[omartelo]

Summary

• A mouse wheel notch on Wayland reaches Gio as one 150-pixel delta (the compositor's 15 times Gio's discrete scale of 10). The terminal turned it into about eight rows in a single frame, a visible jump, and sent about eight wheel steps to a program tracking the mouse: nvim scrolls three lines a step, so a notch ran through half a screen.
• A delta of whole notches is now read as a wheel: three rows a notch through scrollback or as arrow keys (as Ghostty and xterm scroll), one wheel step a notch to a program tracking the mouse, which scrolls its own distance.
• Any other delta is a touchpad's and keeps the old rule, a row per cell height. Gio reports both the same way, so the size is what tells them apart.
• Whatever a scroll owes is paid out over the coming frames, a third of the rest per frame, instead of in the one that received it. A turn the other way drops what was still owed.
• wheelNotch per platform, from Gio's own scaling: 150 on Wayland and 10 on X11 (picked by WAYLAND_DISPLAY, the check Gio itself opens Wayland on), 120 on Windows (WHEEL_DELTA), 10 on macOS.
• CHANGELOG [Unreleased] › Fixed entry.

Test plan

• TestWheelNotchesScrollTheScrollbackOverSeveralFrames: two notches up leave the viewport where it was until a frame, move part of the way on the first and six rows once drained.
• TestWheelNotchesReachAFullScreenProgramOverSeveralFrames: three notches send nine arrow keys, or three wheel steps under mouse tracking, spread over frames.
• TestTouchpadDeltasUnderACellStillScroll: four quarter-row deltas still make one row, as arrow keys and as a wheel step.
• TestMouseGoesToTheProgramThatTracksIt and TestWheelMovesTheCursorOnTheAlternateScreen now scroll by notches and collect what the frames send: the contract changed, a wheel now counts notches and pays out over frames.
• Wheel deltas measured in a rig window on Hyprland: every notch arrived as exactly ±150, touchpad deltas as 1 to 5 pixels.
• The wheel tests pass under both the Wayland and the X11 notch size; local gate in native/: gofmt, go vet ./..., go test ./....