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MSFS20 GDI+ Setting Polygon as a clipping region does not work.

H

HornetJockey

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us-newyork
Hello all,

Continued from my previous post, I cannot seem to set a clip, using a polygon. If I just define and fill a polygon, no problem, comes out just as it is supposed to. But setting this same polygon as a clip region is NOT working.

Here is the code:
C++: 
    GraphicsPath VSIClip;
    VSIClip.AddPolygon(p.hFrameShape, p.hFrameShapeCount);
    gfx->SetClip(&VSIClip); // doesnt work

    gfx->FillPolygon(&brushDarkOverlay, p.hFrameShape, p.hFrameShapeCount); // this does work, the polygon is rendered

Anyone have an idea about this one?
 
VSIClip.Reset() before you add the polygon. Also, a clip just restricts where rendering can be done... it doesn't do anything else on it's own.
 
Thanks for your suggestion, unfortunately no luck. This is the VSI area, basically a 10 point polygon, (on the left) and this is what I get when I use the same polygon as a clip mask (on the right):

1764216148766.png
1764216291613.png


No idea what is going on. Since I need to clip only the right portion of the needle, I resorted to adding a clipping rectangle along its right edge, and that works. But a proper way would be to just add the same polygon used for the darkened VSI area.
 
I don't write anything for the new sim as it's not 100% working, and you may have found a new issue. This is not a GDI+ issue as I've used code like this in Prepar3D. MSFS20/24 don't actually use GDI+, it's something else that's got a GDI+ looking front-end.
 
Yep. From the SDK docs:

'GDI+
This library provides the implementation of the WIN32 GDI+ API, as a Wrapper of the Low Level API via NanoVG.'

So they have mucked about with the basic GDI+ implementation in an attempt to sandbox it.
 
Might I suggest you create the shape using lines instead of a polygon and see if that works?
 
A whole ten minutes of reading up on NanoVG leads me to think that the following is happening:

- the GDI+ calls are being intercepted by the sim and converted to NanoVG
- NanoVG is then doing the on-screen drawing
- the conversion from GDI+ calls to NanoVG calls is incomplete as WarpD suggests
- all the above is pretty much confirmed by this topic here: NanoVG API

You may be better off converting to direct NanoVG drawing in future.
 
Whoa! I guess I'll have to look into NanoVG to implement things GDI is failing at.

I didnt see anything there about the dashed line not working (as per my other post)...

Thanks for looking into this, guys!!
 
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