Files
vt1200/xie/evidence/dec_23_client_built.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: DEC'S OWN XIE 2.3 CLIENT LIBRARY IS BUILT AND RUNNING AGAINST THE
TERMINAL. ITS EXPORT FAILS WITH BadMatch (8), NOT BadValue (2).
A) BUILD
Sources: xie/docs/dec/xie23-src/lib/xie/*.c (9 files, 9,723 lines)
Headers shimmed into xie/build/dec/{,X11/extensions/} and X.h copied.
Compile: gcc -std=gnu89 -fcommon -w -I xie/build/dec -I <src>/include \
-I <src>/lib/xie
8/9 files built clean; XieConvert.c needed X.h. All 9 linked into
xie/build/dec/libXie.a (140,164 bytes), exporting the full client API
(XieCreateImage, XieCreatePhoto, XiePutImage, XiePutTile, XieExport,
XieQueryExport, XieCrop, XieScale, ...).
Client program: xie/decclient.c -> xie/build/dec/decclient
(needs one stub: unsigned long (*xieDdxProc[1])() = {0}; the client never
calls the DDX dispatch table.)
B) RUN AGAINST THE VT1200 (192.168.99.2:0)
display opened; root depth = 1 (xdpyinfo: "depths (1): 1",
"depth of root window: 1 plane") -- so drawable depth MATCHES the 1-bit image.
XieCreateImage -> ok (w=64 h=64)
XiePutImage -> photomap created
XieExport -> **BadMatch (invalid parameter attributes)**
Major opcode 129 (Xie), Minor opcode 21 (Export)
That is a DIFFERENT error from my hand-rolled client, which got BadValue (2).
Per the server source, ProcExport's MatchOkIf_ is
MatchOkIf_( Constrained_(img), stuff->photo_id )
and Constrained_(img) = ( *cmplvl > 0 ) set at photomap creation.
C) VARIANT ATTEMPTED
Replaced XiePutImage with XieCreatePhoto + XiePutTile + XieExport (the
library's own encoding of the sequence my hand-rolled probe uses).
The process CRASHED (core dumped) in that combination -- not yet diagnosed.
D) STATE
No client-chosen image has been displayed. Window unchanged.
xshow (core X) remains the only viewer that has shown an image.
WHAT THIS BUYS: a genuine 2.3 client now exercises the terminal, so the wire
format is no longer in question -- the remaining difference is server-side state
(the photomap's Constrained_ flag / creation attributes) or an incompatibility
between the image and the drawable that BadMatch is telling us about.