Key and mouse Interaction

Notation

Key combinations are written:

(modifier key 1) - (modifier key 2) - key

... to show which modifier keys are pressed with which key. There can be zero or more modifier keys, depending on the keyboard:

Shorthand	Key
A	alt/option
C	control
M ("meta")	Command/Win/Tux
S	shift

So, for example, M-enter means hold down the Command/Win/Tux key and press enter, whereas C-M-left means hold down the control and Command/Win/Tux keys while pressing the left arrow key.

If we eventually expand to allow emacs-style key sequences, the notation above would expand to allow a series of one or more key combinations, separated by spaces. For example, to encode pressing control + c two times we would write C-c C-c, whereas C-c A-a would represent control + c followed by Alt + a.

An additional special case for mouse gestures:

One would write mouse-1 to indicate clicking with the first (on Macs, only) mouse button, which can also be combined with keys presses as above.

Conventions

Selection/execution

M- selects the current expression and highlights it (not just the surrounding parens). While M- is held,

• Tapping M-1 further expands the selection to the next larger expression, up to the top-level expression.
• Tapping M-2 retracts the selection to the next lesser expression, down to the one initially highlighted.

Pressing M-S- selects the current top-level expression.

Releasing M- at any point clears the selection.

Character-by-character mouse-based selection is disabled.

(This kind of behavior is called a "pseudo-mode" in the UI literature, because it is a mode but it doesn't persist after the key is released, so there's no way a user can be unaware that it's on or confused about how to turn it off.)

It would be optimal if one could click-drag the current selection in a structure-preserving way.

In addition to managing selection, the following keys should be bound to M-:

Key	Action
M-enter	execute currently selected expression
M-S-enter	execute current top-level expression
M-x	cut selection
M-c	copy selection
M-v	paste clipboard at cursor, ignoring current selection
M-S-v	paste clipboard, replacing current selection

Movement

Let me know if you need further clarification on any of these movement descriptions.

Key	Action
A-left/right	left/right one atom/expression
A-up	"backward-up-list", move backward up/out one level of parens, "out of"
A-down	"down-list", move forward/down one level of parens, "into"
A-C-up	move up one "definition" (top-level expression)
A-C-down	move down one "definition" (top-level expression)

Code manipulation

Key	Action
M-(	barf
M-)	slurp
M-;	uneval current form
M-A-;	uneval (or comment) top-level form

... more to come ...