9.13. Color Selection
The color selection widget is, not surprisingly, a widget for interactive selection of colors. This composite widget lets the user select a color by manipulating RGB (Red, Green, Blue) and HSV (Hue, Saturation, Value) triples. This is done either by adjusting single values with sliders or entries, or by picking the desired color from a hue-saturation wheel/value bar. Optionally, the opacity of the color can also be set.The color selection widget currently emits only one signal, "color_changed", which is emitted whenever the current color in the widget changes, either when the user changes it or if it's set explicitly through the set_color() method.
Lets have a look at what the color selection
widget has to offer us. The widget comes in two flavours: GtkColorSelection
and GtkColorSelectionDialog.
colorsel = GtkColorSelection() |
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 VBox widget.
colorseldlg = GtkColorSelectionDialog(title) |
where title is an optional string to be used in the titlebar of the dialog.
This is the most common color selection
constructor. It creates a ColorSelectionDialog. It 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 accessing
the "ok_button", "cancel_button"
and "help_button" attributes
of the ColorSelectionDialog, (i.e., colorseldlg.ok_button). The
ColorSelection widget is accessed using the attribute colorsel:
colorsel = colorseldlg.colorsel |
The ColorSelection widget has a number of methods that change its characteristics
or provide access to the color selection.
colorsel.set_update_policy(policy) |
This method sets the update policy. The
default policy is
UPDATE_CONTINUOUS
which means that the current color is updated continuously when the user
drags the sliders or presses the mouse and drags in the hue-saturation
wheel or value bar. If you experience performance problems, you may want
to set the policy to
UPDATE_DISCONTINUOUS
or UPDATE_DELAYED.
colorsel.set_opacity(use_opacity) |
The color selection widget supports adjusting
the opacity of a color (also known as the alpha channel). This is disabled
by default. Calling this method with use_opacity
set to TRUE enables opacity. Likewise, use_opacity
set to FALSE will disable opacity.
colorsel.set_color(color) |
You can set the current color explicitly
by calling this method with an array of color numbers (float). The length
of the array depends on whether opacity is enabled or not. Position 0 contains
the red component, 1 is green, 2 is blue and opacity is at position 3 (only
if opacity is enabled, see the set_opacity() method above). All values
are between 0.0 and 1.0.
color = colorsel.get_color() |
When you need to query the current color, typically when you've received a "color_changed" signal, you use this method. The return value color is a tuple of color numbers either three or four depending on whether opacity is set. See the set_color() method for the description of this array.
The colorsel.py example program demonstrates 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. Figure 9.12 illustrates this program in action:
Figure 9.12 Color Selection Dialog Example
1 #!/usr/bin/env python
2
3 # example colorsel.py
4
5 import gtk
6 import GDK
7
8 class ColorSelectionExample:
9 # Color changed handler
10 def color_changed_cb(self, widget):
11 # Get drawingarea colormap
12 colormap = self.drawingarea.get_colormap()
13
14 # Get current color
15 colordata = self.colorseldlg.colorsel.get_color()
16
17 # Fit to a unsigned 16 bit integer (0..65535) and
18 # insert into the GdkColor structure
19 # And allocate color
20 gdk_color = apply(colormap.alloc,
21 map(lambda color: int(color*65535.0), colordata))
22
23 # Set window background color
24 style = self.drawingarea.get_style().copy()
25 style.bg[gtk.STATE_NORMAL] = gdk_color
26 self.drawingarea.set_style(style)
27
28 # Clear window
29 self.drawingarea.draw_rectangle(style.bg_gc[gtk.STATE_NORMAL],
30 gtk.TRUE, 0, 0, -1, -1)
31
32 # Drawingarea event handler
33 def area_event(self, widget, event):
34 handled = gtk.FALSE
35
36 # Check if we've received a button pressed event
37 if event.type == GDK.BUTTON_PRESS:
38 if self.colorseldlg == None:
39 # Yes, we have an event and there's no colorseldlg yet!
40 handled = gtk.TRUE
41
42 # Create color selection dialog
43 self.colorseldlg = gtk.GtkColorSelectionDialog(
44 "Select background color")
45
46 # Get the ColorSelection widget
47 colorsel = self.colorseldlg.colorsel
48
49 # Connect to the "color_changed" signal
50 # to the colorsel widget
51 colorsel.connect("color_changed", self.color_changed_cb)
52 self.colorseldlg.connect(
53 "delete_event", self.dialog_delete_cb)
54 self.colorseldlg.ok_button.connect_object(
55 "clicked", self.colorseldlg.hide, self.colorseldlg)
56 self.colorseldlg.cancel_button.connect_object(
57 "clicked", self.colorseldlg.hide, self.colorseldlg)
58 # Show the dialog
59 self.colorseldlg.show()
60 return handled
61
62 def dialog_delete_cb(self, widget, event):
63 widget.hide()
64 return gtk.TRUE
65
66 # Close down and exit handler
67 def destroy_window(self, widget, event):
68 gtk.mainquit()
69 return gtk.TRUE
70
71 def __init__(self):
72 self.colorseldlg = None
73 # Create toplevel window, set title and policies
74 window = gtk.GtkWindow(gtk.WINDOW_TOPLEVEL)
75 window.set_title("Color selection test")
76 window.set_policy(gtk.TRUE, gtk.TRUE, gtk.TRUE)
77
78 # Attach to the "delete" and "destroy" events so we can exit
79 window.connect("delete_event", self.destroy_window)
80
81 # Create drawingarea, set size and catch button events
82 self.drawingarea = gtk.GtkDrawingArea()
83 self.drawingarea.size(200, 200)
84 self.drawingarea.set_events(GDK.BUTTON_PRESS_MASK)
85 self.drawingarea.connect("event", self.area_event)
86
87 # Add drawingarea to window, then show them both
88 window.add(self.drawingarea)
89 self.drawingarea.show()
90 window.show()
91
92 def main():
93 gtk.mainloop()
94 return 0
95
96 if __name__ == "__main__":
97 ColorSelectionExample()
98 main()
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