busy(BLT 2.4) busy(BLT 2.4)
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busy - Make Tk widgets busy, temporarily blocking user interactions.
busy hold window ?option value?...
busy release window ?window?...
busy configure window ?option value?...
busy forget window ?window?...
busy isbusy ?pattern?
busy names ?pattern?
busy status window
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The busy command provides a simple means to block keyboard, button, and
pointer events from Tk widgets, while overriding the widget's cursor
with a configurable busy cursor.
There are many times in applications where you want to temporarily
restrict what actions the user can take. For example, an application
could have a "run" button that when pressed causes some processing to
occur. But while the application is busy processing, you probably
don't want the the user to be able to click the "run" button again.
You may also want restrict the user from other tasks such as clicking a
"print" button.
The busy command lets you make Tk widgets busy. This means that user
interactions such as button clicks, moving the mouse, typing at the
keyboard, etc. are ignored by the widget. You can set a special cursor
(like a watch) that overrides the widget's normal cursor, providing
feedback that the application (widget) is temporarily busy.
When a widget is made busy, the widget and all of its descendents will
ignore events. It's easy to make an entire panel of widgets busy. You
can simply make the toplevel widget (such as ".") busy. This is easier
and far much more efficient than recursively traversing the widget
hierarchy, disabling each widget and re-configuring its cursor.
Often, the busy command can be used instead of Tk's grab command.
Unlike grab which restricts all user interactions to one widget, with
the busy command you can have more than one widget active (for example,
a "cancel" dialog and a "help" button).
You can make several widgets busy by simply making its ancestor widget
busy using the hold operation.
frame .top
button .top.button; canvas .top.canvas
pack .top.button .top.canvas
pack .top
. . .
busy hold .top
update
All the widgets within .top (including .top) are now busy. Using
update insures that busy command will take effect before any other user
events can occur.
When the application is no longer busy processing, you can allow user
interactions again by the release operation.
busy release .top
The busy window has a configurable cursor. You can change the busy
cursor using the configure operation.
busy configure .top -cursor "watch"
Finally, when you no longer need to the busy window, invoke the forget
operation to free any resources it allocated.
busy forget .top
Destroying the widget will also clean up any resources allocated by the
busy command.
The following operations are available for the busy command:
busy hold window ?option value?...
Makes the widget window (and its descendants in the Tk window
hierarchy) busy. Window must be a valid path name of a Tk widget.
The busy window is mapped the next time idle tasks are
processed, and the widget and its descendants will be blocked
from user interactions. All events in the widget window and its
descendants are ignored. Normally update should be called immediately
afterward to insure that the hold operation is in effect
before the application starts its processing. The following configuration
options are valid:
-cursor cursorName
Specifies the cursor to be displayed when the widget is
made busy. CursorName can be in any form accepted by
Tk_GetCursor. The default cursor is watch.
busy configure window ?option value?...
Queries or modifies the busy command configuration options for
window. Window must be the path name of a widget previously made
busy by the hold operation. If no options are specified, a list
describing all of the available options for window (see Tk_Con-
figureInfo for information on the format of this list) is
returned. If option is specified with no value, then the command
returns a list describing the one named option (this list
will be identical to the corresponding sublist of the value
returned if no option is specified). If one or more
option-value pairs are specified, then the command modifies the
given widget option(s) to have the given value(s); in this case
the command returns the empty string. Option may have any of
the values accepted by the hold operation.
Please note that the option database is referenced through win-
dow. For example, if the widget .frame is to be made busy, the
busy cursor can be specified for it by either option command:
option add *frame.busyCursor gumby
option add *Frame.BusyCursor gumby
busy forget window ?window?...
Releases resources allocated by the busy command for window,
including the busy window. User events will again be received
again by window. Resources are also released when window is
destroyed. Window must be the name of a widget specified in the
hold operation, otherwise an error is reported.
busy isbusy ?pattern?
Returns the pathnames of all widgets that are currently busy.
If a pattern is given, the path names of busy widgets matching
pattern are returned.
busy names ?pattern?
Returns the pathnames of all widgets that have previously been
made busy (i.e. a busy window is allocated and associated with
the widget). It makes no difference if the window is currently
busy or not. If a pattern is given, the path names of busy widgets
matching pattern are returned.
busy release window ?window?...
Restores user interactions to the widget window again. This
differs from the forget operation in that the busy window is not
destroyed, but simply unmapped. Window must be the name of a
widget specified in a hold operation, otherwise an error is
reported.
busy status window
Returns the status of a widget window previously made busy. An
error is reported if window was never made busy, or the forget
operation was invoked (i.e. does not currently have a busy window
associated with it). If window is presently can not receive
user interactions, 1 is returned, otherwise 0.
The event blocking feature is implemented by creating and mapping a
transparent window that completely covers the widget. When the busy
window is mapped, it invisibly shields the widget and its hierarchy
from all events that may be sent. Like Tk widgets, busy windows have
widget names in the Tk window hierarchy. This means that you can use
the bind command, to handle events in the busy window.
busy hold .frame.canvas
bind .frame.canvas_Busy <Enter> { ... }
Normally the busy window is a sibling of the widget. The name of the
busy window is "widget_Busy" where widget is the name of the widget to
be made busy. In the previous example, the pathname of the busy window
is ".frame.canvas_Busy" The exception is when the widget is a toplevel
widget (such as ".") where the busy window can't be made a sibling.
The busy window is then a child of the widget named "widget._Busy"
where widget is the name of the toplevel widget. In the following
example, the pathname of the busy window is "._Busy"
busy hold .
bind ._Busy <Enter> { ... }
ENTER/LEAVE EVENTS
Mapping and unmapping busy windows generates Enter/Leave events for all
widgets they cover. Please note this if you are tracking Enter/Leave
events in widgets.
When a widget is made busy, the widget is prevented from gaining the
keyboard focus by the busy window. But if the widget already had focus,
it still may received keyboard events. To prevent this, you must move
focus to another window.
busy hold .frame
label .dummy
focus .dummy
update
The above example moves the focus from .frame immediately after invoking
the hold so that no keyboard events will be sent to .frame or any
of its descendants.
busy, keyboard events, pointer events, window, cursor
busy(BLT 2.4)
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