vPLASMA: companion app emulating the cockpit plasma display

The cockpit's second serial device joins vRIO: the 128x32 dot-matrix
plasma on COM2 (9600 8N1) that the game draws mission text and status
graphics on. VPlasma.App opens the device end of a COM port, decodes
the display's command stream, and renders the matrix in plasma orange.

The command set is recovered from two Tesla 4.10 artifacts: the game's
driver (L4PLASMA.CPP — ESC P packed-bitmap row writes, ESC G 0 cursor
hide at boot) and the factory test tool PLASMA.EXE, whose data segment
pairs each command literal with its printf description (BS/HT/LF/VT/CR
motion, ESC @ clear, ESC L home, ESC G cursor, ESC K fonts, ESC H
attributes: intensity/underline/reverse/flash). Text renders through
the classic public-domain 5x7 set standing in for the lost ROM glyphs;
fonts 0-3 give 21x4 cells, fonts 4-7 the doubled 10x2. A Self test
cycles banner/charset/graphics pages through the same parser the wire
feeds, and the wire log shows every decoded command.

Verified end-to-end over the second com0com pair (host writing COM2,
vPLASMA listening on COM12). The verify skill gains the cross-process
combo-box lesson: string-carrying CB_* messages hang across processes,
so select ports by locally computed index via CB_SETCURSEL.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/VPlasma.Core/Protocol/PlasmaProtocol.cs

@@ -0,0 +1,64 @@
+namespace VPlasma.Core.Protocol;
+
+/// <summary>
+/// The cockpit plasma display's serial command set, as recovered from the
+/// Tesla 4.10 sources and tools:
+///
+/// <para>The display is a 128×32 dot-matrix plasma panel on COM2 at
+/// <b>9600 8N1</b>, no flow control. The game side
+/// (<c>CODE\RP\MUNGA_L4\L4PLASMA.CPP</c>) renders everything into a local
+/// 1bpp buffer and streams changed rows with the <c>ESC P</c> graphics
+/// command, sending <c>ESC G 0</c> once at startup to hide the cursor. The
+/// factory test tool (<c>VWETEST\VGLTEST\PLASMA.EXE</c>) additionally
+/// exercises a text mode: printable ASCII renders at a cursor, with escape
+/// commands for clear/home, cursor visibility, font select, and text
+/// attributes (intensity/underline/reverse/flash), plus BS/HT/LF/VT/CR
+/// cursor motion.</para>
+///
+/// <para>Every multi-byte command begins with ESC (0x1B) followed by one
+/// command letter:</para>
+///
+/// <code>
+/// ESC @                     clear screen, reset text state
+/// ESC L                     home the cursor (0,0)
+/// ESC G n                   cursor mode: 00/FF hidden, 01 steady, 03 flashing
+/// ESC K n                   select font n (FF = default font 0)
+/// ESC H n                   text attributes: index 0..16 into the
+///                           intensity/underline/reverse/flash combos the
+///                           test tool enumerates; FF = defaults
+/// ESC P s y x w h  data…    graphics write: screen s (single-screen, ignored),
+///                           top row y (0..31), left byte column x (0..15),
+///                           w bytes per row, h rows, then w*h data bytes,
+///                           MSB = leftmost pixel. The game always sends
+///                           whole rows: x=0, w=16, h=1.
+/// </code>
+///
+/// <para>Where the two sources disagree on <c>ESC G</c> (the game hides the
+/// cursor with 00, the test tool with FF) both operands are treated as
+/// hidden.</para>
+/// </summary>
+public static class PlasmaProtocol
+{
+    /// <summary>Wire bit rate — the game opens PCS_9600, PCS_N81.</summary>
+    public const int BaudRate = 9600;
+
+    public const byte Esc = 0x1B;
+
+    // Single-byte cursor-motion controls (PLASMA.EXE's /b /c /l /t /v options).
+    public const byte BackSpace = 0x08;
+    public const byte HorizontalTab = 0x09;
+    public const byte LineFeed = 0x0A;
+    public const byte VerticalTab = 0x0B;
+    public const byte CarriageReturn = 0x0D;
+
+    // ESC command letters.
+    public const byte CmdClearScreen = (byte)'@';
+    public const byte CmdCursorMode = (byte)'G';
+    public const byte CmdAttributes = (byte)'H';
+    public const byte CmdFontSelect = (byte)'K';
+    public const byte CmdHomeCursor = (byte)'L';
+    public const byte CmdGraphicsWrite = (byte)'P';
+
+    /// <summary>Operand meaning "restore the default" for ESC K / ESC H.</summary>
+    public const byte OperandDefault = 0xFF;
+}