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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Buffers;
using System.Buffers.Binary;
using System.Collections.Immutable;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO.Hashing;
using System.Text;
namespace System.Windows.Forms.UITests;
internal class ScreenRecordService : IDisposable
{
private static readonly Stopwatch s_timer = Stopwatch.StartNew();
/// <summary>
/// Frames captured for the current test. The elapsed time field is a timestamp relative to a fixed but unspecified
/// point in time.
/// </summary>
/// <remarks>
/// <para>Lock on this object before accessing to prevent concurrent accesses.</para>
/// </remarks>
private static readonly List<(TimeSpan elapsed, Bitmap image)> s_frames = [];
private static readonly ArrayPool<byte> s_pool = ArrayPool<byte>.Shared;
private static ScreenRecordService? s_currentInstance;
private Form? _form;
private static readonly ReadOnlyMemory<byte> s_pngHeader = new byte[] { 0x89, (byte)'P', (byte)'N', (byte)'G', (byte)'\r', (byte)'\n', 0x1A, (byte)'\n' };
private static ReadOnlySpan<byte> Ihdr => "IHDR"u8;
private static ReadOnlySpan<byte> Idat => "IDAT"u8;
private static ReadOnlySpan<byte> Iend => "IEND"u8;
private static ReadOnlySpan<byte> Srgb => "sRGB"u8;
private static ReadOnlySpan<byte> Gama => "gAMA"u8;
private static ReadOnlySpan<byte> Phys => "pHYs"u8;
private static ReadOnlySpan<byte> Actl => "acTL"u8;
private static ReadOnlySpan<byte> Fctl => "fcTL"u8;
private static ReadOnlySpan<byte> Fdat => "fdAT"u8;
private enum PngColorType : byte
{
Grayscale = 0,
TrueColor = 2,
Indexed = 3,
GrayscaleWithAlpha = 4,
TrueColorWithAlpha = 6,
}
private enum PngCompressionMethod : byte
{
/// <summary>
/// <see href="https://www.w3.org/TR/png/#dfn-deflate">deflate</see>
/// compression with a sliding window of at most 32768 bytes.
/// </summary>
Deflate = 0,
}
private enum PngFilterMethod : byte
{
/// <summary>
/// Adaptive filtering with five basic filter types.
/// </summary>
Adaptive = 0,
}
private enum PngInterlaceMethod : byte
{
/// <summary>
/// No interlacing.
/// </summary>
None = 0,
/// <summary>
/// Adam7 interlace.
/// </summary>
Adam7 = 1,
}
private enum ApngDisposeOp : byte
{
/// <summary>
/// No disposal is done on this frame before rendering the next;
/// the contents of the output buffer are left as-is.
/// </summary>
None = 0,
/// <summary>
/// The frame's region of the output buffer is to be cleared to
/// fully transparent black before rendering the next frame.
/// </summary>
Background = 1,
/// <summary>
/// The frame's region of the output buffer is to be reverted
/// to the previous contents before rendering the next frame.
/// </summary>
Previous = 2,
}
private enum ApngBlendOp : byte
{
/// <summary>
/// All color components of the frame, including alpha,
/// overwrite the current contents of the frame's output buffer region.
/// </summary>
Source = 0,
/// <summary>
/// The frame should be composited onto the output buffer based on its alpha, using a simple OVER operation as
/// described in
/// <see href="https://www.w3.org/TR/png/#13Alpha-channel-processing">
/// Alpha Channel Processing.
/// </see>
/// </summary>
Over = 1,
}
static ScreenRecordService()
{
DataCollectionService.RegisterCustomLogger(
static fullPath =>
{
lock (s_frames)
{
if (s_frames.Count == 0)
return;
}
// Try to capture an additional frame at the end
s_currentInstance?.CaptureFrame();
(TimeSpan elapsed, Bitmap image)[] frames;
lock (s_frames)
{
if (s_frames.Count < 2)
{
// No animation available
return;
}
frames = [.. s_frames];
}
// Make sure the frames are processed in order of their timestamps
Array.Sort(frames, (x, y) => x.elapsed.CompareTo(y.elapsed));
(TimeSpan elapsed, Bitmap image, Size offset)[] croppedFrames = DetectChangedRegions(frames);
try
{
using var fileStream = new FileStream(fullPath, FileMode.Create, FileAccess.Write);
var crc = new Crc32();
byte[] buffer = s_pool.Rent(4096);
try
{
(TimeSpan elapsed, Bitmap image, Size offset) firstFrame = croppedFrames[0];
(ReadOnlyMemory<byte> signature, ReadOnlyMemory<byte> ihdr, ImmutableArray<ReadOnlyMemory<byte>> idat, ReadOnlyMemory<byte> iend) firstEncoded = EncodeFrame(firstFrame.image);
// PNG Signature (8 bytes)
WritePngSignature(fileStream, buffer);
// IHDR
Write(fileStream, buffer, crc: null, firstEncoded.ihdr.Span);
// acTL
WriteActl(fileStream, buffer, crc, croppedFrames.Length, playCount: 1);
// Write the first frame data as IDAT
WriteFctl(fileStream, buffer, crc, sequenceNumber: 0, size: new Size(firstFrame.image.Width, firstFrame.image.Height), offset: firstFrame.offset, delay: TimeSpan.Zero, ApngDisposeOp.None, ApngBlendOp.Source);
foreach (ReadOnlyMemory<byte> idat in firstEncoded.idat)
{
Write(fileStream, buffer, crc: null, idat.Span);
}
// Write the remaining frames as fDAT
int sequenceNumber = 1;
for (int i = 1; i < croppedFrames.Length; i++)
{
TimeSpan elapsed = croppedFrames[i].elapsed - croppedFrames[i - 1].elapsed;
WriteFrame(fileStream, buffer, crc, ref sequenceNumber, croppedFrames[i].image, croppedFrames[i].offset, elapsed);
}
WriteIend(fileStream, buffer, crc);
}
finally
{
s_pool.Return(buffer);
}
}
finally
{
foreach (var (_, image, offset) in croppedFrames)
{
if (offset != Size.Empty || image.Size != frames[0].image.Size)
{
// This is a cloned/cropped bitmap that needs to be disposed separately from s_frames
}
}
}
},
"",
"apng");
}
public ScreenRecordService()
{
// Release the previous instance, if any
s_currentInstance?.UnregisterEvents();
s_currentInstance = this;
TimeSpan elapsed = s_timer.Elapsed;
if (ScreenshotService.TryCaptureFullScreen() is { } image)
{
lock (s_frames)
{
s_frames.ForEach(frame => frame.image.Dispose());
s_frames.Clear();
s_frames.Add((elapsed, image));
}
}
else
{
lock (s_frames)
{
s_frames.ForEach(frame => frame.image.Dispose());
s_frames.Clear();
}
}
}
private static (TimeSpan elapsed, Bitmap image, Size offset)[] DetectChangedRegions((TimeSpan elapsed, Bitmap image)[] frames)
{
int width = frames[0].image.Width;
int height = frames[0].image.Height;
var bounds = new Rectangle(0, 0, width, height);
const int BytesPerPixel = 4;
List<(TimeSpan elapsed, Bitmap image, Size offset)> resultFrames = new(frames.Length);
var lockedBitmaps = new (Bitmap image, BitmapData data)[2];
try
{
// Even frame indexes go into the first slot of the image buffer. Odd frame indexes go into the second slot.
lockedBitmaps[0] = (frames[0].image, frames[0].image.LockBits(bounds, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb));
int stride = lockedBitmaps[0].data.Stride;
Assert.Equal(0, stride % BytesPerPixel);
int stridePixels = stride / 4;
int totalLockedPixels = stridePixels * lockedBitmaps[0].data.Height;
resultFrames.Add((frames[0].elapsed, frames[0].image, offset: Size.Empty));
for (int i = 1; i < frames.Length; i++)
{
Assert.True(frames[i].image.Width == width);
Assert.True(frames[i].image.Height == height);
int previousFrameBufferIndex = (i - 1) % 2;
int currentFrameBufferIndex = i % 2;
// Call UnlockBits if the buffer is already holding image data in the slot we are about to overwrite
lockedBitmaps[currentFrameBufferIndex].image?.UnlockBits(lockedBitmaps[currentFrameBufferIndex].data);
lockedBitmaps[currentFrameBufferIndex] = (frames[i].image, frames[i].image.LockBits(bounds, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb));
Assert.Equal(stride, lockedBitmaps[currentFrameBufferIndex].data.Stride);
ReadOnlySpan<uint> previousImageData;
ReadOnlySpan<uint> currentImageData;
unsafe
{
previousImageData = new ReadOnlySpan<uint>((void*)lockedBitmaps[previousFrameBufferIndex].data.Scan0, totalLockedPixels);
currentImageData = new ReadOnlySpan<uint>((void*)lockedBitmaps[currentFrameBufferIndex].data.Scan0, totalLockedPixels);
}
int firstChangedLine = -1;
int lastChangedLine = -1;
int firstChangedColumn = -1;
int lastChangedColumn = -1;
for (int line = 0; line < height; line++)
{
ReadOnlySpan<uint> previousFrameLine = previousImageData.Slice(line * stridePixels, width);
ReadOnlySpan<uint> currentFrameLine = currentImageData.Slice(line * stridePixels, width);
for (int column = 0; column < previousFrameLine.Length; column++)
{
if (previousFrameLine[column] != currentFrameLine[column])
{
if (firstChangedLine == -1)
firstChangedLine = line;
lastChangedLine = line;
if (firstChangedColumn == -1 || column < firstChangedColumn)
firstChangedColumn = column;
lastChangedColumn = Math.Max(lastChangedColumn, column);
break;
}
}
for (int column = previousFrameLine.Length - 1; column > lastChangedColumn; column--)
{
if (previousFrameLine[column] != currentFrameLine[column])
{
lastChangedColumn = column;
break;
}
}
}
if (firstChangedLine == -1)
{
// This image is identical to the previous one and can be skipped
continue;
}
else if (firstChangedLine == 0 && firstChangedColumn == 0 && lastChangedLine == height - 1 && lastChangedColumn == width - 1)
{
// This image does not need to be cropped
resultFrames.Add((frames[i].elapsed, frames[i].image, Size.Empty));
}
else
{
var offset = new Size(firstChangedColumn, firstChangedLine);
var cropArea = new Rectangle(firstChangedColumn, firstChangedLine, lastChangedColumn - firstChangedColumn + 1, lastChangedLine - firstChangedLine + 1);
Bitmap croppedSource = frames[i].image.Clone(cropArea, frames[i].image.PixelFormat);
resultFrames.Add((frames[i].elapsed, croppedSource, offset));
}
}
}
finally
{
foreach ((Bitmap image, BitmapData data) in lockedBitmaps)
image?.UnlockBits(data);
}
return [.. resultFrames];
}
private static void WritePngSignature(Stream stream, byte[] buffer)
{
Write(stream, buffer, crc: null, s_pngHeader.Span);
}
private static void WriteIend(Stream stream, byte[] buffer, Crc32 crc)
{
crc.Reset();
WriteChunkHeader(stream, buffer, crc, Iend, dataLength: 0);
WriteCrc(stream, buffer, crc);
}
private static void WriteActl(Stream stream, byte[] buffer, Crc32 crc, int frameCount, int playCount)
{
crc.Reset();
WriteChunkHeader(stream, buffer, crc, Actl, 8);
// num_frames (4 bytes)
WritePngUInt32(stream, buffer, crc, checked((uint)frameCount));
// num_plays (4 bytes)
WritePngUInt32(stream, buffer, crc, checked((uint)playCount));
WriteCrc(stream, buffer, crc);
}
private static void WriteFrame(Stream stream, byte[] buffer, Crc32 crc, ref int sequenceNumber, Bitmap frame, Size offset, TimeSpan delay)
{
WriteFctl(stream, buffer, crc, sequenceNumber++, size: new Size(frame.Width, frame.Height), offset: offset, delay, ApngDisposeOp.None, ApngBlendOp.Source);
(ReadOnlyMemory<byte> _, ReadOnlyMemory<byte> _, ImmutableArray<ReadOnlyMemory<byte>> idats, ReadOnlyMemory<byte> _) = EncodeFrame(frame);
foreach (ReadOnlyMemory<byte> idat in idats)
{
WriteFdat(stream, buffer, crc, sequenceNumber++, idat.Span[8..^4]);
}
}
private static void WriteFdat(Stream stream, byte[] buffer, Crc32 crc, int sequenceNumber, ReadOnlySpan<byte> data)
{
crc.Reset();
WriteChunkHeader(stream, buffer, crc, Fdat, (uint)(data.Length + 4));
// fdAT is sequence number followed by IDAT
WritePngUInt32(stream, buffer, crc, (uint)sequenceNumber);
Write(stream, buffer, crc, data);
WriteCrc(stream, buffer, crc);
}
private static void WriteChunkHeader(Stream stream, byte[] buffer, Crc32 crc, ReadOnlySpan<byte> chunkType, uint dataLength)
{
WriteChunkDataLength(stream, buffer, dataLength);
Write(stream, buffer, crc, chunkType);
}
private static void WriteChunkDataLength(Stream stream, byte[] buffer, uint dataLength)
{
WritePngUInt32(stream, buffer, crc: null, dataLength);
}
private static void WriteCrc(Stream stream, byte[] buffer, Crc32 crc)
{
WritePngUInt32(stream, buffer, crc: null, crc.GetCurrentHashAsUInt32());
}
private static (ReadOnlyMemory<byte> signature, ReadOnlyMemory<byte> ihdr, ImmutableArray<ReadOnlyMemory<byte>> idat, ReadOnlyMemory<byte> iend) EncodeFrame(Bitmap frame)
{
using var stream = new MemoryStream();
frame.Save(stream, ImageFormat.Png);
Memory<byte> memory = stream.GetBuffer().AsMemory()[..(int)stream.Length];
Memory<byte> signature = memory[..8];
if (!signature.Span.SequenceEqual(s_pngHeader.Span))
throw new InvalidOperationException();
ReadOnlyMemory<byte> ihdr = ReadOnlyMemory<byte>.Empty;
List<ReadOnlyMemory<byte>> idat = [];
ReadOnlyMemory<byte> iend = ReadOnlyMemory<byte>.Empty;
for (Memory<byte> remaining = memory[signature.Length..]; !remaining.IsEmpty; remaining = remaining[GetChunkLength(remaining)..])
{
Memory<byte> chunk = remaining[..GetChunkLength(remaining)];
ReadOnlyMemory<byte> chunkType = GetChunkType(chunk);
if (chunkType.Span.SequenceEqual(Ihdr))
{
Assert.True(ihdr.IsEmpty);
ihdr = chunk;
}
else if (chunkType.Span.SequenceEqual(Srgb)
|| chunkType.Span.SequenceEqual(Gama)
|| chunkType.Span.SequenceEqual(Phys))
{
// These are expected chunks in the PNG, but not needed for the final APNG
continue;
}
else if (chunkType.Span.SequenceEqual(Idat))
{
idat.Add(chunk);
}
else if (chunkType.Span.SequenceEqual(Iend))
{
Assert.True(iend.IsEmpty);
iend = chunk;
}
else
{
string type = Encoding.ASCII.GetString(chunkType.ToArray());
throw new NotSupportedException($"Chunk \"{type}\" is not supported.");
}
}
Assert.False(ihdr.IsEmpty);
Assert.NotEqual(0, idat.Count);
Assert.False(iend.IsEmpty);
return (signature, ihdr, idat.ToImmutableArray(), iend);
static ReadOnlyMemory<byte> GetChunkType(ReadOnlyMemory<byte> chunk)
=> chunk[4..8];
static int GetDataLength(ReadOnlyMemory<byte> memory)
=> (int)BinaryPrimitives.ReadUInt32BigEndian(memory.Span);
static int GetChunkLength(ReadOnlyMemory<byte> memory)
{
// Total chunk length = length field + chunk type + data length + crc
return GetDataLength(memory) + 12;
}
}
private static void WriteFctl(Stream stream, byte[] buffer, Crc32 crc, int sequenceNumber, Size size, Size offset, TimeSpan delay, ApngDisposeOp disposeOp, ApngBlendOp blendOp)
{
crc.Reset();
WriteChunkHeader(stream, buffer, crc, Fctl, dataLength: 26);
// sequence_number (4 bytes)
WritePngUInt32(stream, buffer, crc, checked((uint)sequenceNumber));
// width (4 bytes)
WritePngUInt32(stream, buffer, crc, checked((uint)size.Width));
// height (4 bytes)
WritePngUInt32(stream, buffer, crc, checked((uint)size.Height));
// x_offset (4 bytes)
WritePngUInt32(stream, buffer, crc, checked((uint)offset.Width));
// y_offset (4 bytes)
WritePngUInt32(stream, buffer, crc, checked((uint)offset.Height));
if (delay.TotalMilliseconds > ushort.MaxValue)
{
// Specify delay in 1/30 second (max allowed is a bit over 36 minutes)
// delay_num (2 bytes)
WritePngUInt16(stream, buffer, crc, checked((ushort)(delay.TotalMilliseconds / 100)));
// delay_den (2 bytes)
WritePngUInt16(stream, buffer, crc, 10);
}
else
{
// Specify delay in 1/1000 second
// delay_num (2 bytes)
WritePngUInt16(stream, buffer, crc, checked((ushort)delay.TotalMilliseconds));
// delay_den (2 bytes)
WritePngUInt16(stream, buffer, crc, 1000);
}
// dispose_op (1 bytes)
WritePngByte(stream, crc, (byte)disposeOp);
// blend_op (1 bytes)
WritePngByte(stream, crc, (byte)blendOp);
WriteCrc(stream, buffer, crc);
}
private static void WritePngByte(Stream stream, Crc32? crc, byte value)
{
Span<byte> buffer = [value];
crc?.Append(buffer);
stream.WriteByte(value);
}
private static void WritePngUInt16(Stream stream, byte[] buffer, Crc32? crc, ushort value)
{
Span<byte> encoded = stackalloc byte[sizeof(ushort)];
BinaryPrimitives.WriteUInt16BigEndian(encoded, value);
Write(stream, buffer, crc, encoded);
}
private static void WritePngUInt32(Stream stream, byte[] buffer, Crc32? crc, uint value)
{
Span<byte> encoded = stackalloc byte[sizeof(uint)];
BinaryPrimitives.WriteUInt32BigEndian(encoded, value);
Write(stream, buffer, crc, encoded);
}
private static void Write(Stream stream, byte[] buffer, Crc32? crc, ReadOnlySpan<byte> bytes)
{
crc?.Append(bytes);
if (bytes.Length < buffer.Length)
{
bytes.CopyTo(buffer);
stream.Write(buffer, 0, bytes.Length);
}
else
{
for (ReadOnlySpan<byte> remaining = bytes; !remaining.IsEmpty; remaining = remaining[Math.Min(buffer.Length, remaining.Length)..])
{
ReadOnlySpan<byte> current = remaining[..Math.Min(buffer.Length, remaining.Length)];
current.CopyTo(buffer);
stream.Write(buffer, 0, current.Length);
}
}
}
public void Dispose()
{
UnregisterEvents();
s_currentInstance = null;
}
public void RegisterEvents(Form form)
{
ArgumentNullException.ThrowIfNull(form);
Assert.Null(_form);
_form = form;
form.Layout += OnThrottledInteraction;
form.Paint += OnThrottledInteraction;
form.MouseEnter += OnThrottledInteraction;
form.MouseLeave += OnThrottledInteraction;
form.MouseMove += OnThrottledInteraction;
form.MouseDown += OnInteraction;
form.MouseUp += OnInteraction;
form.KeyDown += OnInteraction;
}
public void UnregisterEvents()
{
if (_form is { } form)
{
form.Layout -= OnThrottledInteraction;
form.Paint -= OnThrottledInteraction;
form.MouseEnter -= OnThrottledInteraction;
form.MouseLeave -= OnThrottledInteraction;
form.MouseMove -= OnThrottledInteraction;
form.MouseDown -= OnInteraction;
form.MouseUp -= OnInteraction;
form.KeyDown -= OnInteraction;
}
}
private void OnThrottledInteraction(object? sender, EventArgs e)
{
// This can be increased to 0.5 seconds if tests are capturing too many images
var throttle = TimeSpan.Zero;
lock (s_frames)
{
// Avoid taking too many screenshots for layout updates
if (s_frames.Count > 0 && (s_timer.Elapsed - s_frames[^1].elapsed) < throttle)
return;
}
CaptureFrame();
}
private void OnInteraction(object? sender, EventArgs e)
{
CaptureFrame();
}
public void CaptureFrame()
{
TimeSpan elapsed = s_timer.Elapsed;
if (ScreenshotService.TryCaptureFullScreen() is { } image)
{
lock (s_frames)
{
s_frames.Add((elapsed, image));
}
}
}
}
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