Xfce Foundation Classes

ColorSelection();

You'll probably not be using this constructor directly. It creates an orphan ColorSelection widget which you'll have to parent yourself. The ColorSelection widget inherits from the Gtk::VBox.

ColorSelectionDialog();

      

explicit ColorSelectionDialog(const String& title);

These are the most common color selection constructors. Both constructors create a ColorSelectionDialog, the first with the default title which is just the program name and the second with the 'title' specified. A ColorSelectionDialog consists of a Frame containing a ColorSelection widget, an HSeparator and an HBox with three buttons, "Ok", "Cancel" and "Help". You can reach these buttons by using one of the corresponding accessors:

Gtk::Button* ok_button() const;

      

Gtk::Button* cancel_button() const;

      

Gtk::Button* help_button() const;

The color selection widget supports adjusting the opacity of a color (also known as the alpha channel). This is disabled by default. Calling the following method with 'has_opacity' set to true enables opacity. Likewise, has_opacity set to false will disable opacity.

void
set_has_opacity_control(bool has_opacity);

You can set the current color explicitly by calling Gtk::ColorSelection::set_current_color() with a reference to a Gdk::Color. Setting the opacity (alpha channel) is done with Gtk::ColorSelection::set_current_alpha(). The alpha value should be between 0 (fully transparent) and 65636 (fully opaque).

void
set_current_color(const Gdk::Color&
color);

      

void set_current_alpha(unsigned short alpha);

When you need to query the current color, typically when you've received a 'color_changed' signal, you use these methods:

Gdk::Color
get_current_color() const;

      

unsigned short
get_current_alpha() const;

Color Selection Example

Here's a simple example demonstrating the use of the ColorSelectionDialog. The program displays a window containing a drawing area. Clicking on it opens a color selection dialog, and changing the color in the color selection dialog changes the background color of the window.

The header file for the Color Selection example is <colorselection.hh>:

#include <xfc/main.hh>

#include <xfc/gtk/colorselection.hh>

#include <xfc/gtk/drawingarea.hh>

#include <xfc/gtk/window.hh>

#include <xfc/gdk/color.hh>

      

using namespace Xfc;

      

class ColorSelectionWindow : public Gtk::Window

{

    Gdk::Color color;

    Gtk::DrawingArea *area;

      

protected:

    bool
on_drawing_area_event(const
Gdk::Event& event);

    void
on_color_changed(Gtk::ColorSelection *colorsel);

      

public:

    ColorSelectionWindow();

    virtual
~ColorSelectionWindow();

};

and then source file is <colorselection.cc>:

#include "colorselection.hh"

      

ColorSelectionWindow::ColorSelectionWindow()

{

    set_title("Color Selection Example");

      

    // Create drawing
area

    area= new
Gtk::DrawingArea(250, 200);

      

    // Set the initial
background color    and events to receive

    color.set(0, 0, 65535);

    area->modify_bg(Gtk::STATE_NORMAL, color);

    area->set_events(Gdk::BUTTON_PRESS_MASK);

    area->signal_event().connect(sigc::mem_fun(this,
&ColorSelectionWindow::on_drawing_area_event));

      

    // Add drawing
area to
main window

    add(*area);

    area->show();

    show();

}

      

ColorSelectionWindow::~ColorSelectionWindow()

{

}

      

bool

ColorSelectionWindow::on_drawing_area_event(const Gdk::Event& event)

{

    using namespace
sigc;

    bool handled = false;

      

    if (event.type() ==
Gdk::BUTTON_PRESS)

    {

        handled = true;

        Gtk::ColorSelectionDialog *dialog
= new Gtk::ColorSelectionDialog("Select
background color");

        Gtk::ColorSelection *colorsel =
dialog->colorsel();

       
colorsel->set_previous_color(color);

       
colorsel->set_current_color(color);

       
colorsel->set_has_palette(true);

      

        // Connect
to the "color_changed" signal

       
colorsel->signal_color_changed().connect(bind(mem_fun(this,
&ColorSelectionWindow::on_color_changed), colorsel));

      

        // Show
the dialog

        if
(dialog->run() == Gtk::RESPONSE_OK)

            color =
colorsel->get_current_color();

        else

            
area->modify_bg(Gtk::STATE_NORMAL, color);

      

        dialog->dispose();

    }

    return handled;

}

      

void

ColorSelectionWindow::on_color_changed(Gtk::ColorSelection *colorsel)

{

    Gdk::Color new_color =
colorsel->get_current_color();

    area->modify_bg(Gtk::STATE_NORMAL, new_color);

}

      

int main (int
argc, char *argv[])

{

    using namespace Main;

      

    init(&argc, &argv);

      

    ColorSelectionWindow window;

   
window.signal_destroy().connect(sigc::ptr_fun(&Xfc::Main::quit));

      

    run();

    return 0;

}

Compiling Color Selection

If you compiled and installed XFC yourself, you will find the source code for Color Selection in the <examples/colorselection> source directory along with a Makefile. If XFC came pre-installed, or you installed it from an RPM package, you will find the source code in the </usr/share/doc/xfcui-X.X/examples/colorselection> subdirectory. In this case you will have to create the Makefile yourself (replace X.X with the version number of the libXFCui library you have installed).

To create a Makefile for Color Selection, add the following lines to a new text file and save it using the name "Makefile":

CC = g++

      

CFLAGS = -Wall -O2

      

colorselection: colorselection.cc colorselection.hh

    $(CC) colorselection.cc -o colorselection $(CFLAGS)
`pkg-config xfcui-X.X --cflags --libs`

      

clean: 

    rm -f *.o colorselection

If you cut and paste these lines make sure the whitespace before $(CC) and rm is a tab character. When you compile and run this program you will see the following window appear:

If you press the mouse button down inside the client area of this window a color selection dialog appears. Changing the selected color or hue in this dialog will update the background color of the parent window. Click the OK button to make the color selection permanent.