Fixed issue #1074: PaintTree with poUnbuffered misplaces nodes under a mapping mode

[TetzkatLipHoka]

Fixes #1074.

Cause

SetCanvasOrigin() in VirtualTrees.Utils.pas transformed its shift through LPtoDP before passing it to SetWindowOrgEx:

// The shifting is expected in physical points, so we have to transform them accordingly.
P := Point(X, Y);
LPtoDP(Canvas.Handle, P, 1);
SetWindowOrgEx(Canvas.Handle, P.X, P.Y, nil);

SetWindowOrgEx however expects logical units — the same units the tree calculates with. On a canvas with a mapping mode (the issue uses MM_ANISOTROPIC with a 2x viewport) the shift therefore got scaled twice, so the unbuffered paint path drew every node at twice its offset: node contents, tree lines, buttons and grid lines all drift apart, exactly as shown in the issue's screenshot. With the default MM_TEXT mapping LPtoDP is the identity, which is why the ordinary paint paths never showed the problem.

Fix

Pass the shift to SetWindowOrgEx untransformed.

Verification (all measured offscreen via pixel analysis)

• With a 2x MM_ANISOTROPIC mapping, the unbuffered rendering now places all grid lines and tree lines pixel-identical to the buffered rendering, and exactly at twice the unmapped positions.
• The MM_TEXT rendering is byte-identical to the one before the fix — no change for normal painting.
• TBaseVirtualTree.Print is unaffected: it renders into an unmapped bitmap and scales via StretchBlt.
• New regression test Tests/VTPaintTreeIssue1074Tests.pas asserts both properties (unbuffered = buffered under mapping, mapped = 2x unmapped); without the fix both assertions fail. Full suite: no new failures (the two TestCopyHTML failures also occur on unmodified master).

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