On Linux Mint 17.3, using a direct-from-github compilation of the release branch, certain long-running notifications such as “Compiling Shaders” from the engine have trouble staying on top of certain windows.
Whenever the engine window is focused, the notification drops below the selected window and remains that way until either the main editor window is moved, or its title bar is clicked. The behaviour is identical for other windows spawned by the editor, such as the content browser or Blueprint editor.
On occasion, even clicking the editor title bar does not raise the notification, and since no other indication that a long-running operation is active can be seen, it is commonly an issue during material and level editing.
Linux Mint 17.3 Rosa (64-bit)
Nvida GeForce GTX 660Ti, 2048MB
Engine Version: 4.10.1-0+++depot+UE4-Releases+4.10