Debug Scripts

The debug process with CS is quite time consuming and the provided tools are not really satisfying.

So here are some hints for debugging scripts in case you have unexpected results.

Script Processing

First of all, you should take a look at the Script Processing article to get a basic understanding of how the different script types work.

Remember that only quest scripts are considered to run constantly in a defined schedule.

Object scripts may run every frame, but they also may not execute for quite a while if player is not near. There are even cases where AI packages prevent script running. This is true for Follow-Packages if they check on conditions related to script variables in the same object and these conditions are satisfied.

To find out if your script is executed, simply put a code like the following into your script and control it afterwards ingame:

; use long, if you want to watch the frames 
; for a longer time period
short FramesRun

Begin GameMode
Set FramesRun To FramesRun + 1

... your code

End

Control variable content

There are different ways to control the current content of your variables.

The most convenient and reliable way is using the Console Functions, especially prid and tst or sv. You always will get the real current content.

So, first activate or focus the object you want to examine (talk to your NPC, open the book ...) then open the console. You now will see in the upper part of the screen the formID of your object. If not, left-click the object with your mouse.

If the object you want to examine cannot be left-clicked (because it's in a different cell, or disabled), you can select with the prid command if you know its form ID. The prid command will change to any object given, so if you want to examine your NPC script and your NPC has shown a formID of 0b002089 you simply enter:

prid 0b002089

If you have not too much variables in the script, than you can use the ShowVars/sv command to show the content of all variables. Simply type

sv

If you use many variables, you may only see the last ones. In this case, press Page-Up to view the rest of the list.

To get a special variable content, use the Show/tst command. So if you want to control how much times the script has executed until now, if you have set a FrameRuns variable, you just type:

show FrameRuns

If that variable is not getting bigger and bigger everytime you leave the console and enter it again, you may just have the case that some AI package is preventing your script from running.

To see all of the variables within a particular quest, use ShowQuestVariables (or sqv for short):

sqv QuestID

Take care if you use Message or MessageBox functions inside of your script!

Message can be useful for showing which segment of code is executing, or the value of a variable at a particular moment, but because messages always stay on the screen for one second, consecutive messages will be delayed. This means the value of a variable displayed in a message may have changed before the message gets displayed. OBSE's PrintToConsole function can make debug messages easier to use.

MessageBox behaves in another way. If you want to have different message boxes that pop up to show some variable content, you may end up with having only the last defined message box shown and all other ignored. Don't ask me why, but it seems to work this way

At least MessageBox gives you the current values in the script.

Find bugs not reported by CS or Oblivion

CS usually gives you some hints when you save a script. But this is not reliable at all. It only reports syntax errors - for instance, referring to objects which don't exist or are not persistent, or mismatched if-endif blocks.

You still can make syntax errors that are not discovered or use functions that work as a return statement.

Unfortunately, Oblivion does not provide any error messages within the game itself. If it encounters an error within a script, it will immediately terminate that script without notifying you. That's why it's useful to have a variable in your script that increments every frame - by checking that variable in the console, you can determine if your script has stalled.

Here's an example: It took me a whole day to find out why my script was not executed. And the reason was that I mixed the commands GetCurrentAIPackage and GetIsCurrentPackage.

So the statement

If ( GetCurrentAIPackage "00MyPackage1" )
   Set PackageLoaded To 1
ElseIf ( GetCurrentAIPackage "00MyPackage2" )
   Set PackageLoaded To 2
...

caused the interpreter to leave the script, whenever it reached this code block. If you wonder about the "00MyPackage", the apostrophes are recommended, whenever your EditorIDs start with a number. I used two zeros to have my objects always listed at the top

And it was right, because what I meant to do was the following

If ( GetIsCurrentPackage "00MyPackage1" )
   Set PackageLoaded To 1
ElseIf ( GetIsCurrentPackage "00MyPackage2" )
   Set PackageLoaded To 2
...

But the script saved without any problems and ingame I didn't get a message that something went wrong. This is because the compiler frequently ignores extra parameters. For instance, these lines, while incorrect, compile fine:

disable objectID 1
PickIdle My name is Bob

Ingame starting debug messages at defined points

If you want to evoke messages or messageboxes at defined point, it helps, if you define a debugOn variable in the script and set it via general topic or quest topic.

All code inside would look like:

short debugOn
... your code
If debugOn
   Message "whatever you want to say %.0f" MyVar
EndIf
... your code
If debugOn
   Message "whatever you want to say %.0f" MyVar2
EndIf
... and so on
; and if you want to have the messages for each frame
; slowly passing by, you add a ShowEnchantment at the 
; beginning or the end of the GameMode block, like 
If debugOn
   ShowEnchantment
EndIf

You may also want to start the debug session on a defined point in your code. Nothing easier than that:

short debugOn
; save setting, for avoiding to be overruled by topics
; comment it out, if necessary
Set debugOn to 0
... your code
If debugOn
   Message "whatever you want to say %.0f" MyVar
EndIf
... your code
If YourConditionBlockToInspect
  Set debugOn to 1
  ; get from here on all your messages
  If debugOn
     Message "whatever you want to say %.0f" MyVar2
  EndIf
  ; and if you want to have the messages for each frame
  ; slowly passing by, you add a ShowEnchantment at the 
  ; very end of the inspection block this time, like 
  ShowEnchantment
  ; I didn't check in all cases, if ShowEnchantment works 
  ; like a return function (Usually it works fine and not 
  ; as a return function).  But be aware of scripts that  
  ; may not execute further than this point or comment it out ;)
  ; now stop getting messages for this frame
  Set debugOn to 0
EndIf
... and so on