Improve return values of some actions + some improvements

[dmaluka]

Currently most actions always return true, regardless of whether they succeeded to do their job or not. This means that for most actions the user cannot really take advantage of action chaining with | or &.

So, to facilitate efficient usage of action chaining, improve return values of some actions, namely:

• Undo
• Redo
• Deselect
• UnhighlightSearch
• ClearInfo
• ClearStatus
• NextTab
• PreviousTab
• NextSplit
• PreviousSplit
• RemoveMultiCursor
• RemoveAllMultiCursors

The rules are straightforward: Undo returns false if there is nothing to undo, Deselect return false if there is nothing selected, NextTab returns false if there is just one tab, and so on.

Additionally:

• Some fixes and improvements in the behavior of RemoveMultiCursor, RemoveAllMultiCursors and SkipMultiCursor actions.
• Removed ClearStatus action as redundant (since ClearInfo does the same things). I've changed my mind and restored it (compatibility concerns) but documented that it is an alias for ClearInfo.
• Refactored action execution code, to make it both simpler and more correct.

[dmaluka]

Besides the actions improved in this PR, there are also lots of cursor movement and selection actions (CursorUp, SelectWordLeft and so on) which also always return false and could be similarly improved. For example, CursorUp could return false if the cursor is already at the first line of the buffer.

But that is more complicated and debatable. For instance, CursorUp actually not just moves the cursor up one line, it also does the following:

• If the cursor is already at the first line, move the cursor to the beginning of the first line.
• If the cursor is already at the beginning of the first line, reset its LastVisualX value to 0 (which affects where will the next CursorDown move).

All this makes it not obvious what should be its return value in what cases.

So leave those actions as they are for now, to avoid complicating things prematurely.

[masmu]

Amazing refactoring! It is way clearer now what the code is suppose to do. And you squashed a bug along the way. In the original implementation the correct cursors reference gets lost after switching to a different BufPane.

[masmu]

The cursors assignment would need to be moved 2 lines down into the actions loop. Otherwise you would still use the cursors of the original pane even though you switched to a new one in a next iteration. Line 170 updates the reference to h. 👍

[masmu]

I verified all the following methods to work correctly.
- Undo
- Redo
- Deselect
- UnhighlightSearch
- ClearInfo
- ClearStatus
- NextTab
- PreviousTab
- NextSplit
- PreviousSplit
- RemoveMultiCursor
- RemoveAllMultiCursors
- SkipMultiCursor

I noticed that there is no counterpart for SkipMultiCursor. And since this action just changes selections (not text) this cannot be undone via Undo.

Not sure if this is the right time, but I would suggest a change for NextTab, PreviousTab, NextSplit and PreviousSplit.
Currently those methods are topologically designed as rings. So once you reached the last (lets say a) tab, the next action gets you back to the first tab and vice versa.

My suggestion is change this topologically to a line for all mentioned methods. So e.g. in case you want to switch to the next tab, but you are already on it, return false.

After adding the following new actions:

// FirstTab switches to the first tab in the tab list
func (h *BufPane) FirstTab() bool {
    if Tabs.Active() == 0 {
        return false
    }
    Tabs.SetActive(0)
    return true
}

// LastTab switches to the last tab in the tab list
func (h *BufPane) LastTab() bool {
    lastTabIndex := len(Tabs.List) - 1
    if Tabs.Active() == lastTabIndex {
        return false
    }
    Tabs.SetActive(lastTabIndex)
    return true
}

// FirstSplit changes the view to the first split
func (h *BufPane) FirstSplit() bool {
    if h.tab.active == 0 {
        return false
    }
    h.tab.SetActive(0)
    return true
}

// LastSplit changes the view to the last split
func (h *BufPane) LastSplit() bool {
    lastTabIndex := len(h.tab.Panes) - 1
    if h.tab.active == lastTabIndex {
        return false
    }
    h.tab.SetActive(lastTabIndex)
    return true
}

you can restore the old behavior by the following settings:

    // this would be my recommendation for the defaults
    "Alt-,": "PreviousTab|LastTab",
    "Alt-.": "NextTab|FirstTab",

    // just for the sake of completeness
    "CtrlPageUp":     "PreviousTab|LastTab",
    "CtrlPageDown":   "NextTab|FirstTab",
    "Ctrl-w":         "NextSplit|FirstSplit",

But why breaking those actions into smaller actions in the first place?
It adds a lot of flexibility for the user. You can use combinations of splits and tabs, like:

    "Alt-,": "PreviousSplit|PreviousTab|LastTab",
    "Alt-.": "NextSplit|NextTab|FirstTab",

Is this a breaking change? Potentially yes, but IMHO a small one. It only affects people having bindings for NextTab, PreviousTab, NextSplit and PreviousSplit in their own bindings.json.

[dmaluka]

I noticed that there is no counterpart for SkipMultiCursor. And since this action just changes selections (not text) this cannot be undone via Undo.

Yeah, it might be good to add SkipMultiCursorBack or something like that.

Not sure if this is the right time, but I would suggest a change for NextTab, PreviousTab, NextSplit and PreviousSplit.

[...]

It adds a lot of flexibility for the user. You can use combinations of splits and tabs, like:

[...]

Is this a breaking change? Potentially yes, but IMHO a small one. It only affects people having bindings for NextTab, PreviousTab, NextSplit and PreviousSplit in their own bindings.json.

Yeah, sounds good.

[JoeKar]

Looks like a small rebase is needed due to conflicts.