Vimium C has a powerful command named runKey. Not only it can run different keys on different page conditions, but also it supports command "trees" and runs different commands according to whether a previous command succeeds or not.

When an key sequence item in keys in runKey's options has (, ), ?, :, + or %, it will be parsed as a command tree. The basic syntax is:

• there're 3 types of node in a tree: key node, list node and branching node
• a key node means a single mapped command.
  • it can be count prefix + mapped key sequence, or one of available command names
  • when it means a mapped key, its key name can only include English letters and numbers.
    • for example, 3<c-f1> will work as expected, but <c-=> is invalid and causes an error tip when running
      • since v1.96, this limit has been removed
    • when it means <v-...>, then <v- and > can be omitted
  • if it include $c or %c, then its count will be multipled by the count prefix of runKey, like $c3g0
  • since v1.93, it may have a suffix of #key=url-encoded-val&key2=val2 as inline options
• a list node may include any number of child nodes
  • + is used to join its children, and it can be omitted if there's no ambiguity
  • for example, 3f1c means to run <v-f1c> by 3 times; while 3f%cf means 3f and %cf
• a branching node means if ... then ... else ...
  • it syntax is <condition> ["?" <then-branch>] [":" <else-branch>]
  • either ? or : can be omitted, so both (a?) and (b:2c) will work
• to specify priorities, use ( and ) to join some nodes into a list (node)

• a key node runs a single command and returns "success" or "failure"
• a list node runs its children one by one
  • when a child node fails:
    • if the child is a key node, the list itself fails immediately, ignoring following nodes
    • otherwise, if the child is not the last one, then the list continues to run a next child
  • it returns the result of its last child node, or "success" if it's empty
• a branching node runs its condition node firstly
  • and then choose one between then and else branches according to whether the condition succeeds or not
  • it returns the result of its selected branch

Since v1.93, the syntax of inline options is:

• such string of inline options will end before /[()?:+]/, unless it matches /(^|&)#/
• option values are URL-decoded by default, except those after a second # character
• e.g.: #a=1&b=2%2B3&#c=a?b:c&#4=+5%25 means { "a": 1, "b": "2+3", "c": "a?b:c&#4=+5%25" }

To assign shared options, there're some ways:

• add options={"key1":"val1","key2":"val2"} to a runKey mapping
• add "o." prefix to option items, such as o.key1="val1" o.key2="val2"
• since v1.93, add a valid inline option string as the prefix of a key sequence.
  • for example, #text=hello%20world+showHUD will show a tip of "hello world"

Since v1.93.0, map aaa runKey keys="bbb,ccc" can be simplified into run aaa bbb,ccc.

To focus an input in a current frame, and when it fails, go to the top frame / scroll to top and then find an input again, we may write:

map W scrollToTop
map i runKey keys="focusInput?:(mainFrame:W+150wait)%cfocusInput" \
  o.keep o.select="all-line" o.reachable \
  o.prefer="#js-issues-search,#searchEngines"

In the mapping above, 150wait means to wait for 150 milliseconds, which allows page scripts to update UI state.

Here're some other valid examples in v1.93:

map <v-de> dispatchEvent

# simluate `Escape` on page scripts by press `Ctrl+]`
run <c-]:i> #key=Escape%2C27+de-de

# simulate `ArrowDown` and `ArrowUp` by `Ctrl+J` and `Ctrl+K`
env s element="select"
env t element="textarea"
run <c-j:i> #key=ArrowDown%2C40+de+-de,#key=ArrowUp%2C38+de+-de \
  expect="t:editText#run=auto%2ccount%2cline;s:scrollSelect"
run <c-k:i> -<c-j:i>

There's a simpler way to run another key or command after one command: use $then and $else options since v1.92.

Most commands support 3 options of $then: string, $else: string and $retry: number.

• If such a command succeeds, then it triggers the mapped key or command name in $then; otherwise it triggers $else.
• By default, such a key mapping chain can include up to 7 commands (1 head and 6 following)
• If you want to allow a longer chain, use $retry to specify a longer number
  • if $retry is in 7 ~ 20, then it's treated as 6; if it's negative, then use its absolute number

Since v1.93, $then and $else can also include a suffix of inline options, like "showHUD#text=hello"

For example,

map i scrollToTop $then="focusInput" $else="<v-m>"
map <v-m> mainFrame $then="focusInput"

means:

• find an scrollable element and scroll to top
• if something is scrolled, then run focusInput
• otherwise, focus the main (top) frame and then run focusInput

There're multiple ways to do so:

# every line should work independently, with pre-defined mapping from `o` to `Vomnibar.activate`
map t createTab $then="Vomnibar.activate"
map t createTab $then="o"
map t runKey keys="createTab+Vomnibar.activate" # since v1.93.0
shortcut createTab $then="o"