RFR: 8251862: Wrong position of Popup windows at the intersection of 2 screens

[Kevin Rushforth]

On Wed, 7 Dec 2022 20:12:56 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> On Windows platforms with more than one screen, a PopupWindow created for a Stage that straddles two windows will be drawn with an incorrect position and screen scale if the majority of the Stage is on one screen, and the popup is positioned on the other screen. In this case, the Stage is drawn using the screen scale of the screen that most of the window is on, while the popup is drawn using the scale of the screen that it is (typically entirely) on.
> 
> The most common way this can happen is when you have two screens of a different scale with the secondary screen on the left or above the primary screen. If you position the Stage such that most of it is still on the primary screen (thus the Stage is drawn using the scale of the primary screen), with a menu, a control with a context menu, or a control with a Tooltip now on the secondary screen, the popup window for the menu or Tooltip will be drawn using the screen scale of the secondary window and thus won't be positioned or sized correctly relative to the menu bar, or control in the main window.
> 
> The fix implemented by this PR is to always use the screen of the owner window, including the screen scales, when rendering a popup window. This matches the behavior of native Windows apps, such as Notepad.

This particular bug and PR is Windows-specific, although it would be helpful to know what happens on Mac.

I tried macOS 12.5.1 and macOS 12.6.1, and by default, windows only show on one screen or the other, so it doesn't look like a new setting. I checked to see whether there is an option to enable windows to span two displays, and there is (uncheck "Displays have separate spaces" in the "Mission Control" panel), but we don't have any special code on macOS to handle this. Anything we do for Mac would be a separate issue.

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PR: https://git.openjdk.org/jfx/pull/971