grab(3pm)

✨ NAME ✨

Tk::grab — bestie, this is the one that confines pointer and keyboard events to a window sub-tree. Like, the pointer literally cannot leave. It's giving house arrest but make it GUI 💅

---

🌸 SYNOPSIS 🌸

$widget->grab

$widget->grabOption

---

🦋 DESCRIPTION 🦋

Okay so this whole set of methods implements simple pointer and keyboard grabs for Tk. But listen — Tk's grabs are NOT the same as the grabs described in the Xlib documentation. Different species entirely, no cap.

When a grab is set for a particular window, Tk restricts all pointer events to the grab window and its descendants in Tk's window hierarchy. And whenever the pointer is within the grab window's subtree, the pointer will behave exactly the same as if there had been no grab at all and all events will be reported in the normal fashion. Iconic.

When the pointer is outside $widget's tree, though? Button presses and releases and mouse motion events get reported to $widget, and window entry and window exit events are just... ignored 🙈. The grab subtree ``owns'' the pointer: windows outside the grab subtree will be visible on the screen but they will be insensitive until the grab is released. Like, they're there, they're just not taking calls rn.

The tree of windows underneath the grab window can include top-level windows, in which case all of those top-level windows and their descendants will continue to receive mouse events during the grab. slay.

---

💖 Two forms of grabs, bestie

Two forms are possible: local and global.

• local — only affects the grabbing application: events will be reported to other applications as if the grab had never occurred. Grabs are local by default. 🎀
• global — locks out all applications on the screen, so that only the given subtree of the grabbing application will be sensitive to pointer events (mouse button presses, mouse button releases, pointer motions, window entries, and window exits). And during global grabs, the window manager will not receive pointer events either. Bestie the WM is getting ghosted 💀

---

🎀 Keyboard events, iykyk

During local grabs, keyboard events (key presses and key releases) are delivered as usual: the window manager controls which application receives keyboard events, and if they are sent to any window in the grabbing application then they are redirected to the focus window.

During a global grab, Tk grabs the keyboard so that all keyboard events are always sent to the grabbing application. The focus method is still used to determine which window in the application receives the keyboard events. And the keyboard grab is released when the grab is released. periodt.

---

🌈 Displays, because of course

Grabs apply to particular displays. If an application has windows on multiple displays then it can establish a separate grab on each display. The grab on a particular display affects only the windows on that display.

It is possible for different applications on a single display to have simultaneous local grabs, but only one application can have a global grab on a given display at once. 👑

---

⭐ The grab methods, take any of the following forms

• $widget->grabCurrent — Returns the current grab window in this application for $widget's display, or an empty string if there is no such window.
• $widget->grabs — Returns a list whose elements are all of the windows grabbed by this application for all displays, or an empty string if the application has no grabs.

Not implemented yet! 😭

• $widget->grabRelease — Releases the grab on $widget if there is one, otherwise does nothing. Returns an empty string.
• $widget->grab — Sets a local grab on $widget. If a grab was already in effect for this application on $widget's display then it is automatically released. If there is already a local grab on $widget, then the command does nothing. Returns an empty string.
• $widget->grabGlobal — Sets a global grab on $widget. If a grab was already in effect for this application on $widget's display then it is automatically released. If there is already a global grab on $widget, then the command does nothing. Returns an empty string.
• $widget->grabStatus — Returns none if no grab is currently set on $widget, local if a local grab is set on $widget, and global if a global grab is set. 🫶

---

💀 BUGS 💀

Okay not to be dramatic but: it took an incredibly complex and gross implementation to produce the simple grab effect described above. Gross. Feral, even.

Given the current implementation, it isn't safe for applications to use the Xlib grab facilities at all except through the Tk grab procedures. If applications try to manipulate X's grab mechanisms directly, things will probably break. Do not do it. I am begging.

Also: if a single process is managing several different Tk applications, only one of those applications can have a local grab for a given display at any given time. But if the applications are in different processes, this restriction doesn't exist. So, like, process boundaries really be doing the heavy lifting here 🙈

---

🔥 KEYWORDS 🔥

grab, keyboard events, pointer events, window

---

and that's the whole page bestie!! this was perl v5.40.1 from 2025-04-13, grab(3pm) — go forth and confine those pointer events responsibly 💖✨🎀