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const std = @import("std");
const Allocator = std.mem.Allocator;
const assert = std.debug.assert;
const size = @import("size.zig");
/// The possible reference locations for a point. When someone says "(42, 80)"
/// in the context of a terminal, that could mean multiple things: it is in the
/// current visible viewport? the current active area of the screen where the
/// cursor is? the entire scrollback history? etc.
///
/// This tag is used to differentiate those cases.
pub const Tag = enum {
/// Top-left is part of the active area where a running program can
/// jump the cursor and make changes. The active area is the "editable"
/// part of the screen.
///
/// The bottom-right of the active tag differs from all other tags
/// because it includes the full height (rows) of the screen, including
/// rows that may not be written yet. This is required because the active
/// area is fully "addressable" by the running program (see below) whereas
/// the other tags are used primarily for reading/modifying past-written
/// data so they can't address unwritten rows.
///
/// Note for those less familiar with terminal functionality: there
/// are escape sequences to move the cursor to any position on
/// the screen, but it is limited to the size of the viewport and
/// the bottommost part of the screen. Terminal programs can't --
/// with sequences at the time of writing this comment -- modify
/// anything in the scrollback, visible viewport (if it differs
/// from the active area), etc.
active,
/// Top-left is the visible viewport. This means that if the user
/// has scrolled in any direction, top-left changes. The bottom-right
/// is the last written row from the top-left.
viewport,
/// Top-left is the furthest back in the scrollback history
/// supported by the screen and the bottom-right is the bottom-right
/// of the last written row. Note this last point is important: the
/// bottom right is NOT necessarily the same as "active" because
/// "active" always allows referencing the full rows tall of the
/// screen whereas "screen" only contains written rows.
screen,
/// The top-left is the same as "screen" but the bottom-right is
/// the line just before the top of "active". This contains only
/// the scrollback history.
history,
};
/// An x/y point in the terminal for some definition of location (tag).
pub const Point = union(Tag) {
active: Coordinate,
viewport: Coordinate,
screen: Coordinate,
history: Coordinate,
pub inline fn coord(self: Point) Coordinate {
return switch (self) {
.active,
.viewport,
.screen,
.history,
=> |v| v,
};
}
};
pub const Coordinate = struct {
/// x can use size.CellCountInt because the number of columns
/// can't ever be more than a valid number of columns in a Page.
x: size.CellCountInt = 0,
/// y does not use size.CellCountInt because certain coordinate
/// usage such as screen/history can have more rows than are possible
/// in a single page.
y: u32 = 0,
pub fn eql(self: Coordinate, other: Coordinate) bool {
return self.x == other.x and self.y == other.y;
}
};
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