I don't really understand if blendColor could be used to match the video behind rectangle 1 somehow? Would rectangle 2 cause only the overlapped portion of rectangle 1 to become transparent to the video? That would be awesome, that's what you want.
My guess is you'd need to have this triangle and stuff above it on a blended patch so it stands out from the video. Even if you get the transparent thing to work, how will you know what color to set your widget so that it's not getting lost in the video when they happen to be similar color?
Actually, I would like to draw a rectangle with a triangle centered on the bottom. The current scrubbing speed will display within the rectangle. I'd like to use vector artwork (instead of a bitmap) since I'd like the scrubbing indicator to be able to change colors.
[...] 2 other rectangles are colored to match the screen color and placed on top of the first rectangle, rotated by 45 degrees or whatever you want to shape your triangle.