react to double clicks on list items

docs/changelog.txt

@@ -78,9 +78,10 @@ changelog.txt uses a syntax similar to RST, with a few special sequences:
 - `helpdb`: new function: ``helpdb.refresh()`` to force a refresh of the database. Call if you are a developer adding new scripts, loading new plugins, or changing help text during play
 - `helpdb`: changed from auto-refreshing every 60 seconds to only refreshing on explicit call to ``helpdb.refresh()``. docs very rarely change during a play session, and the automatic database refreshes were slowing down the startup of `gui/launcher` and anything else that displays help text.
 - ``widgets.Label``: ``label.scroll()`` now understands ``home`` and ``end`` keywords for scrolling to the top or bottom
+- ``widgets.List``: new callbacks for double click and shift double click
 - ``dfhack.units.getCitizens()``: gets a list of citizens
 - ``gui.ZScreen``: new attribute: ``defocusable`` for controlling whether a window loses keyboard focus when the map is clicked
-- ``Label``: token ``tile`` properties can now be either pens or numeric texture ids
+- ``widgets.Label``: token ``tile`` properties can now be either pens or numeric texture ids
 - `tiletypes`: now has a Lua API! ``tiletypes_setTile``
 
 ## Removed

docs/dev/Lua API.rst

@@ -4875,6 +4875,10 @@ It has the following attributes:
             key/click and calls the callback as ``on_submit(index,choice)``.
 :on_submit2: Shift-click callback; if specified, the list reacts to the click and
              calls the callback as ``on_submit2(index,choice)``.
+:on_double_click: Mouse double click callback; if specified, the list reacts to the
+            click and calls the callback as ``on_double_click(index,choice)``.
+:on_double_click2: Shift-double click callback; if specified, the list reacts to the click and
+             calls the callback as ``on_double_click2(index,choice)``.
 :row_height: Height of every row in text lines.
 :icon_width: If not *nil*, the specified number of character columns
              are reserved to the left of the list item for the icons.

library/lua/gui/widgets.lua

@@ -1537,6 +1537,8 @@ List.ATTRS{
     on_select = DEFAULT_NIL,
     on_submit = DEFAULT_NIL,
     on_submit2 = DEFAULT_NIL,
+    on_double_click = DEFAULT_NIL,
+    on_double_click2 = DEFAULT_NIL,
     row_height = 1,
     scroll_keys = STANDARDSCROLL,
     icon_width = DEFAULT_NIL,
@@ -1557,6 +1559,8 @@ function List:init(info)
         self.choices = {}
         self.selected = 1
     end
+
+    self.last_select_click_ms = 0 -- used to track double-clicking on an item
 end
 
 function List:setChoices(choices, selected)
@@ -1765,6 +1769,16 @@ function List:submit2()
     end
 end
 
+function List:double_click()
+    if #self.choices == 0 then return end
+    local cb = dfhack.internal.getModifiers().shift and
+            self.on_double_click2 or self.on_double_click
+    if cb then
+        cb(self:getSelected())
+        return true
+    end
+end
+
 function List:onInput(keys)
     if self:inputToSubviews(keys) then
         return true
@@ -1776,6 +1790,18 @@ function List:onInput(keys)
     elseif keys._MOUSE_L_DOWN then
         local idx = self:getIdxUnderMouse()
         if idx then
+            local now_ms = dfhack.getTickCount()
+            if idx ~= self:getSelected() then
+                self.last_select_click_ms = now_ms
+            else
+                if now_ms - self.last_select_click_ms <= DOUBLE_CLICK_MS then
+                    self.last_select_click_ms = 0
+                    if self:double_click() then return true end
+                else
+                    self.last_select_click_ms = now_ms
+                end
+            end
+
             self:setSelected(idx)
             if dfhack.internal.getModifiers().shift then
                 self:submit2()