Vim - Menus
Our beloved Vim offers some possibilities to create and use menus to execute various kinds of commands. I know the following solutions ...
the menu command family
the confirm function
the insert user completion (completefunc)
I will not bother you with a detailed tutorial. For more information I always recommend the best place to learn about Vim - the integrated help.
:menu
Let's start with the most obvious one, the menu commands. The menu commands can be used to create menus that can be called via GUI (mouse and keyboard) and via ex-mode. A good use-case is to create menus entries for commands that are not needed often, for which a mapping would be a waste of valueable key combinations and which can probably not be remembered anyway as they are used less frequently.
I'll keep it short here and as there are already tutorials out there. And of course the Vim help is the best place to read about it. :h creating-menus
Vim offers several menu commands. Depending on the current Vim mode your menu changes accordingly. Means if you are in normal mode you will see your normal mode menus, in visual mode you can see only the menus that make sense in visual mode, and so on.
Let's say we want to have a command in the menu that removes duplicate lines and keeps only one. We want that in normal mode the command runs for the whole file and that in visual mode, by selecting a range of lines, the command shall run only for the selected lines. We could put the following lines in our vimrc.
nmenu Utils.DelMultDuplLines :%s/^\(.*\)\(\n\1\)\+$/\1/<cr> vmenu Utils.DelMultDuplLines :s/^\(.*\)\(\n\1\)\+$/\1/<cr>
The here used commands are quite simple. After the menu command you see only 2 parameters. First one is the menu path. I say path because by using the period you can nest your menus. Here it is only the command directly under the Utils menu entry. The second parameter is the command to be executed just like you would do from normal mode.
There are 2 special characters that can be used in the first parameter. & and <tab>. & can be used to add a shortcut key to the menu and <tab> to add a right aligned text in the menu. Try it out!
Remember that you can access the menu also via ex-mode.
:menu Utils.DelMultDuplLines
But please don't type all the text and use the tabulator key to do the autocompletion for you. ;-)
confirm()
The confirm function. Luckily I already wrote about this possibility. So instead of copy-pasting the text I just link to it.
vim-confirm-function
set completefunc
Let's get dirty now. I guess the insert completion pop-up menu is well known by everyone. But did you know that you can misuse it for more than just auto-completion? I did not. I will show you what I mean.
Usually the auto-completion is triggered by pressing Ctrl-n, Ctrl-p or Ctrl-x Ctrl-something in insert mode. One of these key mappings is Ctrl-x Ctrl-u which triggers an user specific function. Means we can write a function that does what we want and assign it to the completefunc option. Let's check what we need to consider when writing such a function.
The completefunc you have to write has 2 parameters. And the function gets called twice by Vim. When calling the function the first time, Vim passes the parameters 1 and empty. In this case it is your task to usually find the beginning of the word you want to complete and return the start column. One the second call Vim passes 0 and the word the shall be completed.
function! MyCompleteFunc(findstart, base) if a:findstart " write code to find beginning of the word else " write code to create a list of possible completions end endfunction set completefunc=MyCompleteFunc
For more information and an example check :h complete-functions.
Now let's re-create the LaTeX example using the completefunc. Here is a possible solution that supports nested menus, so for 1 level menus the code can be reduced a lot.
https://gist.github.com/marcotrosi/e2918579bce82613c504e7d1cae2e3c0
Okay let's go through it step by step.
In the beginning you see 2 variables. InitMenu and NextMenu. InitMenu defines the menu entry point and NextMenu remembers the name of the next menu. I just wanted to have nested menus and that's what is this for.
Next is the completefunc we have to write. I called mine LatexFont. As shown before it consists of an if-else-block, where the if-true-block gets the word before the cursor and the else-block will return a list that contains some information. In the simplest form this would only be a list of strings that would be the popup-menu-entries. See the CompleteMonths example from the Vim help. But I added some more information. Let's see what it is.
The basic idea is to have one initial menu and many sub-menus, they are all stored in a single dictionary name menus and are somehow connected and I want to decide which one to return. As I initialized my InitMenu variable with "Font" this must be my entry point. After the declaration of the local menus dictionary you can see an if clause that checks if s:NextMenu is empty. So if s:NextMenu is empty it will be initialized with my init value I defined in the very beginning. And at the end I return one of the menus so that Vim can display it as a popup menu.
Now let's have a closer look at the big dictionary. You can see 4 lists named Font, FontFamily, FontStyle and FontSize. Each list contains the popup-menu entries. I use the key user_data to decide whether I want to attach a sub-menu or if the given menu is the last in the chain. To attach a sub-menu I just provide the name of the menu and when the menu ends there I use the string "_END_". So the restriction is that you can't name a menu "_END_" as it is reserved now. By the way, I didn't try it, but I guess that user_data could be of any datatype and is probably not limited to strings.
Let's see what the other keys contain. There are the keys word, abbr and dup. word contains the string that replaces the word before the cursor, which is also stored in a:base. abbr contains the string that is used for display in the popup-menu. From the insert auto-completion we are used to the word displayed is also the word to be inserted. Luckily Vim can distinguish that. This gives me the possibility to display a menu (like FontFamily, FontStyle, FontSize) but at the same time keeping the original unchanged word before the cursor. This is basically the whole trick. Plus the additional user_data key that allows me to store any kind of information for re-use and decisions. With the dup key I tell Vim to display also duplicate entries. For more information on supported keys check :h complete-items.
Now let's get to the rest of the nested menu implementation. Imagine you have selected an entry of the initial menu. You confirm by pressing SPACE and now I want to open the sub-menu automatically. To achieve that I use a Vim event named CompleteDone which triggers my LatexFontContinue function, and the CompleteDone event is triggered when closing the popup menu either by selecting a menu entry or by aborting. Within that function I decide whether to trigger the user completion again or to quit. Beside the CompleteDone event Vim also has a variable named v:completed_item that contains a dictionary with the information about the selected menu item. The first thing I do is saving the user_data value in a function local variable.
let l:NextMenu = get(v:completed_item, 'user_data', '')
The last parameter is the default value for the get function and is an empty string just in case the user aborted the popup-menu in which case no user_data would be available.
One more info - this line ...
inoremap <expr><esc> pumvisible() ? "\<c-e>" : "\<esc>"
... allows the user to abort the menu by pressing the ESC key intead of Ctrl-e.
And last but not least the if clause that either sets the script variable s:NextMenu to empty string when the local l:NextMenu is empty or "_END_" and quits the function without doing anything else, or the else branch that stores the next menu string in s:NextMenu and re-triggers the user completion.
The rest of the file is self-explanatory.
I'm sure we can change the code a bit to execute also other command types, e.g. by storing a command as a string and executing it.
Let me know what you did with it.