Selection expands by word or line on double or triple click followed by drag.

data/core/docview.lua

@@ -224,6 +224,7 @@ function DocView:scroll_to_make_visible(line, col)
   end
 end
 
+
 function DocView:on_mouse_moved(x, y, ...)
   DocView.super.on_mouse_moved(self, x, y, ...)
 
@@ -235,7 +236,7 @@ function DocView:on_mouse_moved(x, y, ...)
 
   if self.mouse_selecting then
     local l1, c1 = self:resolve_screen_position(x, y)
-    local l2, c2 = table.unpack(self.mouse_selecting)
+    local l2, c2, snap_type = table.unpack(self.mouse_selecting)
     if keymap.modkeys["ctrl"] then
       if l1 > l2 then l1, l2 = l2, l1 end
       self.doc.selections = { }
@@ -243,12 +244,33 @@ function DocView:on_mouse_moved(x, y, ...)
         self.doc:set_selections(i - l1 + 1, i, math.min(c1, #self.doc.lines[i]), i, math.min(c2, #self.doc.lines[i]))
       end
     else
+      if snap_type then
+        l1, c1, l2, c2 = self:mouse_selection(self.doc, snap_type, l1, c1, l2, c2)
+      end
       self.doc:set_selection(l1, c1, l2, c2)
     end
   end
 end
 
 
+function DocView:mouse_selection(doc, snap_type, line1, col1, line2, col2)
+  local swap = line2 < line1 or line2 == line1 and col2 <= col1
+  if swap then
+    line1, col1, line2, col2 = line2, col2, line1, col1
+  end
+  if snap_type == "word" then
+    line1, col1 = translate.start_of_word(doc, line1, col1)
+    line2, col2 = translate.end_of_word(doc, line2, col2)
+  elseif snap_type == "lines" then
+    col1, col2 = 1, math.huge
+  end
+  if swap then
+    return line2, col2, line1, col1
+  end
+  return line1, col1, line2, col2
+end
+
+
 function DocView:on_mouse_released(button)
   DocView.super.on_mouse_released(self, button)
   self.mouse_selecting = nil