Allow stylus support on windows #165323

CodeDoctorDE · 2025-03-17T16:27:27Z

This is my attempt for adding support for stylus on windows.
It's work in progress! I post it here to indicate that I'm working on it and that the same work is not done twice

I'm working on the flutter_window.cpp file. Maybe I need to touch some other code to allow additional information like pressure, rotation and more.

Would fix #102836 and #65248

There should be no breaking change other than stylus would be reported as stylus instead of touch.

Tested with flutter master on my test project:

https://github.com/CodeDoctorDE/flutter-input-demo

Tests are currently not there, I will add them next.

Pre-launch Checklist

I read the Contributor Guide and followed the process outlined there for submitting PRs.
I read the Tree Hygiene wiki page, which explains my responsibilities.
I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
I signed the CLA.
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is test-exempt.
I followed the breaking change policy and added Data Driven Fixes where supported.
All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

CodeDoctorDE · 2025-03-17T16:55:12Z

Looks like we can also identify hovering, I will work on this next

CodeDoctorDE · 2025-03-17T19:20:56Z

Dont know why mac and linux ci fails, but my changes doesnt break any windows test so it looks good. Now i need to add my own tests

Piinks · 2025-06-04T23:32:33Z

Hey @CodeDoctorDE welcome! Thanks for contributing! It looks like this never entered the review queue since it was marked a draft. Is this still something you would like to work on?

CodeDoctorDE · 2025-06-05T04:31:58Z

Hello, oh yeah, but it currently has some problems I need to fix

Piinks · 2025-08-05T22:43:06Z

Hello again @CodeDoctorDE, this came back around to stale PR triage. :)
Still have plans to work on this?

CodeDoctorDE · 2025-08-06T06:31:11Z

Hello,
Yeah, Im happy to work again here, but in the current time, I hadn't enough time because of studying. I will continue here in a month

Piinks · 2025-08-06T15:24:23Z

Quite alright! Thanks for letting us know. I am going to close this for now to remove it from our review queue and CI tasks. Feel free to reopen when you are ready to return to it. Thanks!

CodeDoctorDE · 2025-08-10T12:36:31Z

Hello, I finished my changes but I don't have the option to reopen it.
Can you reopen it or should I make a new one?

fluttergithubbot · 2025-08-11T05:21:25Z

An existing Git SHA, 7446780b1c60f45e90729911b67d6ad0f7d1ea28, was detected, and no actions were taken.

To re-trigger presubmits after closing or re-opeing a PR, or pushing a HEAD commit (i.e. with --force) that already was pushed before, push a blank commit (git commit --allow-empty -m "Trigger Build") or rebase to continue.

@Demohstens

by @Demohstens Adds six unittests for different pointer events. Added methods to WindowsProcTable for Pointer functions to allow for overloading in tests. Ensured all unittest pass Co-authored-by: Demohstens <[email protected]>

CodeDoctorDE · 2025-08-13T16:16:38Z

PR can be reviewed, not sure why mac fais

tirth-patel-nc · 2025-08-13T17:13:44Z

PR can be reviewed, not sure why mac fais

It is passing. Tree status would be green on its own

loic-sharma · 2025-08-18T21:15:48Z

engine/src/flutter/shell/platform/windows/flutter_window.cc

    auto that = static_cast<FlutterWindow*>(cs->lpCreateParams);
    that->window_handle_ = window;
    that->text_input_manager_->SetWindowHandle(window);
-    RegisterTouchWindow(window, 0);


Could you confirm that multi-touch gestures like pinching on a trackpad still works after this change?

(This line was added by flutter/engine#27863 for multi-touch support, I'd like to double-check we're not regressing that behavior with this new implementation!)

Removing this line disables WM_GESTURE & WM_TOUCH messages. The first is not handled and the latter is replaced by the new implementation so this should not impact the trackpad at all. Local tests seem to confirm this but i'm not entirely confident they cover all cases. This might have been necessary for supporting windows 7 and older as WM_POINTER* were not supported before that.

Ah gotcha, thanks for the details!

cc @jnschulze in case you have any concerns since you added this back in: flutter/engine#27863

loic-sharma · 2025-08-18T21:18:42Z

engine/src/flutter/shell/platform/windows/flutter_window.cc

+        } else if (message == WM_POINTERUPDATE) {
+          // POINTER_FLAG_INCONTACT indicates the stylus is touching the screen
+          // When not set, it means the stylus is hovering
+          OnPointerMove(x, y, device_kind, touch_id, rotation, pressure, 0);


For these non-obvious default values, could you add a comment like /*argument_name=*/ to make these a little more obvious? For example:

Suggested change

OnPointerMove(x, y, device_kind, touch_id, rotation, pressure, 0);

OnPointerMove(x, y, device_kind, touch_id, rotation, pressure, /* modifiers_state=*/0);

loic-sharma · 2025-08-18T21:21:35Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces stylus support on Windows by migrating from WM_TOUCH to the more modern WM_POINTER* APIs. This is a significant improvement, allowing for the capture of additional input data like pressure and rotation. The changes are well-structured, touching the embedder API, the Windows-specific implementation, and adding a comprehensive suite of unit tests for the new functionality. The overall approach is solid. I have a few suggestions to enhance code clarity and maintainability.

gemini-code-assist · 2025-08-18T21:22:59Z

engine/src/flutter/shell/platform/windows/flutter_window.cc

+    case WM_POINTERDOWN:
+    case WM_POINTERUPDATE:
+    case WM_POINTERUP:
+    case WM_POINTERLEAVE: {
+      xPos = GET_X_LPARAM(lparam);
+      yPos = GET_Y_LPARAM(lparam);
+      auto x = static_cast<double>(xPos);
+      auto y = static_cast<double>(yPos);
+      auto pointerId = GET_POINTERID_WPARAM(wparam);
+      POINTER_INFO pointerInfo;
+      if (windows_proc_table_->GetPointerInfo(pointerId, &pointerInfo)) {
+        UINT32 pressure = 0;
+        UINT32 rotation = 0;
+        if (pointerInfo.pointerType == PT_PEN) {
+          POINTER_PEN_INFO penInfo;
+          if (windows_proc_table_->GetPointerPenInfo(pointerId, &penInfo)) {
+            pressure = penInfo.pressure;
+            rotation = penInfo.rotation;
          }
        }
-        CloseTouchInputHandle(touch_input_handle);
+        auto touch_id = touch_id_generator_.GetGeneratedId(pointerId);
+        FlutterPointerDeviceKind device_kind = kFlutterPointerDeviceKindMouse;
+        switch (pointerInfo.pointerType) {
+          case PT_TOUCH:
+            device_kind = kFlutterPointerDeviceKindTouch;
+            break;
+          case PT_PEN:
+            device_kind = kFlutterPointerDeviceKindStylus;
+            break;
+          case PT_MOUSE:
+            device_kind = kFlutterPointerDeviceKindMouse;
+            break;
+        }
+        if (message == WM_POINTERDOWN) {
+          OnPointerDown(x, y, device_kind, touch_id, WM_LBUTTONDOWN, rotation,
+                        pressure);
+        } else if (message == WM_POINTERUPDATE) {
+          // POINTER_FLAG_INCONTACT indicates the stylus is touching the screen
+          // When not set, it means the stylus is hovering
+          OnPointerMove(x, y, device_kind, touch_id, rotation, pressure, 0);
+        } else if (message == WM_POINTERUP) {
+          OnPointerUp(x, y, device_kind, touch_id, WM_LBUTTONUP);
+          // keep tracking the pointer (especially important for stylus)
+          // This allows a stylus to "hover" over the window
+        } else if (message == WM_POINTERLEAVE) {
+          OnPointerLeave(x, y, device_kind, touch_id);
+          touch_id_generator_.ReleaseNumber(pointerId);
+        }
      }
-      return 0;
+      break;
    }


This block for handling pointer messages is quite large and adds significant complexity to the HandleMessage method. To improve readability and maintainability, consider extracting this logic into a new private helper method, for example HandlePointerMessage(UINT const message, WPARAM const wparam, LPARAM const lparam).

Personally, I think this is fine as-is. If you want to split this up, I'd consider adding a ToPointerDataKind helper function for mapping from win32 pointer input types to Flutter's pointer device kinds.

engine/src/flutter/shell/platform/windows/flutter_window.cc

gemini-code-assist · 2025-08-18T21:23:00Z

engine/src/flutter/shell/platform/windows/flutter_window_unittests.cc

+  // Test that the mock is working by calling it directly
+  POINTER_INFO test_pointer_info = {};
+  BOOL result = mock_proc_table->GetPointerInfo(1, &test_pointer_info);


These lines appear to be for debugging and are not used in the test's assertions. They can be removed.

gemini-code-assist · 2025-08-18T21:23:00Z

engine/src/flutter/shell/platform/windows/flutter_window_unittests.cc

+  LRESULT message_result =
+      win32window.InjectWindowMessage(WM_POINTERDOWN, wparam, lparam);


The message_result variable is unused. The call to InjectWindowMessage can be made without assigning its return value.

Suggested change

LRESULT message_result =

win32window.InjectWindowMessage(WM_POINTERDOWN, wparam, lparam);

win32window.InjectWindowMessage(WM_POINTERDOWN, wparam, lparam);

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc

engine/src/flutter/shell/platform/windows/flutter_window.cc

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc

* Added kMaxPenPressure constant * Added cmath as dependancy to windows

loic-sharma · 2025-08-22T21:45:32Z

I'll be on vacation for the next 10 days and won't be able to review. Apologies for the delay!

Demohstens · 2025-09-04T18:23:03Z

I'm having some issues with my setup and am unable to build the engine on my laptop atm.

I will get to your comments, @loic-sharma, next week when I'm home!

trackpad device type

loic-sharma · 2025-09-22T18:28:35Z

@Demohstens please feel free to ping me when this is ready for another review :)

Demohstens · 2025-09-22T19:30:55Z

Should be ready @loic-sharma - I totally forgot to mention you, sorry!

If someone has a pen with rotation capabilities it'd be great to test that property. The tests don't account for the transformation as they intercept the function before it's sent to the framework and my pen does not support rotation :/

engine/src/flutter/shell/platform/windows/flutter_window.cc

loic-sharma · 2025-10-22T21:08:10Z

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc

    auto state = GetOrCreatePointerState(device_kind, device_id);
    state->buttons |= flutter_button;
+    state->rotation = rotation;
+    state->pressure = pressure;


Should we reset these values in OnPointerUp?

It's a month ago I looked at it, but I think it could also be useful to get the last value that is captured instead of just having a default value.

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc

CodeDoctorDE · 2025-11-15T18:55:17Z

Sorry for the late update, the start of the semester held me up. It’s ready now!

loic-sharma · 2025-11-19T20:00:21Z

cc @mattkae

mattkae

A few comments, but nothing huge on my side. I have no hardware to test though, so I'll have to trust 😄

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc

engine/src/flutter/shell/platform/windows/flutter_window.cc

mattkae

Nice tests 😄 I just have one final piece of feedback here

engine/src/flutter/shell/platform/windows/flutter_window.cc

Co-authored-by: Matthew Kosarek <[email protected]>

mattkae

I am perfectly happy with this, thanks for putting in so much work on testing 🎉

@loic-sharma Would you have anything to add? I cannot test on my end unfortunately

loic-sharma · 2025-12-19T00:29:25Z

The tests that failed look like infra problems. I reran them!

loic-sharma · 2025-12-19T19:06:34Z

FYI it looks like you have a formatting issue: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8695098116792788577/+/u/test:_test:_Check_formatting/stdout

To fix, run `et format` or:
git apply <<DONE
diff --git a/engine/src/flutter/shell/platform/windows/flutter_window.cc b/engine/src/flutter/shell/platform/windows/flutter_window.cc
index ef55c834cbe..00000000000 100644
--- a/engine/src/flutter/shell/platform/windows/flutter_window.cc
+++ b/engine/src/flutter/shell/platform/windows/flutter_window.cc
@@ -577,7 +577,8 @@ FlutterWindow::HandleMessage(UINT const message,
device_kind = kFlutterPointerDeviceKindTrackpad;
break;
default:
-            FML_LOG(ERROR) << "Unrecognized device key " << pointerInfo.pointerType;
+            FML_LOG(ERROR) << "Unrecognized device key "
+                           << pointerInfo.pointerType;
break;
}
if (message == WM_POINTERDOWN) {
DONE

Start replacing WM_TOUCH usage with WM_POINTER

2bc5b1b

github-actions bot added engine flutter/engine related. See also e: labels. platform-windows Building on or for Windows specifically a: desktop Running on desktop labels Mar 17, 2025

CodeDoctorDE mentioned this pull request Mar 17, 2025

Support stylus input on Windows 10 devices #65248

Open

CodeDoctorDE added 2 commits March 17, 2025 17:31

Fix button in pointer events

b12eb57

Add check for incontact to remove hover recognized as move

91226c4

CodeDoctorDE added 2 commits March 18, 2025 14:27

Add pressure information to embedder and windows shell

b1accc1

Merge branch 'master' into windows/pointer

71b8d3a

Piinks closed this Aug 6, 2025

Merge branch 'flutter:master' into windows/pointer

107d37a

tirth-patel-nc reopened this Aug 11, 2025

Finish pointer tests and win calls

f649c11

by @Demohstens Adds six unittests for different pointer events. Added methods to WindowsProcTable for Pointer functions to allow for overloading in tests. Ensured all unittest pass Co-authored-by: Demohstens <[email protected]>

CodeDoctorDE force-pushed the windows/pointer branch from 7446780 to f649c11 Compare August 11, 2025 07:47

CodeDoctorDE marked this pull request as ready for review August 11, 2025 07:47

CodeDoctorDE requested review from chinmaygarde and loic-sharma as code owners August 11, 2025 07:47

loic-sharma reviewed Aug 18, 2025

View reviewed changes

gemini-code-assist bot reviewed Aug 18, 2025

View reviewed changes

loic-sharma reviewed Aug 18, 2025

View reviewed changes

engine/src/flutter/shell/platform/windows/flutter_window.cc Show resolved Hide resolved

loic-sharma reviewed Aug 18, 2025

View reviewed changes

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc Outdated Show resolved Hide resolved

Demohstens added 2 commits August 19, 2025 21:20

Added kMaxPenPressure constant (#3)

94c65e0

Added cmath dependancy to windows (#4)

85b1c7a

* Added kMaxPenPressure constant * Added cmath as dependancy to windows

Adressed comments by refactoring as well as adding (#5)

38b7e10

trackpad device type

loic-sharma reviewed Oct 9, 2025

View reviewed changes

engine/src/flutter/shell/platform/windows/flutter_window.cc Outdated Show resolved Hide resolved

loic-sharma reviewed Oct 22, 2025

View reviewed changes

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc Outdated Show resolved Hide resolved

Address variable naming issues and docs link

37b4998

CodeDoctorDE requested a review from loic-sharma November 15, 2025 18:55

Merge branch 'master' into windows/pointer

eb15193

CodeDoctorDE mentioned this pull request Nov 15, 2025

[Bug]: Lenovo Ideapad: Stylus buttons are not correctly recognized LinwoodDev/Butterfly#968

Open

1 task

Rename x and y pos variables on all places inside handle message

27dbb44

CodeDoctorDE force-pushed the windows/pointer branch from 90f0db5 to 27dbb44 Compare November 15, 2025 19:21

mattkae reviewed Nov 26, 2025

View reviewed changes

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc Outdated Show resolved Hide resolved

engine/src/flutter/shell/platform/windows/flutter_window.cc Outdated Show resolved Hide resolved

engine/src/flutter/shell/platform/windows/flutter_window.cc Show resolved Hide resolved

CodeDoctorDE added 2 commits December 1, 2025 13:27

Apply review suggestions

1a3d647

Merge branch 'master' into windows/pointer

cf6c9a0

mattkae reviewed Dec 10, 2025

View reviewed changes

engine/src/flutter/shell/platform/windows/flutter_window.cc Outdated Show resolved Hide resolved

Update engine/src/flutter/shell/platform/windows/flutter_window.cc

7652f80

Co-authored-by: Matthew Kosarek <[email protected]>

mattkae approved these changes Dec 11, 2025

View reviewed changes

	OnPointerMove(x, y, device_kind, touch_id, rotation, pressure, 0);
	OnPointerMove(x, y, device_kind, touch_id, rotation, pressure, /* modifiers_state=*/0);

		LRESULT message_result =
		win32window.InjectWindowMessage(WM_POINTERDOWN, wparam, lparam);

Allow stylus support on windows #165323

Are you sure you want to change the base?

Allow stylus support on windows #165323

Uh oh!

Conversation

CodeDoctorDE commented Mar 17, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Pre-launch Checklist

Uh oh!

CodeDoctorDE commented Mar 17, 2025

Uh oh!

CodeDoctorDE commented Mar 17, 2025

Uh oh!

Piinks commented Jun 4, 2025

Uh oh!

CodeDoctorDE commented Jun 5, 2025

Uh oh!

Piinks commented Aug 5, 2025

Uh oh!

CodeDoctorDE commented Aug 6, 2025

Uh oh!

Piinks commented Aug 6, 2025

Uh oh!

CodeDoctorDE commented Aug 10, 2025

Uh oh!

fluttergithubbot commented Aug 11, 2025

Uh oh!

CodeDoctorDE commented Aug 13, 2025

Uh oh!

tirth-patel-nc commented Aug 13, 2025

Uh oh!

loic-sharma Aug 18, 2025

Choose a reason for hiding this comment

Uh oh!

Demohstens Aug 19, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

loic-sharma Aug 20, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

loic-sharma Aug 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

loic-sharma commented Aug 18, 2025

Uh oh!

gemini-code-assist bot left a comment

Choose a reason for hiding this comment

Code Review

Uh oh!

gemini-code-assist bot Aug 18, 2025

Choose a reason for hiding this comment

Uh oh!

loic-sharma Aug 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

gemini-code-assist bot Aug 18, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Aug 18, 2025

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

loic-sharma commented Aug 22, 2025

Uh oh!

Demohstens commented Sep 4, 2025

Uh oh!

loic-sharma commented Sep 22, 2025

Uh oh!

Demohstens commented Sep 22, 2025

Uh oh!

Uh oh!

loic-sharma Oct 22, 2025

Choose a reason for hiding this comment

CodeDoctorDE commented Mar 17, 2025 •

edited

Loading

Demohstens Aug 19, 2025 •

edited

Loading

loic-sharma Aug 20, 2025 •

edited

Loading

loic-sharma Aug 18, 2025 •

edited

Loading

loic-sharma Aug 18, 2025 •

edited

Loading