When you zoom text out too much all that is left are some blobs of pixels.
In such a case instead of using the slow drawing text; just draw a rect
or a line.  This speeds up the painting immensely since the side effect
of zooming out < 20% is that you see a lot more text on the screen at the
same time.  This makes that responsive again on all systems.
Note that I calculate the amount of pixels that the text line would take, so
this is the most correct manner of doing this I can think of.

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