Gestures

The MDD displays have no physical button, so the glass provides wake, lock, home, back and escape. A small set of system gestures from the screen edges does the work of those buttons, following the iPhone, and a smaller set of page gestures acts on the page itself. Each gesture means the same thing on every page.

Figure 1: The system gesture zones on the 720 × 720 canvas.

Give each gesture one meaning everywhere

A gesture means the same thing on every page. No page gives a system gesture a meaning of its own, and no page blocks one.

• Reason. A gesture that changes meaning from page to page cannot become a habit, and a sailor working by feel at night relies on habit.
• Source. ux/specs/interaction/touch.md, principles. UX concept register, SCY-SW-NOTE-UXCONCEPTS-001, "One meaning per gesture across the product".

Use the system gestures for what a button would do

A system gesture starts within 30 px of a screen edge and travels at least 120 px inward. It takes priority over any page gesture.

Gesture	Locked	Unlocked
Swipe up from the bottom edge	Unlock, returning to the last page	Home, from anywhere
Swipe up from the bottom edge and pause before lifting	Unlock only	The page selector, a set of shortcuts to every page
Swipe down from the top-right corner	Nothing	The control panel: brightness, night mode, lock and settings
Swipe down from the rest of the top edge	Nothing	The alerts list
Swipe in from the left or right edge	Nothing	The next or previous page, as a page swipe

• The top-right corner is the right third of the top edge, from x = 480 to the corner, kept inside the MDD500 corner arc.
• A pause is the finger held still for 300 ms after the swipe has travelled 120 px.
• Unlock needs a longer swipe, at least 240 px, to reject water running down the glass.
• Reason. Each gesture copies an iPhone gesture with the same purpose, so it is already learned. The swipe up also matches the MDD400's own unlock.
• Source. ux/specs/interaction/touch.md, system gestures.

Treat a swipe from a side edge as a page swipe

A swipe that starts at a side edge changes page, exactly like a swipe that starts mid-page. There is no back gesture from the side.

• Reason. A gloved finger cannot reliably aim for an edge or away from one, so the two must mean the same thing. Back is provided by a visible control instead, as described under Page navigation.
• Source. ux/specs/interaction/touch.md, system gestures.

Use the page gestures for the page itself

Gesture	Meaning
Swipe left or right, anywhere on the page	Next or previous page
Tap	Act on the control under the finger
Long press, 500 ms	Open the options for the item under the finger, such as the data a cell shows
Long press, then drag	Move the item, such as a data cell to another position
Swipe down on a dialog or panel	Close it
Drag on a slider or picker	Change its value

• Every drag has a non-drag alternative, as described under Touch accessibility.
• Source. ux/specs/interaction/touch.md, page gestures.

Tune the thresholds for a moving boat

The gesture thresholds are set wider and longer than phone defaults, because the boat moves and the finger may be gloved.

Setting	Value	Basis
Long press	500 ms	LVGL and Android use 400 ms. Lengthened for motion
Long-press repeat	100 ms	LVGL default, for a stepper held down
Tap cancel distance	16 px	LVGL uses 10 px. Widened for a moving boat
Gesture distance	50 px	LVGL default
Edge zone	30 px	Inside the visible window of both MIPI products
Unlock and edge travel	240 px and 120 px	One third and one sixth of the screen

• Source. ux/specs/interaction/touch.md, thresholds.

Not yet ruled

• The long-press time, the tap-cancel distance and the 300 ms pause, which are assumptions until tested at sea with wet hands and gloves.
• How a tap on a data cell, which selects the series its graph strip plots, sits beside a tap on the cell's unit, which toggles the unit. The proposal is separate hit zones, the unit area toggling and the value area selecting.

These are tracked in ux/specs/interaction/touch.md, open items.