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Revision as of 12:21, 13 July 2023

215 bytes added ,  13 July 2023
noted the best use of this folder (setting up macro functions); various wording and formatting tweaks
m (→‎Built-in overriding: wording, formatting)
(noted the best use of this folder (setting up macro functions); various wording and formatting tweaks)
 
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'''global''' is a sort of secret subfolder of [[IGMD|IGMD]]; a regular installation of Oni doesn't have it at all. But if you create it manually, you'll find it can serve a very special purpose: functions in the '''global''' folder can be called from every one of Oni's levels.
'''global''' is a sort of secret subfolder of [[IGMD|IGMD]]; a regular installation of Oni doesn't have it at all. But if you create it manually, you'll find it can serve a very special purpose: functions in the '''global''' folder can be called from every one of Oni's levels. This can be used to set up "macros" which you can call from the [[Developer Mode]] console. Some extended applications are considered below.
__NOTOC__
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==Code reuse==
==Code reuse==
One obvious use for this feature is that when writing a script that affects multiple levels, you can place common BSL functions in '''global''' instead of duplicating that code in each level's BSL files. However, you are still going to have to modify each level's BSL to ''call'' this global function.
One obvious use for this feature is that when writing a script that affects multiple levels, you can place common BSL functions in '''global''' instead of duplicating that code in each level's BSL files. However, you are still going to have to modify each level's BSL to ''call'' this global function if you want it to run automatically.


Let's say you want Oni to run a function every time you load a level. You have to go in every level's IGMD folder, open the file where <tt>func void main(void)</tt> is declared and modify it as follows :
Let's say you want Oni to run a function every time you load a level. You have to go in every level's IGMD folder, open the file where <tt>func void main(void)</tt> is declared and modify it as follows :
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  }
  }


You might be tempted to use <tt>[[BSL:Functions|fork]] some_global_function</tt>, but it's usually better to call the function "inline" (that is, no <tt>fork</tt>) to make sure that it fully executes before the original level logic resumes. You can always <tt>fork</tt> what you want to be <tt>fork</tt>ed inside your global function. Just be aware that anything you add, such as a <tt>sleep</tt> command, will delay the execution of the original logic, unless you do decide to use <tt>fork</tt>.
You might be tempted to use <code>[[BSL:Functions|fork]] some_global_function</code> in <tt>main()</tt>, but it's probably better to call the function inline (that is, no "fork") to make sure that it fully executes before the original level logic resumes. You can always fork specific code from inside your global function. Just be aware that any commands you insert into the level scripting will delay the execution of the original logic unless you do decide to use <tt>fork</tt>.


==Code overriding==
==Code overriding==
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  {
  {
     dmsg "Where's the kaboom?!"
     dmsg "Where's the kaboom?!"
     sleep 60
     sleep 120
     dmsg "There was supposed to be an Earth-shattering kaboom!"
     dmsg "There was supposed to be an Earth-shattering kaboom!"
  }
  }
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The original function by that name, [[BSL:Tutorial/airport1_level_logic.bsl#func_bomber_boom|found here]] in airport1_level_logic.bsl, is what causes the explosion of the ramp in the airport. Now, instead of creating an explosion particle and deleting the ramp, Oni just prints that message. Seemingly one could use this method to "patch" level BSL. However....
The original function by that name, [[BSL:Tutorial/airport1_level_logic.bsl#func_bomber_boom|found here]] in airport1_level_logic.bsl, is what causes the explosion of the ramp in the airport. Now, instead of creating an explosion particle and deleting the ramp, Oni just prints that message. Seemingly one could use this method to "patch" level BSL. However....


'''Big catch''': there may be unpredictable results; for instance, this override causes random problems in the level like changing Konoko's spawn location, though the dmsg will print appropriately when you reach the point where the ramp is supposed to explode.
'''Big catch''': There may be unpredictable results; for instance, the above override causes random problems in the level such as changing Konoko's spawn location, though the dmsg will print appropriately when you reach the point where the ramp is supposed to explode.


===Built-in overriding===
===Built-in overriding===
Here's an even more astounding application of BSL overriding: you can replace Oni's [[BSL:Functions|built-in functions]]. This is because another BSL rule is that <u>functions declared in BSL files override built-in (hardcoded) ones by the same name</u>. This means that you can create a pseudo-[[wikipedia:Hooking|hook]], like this one:
Here's an even more astounding application of BSL overriding: you can replace Oni's [[BSL:Functions|built-in functions]]. This is because another BSL rule is that <u>functions declared in BSL files override built-in (hardcoded) ones by the same name</u>. This means that you can create a pseudo-[[wp:Hooking|hook]] like this one:


  # The built-in env_show function takes two ints, so we'll do that here too
  # The built-in env_show function takes two ints, so we'll match that function signature
  func env_show(int a, int b)
  func env_show(int a, int b)
  {
  {
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  }
  }


Now Oni's level scripts cannot hide objects in the environment by calling <tt>env_show ''x'' 0</tt>, and as you play a level you will see the effect of this. One obvious change is found in the introductory cutscene in Chapter 2. Ah, that must be the seat the receptionist wanted you to take! ^_^
Now Oni's level scripts cannot hide objects in the environment by calling <code>env_show ''x'' 0</code>, and as you play a level you will see the effects of this. One obvious change is found in the introductory cutscene in Chapter 2. Ah, that must be the seat the receptionist wanted you to take! ^_^


'''Big catch''': pseudo-hooks like this are of limited value because there's no way to call the original function once you've overridden its name with your own declaration. Therefore, you can't add code to the beginning or end of a built-in function as you should be able to with a true hook; you can only prevent the built-in function from running, and run your own code instead. In theory you might be able to reconstruct a built-in call's effects using equivalent BSL commands. This is attempted by Gumby's cutscene-skipping script, which replaces [[BSL:Functions#cutscene|<tt>begin_cutscene</tt> and <tt>end_cutscene</tt>]] with its own implementations so it can add a "skip cutscene" key, with somewhat unpredictable results.
'''Big catch''': Pseudo-hooks like this are of limited value because there's no way to call the original function once you've overridden its name with your own declaration. Therefore, you can't add code to the beginning or end of a built-in function as you should be able to with a true hook; you can only prevent the built-in function from running, and run your own code instead. In theory you might be able to reconstruct the whole built-in function using equivalent BSL commands. This is attempted by Gumby's cutscene-skipping script, which replaces [[BSL:Functions#cutscene|<tt>begin_cutscene</tt> and <tt>end_cutscene</tt>]] with its own implementations so it can add a "skip cutscene" key, with somewhat unpredictable results.


Thus, the override "feature" is not recommended for use.
In light of the above considerations, the override "feature" is not recommended for use.


[[Category:Game directory map]][[Category:Modding tutorials]]
[[Category:Game directory map]][[Category:Modding tutorials]]
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