is running on.

Note for users transitioning from gtk+ 1.2: the Get_System call is now obsolete, and you should use Gtk.Widget.Get_Default_Colormap instead.

- Gdk.Color Types
- Gdk.Color Subprograms
- Gdk.Color Example

## Types

    type Gdk_Color is private;
| A color to be displayed on the screen. Currently, GtkAda only supports the RGB standard, ie each color is set by its red, green and blue components. An extra field (Pixel) is the internal representation of the color, which is set once the color has been allocated.
    type Gdk_Color_Array is array (Natural range <>) of Gdk_Color;
| An array of colors.
    subtype Gdk_Colormap is Gdk.Gdk_Colormap;
| The set of colors the can be displayed on the screen. When the screen is not a true-color screen (ie there is only a limited number of possible colors, like 256), the colors are in fact indexes into a colormap, which gives the components of the color. This is the same concept as a palette.

## Subprograms

    function Gdk_Color_Type        return Glib.GType;
| Return the internal gtk+ types associated with a color
    function Gdk_Colormap_Type     return Glib.GType;
| Return the internal gtk+ types associated with a colormap
### Setting/Getting the fields of Gdk_Color
    procedure Set_Rgb
      (Color              : out    Gdk_Color;
       Red, Green, Blue   :        Guint16);
| Modify the fields of the color. You then have to allocate the color with one of the Alloc* functions above.
    procedure Set_Pixel
      (Color              : in out Gdk_Color;
       Pixel              :        Guint32);
| This function should almost never be used. Instead, use Alloc_Color.
    function Red
      (Color              :        Gdk_Color)
       return Guint16;
| Return the Red field of Color.
    function Green
      (Color              :        Gdk_Color)
       return Guint16;
| Return the Green field of Color.
    function Blue
      (Color              :        Gdk_Color)
       return Guint16;
| Return the Blue field of Color.
    function Pixel
      (Color              :        Gdk_Color)
       return Guint32;
| Return the Pixel field of Color.
### Creating and Destroying colors
    procedure Gdk_New
      (Colormap           : out    Gdk_Colormap;
       Visual             :        Gdk.Visual.Gdk_Visual;
       Private_Cmap       :        Boolean);
| Create a new colormap for the visual. If Private_Cmap is true, then the colormap won't be modifiable outside this scope. This might result in some strange colors on the display...
    procedure Ref
      (Colormap           :        Gdk_Colormap);
| Increment the ref-count for the color.
    procedure Unref
      (Colormap           :        Gdk_Colormap);
| Unref is the only way to destroy a colormap once you no longer need it. Note that because gtk+ uses reference counts, the colormap will not be actually destroyed while at least one object is using it.
    procedure Change
      (Colormap           :        Gdk_Colormap;
       Ncolors            :        Gint);
| Change the first Ncolors defined in Colormap.
    procedure Alloc_Colors
      (Colormap           :        Gdk_Colormap;
       Colors             : in out Gdk_Color_Array;
       Writeable          :        Boolean := False;
       Best_Match         :        Boolean := True;
       Success            : out    Boolean_Array;
       Result             : out    Gint);
| Allocate a set of colors. The parameters are the same as for Alloc_Color Result is the number of colors not successfully allocated. The size of the Boolean_Array is equal to the length of the Colors_Array. Usage of an array of a different size will probably lead to a Constraint_Error.
    procedure Alloc_Color
      (Colormap           :        Gdk_Colormap;
       Color              : in out Gdk_Color;
       Writeable          :        Boolean := False;
       Best_Match         :        Boolean := True;
       Success            : out    Boolean);
| Allocate a new color. The fields RGB should have been set before calling this function. If Writeable is True, the color will be allocated read/write, that can be changed at any time. Not all visuals support this. On modern systems this usage has become less useful than before, since redrawing the screen with a new color is about as fast. If Best_Match is True, and the exact color can not be allocated, GtkAda will find the closest possible match, and modify the fields Red, Green and Blue of Color. Note that the allocation has more chances to succeed if Writeable is False and Best_Match is True. When you no longer use a color, you should call Free.
    procedure Free_Colors
      (Colormap           :        Gdk_Colormap;
       Colors             :        Gdk_Color_Array);
| Free Colors, assuming they are allocated in Colormap.
    procedure Get_Visual
      (Colormap           :        Gdk_Colormap;
       Visual             : out    Gdk.Visual.Gdk_Visual);
| Get the visual associated with a colormap. The main information you can get from there is the depth of the display.
    procedure Copy
      (Source             :        Gdk_Color;
       Destination        : out    Gdk_Color);
| Copy the Source color to Destination.
    function Parse
      (Spec               :        String)
       return Gdk_Color;
| Parse the string Spec, and get its Red/Green/Blue components. The color is not allocated, and you need to call Alloc_Color. If the string could not be parsed to an existing color, Wrong_Color is raised. The string can be one of : "RGB:FF/FF/FF" where the "FF" substrings are respectively the value of the red, green and blue components. Some other prefixes than RGB are defined in the X11 definition, please see some X11 documentation (or the man page XParseColor on unix systems). "color_name" which can be any color name defined in the file rgb.txt of the user's system. You should always check that Wrong_Color was not raised, in case the color was not known on the user's system. This string is case insensitive. Color names are not supported on Windows systems.
    function Equal
      (Colora, Colorb     :        Gdk_Color)
       return Boolean;
| True if the Red, Green and Blue components of both colors are equal.

## Example

     --  Here is an example how you can allocate a new color, when you know
     --  its red/green/blue components: Note that we allocate white in fact
     --  since the maximal value for color components is 65535.
        Color   : Gdk_Color;
        Success : Boolean;
        Set_Rbg (Color, 65535, 65535, 65535);
        Alloc_Color (Colormap   => Gtk.Widget.Get_Default_Colormap,
                     Color      => Color,
                     Writeable  => False,
                     Best_Match => True,
                     Success    => Success);
        if not Success then
            ...;  --  allocation failed
        end if;

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