Transparent background for the canvas about windowjs

[joaodasilva]

Glad to hear that & thanks for pinging back!

It's intentional that this works, it's just unclear why both calls are needed.

I certainly wanted transparency to be opt-in, and the default to be opaque black; but the clearRect implementation should suffice to make the window transparent. Let's keep the issue open to track that.

[joaodasilva]

This is fixed now. The problem was a synchronization between drawing to the window framebuffer and the skia state. It doesn't reproduce anymore since drawing exclusively with Skia.

This means that a single clearRect() calls is enough to get transparency. I.e. the default background is opaque black, but clearRect() makes it transparent.

[joaodasilva]

The window supports transparency but it's initially cleared with opaque black. So if you clear with a transparent color then you should see through the window.

You can try running examples/squares.js to see a semi-transparent window. The key code snippet is this:

const canvas = window.canvas;
canvas.clearRect(0, 0, canvas.width, canvas.height);
canvas.fillStyle = '#000000b0';
canvas.fillRect(0, 0, canvas.width, canvas.height);

Does that work for you?

Let's leave the issue open because the fillRect call in that snippet shouldn't be necessary, but it doesn't work without it; that's a bug :-)

[joaodasilva]

This is now documented at https://windowjs.org/doc/canvas#canvas.clearRect.

@Bellisario please ping the thread if that code snippet doesn't work on your machine, there might well be more bugs in the implementation.

[Bellisario]

Thanks for your support.
Works using this this "loophole"!