1246346 - screen.left and screen.top does not return the correct value with mixed DPI monitors

Status: RESOLVED FIXED

(Core :: Widget: Win32, defect)

Description

[Masatoshi Kimura [:emk]]

Steps to reproduce.
1. Set two monitors to the following configuration:
   Monitor 1 (primary): 1280*960, 100% scale
   Monitor 2: 1920*1440, 150% scale
2. Open Nightly on the second monitor.
3. Open Web Console and type the following command:
  [screen.left,screen.top,screen.width,screen.height]

Actual result:
  Array [853, 0, 1280, 960]

Expected result:
  Array [1280, 0, 1280, 960]

We will need a similar fix to bug 1240085.

Comment 1

[Liz Henry (:lizzard) (relman/hg->git project)]

Tracking since this looks like a recent regression in 46.

Comment 2

[Liz Henry (:lizzard) (relman/hg->git project)]

Jonathan, can you take a look at this or help find an owner for this bug?

Comment 3

[Jonathan Kew [:jfkthame]]

Yes, I should be able to deal with this.

Comment 4

[Jonathan Kew [:jfkthame]]

Attachment: patch 1 - Expose a DesktopToDevice scale factor on nsDeviceContext

This is a helper to make the next patch much simpler; we already have the deviceContext, so exposing the Desktop-to-Device scale here avoids the need for a QI-dance via nsIBaseWindow or whatever. (I suspect this might turn out to be handy in other places, too.)

Comment 5

[Jonathan Kew [:jfkthame]]

Attachment: patch 2 - Correct the origin of the DOM screen coordinates (screen.left, screen.top) for secondary display on a mixed-DPI configuration

I don't have the exact same monitor configuration as yours in comment 0, but with this I'm seeing sensible results in similar mixed-dpi setups.

Comment 6

[Masatoshi Kimura [:emk]]

Comment on attachment 8718794 [details] [diff] [review]
patch 2 - Correct the origin of the DOM screen coordinates (screen.left, screen.top) for secondary display on a mixed-DPI configuration

LGTM about the correctness (I don't consider about the performance such as talos regressions).

Comment 7

[Jonathan Kew [:jfkthame]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/8c76ded2edb9adf8193020127f059d4b79d5c61c
Bug 1246346 - patch 1 - Expose a DesktopToDevice scale factor on nsDeviceContext. r=emk

https://hg.mozilla.org/integration/mozilla-inbound/rev/fc5233e55fec8b05f8284d407f5e1ff4be6795d0
Bug 1246346 - patch 2 - Correct the origin of the DOM screen coordinates (screen.left, screen.top) for secondary display on a mixed-DPI configuration. r=emk

Comment 8

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/8c76ded2edb9
https://hg.mozilla.org/mozilla-central/rev/fc5233e55fec