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Windows Pen APIs compared

Here's a quick review of some of the differences between the APIs. This information will be useful if you are building an app or library that has to pick which API to use or switch between APIs.

Z position

Reminder: Z position is roughly equivalent "hover height"

API
Z (height)

Wintab

pkZ

WM_POINTER

Not available

WinUI PointerPoint

Not directly

WPF StylusPoint

Not directly

RealTimeStylus

Via PACKET_PROPERTY

Pressure data

Pressure data comes back a bit differently. While 0 always means "no pressure", the data type, max value, and how many unique values vary.

API
Pressure type
Range
Normalization

Wintab

pkNormalPressure (uint)

0 to device-specific max (query via GetMaxPressure())

App divides by max

WM_POINTER

POINTER_PEN_INFO.pressure (uint32)

0 to 1024

App divides by 1024.0

WinUI PointerPoint

Properties.Pressure (float)

0.0 to 1.0

Pre-normalized

WPF StylusPoint

PressureFactor (float)

0.0 to 1.0

Pre-normalized

RealTimeStylus

PACKET_PROPERTY.pkNormalPressure

Device-specific

App normalizes

In Wintab, you might notice this field called pkNormalPressure does not mean normalized pressure (which typically means a pressure from 0 to 1.0). pkNormalPressure means normal force as in the force applied perpendicular to the tablet surface. Normalize it by dividing by GetMaxPressure().

Coordinate precision

There are two coordinate systems in play:

  • The tablet digitizer coordinate system

  • The screen or desktop coordinate system

Tablet digitizers have much higher internal resolution than the screen. A modern tablet is often specified at 5080 LPI. That is about 200 lines per mm. Some devices are closer to 100 lines per mm.

Most pen APIs expose screen-based coordinates. That is usually fine. If you need tablet-native precision, Wintab is the only practical option in a modern Windows app. To get it, you must configure Wintab to use its digitizer high-resolution context.

API
Coordinates
Precision

Wintab (System)

Physical screen pixels

Screen resolution (~200 DPI)

Wintab (Digitizer Hi-Res)

Tablet native units

Tablet resolution (up to 5080+ LPI)

WM_POINTER / WM_POINTERUPDATE

Physical screen pixels

Screen resolution¹

Windows Ink (WinUI PointerPoint)

DIPs (device-independent pixels)

DIP resolution

Windows Ink (WPF StylusPoint)

WPF device-independent units

WPF layout resolution

RealTimeStylus (COM)

HIMETRIC (0.01mm)

Up to ~2540 DPI²

Coordinate precision comparison

The X ranges below use these example assumptions:

  • Screen pixels (3,840): one 4K UHD monitor at 3840×2160 physical pixels

  • DIPs (1,707): the same 4K monitor at 225% scaling, so 3840 / 2.25 = 1707

  • Tablet native (52,600): a Wacom Intuos Pro Large PTK-870 with 349mm active width at 5080 LPI

  • HIMETRIC (26,400): HIMETRIC uses 0.01mm units, so a 264mm-wide tablet is about 26400 units

API
Typical X range
Tablet resolution preserved?

Wintab System

0 to 3840 (screen pixels on a 4K monitor)

No — downscaled to screen pixels

Wintab Digitizer Hi-Res

0 to 52600 (tablet native, varies by device)

Yes — full tablet LPI

WM_POINTER

0 to 3840 (screen pixels on a 4K monitor)

No — screen pixels See footnote 1

WinUI PointerPoint

0 to 1707 (DIPs on a 4K monitor at 225% scaling)

No — DIP resolution

WPF StylusPoint

Framework-dependent

No — layout resolution

RealTimeStylus

0 to ~26400 (HIMETRIC, varies by tablet width)

Partial — HIMETRIC is 0.01mm (~2540 units/inch), but actual resolution depends on hardware and driver. See footnote 2

Are these high-resolution ranges real?

Wacom’s driver diagnostics make the native resolution visible. On a PTK-870 tablet, values near the bottom-right corner reach roughly:

  • 34900 for X

  • 19500 for Y

That works out to about 100 lines per mm on both axes.

Footnotes

1. WM_POINTER precision: Windows tracks higher-resolution pen input internally, but Win32 exposes ptPixelLocation in POINTER_INFO as physical screen pixels. GetPointerInfoHistory gives more samples, not higher-resolution coordinates.

2. RealTimeStylus resolution: The ~2540 DPI figure comes from the HIMETRIC unit definition. It is a unit conversion, not a hardware limit. Actual precision depends on the tablet, driver, and scaling.

Pen buttons

API
Multiple pen buttons

Wintab

pkButtons bitmask

WM_POINTER

Button flags in POINTER_INFO

WinUI PointerPoint

Properties.IsBarrelButtonPressed etc.

WPF StylusPoint

Via StylusButton collection

RealTimeStylus

Via PACKET_PROPERTY

Barrel pressure

API
Barrel pressure

Wintab

pkTangentPressure

WM_POINTER

Not available

WinUI PointerPoint

Not available

WPF StylusPoint

Not available

RealTimeStylus

Via PACKET_PROPERTY

Eraser detection

API
Eraser detection

Wintab

Via cursor type (pkCursor)

WM_POINTER

IS_POINTER_INRANGE_WPARAM + flags

WinUI PointerPoint

Properties.IsEraser

WPF StylusPoint

StylusDevice.Inverted

RealTimeStylus

Via cursor type

Framework compatibility

Wintab

  • WinForms, WPF, WinUI 3, and Avalonia work well through P/Invoke or a .NET wrapper.

  • Win32 works well with the native Wintab.h header.

WM_POINTER

  • WinForms works, but needs extra care. IMessageFilter is the safest route.

  • WPF works through WndProc or HwndSource.

  • WinUI 3 does not expose it directly.

  • Avalonia can use platform interop.

  • Win32 supports it natively.

WinUI PointerPoint

  • WinUI 3 supports it natively.

  • WinForms, WPF, Avalonia, and raw Win32 do not expose it.

WPF StylusPoint

  • WPF supports it natively.

  • WinForms, WinUI 3, Avalonia, and raw Win32 do not expose it.

RealTimeStylus

  • WinForms and WPF work through COM interop.

  • WinUI 3, Avalonia, and Win32 can use it through COM.

Hover / proximity behavior

APIs differ in how they report a pen that is near the tablet but not touching it. This affects cursor preview, brush ghosting, and eraser detection.

API
Proximity detection
Hover data
Notes

Wintab

WT_PROXIMITY message; pkStatus proximity bit

Full pen data during hover: position, tilt, buttons, cursor type

Eraser detection happens on hover. The pkStatus proximity bit is set when the pen leaves range, not when it enters. Packets stop when the pen leaves range.

WM_POINTER

IS_POINTER_INRANGE_WPARAM flag

WM_POINTERUPDATE with INRANGE but not INCONTACT

Pen data is available during hover. WM_POINTERLEAVE fires when the pen exits range.

WinUI PointerPoint

PointerEntered / PointerExited events

IsInContact distinguishes hover from press

Fits the XAML event model. Hover data includes pressure 0, tilt, and position.

WPF StylusPoint

StylusInAirMove event

Position and tilt during in-air movement

StylusDevice.InAir exposes the state. Data is more limited than contact events.

RealTimeStylus

IStylusPlugin::InAirPackets

Position and tilt during hover

Uses a dedicated callback instead of the normal contact packet flow.

Key differences:

  • Wintab provides the richest hover data, including cursor type for eraser detection, but its proximity behavior is quirky.

  • WM_POINTER has cleaner hover semantics, but exposes less pen data.

  • Eraser timing differs. Wintab can report cursor changes before contact. WM_POINTER reports eraser state per event.

Pen orientation data

Orientation describes how the pen is rotated in space. The main components are tilt and twist.

  • Tilt is how far the pen leans, and in which direction.

  • Twist is barrel rotation around the pen’s long axis.

Both are angles. Tilt is usually represented either as altitude plus azimuth, or as TiltX plus TiltY, depending on the API.

API
Tilt representation
Twist
Notes

Wintab

Azimuth and altitude in tenths of a degree

orTwist from 0 to 3600

Full spherical coordinates

WM_POINTER

TiltX and TiltY in degrees from -90 to +90

Rotation in degrees from 0 to 359

Simpler, but less expressive

WinUI PointerPoint

Properties.XTilt and Properties.YTilt

Properties.Twist

Same model as WM_POINTER

WPF StylusPoint

XTiltOrientation and YTiltOrientation

Not directly available

Limited

RealTimeStylus

Azimuth, altitude, and twist

Full

Similar to Wintab

Twist support in hardware is rare. It needs both a compatible tablet and a pen with a rotation sensor, such as a Wacom Art Pen. Most pens and most consumer tablets do not report twist in practice.

Multi-monitor

API
Multi-Monitor

Wintab (System)

Works

Wintab (Digitizer Hi-Res)

Works, but needs special handling

WM_POINTER / WM_POINTERUPDATE

Works

Windows Ink (WinUI PointerPoint)

Works

Windows Ink (WPF StylusPoint)

Works

RealTimeStylus (COM)

Works

Threading

API
Threading

Wintab (System)

Background thread (200+ Hz)

Wintab (Digitizer Hi-Res)

Background thread (200+ Hz)

WM_POINTER / WM_POINTERUPDATE

UI thread (message-driven)

Windows Ink (WinUI PointerPoint)

UI thread

Windows Ink (WPF StylusPoint)

UI thread

RealTimeStylus (COM)

Configurable (sync or async plugin)

Cursor follows pen

A comparison of the available APIs for receiving pen or stylus input on Windows, relevant to drawing and handwriting applications.

API
Threading

Wintab (System)

Background thread (200+ Hz)

Wintab (Digitizer Hi-Res)

Background thread (200+ Hz)

WM_POINTER / WM_POINTERUPDATE

UI thread (message-driven)

Windows Ink (WinUI PointerPoint)

UI thread

Windows Ink (WPF StylusPoint)

UI thread

RealTimeStylus (COM)

Configurable (sync or async plugin)

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