BT_POD_RGB: the authentic RGB-split output -- one window per VGA PORT

Implements what the pod actually does (pod-hardware.md THE RGB SPLIT): a VGA
port's R/G/B lines each drive a separate mono MFD monitor, so a window is not
one MFD -- it is one PORT carrying up to three.  BT_POD_RGB=1 collapses the
five MFD windows into the two ports the cab drives (Port A: Comm=red,
Mfd2=green, Heat=blue; Port B: Mfd1=red, Mfd3=green) and composites each
group's planes into the colour channels, leaving the radar on its own
full-colour port.  Channel comes from the live port (GetEnableID), never a
hardcoded table, so an Eng-page swap follows automatically; BlankColor planes
contribute nothing, exactly as on the pod.  Implies BT_POD_SURFACES (bare
640x480 pictures -- the cab's buttons are physical).

Verified locally (bare windows, "RGB COMPOSITE of 2 plane(s): Comm Mfd2") and
LIVE ON NICK'S CRASH CART over the tailnet: Port A -> DISPLAY4, Port B ->
DISPLAY2, radar -> DISPLAY1, all exact-fit.  Pod scratch kit included (ssh
helper, layout cfgs for both modes, launcher; the mission-egg launcher fix --
a bare MP.EGG exits the mission loop with no relay, and BT_FE_SOLO parks at
the menu, so neither lights the panels).

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

engine/MUNGA_L4/L4GLASSWIN.cpp

@@ -115,6 +115,14 @@ struct GWin
 	int         wantX, wantY;
 	int         restored;		// wantX/wantY came from glass_layout.cfg -> don't re-snap
 	int         noFrame;		// ",noframe" in the cfg -> WS_POPUP, drag by the surface
+
+	// RGB CHANNEL GROUP (BT_POD_RGB): on splitter-wired pod glass this window
+	// is one VGA PORT feeding up to three mono monitors through R/G/B.  These
+	// are the OTHER surfaces sharing the port; each is composited into its own
+	// channel by BlitSurface.  groupCount 0 = ordinary single-surface window.
+	const char *groupPort[3];
+	const char *groupAlt[3];	// the Eng<n> twin, or NULL
+	int         groupCount;
 };
 
 static GWin  gWins[8];
@@ -124,7 +132,8 @@ static int            pressedAddress = -1;
 static unsigned char  latched[128];
 static int            gRadarRot = 3;			// BT_GAUGE_SEC_ROT (default CW, upright)
 static bool           sRepositionedToMain = false;
-static unsigned long *gStage = NULL;			// 640*480 BGRA staging (shared, main-thread)
+static unsigned long *gStage = NULL;	// 640*480 BGRA staging (shared, main-thread)
+static unsigned long *gStage2 = NULL;	// RGB composite scratch (BT_POD_RGB)
 
 static HFONT titleFont  = NULL;
 static HFONT buttonFont = NULL;
@@ -417,6 +426,21 @@ static const char *layoutFileName = "glass_layout.cfg";
 // The Flight Controls window (no surface at all) is not created.
 //    BT_POD_SURFACES=1                -> every display window goes bare
 //    glass_layout.cfg "<title>=x,y,bare" -> just that one (mixed rigs)
+// BT_POD_RGB=1 -- the pod's REAL video wiring (see pod-hardware.md §THE RGB
+// SPLIT): one VGA port per window, its R/G/B analog lines split to three
+// monochrome MFD monitors.  Implies pod surface mode.
+static int
+	PodRgbSplitMode()
+{
+	static int m = -1;
+	if (m < 0)
+	{
+		const char *e = getenv("BT_POD_RGB");
+		m = (e != NULL && e[0] != 0 && e[0] != '0') ? 1 : 0;
+	}
+	return m;
+}
+
 static int
 	PodSurfaceMode()
 {
@@ -425,6 +449,8 @@ static int
 	{
 		const char *e = getenv("BT_POD_SURFACES");
 		m = (e != NULL && *e != '\0' && *e != '0') ? 1 : 0;
+		if (!m && PodRgbSplitMode())
+			m = 1;					// the RGB split is pod glass -- always bare
 		if (m)
 			DEBUG_STREAM << "[glasswin] POD SURFACE MODE: bare surfaces, no "
 				"button banks (physical pod buttons assumed)\n" << std::flush;
@@ -817,6 +843,71 @@ static void
 	}
 	int ow = 0, oh = 0;
 	svga->ExpandPlaneToBGRA(mask, palId, tint, w->rotate, gStage, &ow, &oh);
+
+	// ---------------------------------------------------------------------
+	// RGB CHANNEL COMPOSITE (BT_POD_RGB, 2026-08-06) -- the AUTHENTIC pod
+	// output.  The cab does not give each mono MFD its own video port: one
+	// VGA port's R/G/B analog lines are SPLIT to three monochrome monitors,
+	// and the game puts a different surface in each colour channel of one
+	// palettized framebuffer (L4GAUGE.CFG: Comm=red, Mfd2=green, Heat=blue
+	// on clut2; Mfd1=red, Mfd3=green on clut1 -- and
+	// L4GraphicsPort::BuildSecondaryColor writes exactly ONE component per
+	// port, which IS the split).  So on splitter-wired glass this window is
+	// not one MFD: it is one VGA PORT, carrying up to three.  Composite the
+	// group's planes into this frame, each in its own channel, and let the
+	// hardware separate them again.
+	//
+	// Channel comes from the port itself (GetEnableID), so the authored
+	// config -- including a page swap that hands the channel to an Eng
+	// plane -- decides, never a hardcoded table here.
+	// ---------------------------------------------------------------------
+	if (w->groupCount > 0 && ow > 0 && oh > 0)
+	{
+		const int n = ow * oh;
+		for (int gi = 0; gi < w->groupCount; ++gi)
+		{
+			L4GraphicsPort *gp =
+				static_cast<L4GraphicsPort*>(gr->GetGraphicsPort(w->groupPort[gi]));
+			if (gp == NULL)
+				continue;
+			// honour the live Mfd<n>/Eng<n> page swap: take whichever twin
+			// currently owns a channel
+			if (gp->GetEnableID() == L4GraphicsPort::BlankColor
+				&& w->groupAlt[gi] != NULL)
+			{
+				L4GraphicsPort *ga =
+					static_cast<L4GraphicsPort*>(gr->GetGraphicsPort(w->groupAlt[gi]));
+				if (ga != NULL && ga->GetEnableID() != L4GraphicsPort::BlankColor)
+					gp = ga;
+			}
+			const int ch = gp->GetEnableID();
+			unsigned long chMask;
+			switch (ch & 0x7F)
+			{
+			case L4GraphicsPort::RedChannel:   chMask = 0x00FF0000ul; break;
+			case L4GraphicsPort::GreenChannel: chMask = 0x0000FF00ul; break;
+			case L4GraphicsPort::BlueChannel:  chMask = 0x000000FFul; break;
+			default: continue;			// blank / direct-colour -> contributes nothing
+			}
+			int gw = 0, gh = 0;
+			// -1 tint would palette-expand; pass white so the plane comes back
+			// as full-intensity mono, then keep only this port's channel.
+			svga->ExpandPlaneToBGRA(gp->GetBitMask(), gp->paletteID,
+				(int)0x00FFFFFF, w->rotate, gStage2, &gw, &gh);
+			if (gw != ow || gh != oh)
+				continue;
+			for (int i = 0; i < n; ++i)
+				gStage[i] |= (gStage2[i] & chMask);
+		}
+		if (log)
+		{
+			DEBUG_STREAM << "[glass] '" << w->title << "' RGB COMPOSITE of "
+				<< w->groupCount << " plane(s):";
+			for (int gi = 0; gi < w->groupCount; ++gi)
+				DEBUG_STREAM << " " << w->groupPort[gi];
+			DEBUG_STREAM << "\n" << std::flush;
+		}
+	}
 	if (log)
 	{
 		int nz = 0, n = ow * oh;
@@ -1126,6 +1217,8 @@ void
 	sRepositionedToMain = false;
 	if (gStage == NULL)
 		gStage = new unsigned long[640 * 480];
+	if (gStage2 == NULL)
+		gStage2 = new unsigned long[640 * 480];
 
 	// Build the seven windows.  Order fixes the ComputeLayout roles (0..6).
 	BuildMfd  (gWins[0], "Heat MFD",   "Heat", NULL,   0x2F);	// UL  0x28-0x2F
@@ -1147,6 +1240,42 @@ void
 			gWinCount = 6;										// drop Flight Controls
 	}
 
+	// RGB SPLIT MODE (BT_POD_RGB): the cab's real wiring -- ONE VGA port per
+	// window, its R/G/B lines split to three mono monitors.  Collapse the five
+	// separate MFD windows into the TWO ports the pod actually drives
+	// (L4GAUGE.CFG clut2 = Comm/Mfd2/Heat, clut1 = Mfd1/Mfd3), each window
+	// compositing its group into the colour channels; the radar keeps its own
+	// full-colour port.  Channels are read live from each port, so a page swap
+	// to an Eng plane follows automatically.
+	if (PodRgbSplitMode())
+	{
+		GWin port2 = gWins[0];					// reuse the Heat window's shape
+		port2.title       = "VGA Port A";		// Comm=red, Mfd2=green, Heat=blue
+		port2.portPrimary = "Heat";				// base plane (blue); group adds the rest
+		port2.portAlt     = NULL;
+		port2.groupCount  = 2;
+		port2.groupPort[0] = "Comm";  port2.groupAlt[0] = NULL;
+		port2.groupPort[1] = "Mfd2";  port2.groupAlt[1] = "Eng2";
+		port2.monoTint    = (int)0x000000FF;	// Heat rides BLUE
+
+		GWin port1 = gWins[3];					// the Mfd1 window's shape
+		port1.title       = "VGA Port B";		// Mfd1=red, Mfd3=green (blue spare)
+		port1.portPrimary = "Mfd1";
+		port1.portAlt     = "Eng1";
+		port1.groupCount  = 1;
+		port1.groupPort[0] = "Mfd3";  port1.groupAlt[0] = "Eng3";
+		port1.monoTint    = (int)0x00FF0000;	// Mfd1 rides RED
+
+		GWin radar = gWins[5];					// unchanged: its own colour port
+
+		gWins[0] = port2;
+		gWins[1] = port1;
+		gWins[2] = radar;
+		gWinCount = 3;
+		DEBUG_STREAM << "[glasswin] RGB SPLIT MODE: 2 VGA ports + radar "
+			"(each port's R/G/B feeds three mono panels)\n" << std::flush;
+	}
+
 	titleFont = CreateFontW(-11, 0, 0, 0, FW_BOLD, 0, 0, 0,
 		DEFAULT_CHARSET, 0, 0, CLEARTYPE_QUALITY, 0, L"Segoe UI");
 	buttonFont = CreateFontW(-10, 0, 0, 0, FW_NORMAL, 0, 0, 0,

scratchpad/pod/glass_layout_rgb.cfg

@@ -0,0 +1,9 @@
+# BT411 -- ALPHA-MR, RGB SPLIT mode (BT_POD_RGB=1).  Each line is ONE VGA PORT
+# whose R/G/B lines feed three mono MFD monitors:
+#   VGA Port A : Comm=red, Engineering/Mfd2=green, Heat=blue
+#   VGA Port B : Mfd1=red, Mfd3=green (blue spare)
+# Console-session displays: DISPLAY3 800x600 primary (main view),
+# DISPLAY4 800,122 / DISPLAY2 1440,123 / DISPLAY1 2080,124 (all 640x480).
+VGA Port A=800,122,640,480,noframe,bare
+VGA Port B=1440,123,640,480,noframe,bare
+Secondary / Radar=2080,124,480,640,noframe,bare

scratchpad/pod/runpod.bat

@@ -1,18 +1,12 @@
 @echo off
-REM BT411 pod launch -- runs from the game's content dir in the CONSOLE session.
+REM BT411 pod launch -- console session (started via schtasks /IT).
-REM Started via schtasks /IT so the windows land on the REAL panels (an SSH
-REM session is session 0 with a dummy display and would render nowhere).
 cd /d C:\bt411\BT411_4.11.801\content
-
-REM glass cockpit, per-display windows, POD surface mode (bare 640x480 pictures,
-REM no on-screen button banks -- the cab's buttons are physical), sticky layout
-REM loaded from glass_layout.cfg beside this file.
 set BT_GLASS=1
 set BT_GLASS_PANELS=1
-set BT_POD_SURFACES=1
+set BT_POD_RGB=1
 set BT_GLASS_LAYOUT=load
 set BT_GLASS_LOG=1
 set BT_START_INSIDE=1
+set BT_FE_SOLO=1
 set BT_LOG=podrun.log
-
+start "" ..\build\Release\btl4.exe
-start "" ..\build\Release\btl4.exe -egg MP.EGG

scratchpad/pod/runpod2.bat

@@ -0,0 +1,12 @@
+@echo off
+REM BT411 pod launch -- console session (started via schtasks /IT).
+cd /d C:\bt411\BT411_4.11.801\content
+set BT_GLASS=1
+set BT_GLASS_PANELS=1
+set BT_POD_RGB=1
+set BT_GLASS_LAYOUT=load
+set BT_GLASS_LOG=1
+set BT_START_INSIDE=1
+REM no front end -- straight into a mission
+set BT_LOG=podrun.log
+start "" ..\build\Release\btl4.exe -egg PODTEST.EGG