Preview window is too large on one of multiple monitors with different resolution & scaling settings

Bug Description

Hi, I encountered the bug in issue #420 previously that the preview window is too large on my 1080p monitor that I plugged in, so I installed the zip version in the link mentioned by @xupefei in issue 420. Now on the 1080p monitor, the size of preview window is normal now. However, on my main 4k monitor of my laptop, the preview window is too larger instead.

I also viewed the issue #801 and tried the latest Nightly version - QuickLook-3.6.10-27-g826cda0.msi, in this version this bug reported here will not occurred. However, it has another bug that previewing some (not all) png file will frequently crash ("Failed to preview"), so I uninstalled this version in the end. (I could open another new issue if necessary.)

I'm using ASUS ZenBook Pro Duo, it has two built-in monitors itself, a 4k main monitor (3840 * 2160, monitor 1) and a secondary 4k monitor (3840 * 1100, monitor 2) on the top of the keyboard. I am not sure whether the bug is related to my hardware. And I also plug in a third 1080p monitor (1920 * 1080, monitor 3). As settings below. (More detail in the end)

Bug Reproduce

I am not sure whether this issue is caused by my specific laptop and can only be reproduced on my laptop.

Steps to reproduce the behavior:

1. Find a file to be tested, for example, a PDF file.
2. Select this file on main monitor, and press space button to preview, and you will see that the preview window is too large.
3. However, if you drag the PDF in this example to the 1080p monitor and press space again, the preview window just has a normal size.

Expected Behavior
The size of the preview window should be appropriate on all monitors with different resolution and scaling settings.

Desktop

• OS Version: Windows 10 1909 - 18363.1316
• Hardware:
  • Laptop: ASUS ZenBook Pro Duo
  • Monitor 1: Main monitor, 3840 * 1100, scaled at 250%
  • Monitor 2: Secondary monitor, 3840 * 1100, scaled at 175%
  • Monitor 3: Plug-in via HDMI cable, 1920 * 1080, not scaled
• QuickLook Version: QuickLook-3.6.10-5-g0243636.msi from here

Screen Shots
Below are the screenshots.

• Preview on the main monitor (i.e., the icon of the file to be previewed is displayed on main 4k monitor)
  On the left is my third (1080p) monitor that I plug in, on the right is my main monitor of my laptop, on the right-bottom is my
  secondary monitor of my laptop. As you can see, the preview window is larger than my main monitor.
  

• Preview on the third monitor (1080p)- the size of preview window is normal
  

Start by reproducing the preview behavior with the reported three-monitor setup and compare the preview window sizing on monitors with different resolutions and scaling settings. Trace the preview window's monitor and DPI handling; done means the window has an appropriate size on each monitor without regressing preview behavior.