Why does using SkBlendMode::kClear produce a black box instead of clearing the area in Skia?

[stephane]

I'm trying to erase a rectangle on an SkCanvas by setting the paint's blend mode to kClear. However, instead of getting a transparent area, I end up with a solid black rectangle. Here's a minimal snippet:

paint.setBlendMode(SkBlendMode::kClear);
canvas->drawRect(rect, paint);


I expected the rectangle to become fully transparent, but I'm seeing black where I cleared.

• Why does this produce black instead of a transparent hole?
• How can I make the rectangle truly transparent?

thanks you by advance

[craste...@gmail.com]

Is it a 32 bit color surface?
Or Alpha 8 bit?

[Greg Daniel]

Can you make an example on fiddle.skia.org please.

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