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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.
namespace Windows.Win32.Graphics.Gdi;
/// <summary>
/// Helper to scope selecting a GDI object into an <see cref="HDC"/>. Restores the original
/// object into the <see cref="HDC"/> when disposed.
/// </summary>
/// <remarks>
/// <para>
/// Use in a <see langword="using" /> statement. If you must pass this around, always pass
/// by <see langword="ref" /> to avoid duplicating the handle and risking a double selection.
/// </para>
/// </remarks>
#if DEBUG
internal class SelectObjectScope : DisposalTracking.Tracker, IDisposable
#else
internal readonly ref struct SelectObjectScope
#endif
{
private readonly HDC _hdc;
public HGDIOBJ PreviousObject { get; }
/// <summary>
/// Selects <paramref name="object"/> into the given <paramref name="hdc"/> using
/// <see cref="PInvokeCore.SelectObject(HDC, HGDIOBJ)"/>.
/// </summary>
public SelectObjectScope(HDC hdc, HGDIOBJ @object)
{
// Selecting null doesn't mean anything
if (@object.IsNull)
{
_hdc = default;
PreviousObject = default;
}
else
{
_hdc = hdc;
PreviousObject = PInvokeCore.SelectObject(hdc, @object);
}
}
public void Dispose()
{
if (!_hdc.IsNull)
{
PInvokeCore.SelectObject(_hdc, PreviousObject);
}
#if DEBUG
GC.SuppressFinalize(this);
#endif
}
}
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