#1968 canvas paths - blend/transparency not working

[Marcin Nalepa]

OS: ubuntu 14.04 x64, ubuntu 16.04 x64, win7 x64
CPU: i5, i7
GPU: GTX660, GTX870m (375.xx drivers)
FG: 2016.4.4, 2017.1.3, latest git

I was trying to create new HUD for airplane using canvas API and I got a problem. Changing blend functions for path objects on canvas is not working. Setup is quite simple - flat object with assigned texture I place canvas on and some draw operations in nasal. My test setup, as seen on picture, contains 3 types of elements: text, path and image. Canvas is set to be half transparent red color. Every top object has selected blending one-zero (blend-source, blend-destination) to show how it looks on its own. It simply replaces existing pixels with new ones and it works as expected. Problem arises when there's need to change blending function. Let for example use simplest one-one, it should add color values together. As seen in the picture text is blended as expected (red + green = yellow), image also (notice black outline becomes red) but path is not affected.

I searched for simmilar issues on both forum and bugtracker and didn't find any possibly connected problems. I tested paths with different shapes: triangle, arc, rectangle but it does not change anything. I checked values in property tree explorer and indeed nasal correctly sets them to supplied values. I also checked different blending settings such as most commom src-alpha - one-minus-src-alpha or zero-zero but still nothing changed for paths. I checked different hardware, OSes and FG versions (including latest git) but it does not have an influence on this problem.

Nasal code I used to set blending functions is for ex.:
.set("blend-source", "one")
.set("blend-destination", "one")

[Nikolai V. Chr.]

This bug is still there.