DPI presets

Set a Logitech mouse's pointer resolution and keep an ordered list of DPI presets, backed by HID++ 0x2201 adjustableDpi, or 0x2202 extendedAdjustableDpi when the older feature is absent. The slider snaps to the values your device actually supports, and the presets can be cycled from a hardware button so you never have to open the window to change DPI.

From the GUI

Select the mouse in the device gallery and open its Pointer tab; the DPI card holds:

• DPI slider — its range is the device's own supported DPI list (min–max, with the step set to the smallest gap between adjacent stops). Dragging only updates the on-screen value; the new DPI is written to the mouse when you release the slider, and the value snaps to the nearest stop the device reports. A single-DPI mouse shows a fixed value instead of a slider.
• Range label — reads {min}–{max} · step {n} once the device's capabilities are known, or a status line while OpenLogi is offline, still reading, or if the read failed.
• Preset chips — each preset is a clickable chip. Clicking one snaps its value to the device grid, applies it, and writes it to the mouse. The chip matching the current DPI is highlighted as active. The × on a chip removes that preset, and + Add appends the current DPI to the list.

Capabilities are discovered lazily the first time the DPI panel renders. If that discovery fails, the panel shows a clickable retry line that re-arms it for the selected device.

The DPI you commit lives in the mouse's RAM and is lost on a power cycle, so OpenLogi also records it as dpi under the device's config block and the agent re-applies it whenever the device reconnects.

Cycling from a button

Two actions drive the preset list from a hardware button:

• CycleDpiPresets — steps to the next preset, wrapping from the last back to the first. This is the default action for the mode-shift (DpiToggle) button, and it is the only DPI-cycle action offered in the GUI's action picker.
• SetDpiPreset — jumps straight to a zero-based preset index (0 is the first preset). It carries that index as data, so it is not in the picker; bind it by hand-editing config.toml.

An empty preset list makes both actions a no-op. Editing the presets or switching devices resets the cycle position to the first entry, since the list changed.

In the config

The list persists per device as dpi_presets under [devices.<key>] in the config:

[devices."receiver:aabbccdd:slot:1"]
dpi_presets = [800, 1600, 3200]
dpi = 1600                        # last committed value, re-applied on reconnect

It is an ordered array of integers, omitted entirely while empty. See Configuration for the full action vocabulary and Per-app profiles for assigning a different DPI action to a button in each app. The preset list itself stays device-wide.

Status: macOS, Linux, and Windows; the device-side DPI write works wherever HID++ does, and firing it from a button rides the OS hook (CGEventTap on macOS, evdev on Linux, WH_MOUSE_LL on Windows). See 0x2201 adjustableDpi for the protocol detail and the roadmap for what's wired up.