Can anyone tell me what option controls the appearance of the above conversion prompts? I feel like I have come across this before but now cannot find the option

@WReach You around?

Simple example:

$test=Table[Association[
    Unique["x"]-><|"val1"->RandomInteger[5],"val2"->RandomInteger[5]|>],{50}]

To sort this list first by val2 and then by val1, is there anything shorter than

SortBy[{Last[#]["val2"] &, Last[#]["val1"] &}][$test]

Especially, can I get rid of the Last[#] inside a Query and still maintain the complete structure after sorting?

@WReach Nevermind, I made of course an error in creating the example :(

@halirutan Perhaps $test // SortBy[#[[-1, {"val2", "val1"}]] &]

or to get a stable sort: $test // SortBy[{#[[-1, {"val2", "val1"}]] &}]

@WReach Yep, thanks. My structure was indeed a whole association which makes things easy.

.. and always remember to use Key explicitly in SortBy when you use it on associations.. god damn it.

(that was a note to myself)

@WReach How did you know about the trick to make SortBy stable? That never occurred to me from the documentation. I just assumed it always broke ties with canonical order once it reached the end of the list. Like it does with just a single sorting function. That's very useful to know. Thanks. I already have one code simplification I know I can make in one of my notebooks now.

SortBy[{{1, 2}, {1, 1}}, First] vs SortBy[{{1, 2}, {1, 1}}, {First}] if anyone was wondering what I'm referring to.

@MichaelHale I can't remember where I first heard about it. It surely wasn't the documentation :) I seem to recall that it might have been a throw-away comment on a Stackoverflow post by someone connected to WRI. Or maybe even on Mathgroup.

Cool. Thanks. I'll send a suggestion to add that to the documentation.

@MichaelHale

Hm. Well the way Andrew explains it there might have actually made me try it on my own. "Note that SortBy[list, f] is the same as SortBy[list, {f, Identity}]" But what the docs actually say made me just assume Identity was just tacked onto the end of it no matter what. "SortBy[e,f] is equivalent to Sort[{f[#],#}&/@e][[All,-1]]"

Suggestion sent.

Does someone remember if and how it is possible to change the background style of the selected item in a ListPicker?

@halirutan I know I've changed the colors before. I think it's in the docs under one of the options.

@halirutan that must have just been the standard background

But this works:

Anybody know what errors I have made in this answer?

@MichaelE2 Hello,

@yode Hi

I'm glad to see your answer,but I don't know apply it in my this anwre

@MichaelE2 This is my Composition version.But it doesn't work..

size = size*.5 should out of the Map here..Confusing

"I don't know how to apply it into my this answer."

Map makes is more difficult. Make each statement a function:

size = 1;
Graphics[
 NestList[
  Composition[
   Map[drawH[#, size] &],
   (size = size*.5; #) &,
   Level[#[[All, 1, 2 ;;]], {-2}] &
   ],
  {drawH[{0, 0}, 1]}, 2]]

Or combine size with Level instead of Map:

size = 1;
Graphics[
 NestList[
  Composition[
   Map[drawH[#, size] &],
   (size = size*.5; Level[#[[All, 1, 2 ;;]], {-2}]) &
   ],
  {drawH[{0, 0}, 1]}, 2]]

@MichaelE2 Thanks very much.. :)

@yode You're welcome. :)

And I have update that answer as your method

@MB1965 Yes, I didn't use this because it has 2 flaws as far as I know: The first major one is that although it changes the background color of the item, the default highlighting color is added to it (which is critical as I want a consistent layout). The second one is that there is no obvious way to extend this to multiple selected elements. But the first one is the main no-go for me, but thanks for giving it a try.

I have debugged through the whole code that turns a listpicker to its box-representation. The final box coloring is defined by ListPickerBoxBackground which is calculated through several steps. The main step is to turn the highlevel Background option for listpicker by using e.g.

GridDump`ColumnRestructure[Background, {{GrayLevel[1], GrayLevel[0.5]}, {1 -> Red}},
   "Rows"]

and

GridDump`ColumnRestructure[Background, {{GrayLevel[1],   GrayLevel[0.5]}, {1 -> Red}},
   "RowsIndexed"]

On the whole way down to the box-representation there doesn't appear a way to influence the high-light color of the selected item.

I fgreped through all the Default.nb and Core.nb style definitions but I started to go in circles. I had the hope that the dynamic highlighting color is exposed somewhere (and maybe it is) but I have no idea what to look for.