iccery-v2-mac/docs/12-print-windows.md

12 — Windows GDI raw printing

Line numbers refer to ICCery v0.8.5 (/tmp/ICCery at analysis time) and the Gronod ArgyllCMS 3.5.0 fork.

Windows (src-tauri/src/print/windows.rs)

Direct Win32. No lp, no XPS, no winprint crate. Evaluated and rejected in #26.

Exact Win32 APIs used

From windows crate 0.61 (Cargo.toml:50-55: Win32_Foundation, Win32_Graphics_Gdi, Win32_Graphics_Printing, Win32_UI_WindowsAndMessaging) plus a local extern "system" block for symbols the crate feature set does not expose.

API	Header / crate	Where	Purpose
EnumPrintersW	Win32::Graphics::Printing	get_printers	Level 4 (PRINTER_INFO_4W) first; fall back to Level 1 (PRINTER_INFO_1W)
OpenPrinterW	Printing	properties + print	PRINTER_HANDLE
ClosePrinter	Printing	both
DocumentPropertiesW	Printing	properties + print	size query (fMode=0), DM_OUT_BUFFER init, DM_IN_PROMPT|DM_IN_BUFFER|DM_OUT_BUFFER dialog
GetForegroundWindow	Win32::UI::WindowsAndMessaging	properties	parent HWND of the modal
DeviceCapabilitiesW	local extern	capabilities	DC_BINS(6), DC_BINNAMES(12), DC_PAPERS(2), DC_PAPERNAMES(16), DC_MEDIATYPES(35), DC_MEDIATYPENAMES(34)
CreateDCW	Win32::Graphics::Gdi	print	printer DC with DEVMODE
DeleteDC	Gdi	print
GetDeviceCaps	Gdi	print	LOGPIXELSX/Y, HORZRES, VERTRES
SetICMMode	local extern	print	ICM_OFF = 1
StartDocW / StartPage / EndPage / EndDoc	local extern	print	GDI job
StretchDIBits	Gdi	print	unmanaged 24-bit BGR DIB

DOCINFOW is a local #[repr(C)] struct (windows.rs:24-31), not the crate type, because StartDocW is also local-extern.

Constants (windows.rs:48-66):

ICM_OFF            = 1
DM_IN_PROMPT       = 4
DM_IN_BUFFER       = 8
DM_OUT_BUFFER      = 2
DM_ORIENTATION     = 0x00000001
DM_DEFAULTSOURCE   = 0x00000200
DM_ICMMETHOD       = 0x00800000
DMICMMETHOD_NONE   = 1
DMORIENT_PORTRAIT  = 1
DMORIENT_LANDSCAPE = 2
DM_MEDIATYPE       = 0x02000000
DC_PAPERS=2, DC_BINS=6, DC_BINNAMES=12, DC_PAPERNAMES=16,
DC_MEDIATYPENAMES=34, DC_MEDIATYPES=35
IDOK = 1

Enumeration (get_printers, windows.rs:78-168)

1. EnumPrintersW(PRINTER_ENUM_LOCAL | PRINTER_ENUM_CONNECTIONS, NULL, 4, …) to get byte count.
2. If bytes_needed == 0, retry at Level 1 (older/limited spooler).
3. Level 4: pPrinterName. Level 1: pName.
4. is_default always false, display_name always None, status always "Ready".
5. Empty list is success, not error.

Capabilities (get_printer_capabilities, windows.rs:171-326)

DeviceCapabilitiesW(printer, NULL port, cap, …). Bin names are 24 WCHARs each; paper and media names 64 WCHARs. Media type IDs are read as u32 via a *mut u16 cast of a Vec<u32> (windows.rs:288-289) — the Win32 API writes DWORDs for DC_MEDIATYPES.

supports_orientation: true unconditionally.

Driver preferences dialog (show_printer_properties, windows.rs:329-401) — #34 / #36

OpenPrinterW
DocumentPropertiesW(..., fMode=0)            → required buffer size
load cached DEVMODE or zeros
if all-zero: DocumentPropertiesW(DM_OUT_BUFFER) to populate defaults
DocumentPropertiesW(DM_IN_PROMPT | DM_IN_BUFFER | DM_OUT_BUFFER)
ClosePrinter
if res == IDOK (1): store out_buf, Ok(())
if res == 2:        user cancel, Ok(())      // IDCANCEL
else:               Err(...)

Parent window is GetForegroundWindow(), not the Tauri webview HWND. The dialog is modal to whatever is foreground.

The entire out_buf (header + dmDriverExtra) is stored. That is the #36 fix: Epson "Print Preview" and other OEM private flags live past dmSize and were previously dropped.

ICM bypass + option overlay (apply_print_options_to_devmode, windows.rs:404-437)

Always:

dmFields |= DM_ICMMETHOD
dmICMMethod = DMICMMETHOD_NONE   // 1

Then, if options present:

• paper_source → dmFields |= DM_DEFAULTSOURCE; dmDefaultSource = tray_id as i16
• orientation == "landscape" (case-insensitive) → DMORIENT_LANDSCAPE else portrait
• media_type parsed as u32 → dmFields |= DM_MEDIATYPE; dmMediaType = id

Not applied: paper_size, ppd_uncorrected_passthrough, cups_options. Private OEM bytes after the public header are not touched (verified by tests.rs:219-276).

GDI raw print path (print_target, windows.rs:440-643)

1. image::open TIFF → to_rgb8(). Crate features: png, tiff (Cargo.toml:40).
2. Pack 24-bit BGR DIB, 4-byte row stride: row_stride = ((w*3+3)/4)*4. Top-down (biHeight negative).
3. OpenPrinterW → DocumentPropertiesW size → reuse cached DEVMODE (resized up if needed) or DM_OUT_BUFFER defaults → apply_print_options_to_devmode.
4. CreateDCW(NULL, printer, NULL, pDevMode).
5. SetICMMode(hdc, ICM_OFF) — "STRICT ICM BYPASS".
6. StartDocW with title ICCery Target - <filename>. lpszDatatype null (driver default, not "RAW").
7. StartPage.
8. Auto-fit scaler (#34):

dpi_x/y  = GetDeviceCaps(LOGPIXELSX/Y)   // used only for BITMAPINFO biX/YPelsPerMeter
page_w/h = GetDeviceCaps(HORZRES/VERTRES)
scale    = min(page_w/img_w, page_h/img_h)
dest     = floor(img * scale), centered

Physical offsets (PHYSICALOFFSETX/Y) from #34's wish-list are not queried. Fit is to the printable DC area (HORZRES/VERTRES), which already excludes hardware margins.

9. StretchDIBits(..., DIB_RGB_COLORS, SRCCOPY). This can resample if dest ≠ source pixels. Color is unmanaged (ICM off, BI_RGB) but geometric interpolation is GDI's. Contrast with ICCery-CPU, which forbids interpolation.

10. EndPage / EndDoc / DeleteDC / ClosePrinter.

Zero-dimension images error out before GDI. Missing TIFF: "Target TIFF file not found: …".

CREATE_NO_WINDOW vs print

CREATE_NO_WINDOW (0x08000000) is not used on the print path. Windows printing is in-process GDI; no child process is spawned.

CREATE_NO_WINDOW is applied to ArgyllCMS console-subsystem children so a black cmd window does not flash (#46):

• src-tauri/src/process_manager.rs:99-103 — every ProcessManager::spawn (targen, printtarg, chartread, colprof, profcheck, instlist, …)
• src-tauri/src/calibration.rs:849-853 — printcal / applycal captured runs

printtarg itself only generates TIFFs; it does not print. Native print is a separate IPC command.

NSIS USB drivers (#127) — not printer drivers

USB install is for spectrophotometer libusb-win32 drivers (i1Pro, ColorMunki, SpyderPrint), not printer OEM drivers.

• Fetch: scripts/fetch-argyll.mjs copies Argyll_V*/usb/ → src-tauri/argyll/usb/ from the Windows zip (ArgyllCMS_install_USB.exe, .inf, .cat, libusb0.sys for x86/amd64/arm64).
• Bundle: tauri.conf.json resources: ["argyll/**/*"] + NSIS installMode: "both" + installerHooks: "windows/hooks.nsh".
• hooks.nsh NSIS_HOOK_PREINSTALL: if elevated, MessageBox Yes/No "Install ArgyllCMS USB instrument drivers?".
• NSIS_HOOK_POSTINSTALL: ExecWait $INSTDIR\argyll\usb\ArgyllCMS_install_USB.exe or $INSTDIR\resources\argyll\usb\.... Not silent. Missing file → exclamation box.
• Uninstall does not run ArgyllCMS_uninstall_USB.exe (would break other Argyll apps).
• Also maps missing HKCU shell-folder drive letters via DefineDosDevice to avoid "Invalid Drive" on domain profiles.

WiX/MSI has no equivalent prompt.

Windows idiosyncrasies / bugs fixed

Issue	Symptom	Fix
#25/#26	Need ACPU-equivalent raw print	GDI + SetICMMode(ICM_OFF) + DMICMMETHOD_NONE + 24-bit BGR DIB
#34	No driver dialog / trays / orientation / scaler	DocumentPropertiesW modal, DeviceCapabilitiesW, auto-fit StretchDIBits dest
#36	Preferences (Epson Print Preview, private OEM) ignored	Cache full DEVMODE buffer including dmDriverExtra; pass that pointer to CreateDCW
#48	"PPD Uncorrected Passthrough" shown on Windows	Hide #cupsOptionsGroup
#46	Argyll console windows cover UI	CREATE_NO_WINDOW on subprocess spawn only — not on print
#67	Duplicate get_windows_printers / print_target_windows	Collapsed to get_printers / print_target_native

Remaining gaps:

• Default printer never flagged.
• paper_size not applied to DEVMODE (DM_PAPERSIZE unused).
• PHYSICALOFFSET* not used; scaler uses HORZRES/VERTRES only.
• StretchDIBits may interpolate when scaling.
• show_printer_properties Tauri result is always None, so the frontend reports cancel even on OK.
• No PrinterProperties / AdvancedDocumentProperties alternative; only DocumentPropertiesW.
• GetForegroundWindow can attach the modal to the wrong top-level window.

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