In an element with mask and opacity, the opacity is not applied
<svg width="400" height="400" xmlns="http://www.w3.org/2000/svg">
<mask id="mask">
<circle cx="200" cy="200" r="200" fill="white"/>
</mask>
<rect width="400" height="400" fill="lime" opacity="0.5" mask="url(#mask)"/>
</svg>
This should render a lime circle at 0.5 opacity, but it renders it at full opacity. The problem is in DrawingCtx::with_discrete_layer
- if there is a mask, the opacity is not applied at all. I'll fix this.