This is how I normally use my MacBook Pro in a desktop setup: I hook it up to a 23″ LG Flatron monitor, and use the MacBook Pro’s display as a secondary screen (I keep the laptop on a stand on my right). Obviously, most of my work happens in the primary monitor area (1), while I usually keep the smaller MacBook Pro’s display (2) for things I need to keep in my peripheral vision, so to speak. 

I didn’t find Mountain Lion’s display management particularly problematic, though I admit it was annoying not being able to have two full-screen applications running side-by-side. So the changes Mavericks introduced in this regard are definitely welcome.

However, I’ve run into a small, but rather annoying issue with MarsEdit, which I’ll try to describe the best I can.

In MarsEdit, my window configuration when I write an article is as follows:

This is happening in my primary display (the external LG monitor). The blog entry editing window occupies most of the screen real estate, and I keep the Preview window aligned on the right. When I add pictures to an article, usually the Media manager window remains hidden in the background behind the other windows. No app window is usually visible on the MacBook Pro’s display: I keep them all gathered in the primary monitor.

Here’s what happens in Mavericks: when I move to a full-screen application (usually Safari or Chrome, because I may have to check a few things while I write an article) and then go back to MarsEdit, the primary monitor where MarsEdit windows reside loses focus (the menu bar gets dimmed), the MacBook Pro’s display gets the focus, and looks like this:

That is, the Blog entry editing window remains where it was (as it should) on the primary monitor, but the Media manager and the Preview windows get displaced and assigned to the MacBook Pro’s display like you see in the figure^[1]. I have to manually drag the Preview window back to where it was (aligned alongside the editing window) and resize it every time, because when the Preview window is moved to the MacBook Pro’s display it gets automatically resized to fit the MacBook Pro’s screen height (900 pixels versus the 1080 of the external monitor).

This behaviour is reproducible, and windows get (dis)placed in the exact same position every time I move to a full-screen app and then return to MarsEdit.

I don’t know if this behaviour is limited to MarsEdit or if it happens with other applications which use multiple windows in their typical workspace configuration. So far I’ve noticed the issue with MarsEdit only — most applications I use have just one main window, so it’s something a bit difficult to verify. Applications like TextEdit or TextWrangler, where it’s normal to have multiple documents open, seem to keep their document windows well arranged.

Has any other MarsEdit user with OS X Mavericks and similar dual-monitor configuration noticed this issue with their setup? I’ll let MarsEdit’s developer know about it, and I’ll update this article with whatever new information I may gather.

Update: Daniel Jalkut of Red Sweater Software, developer of MarsEdit, told me via email that he’s working on a fix for this issue. He passed me a beta release of MarsEdit for testing and the issue appears to have gone. Expect the fix to come with the next MarsEdit minor update.