Left Corner of Header Bar is Not Rounded and Window Controls are Truncated
The top left corner of the window header bar of Gnome Disks is not rounded, when the user chooses to place window-controls (close, minimize, maximize) on the left side of the header bar.
Also, the window-controls are hidden past the left edge of the window, because the left panel in Disks is not wide enough to display the window-controls, the application's name, and the "hamburger" menu.
The window controls can be revealed if the user expands the left "Side Panel" of the Disks application.
Another side-effect of this issue is that the left "Side Panel" can be compressed by sliding the separator to the left, so that the panel, the application title, the and "hamburger" menu are no longer visible.
Contrast this with the Gedit application, which doesn't have this issue. In Gedit, left "Side Panel" has a set minimum width, which allows enough space for all of the controls. The "Side Panel" width can be expanded, but it can not be reduced beyond the preset minimum. (Note, If you test Gedit, remember to enable the "Side Panel" by selecting "View" and "Show Panel" from the hamburger menu).
Version Information: Application Version: gnome-disk-utility 3.32.1-1ubuntu1 GTK Version: libgtk-3-0:amd64 3.24.8-1ubuntu1 Distro and Version: Ubuntu 19.04
Screenshot of the issue:
Screenshot of Disks, with the "Side Panel" expanded. This is what the header bars should look like: