mirror of
https://gitlab.freedesktop.org/libinput/libinput.git
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53 lines
2.2 KiB
Text
53 lines
2.2 KiB
Text
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/**
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@page palm_detection Palm detection
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Palm detection tries to identify accidental touches while typing.
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On most laptops typing on the keyboard generates accidental touches on the
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touchpad with the palm (usually the area below the thumb). This can lead to
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cursor jumps or accidental clicks.
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Interference from a palm depends on the size of the touchpad and the position
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of the user's hand. Data from touchpads showed that almost all palm events on a
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Lenovo T440 happened in the left-most and right-most 5% of the touchpad. The
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T440 series has one of the largest touchpads, other touchpads are less
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affected by palm touches.
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@section palm_exclusion_zones Palm exclusion zones
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libinput enables palm detection on the edge of the touchpad. Two exclusion
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zones are defined on the left and right edge of the touchpad.
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If a touch starts in the exclusion zone, it is considered a palm and the
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touch point is ignored. However, for fast cursor movements across the
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screen, it is common for a finger to start inside an exclusion zone and move
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rapidly across the touchpad. libinput detects such movements and avoids palm
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detection on such touch sequences.
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In the diagram below, the exclusion zones are painted red.
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Touch 'A' starts inside the exclusion zone and moves
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almost vertically. It is considered a palm and ignored for cursor movement,
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despite moving out of the exclusion zone.
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Touch 'B' starts inside the exclusion zone but moves horizontally out of the
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zone. It is considered a valid touch and controls the cursor.
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@image html palm-detection.svg
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@section trackpoint-disabling Palm detection during trackpoint use
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If a device provides a <a
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href="http://en.wikipedia.org/wiki/Pointing_stick">trackpoint</a>, it is
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usually located above the touchpad. This increases the likelyhood of
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accidental touches whenever the trackpoint is used.
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libinput disables the touchpad whenver it detects trackpoint activity for a
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certain timeout until after trackpoint activity stops. Touches generated
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during this timeout will not move the pointer, and touches started during
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this timeout will likewise not move the pointer (allowing for a user to rest
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the palm on the touchpad while using the trackstick).
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If the touchpad is disabled, the @ref t440_support "top software buttons"
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remain enabled.
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*/
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