multiple FlowCoverViewGL in the same view

[eidng8]

The flow covers got screwed when there are more than one flow cover in the same view

[eidng8]

Say, we have two FlowCoverGL instances, A and B. A is just finished rendering, and then B is about the be rendered. Then, B will be rendered improperly. And vice versa.

Currently FlowCoverViewGL doesn't handle multiple view port. Each instance maintains their own view port, putting multiple instance in the same view is likely cause problem.

This issue is much less noticeable if loading image in synchronous mode. Using [imageAtPath:path:async:NO] will force all instance in the same UIView to be drawn one by one, thus much less likely to interfere with other view ports. Even so, when the FlowCoverViewGL (other than the one dragged previously) is dragged, the first frame drawn right after the dragging started is affected by the bug.

However, the error is makes FlowCoverViewGL instances completely unreadable, if drawn in alternating order. That is, when using [imageAtPath:path:async:YES] messages. The rendering sequence of view ports are not controllable. So both view ports will be screwed up.