Add document and half-page motions

src/tui.zig

@@ -324,11 +324,16 @@ pub const Client = struct {
         const gutter_digits = @max(@as(usize, 2), decimalDigits(total_lines));
         const gutter_width = @min(self.viewport.width, gutter_digits + 2);
         const content_width = if (self.viewport.width > gutter_width) self.viewport.width - gutter_width else 0;
+        const first_visible_line = firstVisibleLineForCursor(cursor_line, max_body_lines);
         var visible_line_index: usize = 0;
         var body_lines_used: usize = 0;
         var line_start_byte: usize = 0;
         var line_iter = std.mem.splitScalar(u8, snap.bytes, '\n');
         while (line_iter.next()) |line| : (visible_line_index += 1) {
+            if (visible_line_index < first_visible_line) {
+                line_start_byte += line.len + 1;
+                continue;
+            }
             if (body_lines_used >= max_body_lines) break;
             try appendEditorLine(
                 allocator,
@@ -1076,6 +1081,7 @@ pub const Client = struct {
                 if (std.mem.eql(u8, text, "L") or std.mem.eql(u8, text, "$")) return self.applyProtocol("command move_line_end");
                 if (std.mem.eql(u8, text, "%")) return self.jumpToMatch(null);
                 if (std.mem.eql(u8, text, "m")) return self.openPrefix(.match);
+                if (std.mem.eql(u8, text, "G")) return self.applyProtocol("command move_document_end");
                 if (std.mem.eql(u8, text, "g")) return self.openPrefix(.go);
                 if (std.mem.eql(u8, text, "j")) return self.repeatProtocol("command move_down", self.takeRepeat());
                 if (std.mem.eql(u8, text, "k")) return self.repeatProtocol("command move_up", self.takeRepeat());
@@ -1100,6 +1106,8 @@ pub const Client = struct {
                 .end => try self.applyProtocol("command move_line_end"),
                 .page_up => try self.repeatProtocol("command move_up", @max(@as(usize, 1), self.viewport.height - 2)),
                 .page_down => try self.repeatProtocol("command move_down", @max(@as(usize, 1), self.viewport.height - 2)),
+                .ctrl_u => try self.halfPage(.up),
+                .ctrl_d => try self.halfPage(.down),
                 else => self.unknownPrefixOrInput("normal"),
             },
             .unknown => self.unknownPrefixOrInput("normal"),
@@ -1810,6 +1818,10 @@ pub const Client = struct {
 
     fn applyGoRail(self: *Client, event: input.Event) !void {
         const text = eventText(event) orelse return self.unknownPrefixOrInput("normal");
+        if (std.mem.eql(u8, text, "g")) return self.applyProtocol("command move_document_start");
+        if (std.mem.eql(u8, text, "G")) return self.applyProtocol("command move_document_end");
+        if (std.mem.eql(u8, text, "u")) return self.halfPage(.up);
+        if (std.mem.eql(u8, text, "d")) return self.halfPage(.down);
         if (std.mem.eql(u8, text, "a")) return self.moveParameter(.next);
         if (std.mem.eql(u8, text, "A")) return self.moveParameter(.previous);
         if (std.mem.eql(u8, text, "e")) return self.gotoDiagnostic(.next);
@@ -2201,6 +2213,17 @@ pub const Client = struct {
         self.noteDocumentChanged();
     }
 
+    const PageDirection = enum { up, down };
+
+    fn halfPage(self: *Client, direction: PageDirection) !void {
+        const rows = @max(@as(usize, 1), (self.viewport.height - 1) / 2);
+        const command = switch (direction) {
+            .up => "command move_up",
+            .down => "command move_down",
+        };
+        try self.repeatProtocol(command, rows);
+    }
+
     fn repeatProtocol(self: *Client, line: []const u8, repeat: usize) !void {
         var i: usize = 0;
         while (i < repeat) : (i += 1) try self.applyProtocol(line);
@@ -2571,6 +2594,12 @@ fn countDocumentLines(bytes: []const u8) usize {
     return lines;
 }
 
+fn firstVisibleLineForCursor(cursor_line: usize, max_body_lines: usize) usize {
+    if (max_body_lines == 0) return cursor_line;
+    if (cursor_line < max_body_lines) return 0;
+    return cursor_line - max_body_lines + 1;
+}
+
 fn decimalDigits(value: usize) usize {
     var digits: usize = 1;
     var n = value;
@@ -5143,3 +5172,16 @@ test "regular: insert Enter copies current line indent and Tab follows tab-inden
     snap = try tabs.session.snapshot();
     try std.testing.expectEqualStrings("\titem    x", snap.bytes);
 }
+
+test "regular: vertical viewport follows cursor line" {
+    var client = try Client.init(std.testing.allocator, .{ .width = 32, .height = 6 });
+    defer client.deinit();
+
+    try client.handleTraceLine("open l1\nl2\nl3\nl4\nl5\nl6\nl7\nl8\nl9\nl10\nl11\nl12");
+    try client.applyProtocol("command move_document_end");
+    const frame = try client.render(std.testing.allocator);
+    defer std.testing.allocator.free(frame);
+
+    try std.testing.expect(std.mem.indexOf(u8, frame, "12│") != null);
+    try std.testing.expect(std.mem.indexOf(u8, frame, " 1│") == null);
+}