Remove DeviceContext HWND handling

[hughbe]

DeviceContext has a bunch of overhead - allocations, interop calls etc.

However, in the case of Graphics.CopyFromScreen, which is the only user of the HWND features in DeviceContext, we can avoid all of that and remove a bunch of code from DeviceContext.

Just call IntPtr screenDC = GetDC(IntPtr.Zero) and ReleaseDC(screenDC)

/cc @JeremyKuhne

[ghost]

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Issue Details

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DeviceContext has a bunch of overhead - allocations, interop calls etc.

However, in the case of Graphics.CopyFromScreen, which is the only user of the HWND features in DeviceContext, we can avoid all of that and remove a bunch of code from DeviceContext.

Just call IntPtr screenDC = GetDC(IntPtr.Zero) and ReleaseDC(screenDC)

Author:	hughbe
Assignees:	-
Labels:	area-System.Drawing
Milestone:	-

[JeremyKuhne]

Can you remove IDeviceContext from DeviceContext? I don't think there is a dependency on it...

Looks good otherwise. Going forward, it might be worth trying to kill DeviceContext completely as I have in Windows Forms and using ref struct "scopes" for code clarity / perf.

[safern]

Looks reasonable.

[ghost]

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