diff --git a/tabview.lua b/tabview.lua
index 4975367..353c6bd 100644
--- a/tabview.lua
+++ b/tabview.lua
@@ -1,3 +1,5 @@
+local winhlp = require "winhlp"
+
 local parent = term.current()
 local tabCount = 0
 local allTabs = {}
@@ -80,9 +82,10 @@ local function updateSize()
 end
 
 local function onTouch(touchX, touchY)
-    if currentTab ~= nil then
-        local winx, winy = currentTab.window.getPosition()
-        return currentTab.onTouch(currentTab, touchX - winx + 1, touchY - winy + 1)
+    if currentTab ~= nil and
+            winhlp.contains(currentTab.window, touchX, touchY) and
+            currentTab.onTouch(currentTab, winhlp.translate(currentTab.window, touchX, touchY)) then
+        return true
     end
     return false
 end
diff --git a/test.lua b/test.lua
index af27a31..bcd6efd 100644
--- a/test.lua
+++ b/test.lua
@@ -1,5 +1,7 @@
 local config = require "config"
 local tabview = require "tabview"
+local winhlp = require "winhlp"
+
 local header_lines = 2
 
 -- display working state
@@ -54,11 +56,10 @@ local function on_touch(touch_x, touch_y)
             tabview.switchTab()
             return true
         end
-    elseif tabview_window ~= nil then
-        local winx, winy = tabview_window.getPosition()
-        if tabview.onTouch(touch_x-winx+1, touch_y-winy+1) then
-            return true
-        end
+    elseif tabview_window ~= nil and
+            winhlp.contains(tabview_window, touch_x, touch_y) and
+            tabview.onTouch(winhlp.translate(tabview_window, touch_x, touch_y)) then
+        return true
     end
     return false
 end
diff --git a/update.lua b/update.lua
index 078500e..cb188c6 100644
--- a/update.lua
+++ b/update.lua
@@ -29,6 +29,7 @@ end
 
 if update_update() then
     download_file("permset.lua")
+    download_file("winhlp.lua")
     download_file("tabview.lua")
     download_file("requests.lua")
     download_file("orders.lua")
diff --git a/winhlp.lua b/winhlp.lua
new file mode 100644
index 0000000..d57762e
--- /dev/null
+++ b/winhlp.lua
@@ -0,0 +1,15 @@
+local function translate(window, x, y)
+    local winX, winY = window.getPosition()
+    return x-winX+1, y-winY+1
+end
+
+local function contains(window, x, y)
+    local winX, winY = window.getPosition()
+    local width, height = window.getSize()
+    return x >= winX and y >= winY and x-winX < width and y-winY < height
+end
+
+return {
+    translate=translate,
+    contains=contains,
+}