iWish — Tcl/Tk for iOS

What it is

iWish is a port of AndroWish's undroidwish — the batteries-included, SDL2-rendered Tcl/Tk wish — to iOS and iPadOS (with a Mac Catalyst build alongside).

It runs a real Tcl 8.6 interpreter and the real Tk 8.6 widget set on an iPhone or iPad. Tk is drawn through AndroWish's SdlTk — an X11-on-SDL2 emulation layer — using the AGG anti-aliased renderer for graphics and FreeType for text, composited onto an SDL2 Metal surface. There is no WebView and no native-UIKit-widget bridge: it is the actual Tk canvas and widgets, running on the device.

The whole stack — Tcl, Tk/SdlTk, SDL2, AGG, FreeType — is statically linked into a single sdl2wish binary, compiled for arm64-apple-ios.

Status

0.2 — alpha. The runtime runs a large third-party Tk application end-to-end on a physical iPad: full GUI, the batteries-included extension set, a bundled demo menu, and hardware access over CoreBluetooth. APIs, the build layout, and the bundled extension set are still in flux.

• The core port renders a Tk GUI on the iOS Simulator, Mac Catalyst, and a physical iPad, all screenshot-verified.
• Built with TCL_UTF_MAX=6 (UCS-4) so astral-plane characters and arrows render correctly. Stock builds (UTF_MAX=3) garble them; the UTF6 rebuild is verified by the full Tcl and Tk regression suites.
• A Tcl/Tk espresso application (Decent's de1app) has been booted on a physical iPad and connected to a DE1 espresso machine over CoreBluetooth, on-device rather than in the simulator.
• Published as v0.2-alpha, then v0.2.2 with the AltStore/SideStore .framework packaging fix.

What's included (batteries)

Every build (device and Catalyst) bundles the AndroWish extension set plus built-in demo apps; the bare runtime is not shipped separately.

• ~114–118 bundled packages, of which 56–64 are native arm64-apple-ios dylibs, totaling roughly 80 MB.
• Included: tkimg (jpeg/png/tiff), tls (over LibreSSL), TclCurl, sqlite3, itcl, itk, thread, tdom, Tktable, tktreectrl, zint, Img, tkpath, tkvnc, BLT 2.4, TkBLT (scientific plotting — blt::graph/barchart/vector), Tix, vectcl, tksvg, and more.
• A File ▸ Demos menu in the console launches the bundled demo apps. Four are iWish-specific: bltgraph (live TkBLT plotting + PostScript export), bledemo (a LightBlue-style BLE debugger — scan, connect, browse services/characteristics, read/subscribe/write), borgdemo (the borg iOS device bridge), and paint. Extensions that can't exist on iOS (Windows-only, Linux/Android hardware, fork/exec, huge external native libs) appear greyed-out.
• iOS-native shims re-implement AndroWish's device commands on Apple frameworks:
  • borg → UIScreen brightness, device/screen info, URL opening, AVSpeech text-to-speech, a native toast, plus a platform subcommand (ios / iossimulator / maccatalyst) so Tcl can identify the run target at runtime.
  • ble → CoreBluetooth (scan / connect / read / write / notify), using the peripheral's CoreBluetooth UUID as its address since iOS hides the hardware MAC.
  • hardexit → a one-command dylib that calls _exit(). On iOS, Tcl's normal exit (which runs Tcl_Finalize) hangs and leaves a blank window; routing exit through hardexit gives a clean quit.
• Because iOS sandboxes fork/exec, exec ls/cat/cp/… can never work in a packaged app. iWish supplies pure-Tcl replacements (ls cat head tail grep wc cp mv rm mkdir touch find echo …) wired into init.tcl so they exist in every interpreter, not just the console. They never shadow a name a program already defines.

Building & signing (high level)

The repo is a recipe — build scripts, a set of patches against upstream, and the iOS-native glue code. It does not redistribute AndroWish, SDL2, or Tcl/Tk; you fetch those and apply the patches.

Rough shape of a build:

1. Get an AndroWish checkout and a stock SDL 2.30.11 source tree.
2. Apply the iWish patches (apply-patches.sh).
3. Build the foundation — FreeType, SDL2, AndroWish Tcl, sdl2tk and sdl2wish — all for arm64-apple-ios, at TCL_UTF_MAX=6.
4. Build the loadable extension stack and stage the full battery set into the bundle's lib-batteries/.
5. Compile the src-ios/ shims (borg / ble / hardexit) to dylibs.
6. Assemble the .app: the renamed sdl2wish binary, lib/tcl8.6 + lib/tk8.6, main.tcl + payload, an Info.plist (landscape orientations, status bar hidden, MinimumOSVersion 15.0), and the lib-batteries/.
7. Build the app icon (any image → opaque 1024×1024 → asset catalog via actool).
8. Wrap every native dylib in its own .framework bundle under Frameworks/ (see Implementation notes) — required for AltStore/SideStore.
9. Sign and install to a device.

Signing uses a standard Apple Development certificate plus a provisioning profile that includes the target device's UDID. Distribution is via TestFlight / sideload / EU notarization — App Store policy 2.5.2 forbids interpreters that load downloaded code. (This page omits the project's private signing identities, team IDs, device UDIDs, and local paths.)

Implementation notes

The port reconciles a threaded X11-style toolkit with UIKit's main-thread rules and pixel model. Fixes:

• Keyboard input. SDL2's UIKit backend registers a GameController keyboard and then skips delivering normal key presses, expecting a handler that never fires for ordinary typing — so keys vanished. The fix disables the GameController keyboard path so keys flow through the standard press handlers. Related device fixes eliminated double-typed characters (hardware key + hidden text-field both firing) and made Shift produce shifted symbols (Shift+= → +) via an ANSI shift map gated on Shift, not CapsLock.

• Mouse, drag, and cursor. On Catalyst and iPad the pointer arrives as an indirect (trackpad) touch, not a classic mouse. Fixes route it through the touch handlers, add drag-motion reporting, correct a button-release bug (the pressed bit is already cleared at release time, so releases were lost), and add a cursor driver that morphs the pointer into resize/move shapes — using AppKit's NSCursor via the Objective-C runtime on Catalyst, and a custom bezier double-arrow UIPointerStyle on the device.

• Keyboard-caret crash (SIGABRT). undroidwish runs Tcl/Tk on a secondary thread. Tk's caret update eventually set a UIView frame off the main thread, and UIKit's safe-area recalculation throws when that happens off-main → abort. The fix bounces the frame update to the main thread and skips it when it's a no-op. A recurring lesson across the port: never dispatch_sync from the Tcl thread to the main queue (the main thread is busy in the SDL/Tk loop and not servicing the main queue → deadlock) — always dispatch_async.

• Screen auto-size and fill. On the real device iWish adopts the native screen size automatically; the fixed-resolution pins are all Catalyst-only. Pinning SdlTk's virtual screen to the native size, using SDL_RenderSetLogicalSize to scale the present, and ignoring spurious window-resize events made the Tk surface fill the display and map input back correctly.

• Colour correctness on Catalyst. The whole UI came up red/blue-swapped. SDL_GetWindowPixelFormat reported ABGR8888, but the actual Metal drawable is BGRA; SDL presented without converting. Forcing the surface and textures to ARGB8888 (== BGRA) on Catalyst fixed every colour at the final present, and AGG adapts to match.

• Catalyst beachball. SdlTk's event loop blocks forever on the main thread with SDL_WaitEvent, but on Catalyst AppKit owns the main run loop, so never returning to it reads as "not responding". The fix returns the main thread to AppKit and drives Tk from a per-frame CADisplayLink callback instead.

• AltStore/SideStore packaging. iWish bundles ~64 native dylibs. AltStore/SideStore re-sign with ldid, which only re-signs the executable and nested bundles (Frameworks/*.framework, PlugIns/*.appex) — a loose .dylib, even inside Frameworks/, keeps its original signature and iOS rejects the install (0xe8008001). The fix wraps every dylib in its own .framework bundle and rewrites the Tcl load paths. (A deeper root cause — ldid emitting a legacy SHA-1-primary code directory that iOS 26 rejects — is why a modern, codesign-equivalent signer is ultimately needed for reliable free-account sideloading.)

Repository

Source, build scripts, and patches: https://github.com/johnbuckman/iwish

Part of the Tcl/Tk on modern platforms collection. Sibling projects build the same stack as a native Apple-Silicon macOS binary and as a 32-bit armv7 / iOS 9 full-source snapshot for old jailbroken devices.