919364 - Canvas tag draws incorrectly

Status: RESOLVED WONTFIX

(Core :: Graphics: Canvas2D, defect)

Description

[Tom Jao [:mbrsl]]

Attachment: touchtest.zip

When you draw something on canvas (using lineTo() and other function), it shows weird result. It seems that system is picking wrong pixel on the screen and draw it onto the canvas.

Comment 1

[Tom Jao [:mbrsl]]

Attachment: 2013-09-23-10-46-36.png

The top box with black border is the canvas tag. Some other stuff like status bar on the top also been drawn onto the canvas.

Comment 2

[Tom Jao [:mbrsl]]

This bug occurs in the latest pvtbuild of mozilla-central-unagi. build 2013-08-31-04-02-12 still works fine but build 2013-09-18-15-23-50 is affected by this problem. I didn't test which build actually cause this bug.

Comment 3

[Jason Smith [:jsmith]]

(In reply to Tom Jao [:mbrsl] from comment #2)
> This bug occurs in the latest pvtbuild of mozilla-central-unagi. build
> 2013-08-31-04-02-12 still works fine but build 2013-09-18-15-23-50 is
> affected by this problem. I didn't test which build actually cause this bug.

Can you reproduce on a shipping device such as Buri?

Comment 4

[Jerry Shih[:jerry] (UTC+8) (inactive)]

I don't have unagi device and it seems good on m-c(2013/9/22 09:13:14 2013148216) at nexus4.

Comment 5

[Tom Jao [:mbrsl]]

Attachment: Errors for Buri (build 2013-09-17-18-00-29)

Comment 6

[Tom Jao [:mbrsl]]

(In reply to Jason Smith [:jsmith] from comment #3)
> (In reply to Tom Jao [:mbrsl] from comment #2)
> > This bug occurs in the latest pvtbuild of mozilla-central-unagi. build
> > 2013-08-31-04-02-12 still works fine but build 2013-09-18-15-23-50 is
> > affected by this problem. I didn't test which build actually cause this bug.
> 
> Can you reproduce on a shipping device such as Buri?
Yes, though the errors differ from Unagi. Please refer to the new image I uploaded. I used the pvtbuild for hamachi of 2013-09-17-18-00-29 in this image.
I just randomly choose this build since I failed to flash the latest build.

Comment 7

[Tom Jao [:mbrsl]]

(In reply to Tom Jao [:mbrsl] from comment #5)
> Created attachment 808464 [details]
> Errors for Buri (build 2013-09-17-18-00-29)
P.S. I only drew the upper one. The bottom one showed (wrongly) simultaneously.

Comment 8

[Jason Smith [:jsmith]]

Okay. I need clearer STR to be able to get a regression window. That means exact STR how to reproduce this with expected/actual results. The bug too unclear right now on what to do the regression window against.

Comment 9

[Tom Jao [:mbrsl]]

Sorry that I'm still a newbie to bugzilla, I will try to give a clearer description of this bug.

Overview:
System should draw only the trace of user's touch. But it also draws other things on the canvas.

How to reproduce:
1. Launch the example app from MDN https://mdn.mozillademos.org/en-US/docs/Web/Guide/API/DOM/Events/Touch_events$samples/Example?revision=469951, or install the test app https://bugzilla.mozilla.org/attachment.cgi?id=808374 to your phone and launch "touch test" app.
2. Click the initialize button.
3. Touch the canvas to draw a trace.

Actual result
The system draws something other than users's touch trace. The result could be different from different devices.
For Unagi, see https://bugzilla.mozilla.org/show_bug.cgi?id=919364#attach_808375. Other things on the screen were also been drawn on canvas. The trace only shows a black square because other parts were covered by other pixels while updating.
For Buri, see https://bugzilla.mozilla.org/attachment.cgi?id=808464. Two traces were drawn while user only touched with the upper trace.

Expected result
The system draws only user's touch trace.

Environment
pvtbuild 2013-09-18-15-23-50 (https://pvtbuilds.mozilla.org/pub/mozilla.org/b2g/nightly/mozilla-central-unagi/2013/08/2013-08-31-04-02-12/) for Unagi
pvtbuild 2013-09-17-18-00-29 (https://pvtbuilds.mozilla.org/pvt/mozilla.org/b2gotoro/nightly/mozilla-central-hamachi/2013/09/2013-09-17-18-00-29/) for Buri

Comment 10

[Tom Jao [:mbrsl]]

Not knowing how, but this bug seems to be fix by someone. Canvas works correctly now.