Customizing Mode Maps For Enhanced REPL Experience

Hey guys! Let's dive into a neat idea about customizing mode maps for a better REPL (Read-Eval-Print Loop) experience. The current setup in termint.el has some hard-coded mode maps within the termint-define macro. The idea is to make these mode maps customizable, allowing users to tweak keybindings to their liking and even add new commands. It's all about making your workflow smoother and more personalized.

Understanding the Current Mode Map Implementation

Currently, the termint-define macro is responsible for defining the keymaps. Here's a simplified look at how it works:

(defvar ,keymap-name
         (let ((map (make-sparse-keymap)))
           (define-key map "s" #',start-func-name)
           ;; More key definitions
           map)
         ,(format "Keymap for %s REPL commands." repl-name))

As you can see, the keybindings are directly defined within the macro. This means that if you want to change a keybinding or add a new one, you'd need to modify the macro itself or redefine the REPL. This approach works, but it isn't very flexible for users who want to personalize their REPL experience. This is what we will fix in this article.

The Problem with Hard-Coded Keymaps

The main issue is that hard-coded keymaps limit user customization. Every time a new REPL is defined, the keybindings are set in stone. This means users can't easily:

• Change Existing Keybindings: If a user prefers a different key for a command, they're out of luck without modifying the code.
• Add New Commands: Extending the functionality requires either modifying the core code or creating custom workarounds.
• Consistency Across REPLs: Different REPLs might have similar commands, but the hard-coded approach means keybindings need to be redefined for each one. This is not user-friendly.

The Proposed Solution: Customizable Mode Maps

The goal is to give users more control over their REPL keybindings. Here's the core idea: allowing users to define a variable that holds their preferred keymap configuration. For instance:

(setq termint-repl-mode-map '(("C-c r" . termint--send-region) ("C-c R" . termint--source-region)))

Then, this configuration would be expanded into the keymap definitions, like so:

(defvar ,keycap-name
    (let ((map (make-sparse-keymap)))
        (define-key map (kbd "C-c r") (lambda (session) (interactive "P") (termint--send-region ,repl-name ,session ,other-repl-specific-keys))
        (define-key map (kbd "C-c R") (lambda (session) (interactive "P") (termint--source-region ,repl-name ,session ,other-repl-specific-keys))
         map)
     ,(format "Keymap for %s REPL commands." repl-name))

Benefits of Customizable Mode Maps

This approach offers several significant advantages:

• User-Defined Keymaps: Users can easily customize keybindings without modifying the core code.
• Consistency and Reusability: Once a user defines their preferred keybindings, they apply across all REPLs, promoting consistency.
• Extensibility: Users can define their custom commands as long as they accept the required arguments. This opens up a lot of possibilities.

Implementing Customizable Keymaps: A Step-by-Step Approach

To make this happen, we need to restructure the code. Here's the general plan:

1. Move Command Definitions Out of termint-define: Separate the keymap creation logic from the macro that defines the REPL itself. This allows us to define the keymap separately. This is the first important step.

2. Create Command Definition Helpers: Develop helper functions that take the same arguments as the original commands (repl-name, session, other-repl-specific-keys). These helpers will handle the actual execution of the commands, and will be called by the keybindings. This is critical for making sure everything is working the same way before.

3. Implement Keymap Expansion: Write a function to take user-defined keymap configuration (like the termint-repl-mode-map example) and expand it into the correct define-key calls within the generated keymap. This function will take the user configuration as input and dynamically create the keybindings.

4. Integrate with termint-define: Update the termint-define macro to use the keymap expansion function. The macro will take a keymap variable (or a default if none is provided) and use it to create the keymap. This will allow the user to easily provide their own custom keymap.

Detailed Implementation Steps

Let's break down each step in more detail:

1. Move Command Definitions

Instead of defining the keybindings directly within termint-define, we'll move them to a separate section. This could be in a separate file or a dedicated section within the current file. The keybindings definitions would likely look like this:

(defun termint--send-region-command (repl-name session other-repl-specific-keys)
  "Send the current region to the REPL." 
  (interactive "P")
  (termint--send-region repl-name session other-repl-specific-keys))

(defun termint--source-region-command (repl-name session other-repl-specific-keys)
  "Source the current region in the REPL." 
  (interactive "P")
  (termint--source-region repl-name session other-repl-specific-keys))

2. Create Command Definition Helpers

The command definition helpers are crucial for creating the functions that the keybindings will call. These helpers would receive the same arguments as the original commands, ensuring compatibility. Each helper will wrap the original command and provide an interactive interface to it.

3. Implement Keymap Expansion

This is where the magic happens. We'll create a function that takes a list of keybinding definitions and expands them into define-key calls. It will look like this:

(defun termint-expand-keymap (keymap-name keymap-definition repl-name)
  (let ((map (make-sparse-keymap)))
    (dolist (binding keymap-definition)
      (let ((key (car binding))
            (command (cdr binding)))
        (define-key map (kbd key) (lambda (session) (interactive "P") (funcall command repl-name session (termint-repl-specific-keys repl-name)))))
    map))

This function iterates through the user-defined keymap, creates the keybindings using define-key, and adds them to the map.

4. Integrate with termint-define

Finally, we'll update the termint-define macro to use the termint-expand-keymap function. The macro will take a keymap variable (or a default if none is provided) and use it to create the keymap.

(defmacro termint-define (repl-name &key keymap-variable ...)
  `(progn
     ... ; other REPL definitions
     (defvar ,(intern (concat (symbol-name repl-name) "-mode-map"))
       (termint-expand-keymap
        ,(if keymap-variable
             keymap-variable
           'termint-default-keymap) ; or a default keymap
        ',repl-name)
       ,(format "Keymap for %s REPL commands." repl-name))
     ...))

Conclusion: Empowering Users with Customizable Mode Maps

This approach significantly improves the user experience by providing a flexible and customizable way to manage REPL keybindings. By moving away from hard-coded keymaps and embracing user-defined configurations, we empower users to tailor their REPL environment to their specific needs. Implementing these changes will lead to a more personalized and efficient workflow for everyone. So, what do you all think? Let me know your thoughts and suggestions!

I hope this article provides a good roadmap on how to customize mode maps to provide the ultimate experience! Let me know if you have any questions!