Gtk.Align

Controls how a widget deals with extra space in a single (x or y) dimension.

Alignment only matters if the widget receives a "too large" allocation, for example if you packed the widget with the Gtk.expand flag inside a Gtk.Box, then the widget might get extra space. If you have for example a 16x16 icon inside a 32x32 space, the icon could be scaled and stretched, it could be centered, or it could be positioned to one side of the space.

Note that in horizontal context @GTK_ALIGN_START and @GTK_ALIGN_END are interpreted relative to text direction.

Align.FILL: stretch to fill all space if possible, center if no meaningful way to stretch
Align.START: snap to left or top side, leaving space on right or bottom
Align.END: snap to right or bottom side, leaving space on left or top
Align.CENTER: center natural width of widget inside the allocation