Only the content area shrinks. https://pbs.twimg.com/media/CaX4xMGVIAAipYd.jpg

Thank you, Kimura-san, for your report. I met this bug yesterday. The STR at this time is, 1. Connect Win10 PC to TV with HDMI cable. 2. Open new window on PC and move it to TV. 3. Play the movie with Silverlight. 4. Disconnect HDIM cable from PC. Then, the window in TV moved to PC, but it failed to resize the window.

The problem here is that we get a WM_DPICHANGED message, as expected, but nsWindow::OnDPIChanged skips updating the window size. I can't figure out why it was written like that; I guess it was simply a mistake. Correcting the condition here also fixes the behavior in the case where you resize (rather than move) a window across a display boundary, such that more than half of it ends up on a display with a different DPI. Currently, things go kinda crazy at that point, as the auto-resize-on-DPI-change battles with the user's manual resizing. This patch makes things more stable there, too, so the user keeps control of the window. Which is probably what I originally intended here, just wrote it wrong.

Comment on attachment 8724683 [details] [diff] [review] Resize window appropriately on WM_DPICHANGED messages for dynamic resolution changes Oops, I should have caught this when I reviewed this in bug 890156.

https://hg.mozilla.org/integration/mozilla-inbound/rev/29e1faddbf53b86bf94f7554fe30c3f03f715cfe Bug 1246389 - Resize window appropriately on WM_DPICHANGED messages for dynamic resolution changes. r=emk