manipulate - Question about making TabView remember what tab to open

Background: Consider the following ( for the purpose of illustrating this question ) simplified, but working snippet of code.

 TabView[

  {
   {patt, "Pattern" -> 1},
   {motif, "Motif" -> Column[{
      Button["Type", Print[" NOT IMPLEMENTED YET"], ImageSize -> 100],
      Button["New shape", Print[" NOT IMPLEMENTED YET"], ImageSize -> 100],
      Button["Pixel", Print[" NOT IMPLEMENTED YET"], ImageSize -> 100]}]}
  },
  Dynamic[tab]]

I have a GUI in a Module / Manipulate construction which contains a tabview that displays several views of the same data on its tabs. Each tab contains a series of buttons to further specify the particular view on that tab. Each tab consists several buttons and other controls, i.e. setterbars, 2D sliders. After each click or other action on a control the data is modified and all views are recalculated and displayed on the tabs.

The issue is that after each tab the tabview always returns to page 1. I have already made accomodations by using the following format of TabView:

  TabView[{ 
   {value1, "Tabname"->CodeOnTab1}, 
   {valueN, "Tabname"->CodeOnTabn} }, 
  Dynamic[VAR]

As I understand the Tabview opens tabN if VAR is set to valueN. This leads to the following question: what is the best =coding strategy= to make a TabView aware of the tab it should display ( open ) when it is re-displayed ( considering the last user action ) ? The goal / criteria is: minimal code use.

Answer

I may have misunderstood your problem, but it looks like you just need to create a persistent local variable keeping the value of the tab which was last open. One way to do this:

DynamicModule[{tab},

   myCustomTab[] :=
      TabView[
       {
          {patt, "Pattern" -> 1},
          {motif, "Motif" -> 
             Column[{
               Button["Type", Print[" NOT IMPLEMENTED YET"], ImageSize -> 100],
               Button["New shape", Print[" NOT IMPLEMENTED YET"], ImageSize -> 100],
               Button["Pixel", Print[" NOT IMPLEMENTED YET"], ImageSize -> 100]}]}
       },

       Dynamic[tab]]
]

What matters is that you create a closure, so the variable tab is not local to the function myCustomTab (in the sense that it is not re-initialized on every function's invocation).

EDIT

Ok, it is probably a good time to explain what I mean by code generation, since I mentioned this technique many times already. Basically, I mean that you will be better off by creating your own DSL for UI. I will illustrate it here simplistically with rule application, but generally I would rather use recursion, which is more powerful. You can notice that your code is full of repeated elements, and this is true even for such a small code snippet. Here is one way to reduce the boilerplate:

This is a function written by @Szabolcs, which will be handy here

ClearAll[withRules]
SetAttributes[withRules, HoldAll]
withRules[rules_, expr_] :=

  First@PreemptProtect@Internal`InheritedBlock[
    {Rule, RuleDelayed},
    SetAttributes[{Rule, RuleDelayed}, HoldFirst];
    Hold[expr] /. rules
]

This is the starting point:

myTab = 
  myTabView[
   {"Pattern" -> 1,

     "Motif" -> Column[{
         myButton["Type", noimpl[]],
         myButton["New shape", noimpl[]],
         myButton["Pixel", noimpl[]]}]
    }];

This is an auxiliary function:

Clear[dressTabView];
dressTabView[lrules_] :=
   t : myTabView[{__Rule}] :>

     DynamicModule[{tab},
        Append[
           Replace[t, e : (label_ -> w_) :> {withRules[lrules, label], e}, 2],
           Dynamic[tab]]];

This is a chain of transformations needed to generate your widget with tab memory:

myTab /. dressTabView[{"Motif" :> motif, "Pattern" :> patt}] /.
    myButton[args__] :> Button[args, ImageSize -> 100] /.
       noimpl[] :> Print[" NOT IMPLEMENTED YET"] /.
          myTabView -> TabView

The main point is, as usual, to separate the specific from the general.