Input, Text, Menus, and Inventory

This chapter defines string parsing, keyboard/event handling, text-surface state, menu interaction, and inventory selection. These systems share input events but retain distinct script-visible state.

Dictionary file

The dictionary file begins with 26 unsigned big-endian offsets, one for each lowercase initial letter a through z. An offset of zero means that initial has no entries.

Entries in each initial-letter sequence are prefix-compressed:

prefix_length:u8
encoded_suffix:u8[]
word_id:u16be

prefix_length characters are copied from the preceding decoded word. For each suffix byte, (byte & 0x7f) ^ 0x7f is the lowercase character. Bit 0x80 marks the final suffix byte. The following two bytes are the word identifier in big-endian order.

Dictionary lookup is case-insensitive for ASCII letters.

String slots

Profiles 2.089, 2.230, and 2.272 expose six 40-byte string slots s0..s5. Later promoted profiles expose twelve slots s0..s11. Slot operations use zero-terminated byte strings within that fixed capacity.

• Copying a logic message or normalized parsed word copies no more than 40 bytes into the destination slot.
• Prompted editing clears the destination first. Its storage limit is min(requested_maximum + 1, 40) bytes including the terminator.
• Parsing ignores slot numbers outside the selected profile’s slot range.
• Numeric prompting accepts at most four decimal characters and stores the low eight bits of the resulting unsigned value.

Direct string-slot comparison has its own normalization. It removes space, tab, ., ,, ;, :, apostrophe, !, and -; lowercases ASCII A..Z; and then requires exact equality through both zero terminators. It does not use the dictionary or parsed-word state.

Parser normalization

Parsing begins by clearing f2 (parsed input ready), f4 (parsed input already matched), the parsed word identifiers, and their normalized-token references.

The source slot is normalized into a temporary zero-terminated buffer:

• space and , . ? ! ( ) ; : [ ] { } are separators;
• apostrophe, backtick, hyphen, and double quote are dropped without creating a separator;
• separator runs collapse to one space;
• a trailing space is removed; and
• ASCII dictionary matching ignores letter case.

The normalized buffer is split into tokens and looked up in the dictionary. At most ten nonzero word identifiers are retained.

Parser results

Recognized dictionary entries with word ID zero are ignored. They do not occupy a parsed-word slot or increase the reported parsed position.

Recognized nonzero identifiers are appended in token order. Their normalized token text remains available for the action that copies a parsed word into a string slot.

At the first unknown token:

1. Store its normalized-token reference in the next output position.
2. Set the parser count/error position to retained_nonzero_identifier_count + 1.
3. Store the same one-based position in v9.
4. Set f2 and stop parsing later tokens.

If parsing reaches the end with at least one retained nonzero identifier, set the parser count to that number and set f2. If the input contains only recognized zero-ID words, leave f2 clear.

Parsed-word matching

The variable-length word-sequence condition can run only when f2 is set, the parser count/error position is nonzero, and f4 is clear.

Pattern identifiers are compared with retained parsed identifiers in order:

• 0x0001 matches exactly one parsed identifier;
• 0x270f terminates the pattern successfully without requiring all remaining parsed identifiers to be consumed; and
• every other value requires exact equality.

A full exact match also succeeds. Success sets f4, preventing another word-sequence condition from matching the same parsed input. Failure leaves f4 clear.

A terminator-only pattern can succeed after an unknown-token parse because the nonzero parser error position satisfies the input-presence check even when no dictionary identifier precedes the unknown token.

Profile 2.089 does not recognize 0x270f as a tail terminator. It first requires the pattern count to equal the parser count/error position, then compares every identifier using exact equality or the 0x0001 wildcard. Profiles 2.230, 2.272, and later use the tail-terminator behavior above.

Event queue

Input consumers share a circular queue with 20 physical event slots. Enqueueing fails when advancing the write position would equal the read position, so at most 19 events can be pending at once.

Each event has a type and a 16-bit value:

For a key whose ASCII byte is nonzero, the raw key word contains that byte as its value. For an extended key whose ASCII byte is zero, the scan-code word is retained.

The following extended key words are converted directly to type-2 direction events:

Some input paths normalize key words 0x0101 and 0x0301 to Enter 0x000d, and 0x0201 and 0x0401 to Escape 0x001b.

Profiles 2.411, 2.440, 2.917, 2.936, 3.002.086, and 3.002.102 hold 39 (raw_key_word, status_number) entries; profile 3.002.149 holds 49. A matching type-1 event becomes type 3 with the configured status number. Processing that event makes the matching status condition true.

Raw-key condition

The raw-key condition first checks v19. If it is nonzero, the condition is true without consuming another event.

Otherwise it dequeues until one of these occurs:

• the queue is empty, producing false;
• a type-1 event with nonzero value is found, storing its low byte in v19 and producing true;
• a type-1 event with zero value is found, producing false; or
• a non-type-1 event is discarded, after which polling continues.

Mapped status and movement events are therefore not returned by the raw-key condition.

Tracked key release

Selected extended keys have a pressed latch. A corresponding release clears the latch. When the profile’s release-event gate is nonzero, that release also enqueues type-2 value zero.

In profiles 2.917, 2.936, and 3.002.086, action 0xad increments the byte gate modulo 256. Profiles 2.411 and 2.440 do not expose that action. In profiles 3.002.102 and 3.002.149, 0xad sets the gate to one and 0xb5 clears it.

Text geometry and surfaces

The full-EGA text grid has 40 columns and 25 rows. One text column spans four logical picture pixels; one text row spans eight logical picture rows.

Text rectangle operations use inclusive top/bottom and left/right text-cell bounds. Full-width row clearing covers columns 0 through 39. These operations overwrite the visible text surface; they do not alter a loaded picture payload or re-decode picture commands.

The input/status configuration selects a display base row, input row, and status row. In the normal EGA presentation, display base value n adds 8 * n logical rows to later picture/object presentation. The input and status rows independently choose the eight-logical-row bands used by those text surfaces.

Disabling the input line clears its configured row and prevents ordinary input redraw. Enabling it clears/redraws that row, then draws the prompt marker and input text when present. The prompt marker is the first byte of its selected message; a zero byte suppresses it. Erasing input sends repeated backspace behavior until the visible edit length reaches zero. Refreshing the input line uses the most recently accepted input, not unaccepted live-edit characters.

The status line similarly has enabled and disabled states. Enabling redraws its configured row; disabling clears that row.

Modal text and alternate text mode

A modal message saves the covered visible rectangle, draws and formats its text window, waits for acknowledgement, and restores the prior rectangle when closed. Opening another saved window first closes the current one.

Configured modal-message actions can supply temporary row, column, and width overrides. The width is the maximum formatted text width; a zero width means 30. Row and column override the default centered placement for that single message. Without an override, row is centered within the current display text area and column is centered within the 40-column text surface from the formatted line width.

Entering alternate text-attribute mode suppresses normal object graphics updates and clears/fills the visible full-screen surface using the configured text foreground/background pair. Leaving restores normal graphics presentation and redraws configured status/input areas.

The exact 8-by-8 glyph bitmaps are platform-font inputs, not a portable core interpreter requirement. Text placement, row/column geometry, modal blocking, and save/restore behavior remain normative.

Inventory selection

Each inventory item has a display name and one-byte location. Location 0xff means carried. The inventory action lists only carried items, in item-number order, using two columns when necessary.

When inventory interaction is enabled, Enter stores the selected item number in v25 and Escape stores 0xff. When interaction is disabled, the same list is acknowledgement-only and does not produce a selection result. With no carried items, the UI displays its empty-inventory text.

Profiles 2.089, 2.230, and 2.272 have no interactive inventory variant. They always display the acknowledgement-only carried-item list, do not consult the inventory-interaction flag, and leave v25 unchanged.

Menu construction

Menu setup creates ordered headings and ordered items under the current heading. Each item has display text, a script-visible status number, and an enabled state.

Setup remains mutable until finalization. Finalization disables headings with no items, chooses the root heading and its first item as the current selection, and prevents later heading/item additions from changing the established menu. Enable and disable actions can still change an existing item by status number.

Menu state remembers the current item separately for each heading. A later menu opening resumes from the remembered heading/item state.

Menu interaction

The menu-request action requests interaction only while f14 is set. The v3 profiles add a separate menu interaction gate: a zero value set by 0xb1 prevents a pending request from opening the modal menu; a nonzero value permits it.

While open, raw Enter selects only an enabled current item. Selection enqueues a type-3 event carrying that item’s status number. Enter on a disabled item does nothing and continues waiting. Escape closes without selection.

Type-2 navigation values have these meanings:

Item movement follows the ordered circular item list and does not skip disabled items. Heading-left/right movement skips disabled headings. Leaving a heading stores its current item. Exit restores the saved visible menu rectangle, redraws or clears the status row as configured, and clears the interaction request.

Font boundary

Message substitution and ordinary window layout are specified by their action effects and observed modal geometry. Exact glyph shapes remain a platform-font concern, so full bitmap-identical text-presentation claims must provide a font input. This does not make parser, event, menu, or inventory state provisional.