Merge pull request #2146 from atom/cancel-id

Add "cancelId" option for showMessageBox

atom/browser/api/lib/dialog.coffee

@@ -93,8 +93,23 @@ module.exports =
     options.detail ?= ''
     options.icon ?= null
 
+    # Choose a default button to get selected when dialog is cancelled.
+    unless options.cancelId?
+      options.cancelId = 0
+      for text, i in options.buttons
+        if text.toLowerCase() in ['cancel', 'no']
+          options.cancelId = i
+          break
+
+    # On OS X the "Cancel" is always get selected when dialog is cancelled.
+    if process.platform is 'darwin'
+      for text, i in options.buttons when text is 'Cancel'
+        options.cancelId = i
+        break
+
     binding.showMessageBox messageBoxType,
                            options.buttons,
+                           options.cancelId,
                            [options.title, options.message, options.detail],
                            options.icon,
                            window,