Suggestion : Replace hacky method to auto-close the cmd window

[hironichu]

I have been looking into some way to compile GUI deno app to run on Windows with Tauri before, with great success but without making much FFI effort.

Here is what I have (found & made)

First simple method is to change a byte into the deno compile binary from Typescript after it's done.
the other method is directly a suggestion i have made in the denoland/deno repo that adds the -subsystem option in deno compile in order to select if you wish to bundle a GUI app or a console app (windows only)

From this issue denoland/deno#11638

// --allow-read --allow-write change_exe_subsystem.ts

async function readN(r: Deno.Reader, n: number): Promise<Uint8Array | null> {
  const buf = new Uint8Array(n);
  let nRead = 0;
  // a null value of r.read() will nullish coalesce into NaN and
  // polute nRead, causing (nRead < n) to be false and the loop to exit
  while (nRead < n) {
    nRead += await r.read(buf.subarray(nRead)) ?? NaN;
  }
  return isNaN(nRead) ? null : buf;
}

async function writeAll(w: Deno.Writer, buf: ArrayBufferView): Promise<void> {
  const bytes = new Uint8Array(buf.buffer, buf.byteOffset, buf.byteLength);
  let nWritten = 0;
  while (nWritten < bytes.byteLength) {
    nWritten += await w.write(bytes.subarray(nWritten));
  }
}

function view(buf: ArrayBufferView) {
  return new DataView(buf.buffer, buf.byteOffset, buf.byteLength);
}

// replace 'my_oak_server.exe' with your server binary
const PATH_TO_BINARY = "./my_oak_server.exe";
const bin = await Deno.open(PATH_TO_BINARY, { read: true, write: true });

// we're going to validate (loosely) that its a valid EXE/MZ
 // reset to index 0, just to be sure
await bin.seek(0, Deno.SeekMode.Start);
const magicBytes = await readN(bin, 2);
if (magicBytes == null) {
  console.log("Encountered EOF at magicBytes");
  Deno.exit(1);
}
const binMagic = new TextDecoder().decode(magicBytes);

if ("MZ" != binMagic) {
  console.log(`☹ we didnt find a valid exe at ${PATH_TO_BINARY}`);
  Deno.exit(1);
}

// we now know we have a valid exe file
// next we need to get the offset of the 'PE Header'
const PE_ADDRESS_OFFSET = 0x3C;
await bin.seek(PE_ADDRESS_OFFSET, Deno.SeekMode.Start);
// read the peHeaderPointer as 32bit little-endian int/dword/u32
const peHeaderPointerBytes = await readN(bin, 4);
if (peHeaderPointerBytes == null) {
  console.log("Encountered EOF at peHeaderPointerBytes");
  Deno.exit(1);
}
const peHeaderPointer = view(peHeaderPointerBytes).getUint32(0, true);

// we've got the offset of the PE header now
// we'll go to that offset, then a further 92 bytes
// this is where the subsytem field is
await bin.seek(peHeaderPointer + 92, Deno.SeekMode.Start);

// WINDOWS subsystem (don't show a terminal)
// CONSOLE subsystem (show a terminal when running)
const SUBSYSTEM_WINDOWS = 2;
const SUBSYSTEM_CONSOLE = 3;

// before we modify the value we'll do a very rough check
// to make sure that we are modifying the right field
// we'll need to get it as a little-endian u16
const subsystemBytes = await readN(bin, 2);
if (subsystemBytes == null) {
  console.log("Encountered EOF at subsystemBytes");
  Deno.exit(1);
}
const subsystem = view(subsystemBytes).getUint16(0, true);
if (!(SUBSYSTEM_WINDOWS == subsystem || SUBSYSTEM_CONSOLE == subsystem)) {
  console.log("Oops! The subsystem is not WINDOWS=2 or CONSOLE=3.");
  console.log("We might be editing the wrong field,");
  console.log("  _or_ the EXE uses a different subsystem.");
  Deno.exit(1);
}

// okay, now we are pretty sure about the file
// let's update its subsystem
const newSubsystemData = new Uint16Array(1);
view(newSubsystemData).setUint16(0, SUBSYSTEM_WINDOWS, true);
// go back to the subsytem field
await bin.seek(peHeaderPointer + 92, Deno.SeekMode.Start);
// write out our data.
await writeAll(bin, newSubsystemData);

// finish up with a helpful message
const newSubsystemValue = view(newSubsystemData).getUint16(0, true);
if (SUBSYSTEM_WINDOWS == newSubsystemValue) {
  console.log(`Done! Changed ${PATH_TO_BINARY} subsystem=2, WINDOWS.`);
}
else if (SUBSYSTEM_CONSOLE == newSubsystemValue) {
  console.log(`Done! Changed ${PATH_TO_BINARY} subsystem=3, CONSOLE.`);
}

And my suggestion to add directly to Deno :

denoland/deno#12941

Both are great, but I believe for Astrodon it can be easier to just not "close" the console and instead just make it a real GUI app (Windows will know the difference)

this is a suggestion, let me know what you think.

[marc2332]

If it was added to deno itself, it would be awesome, I will try the script you mentioned asap :)

[denyncrawford]

Implemented on 2ce53e5