Yo, I'm using Xubuntu 16.04, Mousepad 0.4.0, and Thunar 1.6.10. BUG REPRODUCING STEPS: Step 1. Get an SFTP connection open with Thunar. Step 2. Open Mousepad by selecting it from the menu. (not by double-clicking a file, etc.) Step 3. Using non-empty text file FILE_A from the Thunar window from Step 1, drag and drop FILE_A from the Thunar window into the Mousepad instance from Step 2. EXPECTED RESULTS: The contents of FILE_A from Step 3 will be visible in Mousepad. ACTUAL RESULTS (bug): The contents of FILE_A from Step 3 are not visible in Mousepad. MORE INFORMATION: Double-clicking FILE_A from Step 3 results in a Mousepad instance opening and correctly displaying the file contents. (suggesting this bug might be easy to fix) Dragging and dropping FILE_A from a Thunar window representing the local file system instead of an SFTP-connected Thunar window results in a Mousepad instance opening and correctly displaying the file contents. When using the BUG REPRODUCING STEPS, the name of FILE_A is displayed differently in the tab than when not using the BUG REPRODUCING STEPS. For example, file name "new file" will be displayed as "new%20file". I didn't try reproducing this bug in any other environments. Good luck.
Here's the command prompt output when performing the BUG REPRODUCING STEPS: (mousepad:11871): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width 54 and height -3
This bug is not present in Xubuntu 18.04. Nice job, someone.