add ascii to programmer mode

.kiro/specs/calculator/design.md

@@ -619,10 +619,14 @@ Fields (navigable with Up/Down):
 2. DEC(s) - editable signed decimal
 3. DEC(u) - editable unsigned decimal
 4. HEX - editable hex (space-separated bytes: FF 00 AB CD)
-5. OCT - editable octal
-6. BIN - editable binary (nibble-separated: 1111 0000)
-7. ASCII - shows printable ASCII interpretation of the bytes
-   (e.g., `.ELF` or `hell` - dots for non-printable)
+5. ASCII - read-only (derived) view of the bytes, one glyph per byte,
+   MSB first, aligned column-for-column under the HEX row directly above
+   it. Printable bytes (0x20-0x7E) show as themselves; every other byte
+   shows as `.`, matching the `xxd` hex-dump convention (e.g. `.ELF`,
+   `...ascii`). Not part of the Up/Down focus cycle since it has nothing
+   to edit.
+6. OCT - editable octal
+7. BIN - editable binary (nibble-separated: 1111 0000)
 8. Expression - full expression evaluator (& | ^ ~ << >> etc.)
 
 Navigation:

engine/src/formatter.zig

@@ -169,6 +169,49 @@ pub fn formatOctal(buf: []u8, value: u128, bit_width: BitWidth) FormattedValue {
 
     return .{ .display = display, .raw = raw };
 }
+/// Format an integer's bytes as an ASCII representation for programmer mode.
+/// One glyph per byte, most-significant byte first (matching the hex byte view).
+/// Printable bytes (0x20-0x7E) render as themselves; every other byte renders
+/// as '.', matching the convention used by `xxd` and similar hex dumps.
+///
+/// Display: " .  .  .  a  s  c  i  i" - each byte is a leading space + glyph,
+///   space-separated, so the row lines up column-for-column under formatHex.
+/// Raw: "...ascii" - contiguous glyphs, clipboard-friendly.
+pub fn formatAscii(buf: []u8, value: u128, bit_width: BitWidth) FormattedValue {
+    const num_bytes: usize = @as(usize, bit_width.bits()) / 8;
+
+    // Raw: contiguous glyphs, MSB first.
+    var pos: usize = 0;
+    var k: usize = 0;
+    while (k < num_bytes) : (k += 1) {
+        const shift_amt: u7 = @intCast((num_bytes - 1 - k) * 8);
+        const byte: u8 = @intCast((value >> shift_amt) & 0xFF);
+        buf[pos] = asciiGlyph(byte);
+        pos += 1;
+    }
+    const raw = buf[0..pos];
+
+    // Display: " c" per byte, space-separated, so glyph k sits under the
+    // right hex digit of byte k in the hex row.
+    const display_start = pos;
+    k = 0;
+    while (k < num_bytes) : (k += 1) {
+        if (k > 0) {
+            buf[pos] = ' ';
+            pos += 1;
+        }
+        buf[pos] = ' ';
+        pos += 1;
+        const shift_amt: u7 = @intCast((num_bytes - 1 - k) * 8);
+        const byte: u8 = @intCast((value >> shift_amt) & 0xFF);
+        buf[pos] = asciiGlyph(byte);
+        pos += 1;
+    }
+    const display = buf[display_start..pos];
+
+    return .{ .display = display, .raw = raw };
+}
+
 pub fn formatDecimalUnsigned(buf: []u8, value: u128) FormattedValue {
     const raw_len = writeUnsignedInt(buf, value);
     const raw = buf[0..raw_len];
@@ -201,6 +244,13 @@ fn hexDigit(nibble: u4) u8 {
     return 'A' + @as(u8, nibble) - 10;
 }
 
+/// Map a byte to its printable glyph, or '.' if outside the printable ASCII
+/// range (0x20-0x7E), matching the `xxd` hex-dump convention.
+fn asciiGlyph(byte: u8) u8 {
+    if (byte >= 0x20 and byte <= 0x7E) return byte;
+    return '.';
+}
+
 fn writeUnsignedInt(buf: []u8, value: u128) usize {
     if (value == 0) {
         buf[0] = '0';
@@ -437,3 +487,45 @@ test "formatFloat: regular float" {
     const result = formatFloat(&buf, 3.14159);
     try testing.expect(std.mem.indexOf(u8, result.display, "3.14") != null);
 }
+
+test "formatAscii: printable word 64-bit" {
+    var buf: [128]u8 = undefined;
+    // 0x0000006173636969 -> bytes 00 00 00 61 73 63 69 69 -> "...ascii"
+    const result = formatAscii(&buf, 0x0000006173636969, .bits64);
+    try testing.expectEqualStrings("...ascii", result.raw);
+    // Display aligns one glyph per byte, space-separated
+    try testing.expectEqualStrings(" .  .  .  a  s  c  i  i", result.display);
+}
+
+test "formatAscii: 8-bit printable" {
+    var buf: [128]u8 = undefined;
+    const result = formatAscii(&buf, 0x41, .bits8);
+    try testing.expectEqualStrings("A", result.raw);
+    try testing.expectEqualStrings(" A", result.display);
+}
+
+test "formatAscii: 8-bit non-printable becomes dot" {
+    var buf: [128]u8 = undefined;
+    const result = formatAscii(&buf, 0x00, .bits8);
+    try testing.expectEqualStrings(".", result.raw);
+}
+
+test "formatAscii: control and high bytes become dots" {
+    var buf: [128]u8 = undefined;
+    // 0x1B (ESC) and 0xFF are both non-printable
+    const result = formatAscii(&buf, 0x1BFF, .bits16);
+    try testing.expectEqualStrings("..", result.raw);
+}
+
+test "formatAscii: boundary bytes 0x20 and 0x7E are printable" {
+    var buf: [128]u8 = undefined;
+    // 0x20 = space, 0x7E = '~'
+    const result = formatAscii(&buf, 0x207E, .bits16);
+    try testing.expectEqualStrings(" ~", result.raw);
+}
+
+test "formatAscii: 0x7F is non-printable" {
+    var buf: [128]u8 = undefined;
+    const result = formatAscii(&buf, 0x7F, .bits8);
+    try testing.expectEqualStrings(".", result.raw);
+}

src/tui/programmer.zig

@@ -65,6 +65,12 @@ pub fn drawProgrammerMode(app: *tui.App, surface: *vxfw.Surface, width: u16, hei
         draw.writeStr(surface, base_start + 2, 11, hex.display, .{ .fg = C.green });
     }
 
+    // ASCII (derived, read-only): one glyph per byte, aligned under HEX.
+    var ascii_buf: [128]u8 = undefined;
+    const ascii = engine.formatter.formatAscii(&ascii_buf, val, bw);
+    draw.writeStr(surface, base_start + 3, 2, "ASCII:", .{ .fg = C.cyan });
+    draw.writeStr(surface, base_start + 3, 11, ascii.display, .{ .fg = C.orange });
+
     // OCT
     var oct_buf: [256]u8 = undefined;
     const oct = engine.formatter.formatOctal(&oct_buf, val, bw);
@@ -72,11 +78,11 @@ pub fn drawProgrammerMode(app: *tui.App, surface: *vxfw.Surface, width: u16, hei
         .{ .fg = C.bg, .bg = C.purple, .bold = true }
     else
         .{ .fg = C.cyan };
-    draw.writeStr(surface, base_start + 3, 2, "OCT:", oct_style);
+    draw.writeStr(surface, base_start + 4, 2, "OCT:", oct_style);
     if (focused == .oct) {
-        drawFieldWithCursor(surface, base_start + 3, 11, oct.display, app.bit_cursor, 3, bw.bits(), C.purple);
+        drawFieldWithCursor(surface, base_start + 4, 11, oct.display, app.bit_cursor, 3, bw.bits(), C.purple);
     } else {
-        draw.writeStr(surface, base_start + 3, 11, oct.display, .{ .fg = C.purple });
+        draw.writeStr(surface, base_start + 4, 11, oct.display, .{ .fg = C.purple });
     }
 
     // BIN
@@ -86,15 +92,15 @@ pub fn drawProgrammerMode(app: *tui.App, surface: *vxfw.Surface, width: u16, hei
         .{ .fg = C.bg, .bg = C.yellow, .bold = true }
     else
         .{ .fg = C.cyan };
-    draw.writeStr(surface, base_start + 4, 2, "BIN:", bin_style);
+    draw.writeStr(surface, base_start + 5, 2, "BIN:", bin_style);
     if (focused == .bin) {
-        drawFieldWithCursor(surface, base_start + 4, 11, bin.display, app.bit_cursor, 1, bw.bits(), C.yellow);
+        drawFieldWithCursor(surface, base_start + 5, 11, bin.display, app.bit_cursor, 1, bw.bits(), C.yellow);
     } else {
-        draw.writeStr(surface, base_start + 4, 11, bin.display, .{ .fg = C.yellow });
+        draw.writeStr(surface, base_start + 5, 11, bin.display, .{ .fg = C.yellow });
     }
 
     // History
-    const hist_start = base_start + 6;
+    const hist_start = base_start + 7;
     const hist_end = height -| 4;
     if (hist_start < hist_end) {
         tui.drawHistory(app.history.items, surface, hist_start, hist_end);