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fix: 修复上下红外框触摸屏手掌擦橡皮过大的问题 #636

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fix: 修复上下红外框触摸屏手掌擦橡皮过大的问题 #636

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15 changes: 9 additions & 6 deletions Ink Canvas/Ink/Native/NativeInkInputRouter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -300,18 +300,21 @@ private static bool TryGetPalmEraserWidth(
if (policy.IsSpecialScreen && policy.TouchMultiplier == 0)
return false;

var boundWidth = policy.IsQuadIr
? Math.Sqrt(Math.Max(0, pointer.ContactWidthDip * pointer.ContactHeightDip))
: pointer.ContactWidthDip;
var boundWidth = PalmEraserGeometry.GetEffectiveContactWidthDip(
pointer.ContactWidthDip,
pointer.ContactHeightDip,
policy.IsQuadIr);
var threshold = policy.BoundsWidthDip
* policy.ThresholdFactor
* policy.SensitivityMultiplier;
if (boundWidth <= policy.BoundsWidthDip || boundWidth <= threshold)
return false;

eraserWidthDip = boundWidth
* policy.EraserSizeFactor
* (policy.IsSpecialScreen ? policy.TouchMultiplier : 1);
eraserWidthDip = PalmEraserGeometry.ApplyPalmEraserSize(
boundWidth,
policy.EraserSizeFactor,
policy.IsSpecialScreen,
policy.TouchMultiplier);
return true;
}

Expand Down
59 changes: 59 additions & 0 deletions Ink Canvas/Ink/PalmEraserGeometry.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,59 @@
using System;

namespace Ink_Canvas.Ink
{
/// <summary>
/// 手掌擦接触尺寸计算。
/// 上下红外等触摸框可能把接触矩形某一轴异常放大（例如接近全屏宽度的长条），
/// 这里把异常细长接触折算为几何平均宽度，并限制最终手掌橡皮大小。
/// </summary>
internal static class PalmEraserGeometry
{
/// <summary>
/// 手掌橡皮最大宽度（DIP）。用于防止上下红外等设备上报的异常接触矩形
/// 把橡皮放大到远超真实手掌的程度。
/// </summary>
internal const double MaxPalmEraserWidthDip = 200;

/// <summary>
/// 接触矩形长宽比超过该值时，认为某一轴可能是红外框的异常放大结果，
/// 改用几何平均 sqrt(width*height) 来估算有效接触宽度。
/// </summary>
private const double ElongatedAspectRatioThreshold = 3.0;

internal static double GetEffectiveContactWidthDip(
double contactWidthDip,
double contactHeightDip,
bool isQuadIr)
{
if (contactWidthDip <= 0)
return 0;

// 部分设备不提供高度，仍回退到宽度，避免破坏原有行为。
if (contactHeightDip <= 0)
return contactWidthDip;

var min = Math.Min(contactWidthDip, contactHeightDip);
var max = Math.Max(contactWidthDip, contactHeightDip);

@augmentcode augmentcode Bot Aug 20, 2026 •
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In Ink Canvas/Ink/PalmEraserGeometry.cs:37, this early return also applies when isQuadIr is true, changing the previous quad-IR result for a zero-height contact from 0 to the raw width. A quad-IR frame with a screen-wide width and a missing/degenerate height can therefore activate an oversized palm eraser again rather than being rejected by the existing threshold checks.

Severity: medium

Fix This in Augment

🤖 Was this useful? React with 👍 or 👎, or 🚀 if it prevented an incident/outage.

var elongated = min <= 0 || max / min > ElongatedAspectRatioThreshold;

if (isQuadIr || elongated)
return Math.Sqrt(Math.Max(0, contactWidthDip * contactHeightDip));

return contactWidthDip;
}

internal static double ApplyPalmEraserSize(
double effectiveContactWidthDip,
double eraserSizeFactor,
bool isSpecialScreen,
double touchMultiplier)
{
var widthDip = effectiveContactWidthDip * eraserSizeFactor;
if (isSpecialScreen)
widthDip *= touchMultiplier;

return Math.Min(widthDip, MaxPalmEraserWidthDip);
}
}
}
17 changes: 11 additions & 6 deletions Ink Canvas/MainWindow_cs/MW_TouchEvents.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1864,8 +1864,10 @@ private void Main_Grid_TouchDown(object sender, TouchEventArgs e)
public double GetTouchBoundWidth(TouchEventArgs e)
{
var args = e.GetTouchPoint(null).Bounds;
if (!Settings.Advanced.IsQuadIR) return args.Width;
return Math.Sqrt(args.Width * args.Height);
return Ink_Canvas.Ink.PalmEraserGeometry.GetEffectiveContactWidthDip(
args.Width,
args.Height,
Settings.Advanced.IsQuadIR);
}

/// <summary>
Expand Down Expand Up @@ -2086,18 +2088,21 @@ private void InkCanvas_PreviewTouchDown(object sender, TouchEventArgs e)

if (boundWidth > BoundsWidth * EraserThresholdValue * thresholdMultiplier)
{
boundWidth *= Settings.Startup.IsEnableNibMode
var eraserSizeFactor = Settings.Startup.IsEnableNibMode
? Settings.Advanced.NibModeBoundsWidthEraserSize
: Settings.Advanced.FingerModeBoundsWidthEraserSize;
var palmEraserWidth = Ink_Canvas.Ink.PalmEraserGeometry.ApplyPalmEraserSize(
boundWidth,
eraserSizeFactor,
Settings.Advanced.IsSpecialScreen,
Settings.Advanced.TouchMultiplier);

if (Settings.Advanced.IsSpecialScreen)
boundWidth *= Settings.Advanced.TouchMultiplier;
palmEraserPreviousEditingMode = inkCanvas.EditingMode;
inkCanvas.EditingMode = InkCanvasEditingMode.EraseByPoint;
isPalmEraserActive = true;

EnableEraserOverlay();
eraserWidth = boundWidth;
eraserWidth = palmEraserWidth;
UpdateEraserStyle();
touchPoint = e.GetTouchPoint(inkCanvas);
EraserOverlay_PointerDown(sender);
Expand Down
1 change: 1 addition & 0 deletions InkCanvas.NativeInk.Tests/InkCanvas.NativeInk.Tests.csproj
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
<Compile Include="..\Ink Canvas\Ink\Native\NativeInkPerfProbe.cs" Link="Ink\Native\NativeInkPerfProbe.cs" />
<Compile Include="..\Ink Canvas\Ink\Native\NativePointerUpdatePump.cs" Link="Ink\Native\NativePointerUpdatePump.cs" />
<Compile Include="..\Ink Canvas\Ink\Native\NativeInkInputRouter.cs" Link="Ink\Native\NativeInkInputRouter.cs" />
<Compile Include="..\Ink Canvas\Ink\PalmEraserGeometry.cs" Link="Ink\PalmEraserGeometry.cs" />
<Compile Include="..\Ink Canvas\Ink\Native\NativePointerInputBatch.cs" Link="Ink\Native\NativePointerInputBatch.cs" />
<Compile Include="..\Ink Canvas\Ink\Native\NativePointerTimestampConverter.cs" Link="Ink\Native\NativePointerTimestampConverter.cs" />
<Compile Include="..\Ink Canvas\Ink\Native\WetInkCommandMailbox.cs" Link="Ink\Native\WetInkCommandMailbox.cs" />
Expand Down
64 changes: 64 additions & 0 deletions InkCanvas.NativeInk.Tests/NativeInkCoreTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,9 @@ private static void Main()
Run(nameof(RouterMapsLogicalTools), RouterMapsLogicalTools);
Run(nameof(RouterPrefersMultiTouchWritingOverPalmErase), RouterPrefersMultiTouchWritingOverPalmErase);
Run(nameof(RouterAppliesQuadIrPalmThresholdAndSpecialMultiplier), RouterAppliesQuadIrPalmThresholdAndSpecialMultiplier);
Run(nameof(RouterUsesGeometricMeanForElongatedTopBottomIrPalm), RouterUsesGeometricMeanForElongatedTopBottomIrPalm);
Run(nameof(RouterKeepsWidthForNormalPalmContact), RouterKeepsWidthForNormalPalmContact);
Run(nameof(RouterCapsPalmEraserWidth), RouterCapsPalmEraserWidth);
Run(nameof(RouterAllowsDelayedTwoFingerTakeover), RouterAllowsDelayedTwoFingerTakeover);
Run(nameof(RouterKeepsCapturedInkAndSuppressesBarrelPoints), RouterKeepsCapturedInkAndSuppressesBarrelPoints);
Run(nameof(PointerBatchCopiesSamples), PointerBatchCopiesSamples);
Expand Down Expand Up @@ -540,6 +543,67 @@ private static void RouterAppliesQuadIrPalmThresholdAndSpecialMultiplier()
Equal(NativeInputRoute.Ink, disabledOnSpecialScreen.Route);
}

private static void RouterUsesGeometricMeanForElongatedTopBottomIrPalm()
{
// 上下红外框常见异常：接触矩形接近全宽长条（width 异常大、height 接近真实手掌）。
// 非四边红外模式下也应使用几何平均，避免橡皮被放大到远超手掌。
var decision = NativeInkInputRouter.DecideDown(
Pointer(NativeInkInputKind.Touch, contactWidthDip: 1920, contactHeightDip: 120),
Context(
LogicalInkTool.Pen,
palm: Palm(
enabled: true,
isQuadIr: false,
isSpecialScreen: true,
boundsWidthDip: 10,
thresholdFactor: 2,
sensitivityMultiplier: 2,
eraserSizeFactor: 0.8,
touchMultiplier: 0.3)));
Equal(NativeInputRoute.PointErase, decision.Route);
True(Math.Abs(decision.PalmEraserWidthDip - 115.2d) < 0.001);
}

private static void RouterKeepsWidthForNormalPalmContact()
{
// 普通触摸屏接触矩形不细长时，继续使用宽度，避免改变原有行为。
var decision = NativeInkInputRouter.DecideDown(
Pointer(NativeInkInputKind.Touch, contactWidthDip: 80, contactHeightDip: 100),
Context(
LogicalInkTool.Pen,
palm: Palm(
enabled: true,
isQuadIr: false,
isSpecialScreen: false,
boundsWidthDip: 10,
thresholdFactor: 2,
sensitivityMultiplier: 2,
eraserSizeFactor: 0.8,
touchMultiplier: 1)));
Equal(NativeInputRoute.PointErase, decision.Route);
Equal(64d, decision.PalmEraserWidthDip);
}

private static void RouterCapsPalmEraserWidth()
{
// 即使两个轴都异常大，最终手掌橡皮也不能超过保护上限。
var decision = NativeInkInputRouter.DecideDown(
Pointer(NativeInkInputKind.Touch, contactWidthDip: 500, contactHeightDip: 500),
Context(
LogicalInkTool.Pen,
palm: Palm(
enabled: true,
isQuadIr: false,
isSpecialScreen: false,
boundsWidthDip: 10,
thresholdFactor: 2,
sensitivityMultiplier: 2,
eraserSizeFactor: 1,
touchMultiplier: 1)));
Equal(NativeInputRoute.PointErase, decision.Route);
Equal(Ink_Canvas.Ink.PalmEraserGeometry.MaxPalmEraserWidthDip, decision.PalmEraserWidthDip);
}

private static void RouterAllowsDelayedTwoFingerTakeover()
{
var decision = NativeInkInputRouter.DecideDown(
Expand Down