[Bug 36891] New: Polygon() draws different edges than in Windows

[wine-bugs at winehq.org]

https://bugs.winehq.org/show_bug.cgi?id=36891

            Bug ID: 36891
           Summary: Polygon() draws different edges than in Windows
           Product: Wine
           Version: 1.7.22
          Hardware: x86
                OS: Linux
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: gdi32
          Assignee: wine-bugs at winehq.org
          Reporter: sashoalm at gmail.com

The Polygon() function does not draw in the same way in Wine as in Windows.
While it looks very similar visually, there are some pixels at the edges that
are different. Since the goal of Wine is to replicate Windows behavior
perfectly, this deviation would be a bug.

The difference is difficult to spot, but it can be noticed if you rapidly
switch between the images, or if you compare them pixel by pixel with a
program.

I have made a test program that draws an inclined rectangle using XFORM and
Polygon() into a memory DC, which I then save to a bitmap. The resulting
bitmaps when ran under Windows and Wine are slightly different.

Image under Windows:
https://drive.google.com/file/d/0B9PGUhmmnsm1Q00waFJLSGtEeEU/edit?usp=sharing
Image under Wine:
https://drive.google.com/file/d/0B9PGUhmmnsm1X1ZVR1UtbDBPMHc/edit?usp=sharing

This is the relevant code I used to draw the image. Note that it's the XFORM
matrix that makes the rectangle be inclined (it would be parallel to the
coordinate system without a world-transform):

    XFORM xform;
    memset(&xform, 0, sizeof(xform));
    double angle = 15*(PI/180); // 15 degrees incline.
    xform.eM11 = cos(angle);
    xform.eM12 = sin(angle);
    xform.eM21 = -sin(angle);
    xform.eM22 = cos(angle);
    xform.eDx = 0;
    xform.eDy = 0;
    SetGraphicsMode(hdc, GM_ADVANCED);
    SetWorldTransform(hdc, &xform);

    HBRUSH hbr = CreateHatchBrush(HS_BDIAGONAL, RGB(255, 0, 0));
    SelectObject(hdc, hbr);
    POINT p[4]={100,0,200,0,200,100,100,100};
    Polygon(hdc, p, 4);

I can provide the full test project if requested.

Note: I have tested on both Windows 7 and Windows XP, and they produce exactly
the same images, only Wine produces a different image.

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