busy(n)

✨ NAME ✨

okay bestie, meet busy(n) from Tk Built-In Commands. It’s called busy and its whole thing is: make Tk widgets busy, temporarily blocking user interactions. Iconic behavior, honestly. 💅

🎀 SYNOPSIS 🎀

tk busy window ?options?
tk busy busywindow window
tk busy hold window ?options?
tk busy configure window ?option value?...
tk busy forget window ?window ?...
tk busy current ?pattern?
tk busy status window

💖 DESCRIPTION 💖

The tk busy command is your simple little means to block mouse pointer events from Tk widgets while overriding the widget’s cursor with a configurable busy cursor. Slay for feedback. Important vibe check: this command does not prevent keyboard events from being sent to the widgets made busy. No cap.

🦋 INTRODUCTION 🦋

There are so many times in apps where you want to temporarily restrict what actions the user can take. For example, an app could have a “Run” button that, when pressed, causes some processing to occur. But while the app is busy processing, you probably don’t want the user to be able to click the “Run” button again. You might also want to restrict the user from other tasks, like clicking a “Print” button.

The tk busy command lets you make Tk widgets busy. That means 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, giving feedback that the application/widget is temporarily busy. It’s giving “please hold, main character is processing” energy. ☕

When a widget is made busy, the widget and all of its descendants will ignore pointer events. It’s easy to make an entire panel of widgets busy: just make the toplevel widget (such as .) busy. That is easier and far much more efficient than recursively traversing the widget hierarchy, disabling each widget, and re-configuring its cursor. Lowkey a glow-up for your event handling.

Often, the tk busy command can be used instead of Tk’s grab command. Unlike grab, which restricts all user interactions to one widget, with tk busy you can have more than one widget active (for example, a “Cancel” dialog and a “Help” button). Bestie said multitasking. 🫶

🌸 EXAMPLE 🌸

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
# . . .
tk busy hold .top
update

All the widgets within .top (including .top) are now busy. Using update insures that the tk 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 and free any resources it allocated by using the forget operation.

tk busy forget .top

The busy window has a configurable cursor. You can change the busy cursor using the configure operation.

tk busy configure .top -cursor "watch"

Destroying the widget will also clean up any resources allocated by the tk busy command. We love automatic cleanup. 🧚

👑 OPERATIONS 👑

The following operations are available for the tk busy command:

• tk busy window ?option value?... — Shortcut for the tk busy hold command.
• tk busy busywindow window — Returns the pathname of the busy window (i.e. the transparent window shielding the window appearing busy) created by the tk busy hold command for window, or the empty string if window is not busy.
• tk busy cget window option — Queries the tk busy command configuration options for window. window must be the path name of a widget previously made busy by the hold operation. The command returns the present value of the specified option. option may have any of the values accepted by the hold operation.
• tk busy configure window ?option value?... — Queries or modifies the tk 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 is returned (see Tk_ConfigureInfo for information on the format of this list). 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 window. 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

• tk busy current ?pattern? — Returns the pathnames of all widgets that are currently busy. If a pattern is given, only the path names of busy widgets matching pattern are returned.
• tk busy forget window ?window?... — Releases resources allocated by the tk busy command for window, including the transparent window. User events will again be received 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.
• tk busy hold window ?option value?... — Makes the specified window (and its descendants in the Tk window hierarchy) appear busy. window must be a valid path name of a Tk widget. A transparent window is put in front of the specified window. This transparent window is mapped the next time idle tasks are processed, and the specified window and its descendants will be blocked from user interactions. Normally update should be called immediately afterward to insure that the hold operation is in effect before the application starts its processing. The command returns the pathname of the busy window that was created (i.e. the transparent window shielding the window appearing busy). 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 wait on Windows and watch on other platforms.
• tk busy status window — Returns the status of a widget window. If window presently can not receive user interactions, 1 is returned, otherwise 0.

💜 EVENT HANDLING 💜

🎀 BINDINGS 🎀

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:

tk busy hold .frame.canvas
bind [tk busy busywindow .frame.canvas] <Enter> { ... }

or

set busyWin [tk busy hold .frame.canvas]
bind $busyWin <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. 👀

⌨️ KEYBOARD EVENTS ⌨️

When a widget is made busy, the busy window prevents the widget from gaining keyboard focus when a user clicks on it. But if the widget already had focus, it still may receive keyboard events. The widget can also still receive focus through keyboard traversal. To prevent this, you must move focus to another window and make sure the focus can not go back to the widgets made busy (e.g. by restricting focus to a cancel button).

pack [frame .frame]
pack [text .frame.text]
tk busy hold .frame
pack [button .cancel -text "Cancel" -command exit]
focus .cancel
bind .cancel <Tab> {break}
bind .cancel <Shift-Tab> {break}
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. It also makes sure it’s not possible to leave button .cancel using the keyboard. Periodt. ⌨️✨

🧚 PORTABILITY 🧚

Note that the tk busy command does not currently have any effect on macOS when Tk is built using Aqua support. Noted, bestie.

🔥 SEE ALSO 🔥

grab(n)

⭐ KEYWORDS ⭐

busy, keyboard events, pointer events, window

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🏁 okay that’s the whole busy(n) page, bestie! Source/version: Tk; manual: busy(n); and the footer doesn’t show a date, so no fake date era — periodt. 💖