Don't redraw volatile previews on ticker period

[neeshy]

Fixes #542
There's probably a more elegant solution to this though.

[gokcehan]

@neeshy Thanks for the solution. Would it not be possible to simply add a conditional to the ticker since it is only different in a single place? Something like:

diff --git a/app.go b/app.go
index 611292d..2905fca 100644
--- a/app.go
+++ b/app.go
@@ -352,7 +352,9 @@ func (app *app) loop() {
                        app.ui.draw(app.nav)
                case <-app.ticker.C:
                        app.nav.renew()
-                       app.ui.loadFile(app.nav)
+                       if !app.nav.volatilePreview {
+                               app.ui.loadFile(app.nav)
+                       }
                        app.ui.draw(app.nav)
                }
        }

This seems to work with the non-caching version of my preview highlight script. I don't have an image setup yet so I'm not sure if it works.

[neeshy]

@gokcehan The problem with that patch is that the preview won't be regenerated when the modification time changes. So, disabling calling the ui.loadFile method altogether isn't sufficient. Somehow the call to nav.checkReg has to be retained, which my patch does.

[gokcehan]

@neeshy Ah, I see, don't mind me, I will just merge this patch then, thanks.