Automating Esc [[ Esc formatting?

Question

Is it possible to program the Front End to automatically format double square brackets without having to type Esc[[Esc each time? It's awful to have to type Esc four times for each Part expression, and even more annoying to visually parse the unformatted double brackets.

See also this entry in MathGroup archive: adding a keyboard shortcut for double brackets

Answer 1

Some approaches are discussed in this question on StackOverflow. Original references to these go to Szabolcs's webpage and a MathGroup posting by Mr.Wizard.

To summarize, you copy the file: $InstallationDirectory/SystemFiles/FrontEnd/TextResources/Macintosh/KeyEventTranslations.tr to $UserBaseDirectory/ (with the same directory tree) and add the following modifications after EventTranslations[{ in the file:

Item[KeyEvent["[", Modifiers -> {Control}],
        FrontEndExecute[{
            FrontEnd`NotebookWrite[FrontEnd`InputNotebook[],
                "\[LeftDoubleBracket]", After]
        }]],
Item[KeyEvent["]", Modifiers -> {Control}],
        FrontEndExecute[{
            FrontEnd`NotebookWrite[FrontEnd`InputNotebook[],
                "\[RightDoubleBracket]", After]
        }]], 
Item[KeyEvent["]", Modifiers -> {Control, Command}],
        FrontEndExecute[{
            FrontEnd`NotebookWrite[FrontEnd`InputNotebook[],
                "\[LeftDoubleBracket]", After],
            FrontEnd`NotebookWrite[FrontEnd`InputNotebook[],
                "\[RightDoubleBracket]", Before]
        }]], 

These provide the following shortcuts:

• 〚 using Ctrl+[
• 〛 using Ctrl+]
• 〚〛 using Ctrl+Cmd+]

Replace Command with Alt for Windows/Linux and modify the paths above accordingly.

You can also try Andrew Moylan's suggestion, in the same post, but I haven't tried it.

Answer 2

Edit the KeyEventTranslations.tr file in a plain text editor by adding the following definitions to the first section of the file:

EventTranslations[{

(* Custom shortcuts *)
Item[KeyEvent["[",Modifiers->{Control}],
    FrontEndExecute[{FrontEnd`NotebookWrite[FrontEnd`InputNotebook[],
    "[\[SelectionPlaceholder]]"],FrontEndToken["MovePreviousPlaceHolder"]}]],

Item[KeyEvent["]",Modifiers->{Control}],
    FrontEndExecute[{FrontEnd`NotebookWrite[FrontEnd`InputNotebook[],
    "\[LeftDoubleBracket]\[SelectionPlaceholder]\[RightDoubleBracket]"],
    FrontEndToken["MovePreviousPlaceHolder"],FrontEndToken["MovePreviousPlaceHolder"]}]],

(* Evaluation *)

Note that these shortcuts are set up to use the "Control" modifier to insert a template for pairs of single/double brackets.