Amiga Screen Resolutions, Modes & Overscan

[Zac67]

Don't know if I got you right but screen dimensions and display mode are somewhat independent on the Amiga. You can e.g. open a 320 wide screen in Hires, filling only part of the screen. The overscan settings define the maximum visible size within a certain mode. Overscan just widens the window in which screen data is displayed. It doesn't do anything to the pixels themselves.

[Zac67]

AFAIR RemakeDisplay() and RethinkDisplay() are only necessary when you're working with custom Copper lists.

[...]
Yes, here it is:

RethinkDisplay()

RethinkDisplay() reworks Intuition's internal state data, rethinks the relationship of all of the
screen ViewPorts to each other and reconstructs the entire Intuition display by calling the
graphics primitives MrgCop() and LoadView(). This includes all the screens in the display, not
just the ones controlled by your program. It is especially handy if you are creating custom
screens and want to make up your own lists of Copper instructions for handling the display.
For more information about the Copper, see the Amiga ROM Kernel Manual and Amiga
Hardware Reference Manual.

RethinkDisplay() makes calls to the graphics primitives MrgCop() and LoadView(), which causes
the display of Intuition's screens to be reconstructed. MrgCop() merges all the various Copper
instructions for different ViewPorts of the display into a single instruction stream. This creates
a complete set of instructions for each display field (complete scanning of the video beam from
top to bottom of the video display). LoadView() uses this merged Copper instruction list to
create the display. Before calling RethinkDisplay(), you may wish to call MakeScreen() to create
the Copper instruction list for your own custom screens.
Note that RethinkDisplay() can take several milliseconds to run, and it locks out all other tasks
while it runs. This can seriously degrade the performance of the multi-tasking Executive, so
don't use this routine lightly.

RemakeDisplay()

The function RemakeDisplay reconstructs the entire Intuition display. It calls MakeScreen() for
every screen in the system and then calls RethinkDisplay(). As with RethinkDisplay(), RemakeDisplay()
can take several milliseconds to run, and it locks out all other tasks while it runs.
This can seriously degrade the performance of the multi-tasking Executive, so do not use this
routine lightly.