DroidDeck/docs/development/steam-touch-controls.md

Steam's touch controls

Drawer → Controller → On-screen controls: Steam touch (beta) replaces DroidDeck's own on-screen pad, in a Steam session, with Steam's touch controller: the one the Steam Link apps use. Bindings, action sets, per-game configs, Valve's touch templates, official and community touch configs and Steam Cloud sync are all Steam's; DroidDeck draws the controls and turns touches into the controller's input. The research behind this (how Steam Link's touch controller works, the experiments on the Thor) is in steam-touch-controller.md on the research/steam-touch-controller branch.

How it fits together

SteamTouchControls (overlay)  →  SteamTouchDevice (shared file)  →  libfakeinput /dev/hidraw17
        ↑ layout                          ↑ app / action set                 ↓ 0000:11fb
SteamTouchConfig (Steam's configs)  ←───  output reports  ←──  Steam client: Mobile Touch controller
                                                                      ↓ Steam Input
                                                                  virtual pad → game

• The device. Steam builds its touch controller (Steam Input's Mobile Touch type) for any HID device with the ids 0000:11fb. libfakeinput offers one to the client as /dev/hidraw17 beside the Deck pad, with its sysfs written by SteamDeckPad.prepare(touch = true). It needs a Generic Desktop / Game Pad report descriptor: for a non-Valve vendor id the client ignores a vendor-page device. Offered only with the Deck pad (Steam controller set to Deck); Download/droiddeck-no-steam-touch turns it off.
• The shared file (touchctl in the session's pad directory, FAKE_TOUCHCTL_RING; SteamTouchDevice.kt / TouchRingFile in fakeinput_steam.cpp). The app writes the 40-byte input report under a seqlock, whether the device is plugged in, and the battery; libfakeinput writes back what the client tells the device.
• The report (Steam Link's CVirtualController): bytes 0-7 button bits (the Deck's low word for face buttons, bumpers, triggers, d-pad, Steam, menu buttons; 22/26 stick clicks; 46/47 sticks touched; 27/19/20 trackpads touched; 32-39 macros; 48/49 one- and two-finger macros), 8-15 sticks (int16, Y up), 16-27 three trackpads, 28-33 accelerometer, 34-39 gyro (from PadMotion, in the Deck's units).
• Output reports from the client: 4 = app id and action set (decides which layout is shown), 5/6 = action set layer added/removed, 1 = rumble (also sent to the app's vibration like any pad's), 3 = a setting. Feature report 2 is the battery.
• Plugging. The device is plugged in only while Steam's controls are shown: always in a Steam session with that choice, since a handheld's built-in pad would keep Auto off for good. Unplugging ends the device's report stream (the client lets the controller go); either way libfakeinput sends a udev event through udevmon.c's stand-in monitor (bl_udevmon_inject), since the sandbox gives the client no kernel uevents and its HID discovery would never look again.

Layouts

SteamTouchConfig.load finds the game's touch config: the app's own saved config when the configset (configset_controller_mobile_touch.vdf) points at one, otherwise the file the client's console log says it loaded for the touch controller (a template, an official or a workshop config). touch_layout in it is a hex CVirtualControllerLayouts protobuf: per action set, each control's type, visibility, centre (fractions of the screen) and scale. Controls with no layout go where Steam Link puts them by default; only controls the config's active sources bind are shown.

Editing (drawer → Steam touch layout → Edit): drag, pinch or −/+ to resize, Hide, Reset, Cancel, Save. Save writes touch_layout into the game's autosave config (<account>/config/<appid>/controller_mobile_touch.vdf, made from the config in use) and points the configset at it, as the client does when Steam Link saves a layout; the device is then replugged so the client reads it again. Steam Cloud uploads the file like any autosaved config (seen in userdata/<account>/241100/remotecache.vdf).

Verified on the Thor

• Big Picture: Steam shows "Controller Connected - Remote Play Touch Controller"; the Steam button opens the menu, the d-pad moves focus.
• A game (Geometry Wars: Retro Evolved): Valve's Gamepad touch template loaded, the stick flies the ship.
• A saved layout survives a session restart and was uploaded to Steam Cloud.
• Touch menus: a touch menu bound to a trackpad is drawn by Steam's own overlay when the trackpad is held.
• Unplug and replug mid-session; two touch devices at once (research branch).

Open

• Gyro: motion reaches the device's report, but a gyro_to_joystick binding did not move the stick in the one test made (injected rates, sensors paused). Needs a look at what the client wants (calibration, an enable setting).
• Custom touch icons (SetTouchIconData on Steam Link) are not drawn; controls use text labels.
• Not tried on a retail phone with SELinux enforcing (the Deck pad's sysfs works there).

Icons, labels and colours

Each control shows what its binding carries, as Steam Link does: a binding is <action>, <label>, <icon>, <#foreground #background> (e.g. xinput_button A, Attack, ghost_010_wpn_0070.png, #FFFFFF #AD0000). Icons are looked up as Steam does: the game's own TouchMenuIcons folder, then tenfoot/resource/images/library/controller/binding_icons (459 icons). They are drawn as Steam draws binding icons: the icon multiplied by the foreground colour on a disc of the background colour. A binding with no icon shows its label, else a glyph for what it presses (LB, Esc, ⏎…), else the button's own name.

In the layout editor, Icon opens a picker for the selected control (a D-pad direction: the one tapped): label, an icon from the game's own and Steam's library, foreground and background from Steam's binding-icon palette. Colour sets the layout's colour and opacity. Save rewrites only those binding strings in the game's touch config (byte for byte otherwise) along with touch_layout. Verified with Castle Crashers (its config ships icons on the shoulders and stick click): icons drawn; A set to a knife, white on red, "Attack" and B to another icon; both written in Steam's format and loaded back after a session restart.

The pickers are panels in the session's window, not dialogs.

Steam Link's menu and editor

• Menu button (…): touch input Controller / Mouse / Controller + mouse; mouse as direct touch or trackpad; trackpad speed. Like Steam Link these are per game, saved in the game's touch_layout (CVirtualControllerLayouts fields 2-4), so they sync with the config. In Controller mode touches outside the controls do nothing; in Mouse mode only the menu button is drawn and the screen is the mouse. Also: vibrate on touch, fade when not touched, gyroscope (Steam Link's global options, kept per device), the layout editor and DroidDeck's own menu.
• Editor: ◀ ▶ steps through every action set of the game's config (each saved to its own layout), Add (the tray: bound controls not on screen, and the optional Paste button), More (colour and opacity, copy a layout, paste it into another game, reset), W−/W+/H−/H+ and axis-wise pinch for a control's width and height (ovals).
• Paste control: Ctrl+V into the session (the Android clipboard is shared with it).

Not done: Steam Link's magnifying glass / pinch zoom, record and playback of input, shake to fade, and its custom tray drag-in animation. Gyro: the report now carries motion only while the client asks (setting report 0x30) at Steam Link's scale (1000 °/s full scale); a gyro_to_joystick binding still did not move a game's stick with injected rates, so gyro remains unconfirmed.

DroidDeck's look

With feature parity reached, the overlay keeps Steam Link's controls (outlined, white, Steam's face colours) but is DroidDeck's own: the guide button carries the split-D mark (artwork/droiddeck-mark.svg) instead of Steam's logo, and the menu, tray and pickers use the app's palette (ui/Theme.kt: surfaces #121417 / #1A1D22, hairlines #262A31, text #F2F4F7 / #9AA3AF, accent #1A9FFF), rounded corners and switches rather than Steam Link's navy panels and blue gradient tiles.

Shake to hide: a toggle in the menu (Steam Link's shake_fade). Three jolts above 2.3 g within about a second hide the controls (touches then reach the game as with the controls off); shaking again brings them back.