Changing color distribution with 'd' and scrolling changes the zoom

[hcferguson]

Using a trackpad on a mac, I find that if I try change the color distribution using the 'd' shortcut and the scrolling, it does change the color distribution, but it also tends to leave me at a different zoom.

[ejeschke]

@hcferguson, pinch gesture was unintentionally enabled by default and what was happening is that there are usually a few pinch events that get rolled into a scroll motion on the trackpad under Qt, and these were getting picked up into a zoom operation.

Commit a9bcc1b2fadd624282f10a3c8e4d6e7c62a2cb28 contains a fix. If you want to get the pinch behavior back, checkout the examples directory and the bindings.cfg.trackpad, which can be copied to your $HOME/.ginga/bindings.cfg and customized for a better fit with trackpads.

Probably this issue should be left open until either pinch is disabled under dist mode, or a better way of cycling through the selections than scrolling is found. I find the scrolling to work well with a mouse wheel for this purpose, but it changes too fast when scrolling with fingers on a trackpad.