Fix stack splitting (without breaking the world)

Close #63, for real this time.

Bagshui.lua

@@ -717,6 +717,7 @@ local Bagshui = {
 		CloseAllWindows = "CloseAllWindows",
 		DeleteCursorItem = "ClearCursor",
 		MoneyFrame_UpdateMoney = "MoneyFrame_UpdateMoney",
+		OpenStackSplitFrame = "OpenStackSplitFrame",
 		PickupBagFromSlot = "PickupInventoryItem",
 		PickupInventoryItem = "PickupInventoryItem",
 		PutItemInBag = "PickupInventoryItem",

Components/Bagshui.BlizzFixes.lua

@@ -26,4 +26,54 @@ function Bagshui:MoneyFrame_UpdateMoney(wowApiFunctionName)
 end
 
 
+
+--- Hack to make stack splitting work consistently.
+--- Without this, mouseover events can reset the ID of a group's parent frame,
+--- changing the bag number of the pending split. As a result, the split ends
+--- up targeting the wrong item. We work around it by doing a hard capture of
+--- the bag/slot numbers in `Bagshui:PickupItem()` into the `pending` properties
+--- just before calling `ContainerFrameItemButton_OnClick()`. Then once the
+--- Blizzard code has done its thing and calls `OpenStackSplitFrame()`, we intercept
+--- the call and reassign the frame's `SplitStack` property, which is the callback
+--- used when the split is invoked.
+---@param wowApiFunctionName string Hooked WoW API function that triggered this call. 
+---@param maxStack any `OpenStackSplitFrame()` parameter.
+---@param parent any `OpenStackSplitFrame()` parameter.
+---@param anchor any `OpenStackSplitFrame()` parameter.
+---@param anchorTo any `OpenStackSplitFrame()` parameter.
+function Bagshui:OpenStackSplitFrame(wowApiFunctionName, maxStack, parent, anchor, anchorTo)
+
+	-- Reset just teo be safe.
+	self.splitStackBagNum = nil
+	self.splitStackSlotNum = nil
+
+	-- Create our override function only once.
+	if not self.SplitStackOverride then
+		function self.SplitStackOverride(button, amount)
+			_G.SplitContainerItem(self.splitStackBagNum, self.splitStackSlotNum, amount)
+		end
+	end
+
+	-- Detect values set by `Bagshui:PickupItem()` and prepare them for
+	-- `self.SplitStackOverride() to consume. This will only execute
+	-- when Bagshui code has set things up and won't interfere with normal
+	-- stack splitting functionality.
+	if
+		type(parent) == "table"
+		and self.pendingSplitStackBagNum
+		and self.pendingSplitStackSlotNum
+	then
+		self.splitStackBagNum = self.pendingSplitStackBagNum
+		self.splitStackSlotNum  = self.pendingSplitStackSlotNum
+		self.pendingSplitStackBagNum = nil
+		self.pendingSplitStackSlotNum = nil
+		-- Replace the callback set by 
+		parent.SplitStack = self.SplitStackOverride
+	end
+
+	-- Pass along to the normal `OpenStackSplitFrame()` to handle everything.
+	self.hooks:OriginalHook(wowApiFunctionName, maxStack, parent, anchor, anchorTo)
+end
+
+
 end)

Components/Bagshui.Cursor.lua

@@ -14,6 +14,11 @@ Bagshui:LoadComponent(function()
 ---@param callPickupContainerItem boolean?
 function Bagshui:PickupItem(item, inventoryClass, itemSlotButton, callPickupContainerItem)
 
+	self.pendingSplitStackBagNum = nil
+	self.pendingSplitStackSlotNum = nil
+	self.splitStackBagNum = nil
+	self.splitStackSlotNum = nil
+
 	-- Track where the pickup call came from so we know whether it's being put down
 	-- in the same inventory or moved to a different one.
 	local owningFrame = inventoryClass and inventoryClass.uiFrame or _G.this
@@ -157,6 +162,10 @@ function Bagshui:PickupItem(item, inventoryClass, itemSlotButton, callPickupCont
 		else
 			-- Don't need to (and can't) pass bagNum/slotNum to ContainerFrameItemButton_OnClick(),
 			-- since it pulls them from _G.this:GetId()/_G.this:GetParent():GetId().
+			if _G.IsShiftKeyDown() then
+				self.pendingSplitStackBagNum = item.bagNum
+				self.pendingSplitStackSlotNum = item.slotNum
+			end
 			_G.ContainerFrameItemButton_OnClick("LeftButton")
 		end
 	end