Slow destroying widgets

[Michal Koranda <adhc volny cz>]

I created an Gtk3 application in C for configuring measurement as my school work. There is a notebook and its 
tabs contains large fomulars containing many special tables. Each table (GtkGrid) has many cells, containing 
some entries, butons, labels, and combo boxes.
When I tested program on forms containing altogether about 500 cells it was OK. Now I tested this program on 
real data which contains 2000-4000 cells. Creating form spend about 3-4 sec, it is a bit slow, but it 
corresponding with many of data. The problem is destroying form. It take 20-30 sec. The application is 
unusable, my work is bad...
I discovered - the time spended to destroing one widget is in proportion to count of widget remaining in 
entire application (all tabs). Is there some interaction before destroyed widget and the rest of widgets? Is 
there any way to accelerate closing forms?

I looked on gtk_tree_view, but it not much suitable for this kind of data. Also I need activate cell by first 
mouse click and moving in row by TAB (similarly as spreadsheet).

Thanks much.