The following !set variables affect general operations and parameters that apply during editing.
The Prompt to save modified native cells check box in the Editing Setup panel from the Edit Menu tracks the state (set or unset) of this variable.
When set, rotation angles available in the spin command, and translation angles in the Stretch command, and the vertex editors for polygons and wires, are constrained to multiples of 45 degrees. However, pressing the Shift key will remove the constraint in these commands while the key is held. If the Constrain 45 variable is not set, holding Shift will impose the 45 degree angle constraint. Thus, the Shift key inverts the effective state of the Constrain 45 variable in these commands.
The Constrain angles to 45 degree multiples check box in the Editing Setup panel from the Edit Menu tracks the state (set or unset) of this variable.
By default, when a new box or polygon object is created in the database from the commands in the side menu, the new object is merged with existing boxes and polygons on the same layer, if any touch or overlap, to form a (generally more complex) polygon in the database. New wires will link with existing similar wires in the database that share an endpoint.
If this boolean variable is set, this merging will be disabled. Merging can also be disabled on a per-layer basis with the NoMerge technology file keyword, which prevents merging in all cases on a layer.
The NoMergePolys variable can be set to prevent merging of polygons, and will thus revert the merging behavior to that of releases prior to 3.1.7.
When reading data from a layout file, a different box clipping/merging capability is controlled by the Clip and merge overlapping boxes setting in the Setup page or the Import Control panel, and the corresponding MergeInput variable.
This variable tracks the state of the Clip and merge new boxes only, not polys check box in the Editing Setup panel from the Edit Menu.
If NoFixRot45 is set, the offset fix is not done. This solves the problem of gaps appearing between rotated objects, but has its own problems. Namely, rectangles aren't preserved, angles can differ from 45s. Try rotating a small rectangle, say 3x5 internal units, by 45s in this mode, and one can see it is a mess. Larger rectangles are not visually distorted, but there are 1-unit errors in the vertex placements relative to preservation of 45s or 90s. This is probably not acceptable for most work.
Really, rotating by 45 degrees is something best avoided.