[modfox]

After clicking into Clip Studio Paint with the pen:

• sometimes it wouldn't draw at all
• sometimes it drew, but flipping to the eraser still drew

Cause

A pen tap raised Clip Studio's window but never made it the active app. A listen-only event tap showed the terminal staying frontmost through the whole pen session. Clip Studio only became active, for about 12ms, on the next trackpad click. macOS delivers tablet proximity events (which carry whether the pen tip or the eraser is in range) only to the frontmost app, so Clip Studio never received them. Qt apps look up the tool by the device ID from the last proximity event, so Clip Studio either didn't recognise the pen or kept a stale tool.

Comparing a trackpad click with a nib click field by field showed nib's events had no source state (synthetic), no event number, no hardware sender ID, and nib's PID as source. Giving them an HID-state source alone didn't let the click activate the app.

Fix

• Activate on press (main.swift): on each tip or eraser press over a normal window (layer 0) of a non-frontmost app, nib activates that app by setting kAXFrontmostAttribute through Accessibility, with a 0.25s AX timeout. If that fails it falls back to NSRunningApplication.activate(). The menu bar, Dock, panels and overlays are left alone. This goes through EventEmitter.willPress.
• Re-announce proximity (EventEmitter): when the frontmost app changes (NSWorkspace.didActivateApplicationNotification), nib re-sends proximity-enter with the current pointer type. It also does this when the pen end changes without a reported exit.
• HID-state event source (EventEmitter, TouchGesture): events now carry sourceStateID = 1 like hardware input, with local event suppression disabled so the keyboard isn't muted after posting.

Testing

• swift test: 47 tests pass. 4 new: proximity re-announce, re-announce on flip in range, willPress fires once per press, HID source state.
• Checked on the Cintiq Pro 24 with a listen-only event tap: a pen tap from the terminal makes Clip Studio frontmost before the press arrives, then pen draws, eraser erases, and pen draws again.

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