I am almost OCD about this.
When I moved into this city house, the shower screen had all this white "gunk" on the edges and bottom.
I believe it was a calcium build up, and I ended up tearing out the bathroom and re-doing it -well not ME exactly -I paid to have it all done.
From then on I realised that the water here has so much calcium that I would have to wipe the shower each time!
Never done this before and never had a problem with calcium before.
However I do wipe it over with an Enjo cloth after each shower.