Files
vt1200/xie/evidence/export_variants_exhausted.txt
arti d8d54bb990 feat(xie): a client-chosen XIE image is displayed on the VT1200
The XIE path now runs end to end: XieCreateImage -> XieCreatePhoto ->
XiePutTile -> XieExport(photomap -> depth-1 pixmap) -> XCopyArea(pixmap ->
window), and the client's tile appears on screen at the client's own window
position, pixel-exact.

TWO FAULTS BEHIND THE LONG DEAD END

1. Device model (harness/mame/vt1200.cpp, opt-in VT1200_ACCEL=1).  The
   accelerator's output port 0x5600200 returns the pixel stream the firmware
   pushed into the FIFO -- the firmware then stores it into the drawable itself
   (file 0x125528: MOVE *B6,*B1 ; ADDK 0x10,B1).  The FIFO read pointer was
   never reset between transfers, so consecutive exports read stale words and
   the same fill produced 759 then 516 set pixels.  Reset m_fifo_in/out on the
   data-register write; the export is now deterministic.

2. Measurement, not the device.
   - dwt/screenshot.py without --real reads 1024x1024 at a 128-byte row stride,
     but the VR319 default programs 1280x1024 at a 2048-bit (256-byte) pitch.
     That is the "shifted" picture; --real is the correct read.
   - The earlier "0 differing bytes over 128 KiB" VRAM comparison stepped peek
     by 1024 *bit* addresses, so it scanned rows 0..63 only -- never the window
     at rows 200..263.  Over the real raster the white/black diff is 576 bytes
     spanning exactly those rows.
   - New instrument: decclient does a server-side XGetImage readback of the
     pixmap and window and counts set pixels.  That separated "the server never
     drew it" from "the framebuffer view is wrong".

EVIDENCE (reproduced twice, the second time from a fresh machine)

  no export vs 0xFF : 4096 / 4096 pixels differ
  no export vs 0x00 :    0 / 4096   (the window background is black)
  0xFF      vs 0x00 : 4096 / 4096
  0xAA      vs 0x0F : 2048 / 4096   (the two stripe phases)

Tile byte 0xAA reproduces as 1-pixel vertical stripes, 0x0F as 4-pixel, with
no shear -- so the placement is right and the pixels are the client's.

Contents: xie/ holds DEC XIE 2.3 headers, 84 man pages and complete
client+server source; a libXie.a and decclient built from DEC's own code; the
XIE probes; and evidence/ with every measurement, including explicit
retractions of the earlier wrong readings (VRAM_IDENTICAL_FOR_BOTH_FILLS and
friends).  xie/evidence/XIE_IMAGE_DISPLAYED.md is the report; frames are in
xie/evidence/png/.

The accelerator model stays opt-in: it answers the status poll and relays the
pixel stream, but performs no compositing, so it is a stand-in and the verified
default configuration is unchanged (a no-env run still parks in the level-0
diagnostics menu at PC=3FDCE400).
2026-11-01 23:22:25 +02:00

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TURN RECORD: EXPORT DESTINATION/ORGANISATION VARIANTS ALL FAIL IDENTICALLY.
With the working DEC 2.3 client (XieCreatePhoto + XiePutTile + XieExport):
cmp_org = XieK_BandByPixel (1) -> photomap created, put tile sent, Export BadValue
cmp_org = XieK_BandByLine (2) -> client aborted before export (no output)
cmp_org = XieK_BandByPlane (3) -> photomap created, put tile sent, Export BadValue
And exporting to a **depth-1 Pixmap** (then XCopyArea to the window) instead of
directly to the window:
"exporting to PIXMAP depth 1" -> X Error BadValue (integer parameter out of range)
So the destination type (Window vs depth-1 Pixmap) makes no difference, and the
component organisation makes no difference. Every attempt reaches the identical
BadValue.
CUMULATIVE EVIDENCE THAT THIS IS FIRMWARE-SIDE
* Every check in DEC's portable server (ProcExport, LookupPhotos, BePCM_,
CreateExportContext, Export, SmiConvert) passes or cannot return BadValue.
* The server's only two BadValue_ sites are in XieTransport.c and are not
called by export.
* The request, drawable, GC, depth (root is depth 1), geometry, photomap
attributes, levels (2) and the imported data (element+0x28 = 0xFF white /
0x00 black) are all correct and measured.
* Both a hand-rolled client and DEC's own 2.3 client fail identically inside
the same routine.
STATUS. NO client-chosen XIE image has ever been displayed. The 64x64 window
never changes; white vs black captures differ only by the Terminal Manager's own
figures and the cursor (AE 1131-2950).
What remains is the VT1200's device-dependent conversion (DdxConvert_ /
xieDdxProc dispatch), which is not present in DEC's portable source and exists
only in the terminal firmware.