...spacesToPrint =
+    sizediff_t spacesToPrint =
         f.width // start with the minimum width
         - digits.length  // take away...

...is D1.  D2 does support appending different width characters to dchar[], I'm not sure...

...release {
    const currentWidth = width;
    const currentHeight = height;
    scope (exit) {
        assert(currentWidth == width);
        assert(currentHeight == height...

...possible):

void move(...)
    in {
        // ...
    } out {
        assert(width == old.width);
        assert(height == old.height);
    } body {
        // moving...

...debug {
        const currentWidth = width;
        const currentHeight = height;
        scope (exit) {
            assert(currentWidth == width);
            assert(currentHeight == height...

...allowed to change in a certain way
	// width and height of this Rectangle need to...

...int currentWidth = width;
    int currentHeight = height;
    // moving the rectangle here
    assert(currentWidth == width);
    assert(currentHeight...

...I solved it with:

void bar(char* buf, int width, int height)

Good old C :)

...struct not class), generalize within reason (character width).

Would have been great to have a...

...may be useful, e.g. for fixed width printing stuff:
  size_t getPhysPos(char[] str...