terminal: add Selection struct

src/terminal/Selection.zig

@@ -0,0 +1,87 @@
+/// Represents a single selection within the terminal
+/// (i.e. a highlight region).
+const Selection = @This();
+
+const std = @import("std");
+const point = @import("point.zig");
+const Point = point.Point;
+
+/// Start and end of the selection. There is no guarantee that
+/// start is before end or vice versa. If a user selects backwards,
+/// start will be after end, and vice versa. Use the struct functions
+/// to not have to worry about this.
+start: Point,
+end: Point,
+
+/// Returns true if the selection contains the given point.
+///
+/// This recalculates top left and bottom right each call. If you have
+/// many points to check, it is cheaper to do the containment logic
+/// yourself and cache the topleft/bottomright.
+pub fn contains(self: Selection, p: Point) bool {
+    const tl = self.topLeft();
+    const br = self.bottomRight();
+
+    // If on top line, just has to be left of X
+    if (p.y == tl.y) return p.x >= tl.x;
+
+    // If on bottom line, just has to be right of X
+    if (p.y == br.y) return p.x <= br.x;
+
+    // If between the top/bottom, always good.
+    return p.y > tl.y and p.y < br.y;
+}
+
+/// Returns the top left point of the selection.
+pub fn topLeft(self: Selection) Point {
+    return switch (self.order()) {
+        .forward => self.start,
+        .reverse => self.end,
+    };
+}
+
+/// Returns the bottom right point of the selection.
+pub fn bottomRight(self: Selection) Point {
+    return switch (self.order()) {
+        .forward => self.end,
+        .reverse => self.start,
+    };
+}
+
+/// The order of the selection (whether it is selecting forward or back).
+const Order = enum { forward, reverse };
+
+fn order(self: Selection) Order {
+    if (self.start.y < self.end.y) return .forward;
+    if (self.start.y > self.end.y) return .reverse;
+    if (self.start.x <= self.end.x) return .forward;
+    return .reverse;
+}
+
+test "Selection: contains" {
+    const testing = std.testing;
+    {
+        const sel: Selection = .{
+            .start = .{ .x = 5, .y = 1 },
+            .end = .{ .x = 3, .y = 2 },
+        };
+
+        try testing.expect(sel.contains(.{ .x = 6, .y = 1 }));
+        try testing.expect(sel.contains(.{ .x = 1, .y = 2 }));
+        try testing.expect(!sel.contains(.{ .x = 1, .y = 1 }));
+        try testing.expect(!sel.contains(.{ .x = 5, .y = 2 }));
+    }
+
+    // Reverse
+    {
+        const sel: Selection = .{
+            .start = .{ .x = 3, .y = 2 },
+            .end = .{ .x = 5, .y = 1 },
+        };
+
+        try testing.expect(sel.contains(.{ .x = 6, .y = 1 }));
+        try testing.expect(sel.contains(.{ .x = 1, .y = 2 }));
+        try testing.expect(!sel.contains(.{ .x = 1, .y = 1 }));
+        try testing.expect(!sel.contains(.{ .x = 5, .y = 2 }));
+    }
+}

src/terminal/main.zig

@@ -2,10 +2,12 @@ const stream = @import("stream.zig");
 const ansi = @import("ansi.zig");
 const csi = @import("csi.zig");
 const sgr = @import("sgr.zig");
+const point = @import("point.zig");
 pub const color = @import("color.zig");
 
 pub const Terminal = @import("Terminal.zig");
 pub const Parser = @import("Parser.zig");
+pub const Selection = @import("Selection.zig");
 pub const Stream = stream.Stream;
 pub const CursorStyle = ansi.CursorStyle;
 pub const DeviceAttributeReq = ansi.DeviceAttributeReq;
@@ -17,6 +19,7 @@ pub const EraseDisplay = csi.EraseDisplay;
 pub const EraseLine = csi.EraseLine;
 pub const TabClear = csi.TabClear;
 pub const Attribute = sgr.Attribute;
+pub const Point = point.Point;
 
 // Not exported because they're just used for tests.
 
@@ -24,9 +27,11 @@ test {
     _ = ansi;
     _ = color;
     _ = csi;
+    _ = point;
     _ = sgr;
     _ = stream;
     _ = Parser;
+    _ = Selection;
     _ = Terminal;
 
     _ = @import("osc.zig");

src/terminal/point.zig

@@ -0,0 +1,7 @@
+/// Point is a point within the terminal grid. A point is ALWAYS
+/// zero-indexed. If you see the "Point" type, you know that a
+/// zero-indexed value is expected.
+pub const Point = struct {
+    x: usize = 0,
+    y: usize = 0,
+};