[Bug]: Middle-click paste does not work in integrated terminal on Linux (Wayland / KDE)

[grpace]

What happened

Middle-clicking inside the integrated terminal window does nothing. To paste text into the terminal, the user is forced to either right-click and select "Paste" from the context menu, or press Ctrl + Shift + V.

Middle-click paste is the standard, foundational workflow across Linux terminal emulators (Konsole, Alacritty, GNOME Terminal, Kitty) as well as integrated terminals in other editors/IDEs (VS Code, JetBrains). It should work out of the box in T3 Code's terminal as well.

Steps to Reproduce

1. Highlight any text in T3 Code or an external application (populating the Linux primary selection buffer).
2. Move the cursor into the T3 Code integrated terminal pane.
3. Middle-click (press the mouse wheel / Button 2).
4. Result: Nothing happens. The click is ignored or swallowed.
5. Expected: The highlighted text is pasted directly into the active terminal shell.

Technical Context

• T3 Code's integrated terminal is rendered via xterm.js / canvas inside Electron.
• In Chromium/Electron on Linux, middle-clicks (auxclick / event.button === 1) on canvas and non-input DOM elements are dropped or treated as autoscroll by default rather than triggering OS primary selection paste.
• In editors like VS Code, the integrated terminal explicitly listens for middle-click pointer events and bridges the selection/clipboard buffer to the pty process.
• When running natively on Wayland (--ozone-platform=wayland), handling needs to ensure primary selection protocol (wp_primary_selection_device_manager_v1) support is wired to the terminal component.

Environment

• App Version: T3 Code (Alpha) v0.0.40 (AppImage)
• OS: Fedora Linux 44 (KDE Plasma Desktop Edition)
• Kernel: Linux 7.1.13-200.fc44.x86_64
• Session Type: Wayland (XDG_SESSION_TYPE=wayland, --ozone-platform=wayland)
• Desktop Environment: KDE Plasma

[juliusmarminge]

Thanks for the report — this is a real gap in the Linux terminal contract, and it is still missing on current main (and on 0.0.40).

What the code does today

The integrated terminal is Ghostty WASM drawn on a canvas, not xterm.js. Paste already works from Ctrl+Shift+V, Shift+Insert, and the right-click menu. Middle-click is not a paste path.

In apps/web/src/terminal/ghostty/surface.ts:

• Browser button 1 (middle) is mapped to Ghostty button 3 via ghosttyMouseButton.
• onPointerDown only starts a selection on left-click (if (event.button !== 0) return).
• When application mouse tracking is on (vim/less/etc.), middle-click is forwarded to the PTY as a mouse press — it is not pasted.
• There is no auxclick handler.

Clipboard I/O is CLIPBOARD-only (navigator.clipboard.readText / writeText, plus Electron clipboard.writeText). Selecting text in the terminal does not write the Linux PRIMARY buffer, and nothing reads PRIMARY on click. Chromium/Wayland can still drop or reinterpret auxclick, but T3 never pastes on that button even when the event arrives.

Not a duplicate of the keyboard-clipboard work

• [Bug]: Shift+Insert does not paste in the integrated terminal #5936 / fix(web): support Shift+Insert terminal paste #5982 — Shift+Insert paste (merged). Keyboard only.
• Integrated terminal ignores Ctrl+Insert copy, breaking tiling-WM universal-clipboard shortcuts #8525 — Ctrl+Insert copy. Keyboard only.
• fix(terminal): honor Linux clipboard shortcuts #7361 — open PR for Linux keyboard shortcuts and menu accelerators. It does not implement middle-click paste or PRIMARY selection. This issue should not ride that PR.

Fix shape

1. Treat middle-click as paste when mouse tracking is off, using the same bracketed-paste path as pasteFromClipboard.
2. On desktop Linux, read/write PRIMARY via Electron clipboard.readText('selection') / writeText(text, 'selection'). navigator.clipboard cannot see PRIMARY.
3. Write PRIMARY when the terminal selection changes so highlight-then-middle-click works inside T3 as well as from other apps.
4. Keep current mouse-tracking behavior (forward the click to the app).
5. Verify on both X11 and Wayland (--ozone-platform=wayland). Wayland PRIMARY (wp_primary_selection) is a second layer after the gesture and Electron clipboard wiring exist.

Workaround: Ctrl+Shift+V or right-click → Paste (CLIPBOARD).

Accepting this as a Linux desktop bug. No merged fix.

[juliusmarminge]

Fixed by #11018 (middle-click paste in the integrated terminal on Linux).