terminal: Screen can hold selection

src/terminal/Screen.zig

@@ -37,9 +37,11 @@ cursor: Cursor,
 /// The saved cursor
 saved_cursor: ?SavedCursor = null,
 
-/// The selection for this screen (if any).
+/// The selection for this screen (if any). This MUST be a tracked selection
-//selection: ?Selection = null,
+/// otherwise the selection will become invalid. Instead of accessing this
-selection: ?void = null,
+/// directly to set it, use the `select` function which will assert and
+/// automatically setup tracking.
+selection: ?Selection = null,
 
 /// The charset state
 charset: CharsetState = .{},
@@ -827,6 +829,32 @@ pub fn manualStyleUpdate(self: *Screen) !void {
     self.cursor.style_ref = &md.ref;
 }
 
+/// Set the selection to the given selection. If this is a tracked selection
+/// then the screen will take overnship of the selection. If this is untracked
+/// then the screen will convert it to tracked internally. This will automatically
+/// untrack the prior selection (if any).
+///
+/// Set the selection to null to clear any previous selection.
+///
+/// This is always recommended over setting `selection` directly. Beyond
+/// managing memory for you, it also performs safety checks that the selection
+/// is always tracked.
+pub fn select(self: *Screen, sel_: ?Selection) !void {
+    const sel = sel_ orelse {
+        if (self.selection) |*old| old.deinit(self);
+        self.selection = null;
+        return;
+    };
+
+    // If this selection is untracked then we track it.
+    const tracked_sel = if (sel.tracked()) sel else try sel.track(self);
+    errdefer if (!sel.tracked()) tracked_sel.deinit(self);
+
+    // Untrack prior selection
+    if (self.selection) |*old| old.deinit(self);
+    self.selection = tracked_sel;
+}
+
 /// Returns the raw text associated with a selection. This will unwrap
 /// soft-wrapped edges. The returned slice is owned by the caller and allocated
 /// using alloc, not the allocator associated with the screen (unless they match).
@@ -4079,6 +4107,26 @@ test "Screen: resize more cols requiring a wide spacer head" {
     }
 }
 
+test "Screen: select untracked" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 10, 10, 0);
+    defer s.deinit();
+    try s.testWriteString("ABC  DEF\n 123\n456");
+
+    try testing.expect(s.selection == null);
+    const tracked = s.pages.countTrackedPins();
+    try s.select(Selection.init(
+        s.pages.pin(.{ .active = .{ .x = 0, .y = 0 } }).?,
+        s.pages.pin(.{ .active = .{ .x = 3, .y = 0 } }).?,
+        false,
+    ));
+    try testing.expectEqual(tracked + 2, s.pages.countTrackedPins());
+    try s.select(null);
+    try testing.expectEqual(tracked, s.pages.countTrackedPins());
+}
+
 test "Screen: selectAll" {
     const testing = std.testing;
     const alloc = testing.allocator;

src/terminal/Selection.zig

@@ -125,8 +125,8 @@ pub fn tracked(self: *const Selection) bool {
 }
 
 /// Convert this selection a tracked selection. It is asserted this is
-/// an untracked selection.
+/// an untracked selection. The tracked selection is returned.
-pub fn track(self: *Selection, s: *Screen) !void {
+pub fn track(self: *const Selection, s: *Screen) !Selection {
     assert(!self.tracked());
 
     // Track our pins
@@ -137,10 +137,13 @@ pub fn track(self: *Selection, s: *Screen) !void {
     const tracked_end = try s.pages.trackPin(end_pin);
     errdefer s.pages.untrackPin(tracked_end);
 
-    self.bounds = .{ .tracked = .{
+    return .{
-        .start = tracked_start,
+        .bounds = .{ .tracked = .{
-        .end = tracked_end,
+            .start = tracked_start,
-    } };
+            .end = tracked_end,
+        } },
+        .rectangle = self.rectangle,
+    };
 }
 
 /// Returns the top left point of the selection.