Fix panic when drawing at the edge of the screen.

[rhogenson]

When pressing tab at the edge of the screen, Helix panics in debug mode subtracting position.col - self.offset.col.

I don't fully understand the logic here, but if cut_off_start < width, then self.offset.col - position.col < width (from the definition of cut_off_start), and so self.position.col + width > self.offset.col, meaning in_bounds is true and the second condition is currently unreachable.

I believe these conditions should be reversed so that the logic for rendering partially visible characters can apply properly.

[pascalkuthe]

this happens to fix the issue but it's only "accidentally" right.

The order of this condition was never supposed to matter. cut_of_start != 0 is only true if the grapheme starts before the left edge of the view and in that case in_bounds should be false (the grapheme is not in bounds).

column_in_bounds(column) should be changed to take the widht into account:

pub fn columns_in_bounds(&self, colum: usize, width: usize) -> bool {
    self.offset.col <= colum && column + width <= self.offset.col + self.viewport.width as usize
}

[rhogenson]

Sounds good. Updated.