Use the secondary menu icon in the display toolbar
When the user is in the Display view (visualizing a virtual or remote machine), they currently get a hamburger menu in the top right of the window.
According to the GNOME HIG (Human Interface Guidelines), these options should be part of a "secondary menu".
Secondary menus are located in the header bar and include menu items for the current view or content item. This differentiates them from primary menus, which include menu items that relate to an entire application (such as Preferences and About).
For more info, see https://developer.gnome.org/hig/stable/secondary-menus.html.en
Dive into the code
In Boxes we set the icon image in the data/ui/display-toolbar.ui#L56 file.
The desired secondary menu image is called "view-more-symbolic".
Submitting your contribution
Firstly, read https://wiki.gnome.org/Git/CommitMessages
Please write a legible commit message. Prefix the first line with "
display-toolbar:" and a short sentence (no longer than 72 chars).
In the body of the message, please link to the HIG section for secondary-menu and explain briefly the reasoning for this change.
At the bottom of your message (after a blank line), add a reference to this issue:
After you are done, please send your changes as a Merge Request.