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■No99458 (ぜん さん) に返信
> しかし、Chrome以外のウインドウだとうまくいくのですが
> Chromeだけは、画像が真っ暗になってしまいます。
対象のウィンドウは "Chrome_WidgetWin_1" クラスですか?
■No99466 (ぜん さん) に返信
> また、DWM Thumbnail APIでもできそうなことが書かれてあるのですが
> これはどうやって使えば良いですか？
> 検索してもいまいち使い方が分かりませんでした。
そうですか? 使い方の説明なら、すぐに出てきましたよ。
使う関数もそう多くは無いですし。
https://docs.microsoft.com/ja-jp/windows/win32/dwm/thumbnail-ovw
Option Strict On
Imports System.Runtime.InteropServices
Public Class Form1
Private ThumbnailId As IntPtr = IntPtr.Zero
Private Function GetChromeHandle() As IntPtr
Throw New NotImplementedException("取得対象の HWND を取得するコードをここに記述")
End Function
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Button1.Text = "描画開始"
End Sub
Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
If ThumbnailId <> IntPtr.Zero Then
DwmUnregisterThumbnail(ThumbnailId)
ThumbnailId = IntPtr.Zero
End If
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If ThumbnailId = IntPtr.Zero Then
Dim chromeHandle As IntPtr = GetChromeHandle()
DwmRegisterThumbnail(Me.Handle, chromeHandle, ThumbnailId)
UpdateThumbnail()
Button1.Text = $"描画停止:{ThumbnailId}"
Else
DwmUnregisterThumbnail(ThumbnailId)
ThumbnailId = IntPtr.Zero
Button1.Text = "描画開始"
End If
End Sub
Private Sub UpdateThumbnail()
If ThumbnailId <> IntPtr.Zero Then
Dim rect = Me.RectangleToClient(PictureBox1.RectangleToScreen(PictureBox1.ClientRectangle))
DwmUpdateThumbnailProperties(ThumbnailId, New DWM_THUMBNAIL_PROPERTIES(rect, False))
End If
End Sub
#Region "DWM サムネイル API"
Private Declare Auto Function DwmRegisterThumbnail Lib "dwmapi" (hwndDestination As IntPtr, hwndSource As IntPtr, <Out> ByRef phThumbnailId As IntPtr) As Integer
Private Declare Auto Function DwmUpdateThumbnailProperties Lib "dwmapi" (hThumbnailId As IntPtr, <[In]> ptnProperties As DWM_THUMBNAIL_PROPERTIES) As Integer
Private Declare Auto Function DwmUnregisterThumbnail Lib "dwmapi" (hThumbnailId As IntPtr) As Integer
<StructLayout(LayoutKind.Sequential)>
Public Structure RECT
Public left As Integer, top As Integer, right As Integer, bottom As Integer
Public Shared Widening Operator CType(r As RECT) As Rectangle
Return Rectangle.FromLTRB(r.left, r.top, r.right, r.bottom)
End Operator
Public Shared Widening Operator CType(r As Rectangle) As RECT
Return New RECT With {.left = r.Left, .top = r.Top, .right = r.Right, .bottom = r.Bottom}
End Operator
End Structure
<Flags>
Private Enum DWM_TNP As UInteger
None = 0
RectDestination = &H1UI
RectSource = &H2UI
Opacity = &H4UI
Visible = &H8UI
SourceClientAreaOnly = &H10UI
End Enum
<StructLayout(LayoutKind.Sequential)>
Private Class DWM_THUMBNAIL_PROPERTIES
Public dwFlags As DWM_TNP = DWM_TNP.None
Public rcDestination As RECT
Public rcSource As RECT
Public opacity As Byte = 255
<MarshalAs(UnmanagedType.Bool)> Public fVisible As Boolean = False
<MarshalAs(UnmanagedType.Bool)> Public fSourceClientAreaOnly As Boolean = False
Public Sub New()
End Sub
Public Sub New(destination As Rectangle, clientOnly As Boolean)
dwFlags = DWM_TNP.RectDestination Or DWM_TNP.SourceClientAreaOnly
rcDestination = destination
fSourceClientAreaOnly = clientOnly
End Sub
End Class
#End Region
End Class
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