implement ncplane_resize() and ncplane_move()

[dankamongmen]

Now that we can create and destroy ncplanes, let's add the functionality necessary to move and resize them. For moving, it's fine to just accept a new origin point (perhaps relative to either the screen or some other ncplane). For resize, rather than ncurses's wresize(), which takes new dimensions but applies them from the origin, i want to accept a new subsection of the ncplane, which will be left where it is (even if the resize is a growth, and it's now partially offscreen). move moves, resize resizes, and the resize is general.

actually, a fully general resize would require:

• section of current ncplane to keep,
• where it ought be RELATIVE TO new ncplane, and
• new dimensions of ncplane

where the new section must be wholly within the new ncplane, but the ncplane can be beyond the screen. note that move is still distinct: in this sceme, the resize is "anchored" by the subsection that we keep.

if you want to resize or move, but don't care about keeping any of it, i guess it can apply to the origin. so to resize down and to the right by 2, currently at yoff/xoff with dimensions ylen/xlen, it would be

ncplane_resize(zero-area section, {0,0}, {ylen + 2, xlen + 2})

and to resize by 2 but put the current origin at the lower right, it would be:

ncplane_resize(zero-area section, {ylen + 2 - 1, xlen + 2 - 1}, {ylen + 2, xlen + 2})

and to resize by 2 to the up and left, it would be:

ncplane_resize(zero-area section, {2, 2}, {ylen + 2, xlen + 2}

in the first example, you get two new empty rows and two new empty columns, retaining all current data. in the second, you lose all data, and have a window with its lower-right corner where the upper-left corner was. in the third, you have two new empty rows and two new empty columns, retaining all current data, but they're above and to the left of you. yeah, i like that.

you still can't implement move() via resize(), which i like. resize() is fundamentally a data-rearranging operation within the ncplane, whereas move() is rearranging data at the notcurses level.

[dankamongmen]

ncplane_move() appears to work perfectly, w00t!

[dankamongmen]

Done! We have unit tests, but I want these integrated into demo code, as well.