Make tab scrolling more flexible (#1384)

* Add `Object:{is_class_of,is_extended_by}` to check inverse relationships

* Make tab scrolling more flexible

This adds tab scrolling commands and connects them to mouse scroll
events.
This way scrolling behavior can be customized more easily.

For example an alternative behavior could be:
```lua
keymap.add({
  ["wheelup"] = "root:switch-to-hovered-previous-tab",
  ["wheeldown"] = "root:switch-to-hovered-next-tab"
})
```

data/core/commands/root.lua

@@ -4,6 +4,7 @@ local DocView = require "core.docview"
 local command = require "core.command"
 local common = require "core.common"
 local config = require "core.config"
+local Node = require "core.node"
 
 
 local t = {
@@ -29,20 +30,6 @@ local t = {
     core.confirm_close_docs(docs, core.root_view.close_all_docviews, core.root_view, true)
   end,
 
-  ["root:switch-to-previous-tab"] = function(node)
-    local idx = node:get_view_idx(core.active_view)
-    idx = idx - 1
-    if idx < 1 then idx = #node.views end
-    node:set_active_view(node.views[idx])
-  end,
-
-  ["root:switch-to-next-tab"] = function(node)
-    local idx = node:get_view_idx(core.active_view)
-    idx = idx + 1
-    if idx > #node.views then idx = 1 end
-    node:set_active_view(node.views[idx])
-  end,
-
   ["root:move-tab-left"] = function(node)
     local idx = node:get_view_idx(core.active_view)
     if idx > 1 then
@@ -133,3 +120,59 @@ command.add(nil, {
     return false
   end
 })
+
+command.add(function(node)
+    if not Node:is_extended_by(node) then node = nil end
+    -- No node was specified, use the active one
+    node = node or core.root_view:get_active_node()
+    if not node then return false end
+    return true, node
+  end,
+  {
+    ["root:switch-to-previous-tab"] = function(node)
+      local idx = node:get_view_idx(node.active_view)
+      idx = idx - 1
+      if idx < 1 then idx = #node.views end
+      node:set_active_view(node.views[idx])
+    end,
+
+    ["root:switch-to-next-tab"] = function(node)
+      local idx = node:get_view_idx(node.active_view)
+      idx = idx + 1
+      if idx > #node.views then idx = 1 end
+      node:set_active_view(node.views[idx])
+    end,
+
+    ["root:scroll-tabs-backward"] = function(node)
+      node:scroll_tabs(1)
+    end,
+
+    ["root:scroll-tabs-forward"] = function(node)
+      node:scroll_tabs(2)
+    end
+  }
+)
+
+command.add(function()
+    local node = core.root_view.overlapping_node
+    if not node then return false end
+    return (node.hovered_tab or node.hovered_scroll_button > 0) and true, node
+  end,
+  {
+    ["root:switch-to-hovered-previous-tab"] = function(node)
+      command.perform("root:switch-to-previous-tab", node)
+    end,
+
+    ["root:switch-to-hovered-next-tab"] = function(node)
+      command.perform("root:switch-to-next-tab", node)
+    end,
+
+    ["root:scroll-hovered-tabs-backward"] = function(node)
+      command.perform("root:scroll-tabs-backward", node)
+    end,
+
+    ["root:scroll-hovered-tabs-forward"] = function(node)
+      command.perform("root:scroll-tabs-forward", node)
+    end
+  }
+)

data/core/keymap-macos.lua

@@ -36,6 +36,8 @@ local function keymap_macos(keymap)
     ["wheel"] = "root:scroll",
     ["hwheel"] = "root:horizontal-scroll",
     ["shift+hwheel"] = "root:horizontal-scroll",
+    ["wheelup"] = "root:scroll-hovered-tabs-backward",
+    ["wheeldown"] = "root:scroll-hovered-tabs-forward",
 
     ["cmd+f"] = "find-replace:find",
     ["cmd+r"] = "find-replace:replace",

data/core/keymap.lua

@@ -304,6 +304,8 @@ keymap.add_direct {
   ["wheel"] = "root:scroll",
   ["hwheel"] = "root:horizontal-scroll",
   ["shift+wheel"] = "root:horizontal-scroll",
+  ["wheelup"] = "root:scroll-hovered-tabs-backward",
+  ["wheeldown"] = "root:scroll-hovered-tabs-forward",
 
   ["ctrl+f"] = "find-replace:find",
   ["ctrl+r"] = "find-replace:replace",

data/core/object.lua

@@ -27,6 +27,13 @@ function Object:is(T)
   return getmetatable(self) == T
 end
 
+---Check if the parameter is strictly of the object type.
+---@param T any
+---@return boolean
+function Object:is_class_of(T)
+  return getmetatable(T) == self
+end
+
 ---Check if the object inherits from the given type.
 ---@param T any
 ---@return boolean
@@ -41,6 +48,22 @@ function Object:extends(T)
   return false
 end
 
+---Check if the parameter inherits from the object.
+---@param T any
+---@return boolean
+function Object:is_extended_by(T)
+  local mt = getmetatable(T)
+  while mt do
+    if mt == self then
+      return true
+    end
+    local _mt = getmetatable(T)
+    if mt == _mt then break end
+    mt = _mt
+  end
+  return false
+end
+
 ---Metamethod to get a string representation of an object.
 ---@return string
 function Object:__tostring()

data/core/rootview.lua

@@ -323,19 +323,10 @@ function RootView:on_file_dropped(filename, x, y)
 end
 
 
-function RootView:on_mouse_wheel(dy, dx)
+function RootView:on_mouse_wheel(...)
   local x, y = self.mouse.x, self.mouse.y
   local node = self.root_node:get_child_overlapping_point(x, y)
-
-  local idx = node:get_tab_overlapping_point(x, y)
-  if idx then
-    local delta = dx == 0.0 and dy or dx
-    local button = delta < 0 and 2 or 1
-    node:scroll_tabs(button)
-    return true
-  end
-
-  return node.active_view:on_mouse_wheel(dy, dx)
+  return node.active_view:on_mouse_wheel(...)
 end