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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.ComponentModel;
using System.Drawing;
namespace Windows.Win32.Graphics.Gdi;
/// <summary>
/// Helper to scope the lifetime of a <see cref="HBRUSH"/>.
/// </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 delete.
/// </para>
/// </remarks>
#if DEBUG
internal class CreateBrushScope : DisposalTracking.Tracker, IDisposable
#else
internal readonly ref struct CreateBrushScope
#endif
{
public HBRUSH HBRUSH { get; }
/// <summary>
/// Creates a solid brush based on the <paramref name="color"/> using <see cref="PInvokeCore.CreateSolidBrush(COLORREF)"/>.
/// </summary>
public CreateBrushScope(Color color)
{
HBRUSH = color.IsSystemColor
? PInvokeCore.GetSysColorBrush(color)
: PInvokeCore.CreateSolidBrush(color);
ValidateBrushHandle();
}
public static implicit operator HBRUSH(in CreateBrushScope scope) => scope.HBRUSH;
public static implicit operator HGDIOBJ(in CreateBrushScope scope) => scope.HBRUSH;
public bool IsNull => HBRUSH.IsNull;
public void Dispose()
{
if (!HBRUSH.IsNull)
{
// Note that this is a no-op if the original brush was a system brush
PInvokeCore.DeleteObject(HBRUSH);
}
#if DEBUG
GC.SuppressFinalize(this);
#endif
}
[Conditional("DEBUG")]
private void ValidateBrushHandle()
{
if (HBRUSH.IsNull)
{
// Take LastError with a grain of salt here as it may not have been set.
#if DEBUG
GC.SuppressFinalize(this);
#endif
throw new Win32Exception("Could not create a GDI brush.");
}
}
}
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