multiple cairo renderers threading suffers from global style state leaks

I am using a Cairo renderer with a background threaded drawing, of which I have 8 threads running.

There are several instances where the global style is referenced and therefor causes unpredictable behavior. For example in:

 void ofCairoRenderer::draw(ofPath & shape){
      ....
      c.a = shape.getStrokeColor().a/255. * ofGetStyle().color.a; 
      ....
 }

This causes frames to intermittently show up blank. @arturoc is this outside of the expected use of Cairo?

Here is a snippet on how it's being used

cairoRenderer.setupMemoryOnly(ofCairoRenderer::IMAGE, false, false, ofRectangle(0,0,videoPixels.getWidth(), videoPixels.getHeight()) );
cairoRenderer.setupGraphicDefaults();
cairoRenderer.background(0);

for (int i = 0; i < contours.size(); i++){
        ofPath contourPath;
        for(int p = 0; p < contours.getPolyline(i).getVertices().size(); p++){
            contourPath.lineTo(contours.getPolyline(i).getVertices()[p]);
        }
        contourPath.close();

        cairoRenderer.setColor(ofColor::white);
        contourPath.setFillColor(ofColor::white);
        cairoRenderer.draw(contourPath);            
    }
}



cairoRenderer.flush();

ofPixels resized = cairoRenderer.getImageSurfacePixels();
resized.setImageType(OF_IMAGE_COLOR);
resized.resize(faceTargetRectangle.getWidth(), faceTargetRectangle.getHeight(), OF_INTERPOLATE_BICUBIC);
resized.pasteInto(outputImage, faceTargetRectangle.x, faceTargetRectangle.y);

Start at ofCairoRenderer::draw, especially the ofGetStyle().color access shown in the report, and trace other global-style references used by the Cairo renderer. Reproduce the memory-only renderer with multiple background drawing threads and verify that frames no longer intermittently appear blank.