What version of FileMaker Pro are you using? On what system, Windows or Mac?
This is on Filemaker Pro Advanced 13.0x on a Mac. It is slowly driving me crazy not being able to find out how to do it or not do it.
The behavior you are describing was the way it worked in version 11 or earlier (color going all the way across).
I have not seen this in version 12 or version 13. In these it only goes as far as the width specified in the Inspector.
When there is an object on your layout that is anchored to the right, or not anchored (to make it stay in the center), then your layout stretches horizontally to accommodate the scaling.
The same goes for vertical expansion.
I always draw a little line wich is 0 pt wide and anchor it to the right and the bottom. Now all my layouts are colored over the complete area.
Thanks for giving me a place to look. I depended on resizing the window and nothing moved so I assumed nothing was unanchored. It turns out one item was not anchored to the left and that displayed the wide header. Funny thing is any object I set as unanchored on that layout does not move with resizing the window.
I have the display I want but why that would be the case is still a mystery. It is a simple layout with 3 tabs and a few portals. Even duplicating the layout keeps the abnormal behavior.