SchOS/tools/splashshot.ps1

# Photograph the boot splash.
#
# The splash is on screen from the moment stage2 draws it until
# console_takeover() clears it at the first exec(), which is a window of a
# couple of seconds -- so a single screendump at a guessed delay is a coin
# flip. This takes a burst instead and keeps every frame, which makes the
# question "what does boot actually look like, second by second" answerable
# rather than a matter of catching it at the right instant.
#
# Same shape as tools/crashshot.ps1: monitor on TCP because QEMU on Windows has
# no unix sockets, serial to a logfile so the transcript survives.
#
#   tools/splashshot.ps1                 frames every 400ms for 8s
#   tools/splashshot.ps1 -Every 200 -For 4

param(
    [int]$Every = 400,        # milliseconds between frames
    [int]$For = 8,            # seconds to keep capturing
    [string]$OutDir = "build/shots",
    [string]$Qemu = (Find-Qemu)
)

# QEMU, on whichever host this is.
#
# PowerShell 7 runs on Linux, macOS and the BSDs as well as Windows, so these
# scripts are usable from all of them -- but the old default was a hardcoded
# scoop path under $env:USERPROFILE, which exists on exactly one of those. PATH
# first, because a package-managed qemu is on it everywhere; the scoop location
# is only a fallback for the Windows install that does not add itself to PATH.
function Find-Qemu {
    $exe = if ($IsWindows -or $env:OS -eq 'Windows_NT') { 'qemu-system-x86_64.exe' }
           else { 'qemu-system-x86_64' }
    $onPath = Get-Command $exe -ErrorAction SilentlyContinue
    if ($onPath) { return $onPath.Source }
    if ($env:USERPROFILE) {
        $scoop = Join-Path (Join-Path $env:USERPROFILE 'scoop/apps/qemu/current') $exe
        if (Test-Path $scoop) { return $scoop }
    }
    foreach ($p in @('/usr/bin', '/usr/local/bin', '/opt/homebrew/bin')) {
        $c = Join-Path $p $exe
        if (Test-Path $c) { return $c }
    }
    throw "qemu-system-x86_64 not found on PATH. Install QEMU, or pass -Qemu <path>."
}

$ErrorActionPreference = 'Stop'
$root = Split-Path $PSScriptRoot -Parent
$log  = Join-Path $root 'build/splashshot.log'
$dir  = Join-Path $root $OutDir

Remove-Item -Recurse -Force $dir -ErrorAction SilentlyContinue
New-Item -ItemType Directory -Force $dir | Out-Null
Remove-Item -Force $log -ErrorAction SilentlyContinue

$hda = Join-Path $root 'schos.img'
# The root filesystem. SchFS is the only root there is: the kernel mounts
# device 1 in forkret() and panics if it is not a SchFS volume, so this is
# not a choice and there is no -SchFS switch any more. It used to default to
# build/fs.img, which stopped being bootable the moment SchFS became root.
$hdb = Join-Path $root 'build/schfs.img'

$monPort = 55556      # not crashshot's port, so the two can run back to back

$psi = New-Object System.Diagnostics.ProcessStartInfo
$psi.FileName = $Qemu
$psi.Arguments = @(
    # -snapshot with file.locking=off, rather than booting from copies. QEMU
    # takes an exclusive lock on its drive images, so an interactive session the
    # developer already has open would otherwise make this fail with "Failed to
    # get write lock" -- and a capture script is exactly the thing you want to
    # run without first shutting down what you were looking at. Copying was the
    # first fix and it meant duplicating build/fs.img, all 153 MB of it, on
    # every run. -snapshot keeps writes in a temporary overlay, so the originals
    # are untouched either way.
    "-drive file=`"$hda`",format=raw,index=0,media=disk,file.locking=off"
    "-drive file=`"$hdb`",format=raw,index=1,media=disk,file.locking=off"
    '-snapshot'
    '-m 1G -smp 1 -cpu qemu64,+rdtscp -machine pc-i440fx-9.2'
    '-display none'
    "-chardev stdio,id=c0,logfile=`"$log`""
    '-serial chardev:c0'
    "-monitor tcp:127.0.0.1:$monPort,server,nowait"
) -join ' '
$psi.RedirectStandardInput = $true
$psi.UseShellExecute       = $false

Write-Host "==> booting" -ForegroundColor Cyan
$p = [System.Diagnostics.Process]::Start($psi)

$frames = @()
try {
    # Connect immediately -- the interesting frames are the early ones, so any
    # fixed warm-up sleep here is time spent missing them.
    $client = $null
    for ($i = 0; $i -lt 40 -and -not $client; $i++) {
        try { $client = New-Object System.Net.Sockets.TcpClient('127.0.0.1', $monPort) }
        catch { Start-Sleep -Milliseconds 100 }
    }
    if (-not $client) { throw "could not reach the QEMU monitor on port $monPort" }

    $writer = New-Object System.IO.StreamWriter($client.GetStream())
    $writer.AutoFlush = $true

    $n = [int](($For * 1000) / $Every)
    $sw = [System.Diagnostics.Stopwatch]::StartNew()
    for ($i = 0; $i -lt $n; $i++) {
        $ms = [int]$sw.ElapsedMilliseconds
        $f = Join-Path $dir ("{0:d5}ms.ppm" -f $ms)
        $writer.WriteLine("screendump $f")
        $frames += $f
        Start-Sleep -Milliseconds $Every
    }
    $writer.WriteLine('quit')
    Start-Sleep -Milliseconds 500
    $client.Close()
} finally {
    if (-not $p.HasExited) { $p.Kill() }
    Start-Sleep -Milliseconds 800
}

# Report each frame by its distinct-colour count. Two colours means a text
# console (or a blank screen); an anti-aliased logo pushes it into the dozens.
# The same reason the full-stack harness counted pixels rather than log lines: a capture
# that exists is not a capture that drew anything.
Write-Host "==> frames" -ForegroundColor Cyan
$kept = 0
foreach ($f in $frames) {
    if (-not (Test-Path $f)) { continue }
    $kept++
    $b = [System.IO.File]::ReadAllBytes($f)
    # PPM P6: "P6\n<w> <h>\n255\n" then raw RGB. Skip three whitespace-run
    # separated header fields rather than assuming a fixed header length --
    # QEMU's is compact but that is not guaranteed.
    $pos = 2; $fields = 0
    while ($fields -lt 3 -and $pos -lt $b.Length) {
        while ($pos -lt $b.Length -and [char]$b[$pos] -match '\s') { $pos++ }
        while ($pos -lt $b.Length -and [char]$b[$pos] -notmatch '\s') { $pos++ }
        $fields++
    }
    $pos++
    $seen = @{}
    for ($i = $pos; $i + 2 -lt $b.Length; $i += 3 * 7) {   # sample every 7th pixel
        $seen[($b[$i] -shl 16) -bor ($b[$i+1] -shl 8) -bor $b[$i+2]] = 1
    }
    $name = Split-Path $f -Leaf
    $c = $seen.Count
    $tag = if ($c -ge 16) { 'graphical' } elseif ($c -le 3) { 'flat/text' } else { 'sparse' }
    $col = if ($c -ge 16) { 'Green' } else { 'DarkGray' }
    Write-Host ("  {0,-12} {1,4} colours  {2}" -f $name, $c, $tag) -ForegroundColor $col
}

if ($kept -eq 0) { Write-Host "FAIL: no frames captured" -ForegroundColor Red; exit 1 }
Write-Host "==> $kept frames in $dir" -ForegroundColor Green

# Convert to PNG if ImageMagick is around, so they can just be looked at.
if (Get-Command magick -ErrorAction SilentlyContinue) {
    foreach ($f in $frames) {
        if (Test-Path $f) { & magick $f ([System.IO.Path]::ChangeExtension($f, '.png')) }
    }
    Write-Host "==> PNGs alongside" -ForegroundColor Green
}