Hmbown/CodeWhale · error · ExecError

region must be integer [x,y,width,height] with positive size

Error message

region must be integer [x,y,width,height] with positive size

What it means

screenshot validates the region argument: it must be an array of exactly 4 integers [x,y,width,height] with positive width and height. It throws this ExecError otherwise, since the region is interpolated directly into a System.Drawing.Rectangle in the PowerShell capture script.

Solutions

1. Pass exactly [x, y, width, height] as integers with width > 0 and height > 0
2. Convert corner-format rects: [x1, y1, x2-x1, y2-y1]
3. Round or Math.trunc computed coordinates to integers before calling
4. Validate array length and integrality on the caller side

Example fix

// before
await screenshot({ region: { x: 0, y: 0, w: 800, h: 600 } });
// after
await screenshot({ region: [0, 0, 800, 600] });

function toRegionInts(rect) {
  const [x1, y1, x2, y2] = Array.isArray(rect) && rect.length === 4
    ? rect
    : [rect.x, rect.y, rect.x + rect.w, rect.y + rect.h];
  const region = [x1, y1, x2 - x1, y2 - y1].map(Math.round);
  if (region.length !== 4 || region.some(n => !Number.isInteger(n)) || region[2] <= 0 || region[3] <= 0) {
    throw new TypeError("region must resolve to integer [x,y,width,height] with positive size");
  }
  return region;
}

const isValidRegion = (r) => Array.isArray(r) && r.length === 4
  && r.every(Number.isInteger) && r[2] > 0 && r[3] > 0;

try {
  return await backend.screenshot({ region });
} catch (e) {
  if (String(e.message).startsWith("region must be integer")) {
    return await backend.screenshot(); // full-screen fallback
  }
  throw e;
}

When it happens

Trigger: Passing region as {x,y,w,h} object instead of array; floats like [10.5, 0, 100, 100]; negative or zero width/height; fewer/more than 4 elements; null when a region was expected.

Common situations: Porting from APIs that take rect objects; computed coordinates producing NaN or floats from scaling; an agent emitting [x1,y1,x2,y2] corner format instead of [x,y,w,h].

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• choose app_ref or region, not both
• display index must be a positive integer
• Invalid native whale body.
• Invalid native whale body.
• region must be [x, y, w, h] in screen points

AI-assisted analysis of Hmbown/CodeWhale@73e0f67d83 (2026-09-22). Data as JSON: /api/errors/624936deb35ff01b. Report an issue: GitHub.

Appendix: source

Thrown at crates/tui/plugins/computer-use/src/backends/win32.mjs:407

    $value = ''; $vp = $null;
    if (-not $cur.Current.IsPassword -and $cur.TryGetCurrentPattern([System.Windows.Automation.ValuePattern]::Pattern, [ref]$vp)) { $value = [string]$vp.Current.Value }
    [void]$els.Add([pscustomobject]@{ index = $els.Count; path = @($path); runtime_id = @($cur.GetRuntimeId()); window_runtime_id = $windowId; role = [string]$cur.Current.ControlType.ProgrammaticName; label = [string]$cur.Current.Name; value = $value.Substring(0, [Math]::Min(120, $value.Length)); enabled = $cur.Current.IsEnabled;
      x = [int]$rect.X; y = [int]$rect.Y; w = [int]$rect.Width; h = [int]$rect.Height; actions = $acts });
    $kids = $cur.FindAll([System.Windows.Automation.TreeScope]::Children, [System.Windows.Automation.Condition]::TrueCondition);
    for ($i = $kids.Count - 1; $i -ge 0; $i--) { $stack.Push(@($kids[$i], ($path + $i))) }
  }
  break;
}
$result = [pscustomobject]@{ found = $found; name = $appName; truncated = $truncated; elements = @($els | ForEach-Object { [pscustomobject]@{ index = $_.index; path = @($_.path); runtime_id = $_.runtime_id; window_runtime_id = $_.window_runtime_id; role = ($_.role -replace 'ControlType.',''); label = $_.label; value = $_.value; enabled = $_.enabled; position = [pscustomobject]@{ x = $_.x; y = $_.y }; size = [pscustomobject]@{ w = $_.w; h = $_.h }; actions = $_.actions } }) };
Write-Output ($result | ConvertTo-Json -Depth 6 -Compress);`, { timeoutMs: 60_000 });
      if (!j.found) throw new ExecError("application window not found in UIA tree — pass app_ref.name as the exact window title from list_windows or list_apps.title");
      return j;
    },
    screenshot: async (args = {}) => {
      if (Object.hasOwn(args, "app_ref") || Object.hasOwn(args, "window_id")) throw unsupportedSelector("Windows screenshot does not support app_ref or window_id; omit them for a desktop screenshot");
      const { display = activeDisplay, region, path: outPath } = args;
      if (display != null && (!Number.isInteger(display) || display < 1)) throw new ExecError("display index must be a positive integer");
      if (region != null && (!Array.isArray(region) || region.length !== 4 || !region.every(Number.isInteger) || region[2] <= 0 || region[3] <= 0)) throw new ExecError("region must be integer [x,y,width,height] with positive size");
      const dir = recordingsDir();
      fs.mkdirSync(dir, { recursive: true });
      const file = path.resolve(outPath || path.join(dir, `shot-${crypto.randomBytes(6).toString("hex")}.png`));
      const meta = await psJson(`Add-Type -AssemblyName System.Windows.Forms; Add-Type -AssemblyName System.Drawing;
$bounds = [System.Windows.Forms.SystemInformation]::VirtualScreen;
${display == null ? "" : `$screens = [System.Windows.Forms.Screen]::AllScreens; if (${display} -gt $screens.Count) { throw 'display index is out of range' }; $bounds = $screens[${display - 1}].Bounds;`}
${region == null ? "" : `$crop = New-Object System.Drawing.Rectangle(${region.join(",")}); if (-not $bounds.Contains($crop)) { throw 'region is outside capture bounds' }; $bounds = $crop;`}
$bmp = New-Object System.Drawing.Bitmap($bounds.Width, $bounds.Height);
try {
  $g = [System.Drawing.Graphics]::FromImage($bmp);
  try { $g.CopyFromScreen($bounds.X, $bounds.Y, 0, 0, $bounds.Size); } finally { $g.Dispose(); }
  $bmp.Save('${file.replace(/'/g, "''")}', [System.Drawing.Imaging.ImageFormat]::Png);
} finally { $bmp.Dispose(); }
@{ x = $bounds.X; y = $bounds.Y; w = $bounds.Width; h = $bounds.Height } | ConvertTo-Json -Compress;`, { timeoutMs: 30_000 });
      if (!fs.existsSync(file) || ![meta.x, meta.y, meta.w, meta.h].every(Number.isFinite) || meta.w <= 0 || meta.h <= 0) throw new ExecError("screenshot did not return a valid raster");
      lastRaster = { file, bytes: fs.statSync(file).size, points: { x: meta.x, y: meta.y, w: meta.w, h: meta.h }, pixels: { w: meta.w, h: meta.h }, scale: 1, capturedAt: new Date().toISOString() };
      return { ...lastRaster };
    },

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