The aspect frame widget is like a frame widget, except that it also enforces the aspect ratio (that is, the ratio of the width to the height) of the child widget to have a certain value, adding extra space if necessary. This is useful, for instance, if you want to preview a larger image. The size of the preview should vary when the user resizes the window, but the aspect ratio needs to always match the original image.
To create a new aspect frame use:
aspect_frame = gtk.AspectFrame(label=None, xalign=0.5, yalign=0.5, ratio=1.0, obey_child=TRUE) |
label specifies the text to be displayed as the label. xalign and yalign specify alignment as with gtk.Alignment widgets. If obey_child is TRUE, the aspect ratio of a child widget will match the aspect ratio of the ideal size it requests. Otherwise, it is given by ratio.
To change the options of an existing aspect frame, you can use:
aspect_frame.set(xalign=0.0, yalign=0.0, ratio=1.0, obey_child=TRUE) |
As an example, the aspectframe.py program uses an AspectFrame to present a drawing area whose aspect ratio will always be 2:1, no matter how the user resizes the top-level window. Figure 10.5, “Aspect Frame Example” illustrates the display of the program:
The source code for aspectframe.py is:
1 #!/usr/bin/env python
2
3 # example aspectframe.py
4
5 import pygtk
6 pygtk.require('2.0')
7 import gtk
8
9 class AspectFrameExample:
10 def __init__(self):
11 window = gtk.Window(gtk.WINDOW_TOPLEVEL);
12 window.set_title("Aspect Frame")
13 window.connect("destroy", lambda x: gtk.main_quit())
14 window.set_border_width(10)
15
16 # Create an aspect_frame and add it to our toplevel window
17 aspect_frame = gtk.AspectFrame("2x1", # label
18 0.5, # center x
19 0.5, # center y
20 2, # xsize/ysize = 2
21 False) # ignore child's aspect
22 window.add(aspect_frame)
23 aspect_frame.show()
24
25 # Now add a child widget to the aspect frame
26 drawing_area = gtk.DrawingArea()
27
28 # Ask for a 200x200 window, but the AspectFrame will give us a 200x100
29 # window since we are forcing a 2x1 aspect ratio
30 drawing_area.set_size_request(200, 200)
31 aspect_frame.add(drawing_area)
32 drawing_area.show()
33 window.show()
34
35 def main():
36 gtk.main()
37 return 0
38
39 if __name__ == "__main__":
40 AspectFrameExample()
41 main()
|