21.3. Methods
21.3.1. Setting up the source widget
The method drag_source_set() specifies a set of target types for a drag operation on a widget.
widget.drag_source_set(start_button_mask, targets, actions ) |
The parameters signify the following:
- widget specifies the drag
source widget
start_button_mask specifies a bitmask of buttons that can start the drag (e.g. BUTTON1_MASK)
targets specifies a list of target data types the drag will support
actions specifies a bitmask of possible actions for a drag from this window
(target, flags, info) |
target specifies a string representing the drag type.
flags restrict the drag application.
flags
can be set to 0 or the following flags:
TARGET_SAME_APP # Target will only be selected for drags within a single application. TARGET_SAME_WIDGET # Target will only be selected for drags within a single widget. |
info is an application assigned integer identifier.
If a widget is no longer required to act
as a source for drag-and-drop operations, the method
drag_source_unset()
can be used to remove a set of drag-and-drop target types.
widget.drag_source_unset() |
21.3.2. Signals on the source widget:
The source widget is sent the following signals during a drag-and-drop operation.Table 21-1. Source widget signals
| drag_begin | def drag_begin_cb(widget, drag_context, data): |
| drag_motion | def drag_motion_cb(widget, drag_context, x, y, time, data): |
| drag_data_get | def drag_data_get_cb(widget, drag_context, selection_data, info, time, data): |
| drag_data_delete | def drag_data_delete_cb(widget, drag_context, data): |
| drag_drop | def drag_drop_cb(widget, drag_context, x, y, time, data): |
| drag_end | def drag_end_cb(widget, drag_context, data): |
21.3.3. Setting up a destination widget:
drag_dest_set() specifies that this widget can receive drops and specifies what types of drops it can receive.drag_dest_unset() specifies that
the widget can no longer
receive drops.
widget.drag_dest_set(flags, targets, actions) widget.drag_dest_unset() |
flags specifies what actions GTK should take on behalf of widget
for drops on it. The possible values of flags are:
DEST_DEFAULT_MOTION If set for a widget, GTK, during a drag over this widget will check if the drag matches this widget's list of possible targets and actions. GTK will then call drag_status() as appropriate. DEST_DEFAULT_HIGHLIGHT If set for a widget, GTK will draw a highlight on this widget as long as a drag is over this widget and the widget drag format and action is acceptable. DEST_DEFAULT_DROP If set for a widget, when a drop occurs, GTK will check if the drag matches this widget's list of possible targets and actions. If so, GTK will call drag_data_get() on behalf of the widget. Whether or not the drop is succesful, GTK will call drag_finish(). If the action was a move, then if the drag was succesful, then TRUE will be passed for the delete parameter to drag_finish(). DEST_DEFAULT_ALL If set, specifies that all default actions should be taken. |
actions is a bitmask of possible actions for a drag onto this
widget. The possible values (defined in GDK.py) that can be or'd for actions
are:
ACTION_DEFAULT ACTION_COPY ACTION_MOVE ACTION_LINK ACTION_PRIVATE ACTION_ASK |
21.3.4. Signals on the destination widget:
The destination widget is sent the following signals during a drag-and-drop operation.Table 21-2. Destination widget signals
| drag_data_received | def drag_data_received_cb(widget, drag_context, x, y, selection_data, info, time, data): |
The dragndrop.py example program demonstrates the use of drag and drop in one application. A button with a xpm pixmap is the source for the drag; it provides both text and xpm data. A layout widget is the destination for the xpm drop while a button is the destination for the text drop. Figure 21.1 illustrates the program display after an xpm drop has been made on the layout and a text drop has been made on the button:
Figure 21.1 Drag and Drop Example
1 #!/usr/bin/env python
2
3 # example dragndrop.py
4
5 import gtk
6 import GDK
7 import string, time
8
9 import gtkxpm
10
11 class DragNDropExample:
12 HEIGHT = 600
13 WIDTH = 600
14 TARGET_TYPE_TEXT = 80
15 TARGET_TYPE_PIXMAP = 81
16 fromImage = [ ( "text/plain", 0, TARGET_TYPE_TEXT ),
17 ( "image/x-xpixmap", 0, TARGET_TYPE_PIXMAP ) ]
18 toButton = [ ( "text/plain", 0, TARGET_TYPE_TEXT ) ]
19 toCanvas = [ ( "image/x-xpixmap", 0, TARGET_TYPE_PIXMAP ) ]
20
21 def layout_resize(self, widget, event):
22 x, y, width, height = widget.get_allocation()
23 if width > self.lwidth or height > self.lheight:
24 self.lwidth = max(width, self.lwidth)
25 self.lheight = max(height, self.lheight)
26 widget.set_size(self.lwidth, self.lheight)
27
28 def makeLayout(self):
29 self.lwidth = self.WIDTH
30 self.lheight = self.HEIGHT
31 box = gtk.GtkVBox(gtk.FALSE,0)
32 box.show()
33 table = gtk.GtkTable(2, 2, gtk.FALSE)
34 table.show()
35 box.pack_start(table, gtk.TRUE, gtk.TRUE, 0)
36 layout = gtk.GtkLayout()
37 self.layout = layout
38 layout.set_size(self.lwidth, self.lheight)
39 layout.connect("size_allocate", self.layout_resize)
40 layout.show()
41 table.attach(layout, 0, 1, 0, 1, gtk.FILL|gtk.EXPAND,
42 gtk.FILL|gtk.EXPAND, 0, 0)
43 # create the scrollbars and pack into the table
44 vScrollbar = gtk.GtkVScrollbar(None)
45 vScrollbar.show()
46 table.attach(vScrollbar, 1, 2, 0, 1, gtk.FILL|gtk.SHRINK,
47 gtk.FILL|gtk.SHRINK, 0, 0)
48 hScrollbar = gtk.GtkHScrollbar(None)
49 hScrollbar.show()
50 table.attach(hScrollbar, 0, 1, 1, 2, gtk.FILL|gtk.SHRINK,
51 gtk.FILL|gtk.SHRINK,
52 0, 0)
53 # tell the scrollbars to use the layout widget's adjustments
54 vAdjust = layout.get_vadjustment()
55 vScrollbar.set_adjustment(vAdjust)
56 hAdjust = layout.get_hadjustment()
57 hScrollbar.set_adjustment(hAdjust)
58 layout.connect("drag_data_received", self.receiveCallback)
59 layout.drag_dest_set(gtk.DEST_DEFAULT_MOTION |
60 gtk.DEST_DEFAULT_HIGHLIGHT |
61 gtk.DEST_DEFAULT_DROP,
62 self.toCanvas, GDK.ACTION_COPY)
63 self.addImage(gtkxpm.gtk_xpm, 0, 0)
64 button = gtk.GtkButton("Text Target")
65 button.show()
66 button.connect("drag_data_received", self.receiveCallback)
67 button.drag_dest_set(gtk.DEST_DEFAULT_MOTION |
68 gtk.DEST_DEFAULT_HIGHLIGHT |
69 gtk.DEST_DEFAULT_DROP,
70 self.toButton, GDK.ACTION_COPY)
71 box.pack_start(button, gtk.FALSE, gtk.FALSE, 0)
72 return box
73
74 def addImage(self, xpm, xd, yd):
75 hadj = self.layout.get_hadjustment()
76 vadj = self.layout.get_vadjustment()
77 style = self.window.get_style()
78 pixmap, mask = gtk.create_pixmap_from_xpm_d(
79 self.window.get_window(), style.bg[gtk.STATE_NORMAL], xpm)
80 pixmapWidget = gtk.GtkPixmap(pixmap, mask)
81 button = gtk.GtkButton()
82 button.add(pixmapWidget)
83 width, height = map(string.atoi, string.split(xpm[0])[:2])
84 button.connect("drag_data_get", self.sendCallback)
85 button.drag_source_set(GDK.BUTTON1_MASK, self.fromImage,
86 GDK.ACTION_COPY)
87 button.show_all()
88 # have to adjust for the scrolling of the layout - event location
89 # is relative to the viewable not the layout size
90 self.layout.put(button, int(xd+hadj.value), int(yd+vadj.value))
91 return
92
93 def sendCallback(self, widget, context, selection, targetType, eventTime):
94 if targetType == self.TARGET_TYPE_TEXT:
95 now = time.time()
96 str = time.ctime(now)
97 selection.set(selection.target, 8, str)
98 elif targetType == self.TARGET_TYPE_PIXMAP:
99 selection.set(selection.target, 8,
100 string.join(gtkxpm.gtk_xpm, '\n'))
101
102 def receiveCallback(self, widget, context, x, y, selection, targetType,
103 time):
104 if targetType == self.TARGET_TYPE_TEXT:
105 label = widget.children()[0]
106 label.set_text(selection.data)
107 elif targetType == self.TARGET_TYPE_PIXMAP:
108 self.addImage(string.split(selection.data, '\n'), x, y)
109
110 def __init__(self):
111 self.window = gtk.GtkWindow(gtk.WINDOW_TOPLEVEL)
112 self.window.set_default_size(300, 300)
113 self.window.connect("destroy", gtk.mainquit)
114 self.window.show()
115 layout = self.makeLayout()
116 self.window.add(layout)
117
118 def main():
119 gtk.mainloop()
120
121 if __name__ == "__main__":
122 DragNDropExample()
123 main()
|