Thank you for the report! Does it feel like it's a lot harder to reveal than before? It would be great to have some consistent repro steps, so that I can reproduce this but also easily determine whether it has been fixed or not. Notions like "not easily" are very subjective and hard to test objectively :-)

It is indeed a lot harder to reveal than before. 
It takes some effort from the user to reveal the shelf (Like move the mouse for 3-4 seconds at the bottom of the screen).
 
Its easier to understand if you try it out. Sync to the chrome version right before this patch [75281dadbaa44f98080c9be2ed0aee7d90fbe294] and then to this patch [ee02be48c59260a48c98ebf3c9a58e1a5dd2b68e]. The difference is quite noticeable and breaks the fitts law.

I can upload a video too if needed.

 Issue 899875  has been merged into this issue.

I noticed this in M-71 while fullscreening a netflix show this weekend. 

I had autohide enabled.
Also, sometimes exiting fullscreen and then re entering helped me show the shelf easier. 

Ok so I've been trying to reproduce this, using a recent (today) build on a Gru device, and using an attached mouse.

The only repro case I can find is the following:

* Move the mouse fairly far away from the edge of the screen where the shelf is.
* Throw the mouse in the direction of the shelf, very quickly, so that the speed of the pointer is as high as possible.
* Notice that the shelf doesn't appear.

Every attempt to show the shelf with a pointer moving at (what I believe to be) "normal" speed resulted in the shelf being shown as expected, and it didn't seem harder than before.

Anyone who can reproduce this, could you tell me if you repro cases sound similar? If not, could you try to give me some precise repro cases? As it is, with my repro cases above, I wouldn't say this is 71-worthy given the time line, but if you can give me repro cases that would be awesome.

It's also worth noting that regardless of how fast I move the pointer, I haven't been able to repro this in a "sandbox" environment (only on a device), which makes debugging harder.

I think I used a pretty normal speed here.

Deleted: shelf_not_showing.webm 4.2 MB

	shelf_not_showing.webm 4.2 MB View Download

Thanks Alex! This does seem well within normal use cases. Which build is that?

This is 72.0.3593.0, but I have M-71 on my device at home and I noticed similar behavior. (Also for a little more signal, I saw this in listnr reports for m-71.)

#6 I am not sure what net device scale factor Gru was on when the test was performed. Perhaps its easier to reproduce on nocturne due to its 2.25 dsf.

FYI pending CL 1316362 adding a test that checks for shelf appearance with different pointer speeds.

This behavior reproduces reliably on my Nocturne and does not go away with crrev.comc/c/1318799 applied

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/61a96a66b2d9e5fb09f23359439804159ed9160d

commit 61a96a66b2d9e5fb09f23359439804159ed9160d
Author: Manu Cornet <manucornet@chromium.org>
Date: Tue Nov 06 16:52:14 2018

CrOS shelf: tentative fix for unresponsive shelf

Extend the shelf hover area to the edges of the screen.

Bug:  899007 
Change-Id: I344e80c9c2272ec70d5c638646bd9d5f0086f87a
Reviewed-on: https://chromium-review.googlesource.com/c/1318799
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605714}
[modify] https://crrev.com/61a96a66b2d9e5fb09f23359439804159ed9160d/ash/shelf/shelf_layout_manager.cc

Per #12, the CL might not fix the problem. Maybe add logging in WindowEventDispatcher::OnEventProcessingStarted [1] to dump out all locations of mouse move events (we can get pixel location and dip location there) and compare that with the shelf hover region to see whether we get any clue.

[1] https://cs.chromium.org/chromium/src/ui/aura/window_event_dispatcher.cc?rcl=793c8566ab6114dbbf54e8dc742bd2898b401af4&l=562

Thanks Vlad for the data point. And thanks Xiyuan for the tip. Still looking into this.

The fix at #c13 affects the behavior at https://cs.chromium.org/chromium/src/ash/shelf/shelf_layout_manager.cc?rcl=d4860fede0e2dc63d6500f98bfe913921959c795&l=1068 which is gated by the shelf being already visible. 
The actual cause of the problem is at https://cs.chromium.org/chromium/src/ash/shelf/shelf_layout_manager.cc?rcl=d4860fede0e2dc63d6500f98bfe913921959c795&l=1051. When the mouse is moving very quickly to the bottom, its position is right on the bottom edge of shelf_region (that is, outside of it).

I might have found a fix: https://chromium-review.googlesource.com/c/chromium/src/+/1320013

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c034b9e7859bf3b3cb1c33a9ca1a89df23782356

commit c034b9e7859bf3b3cb1c33a9ca1a89df23782356
Author: Vladislav Kaznacheev <kaznacheev@google.com>
Date: Tue Nov 06 18:23:13 2018

Fix hidden shelf reveal on mouse hover

On some scale factors the bottom most pixel is outside of
the display bounds. Snapping shelf region to display edge fixes
the problem.

Bug:  899007 
Test: manual
Change-Id: I1eeb342756b46e683d0f30f96f1c428fbb74d7ca
Reviewed-on: https://chromium-review.googlesource.com/c/1320013
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Commit-Queue: Vladislav Kaznacheev <kaznacheev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605748}
[modify] https://crrev.com/c034b9e7859bf3b3cb1c33a9ca1a89df23782356/ash/shelf/shelf_layout_manager.cc

@Vlad I'll also merge my previous CL (referenced in #13) to avoid conflicts -- once the approved label gets applied.should

This bug requires manual review: M71 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: benmason@(Android), kariahda@(iOS), kbleicher@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Approved for ChromeOS M71

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5fb657a6b0cd4fc7b5809d8753f0ece9383f5856

commit 5fb657a6b0cd4fc7b5809d8753f0ece9383f5856
Author: Manu Cornet <manucornet@chromium.org>
Date: Wed Nov 07 21:06:24 2018

CrOS shelf: tentative fix for unresponsive shelf

Extend the shelf hover area to the edges of the screen.

Bug:  899007 
Change-Id: I344e80c9c2272ec70d5c638646bd9d5f0086f87a
Reviewed-on: https://chromium-review.googlesource.com/c/1318799
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#605714}(cherry picked from commit 61a96a66b2d9e5fb09f23359439804159ed9160d)
Reviewed-on: https://chromium-review.googlesource.com/c/1320206
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/branch-heads/3578@{#571}
Cr-Branched-From: 4226ddf99103e493d7afb23a4c7902ee496108b6-refs/heads/master@{#599034}
[modify] https://crrev.com/5fb657a6b0cd4fc7b5809d8753f0ece9383f5856/ash/shelf/shelf_layout_manager.cc

The following revision refers to this bug: 
https://chromium.googlesource.com/chromium/src.git/+/5fb657a6b0cd4fc7b5809d8753f0ece9383f5856

Commit: 5fb657a6b0cd4fc7b5809d8753f0ece9383f5856
Author: manucornet@chromium.org
Commiter: manucornet@chromium.org
Date: 2018-11-07 21:06:24 +0000 UTC

CrOS shelf: tentative fix for unresponsive shelf

Extend the shelf hover area to the edges of the screen.

Bug:  899007 
Change-Id: I344e80c9c2272ec70d5c638646bd9d5f0086f87a
Reviewed-on: https://chromium-review.googlesource.com/c/1318799
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#605714}(cherry picked from commit 61a96a66b2d9e5fb09f23359439804159ed9160d)
Reviewed-on: https://chromium-review.googlesource.com/c/1320206
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/branch-heads/3578@{#571}
Cr-Branched-From: 4226ddf99103e493d7afb23a4c7902ee496108b6-refs/heads/master@{#599034}

 Issue 902913  has been merged into this issue.

 Issue 904143  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3514fd1dd0ceb4476036939277aba7ebab49ae71

commit 3514fd1dd0ceb4476036939277aba7ebab49ae71
Author: Vladislav Kaznacheev <kaznacheev@google.com>
Date: Wed Nov 14 00:36:52 2018

Fix hidden shelf reveal on mouse hover

On some scale factors the bottom most pixel is outside of
the display bounds. Snapping shelf region to display edge fixes
the problem.

Bug:  899007 
Test: manual
Change-Id: I1eeb342756b46e683d0f30f96f1c428fbb74d7ca
Reviewed-on: https://chromium-review.googlesource.com/c/1320013
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Commit-Queue: Vladislav Kaznacheev <kaznacheev@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#605748}(cherry picked from commit c034b9e7859bf3b3cb1c33a9ca1a89df23782356)
Reviewed-on: https://chromium-review.googlesource.com/c/1334840
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/branch-heads/3578@{#674}
Cr-Branched-From: 4226ddf99103e493d7afb23a4c7902ee496108b6-refs/heads/master@{#599034}
[modify] https://crrev.com/3514fd1dd0ceb4476036939277aba7ebab49ae71/ash/shelf/shelf_layout_manager.cc

The following revision refers to this bug: 
https://chromium.googlesource.com/chromium/src.git/+/3514fd1dd0ceb4476036939277aba7ebab49ae71

Commit: 3514fd1dd0ceb4476036939277aba7ebab49ae71
Author: kaznacheev@google.com
Commiter: newcomer@chromium.org
Date: 2018-11-14 00:36:52 +0000 UTC

Fix hidden shelf reveal on mouse hover

On some scale factors the bottom most pixel is outside of
the display bounds. Snapping shelf region to display edge fixes
the problem.

Bug:  899007 
Test: manual
Change-Id: I1eeb342756b46e683d0f30f96f1c428fbb74d7ca
Reviewed-on: https://chromium-review.googlesource.com/c/1320013
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Commit-Queue: Vladislav Kaznacheev <kaznacheev@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#605748}(cherry picked from commit c034b9e7859bf3b3cb1c33a9ca1a89df23782356)
Reviewed-on: https://chromium-review.googlesource.com/c/1334840
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/branch-heads/3578@{#674}
Cr-Branched-From: 4226ddf99103e493d7afb23a4c7902ee496108b6-refs/heads/master@{#599034}

Issue 905067 has been merged into this issue.