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- + Dec 3 + Evennia 1.0 released! + + +
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Sep 17
Project plans and Splitting a Setting in two
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As of today, Evennia changes to use the very permissive BSD license.Now, our previous "Artistic License" was also very friendly. One main feature was that it made sure that changes people made to the core Evennia library (i.e. not the game-specific files) were also made available for possible inclusion upstream. A good notion perhaps, but the licensing text was also quite long and it was clear some newcomers parsed it as more restrictive than it actually was.
-... And let's be honest, it's not like I would have come hunting down anyone not complying fully with the Artistic license's terms. Changing to the much simpler and more well-known BSD license better clarifies the actual licensing situation.
+... And let's be honest, it's not like I would have come hunting down anyone not complying fully with the Artistic license's terms. Changing to the much simpler and more well-known BSD license better clarifies the actual licensing situation.
After all, far too many older MUD-code bases are weighted by a legacy of licensing issues. Anything we can do to avoid this is better in the long run. Indeed we hope this change in licensing will remove eventual licensing doubts for new adopters and have more people join and contribute to the project.
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Second example: Picture this scenario: You are walking down a dark hallway, torch in hand. Suddenly your light goes out and you are thrown into darkness. You cannot see anything now, not even to look in your own backpack. How would you handle this in code? Trivially you can put if statements in your look and inventory commands. They check for the "dark" flag. Fair enough. Next you knock your head and goes 'dizzy'. Suddenly your "navigation" skill is gone and your movement commands may randomly be turned around. Dizziness combined with darkness means your inventory command now returns a strange confused mess. Next you get into a fight ... the number of if statements starts piling up.
+Second example: Picture this scenario: You are walking down a dark hallway, torch in hand. Suddenly your light goes out and you are thrown into darkness. You cannot see anything now, not even to look in your own backpack. How would you handle this in code? Trivially you can put if statements in your look and inventory commands. They check for the "dark" flag. Fair enough. Next you knock your head and goes 'dizzy'. Suddenly your "navigation" skill is gone and your movement commands may randomly be turned around. Dizziness combined with darkness means your inventory command now returns a strange confused mess. Next you get into a fight ... the number of if statements starts piling up.
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Last example: In the hypothetical FishingMUD,. you have lots of detailed skills for fishing. But different types of fishing rods makes different types of throws (commands) available. Also, they all work differently if you are on a shore as compared to being on a boat. Again, lots of if statements. It's all possible to do, but the problem is maintenance; your command body keep growing to handle edge cases. Especially in a MUD, where new features tend to be added gradually over the course of years, this gives lots of possibilities for regressions.
+Last example: In the hypothetical FishingMUD,. you have lots of detailed skills for fishing. But different types of fishing rods makes different types of throws (commands) available. Also, they all work differently if you are on a shore as compared to being on a boat. Again, lots of if statements. It's all possible to do, but the problem is maintenance; your command body keep growing to handle edge cases. Especially in a MUD, where new features tend to be added gradually over the course of years, this gives lots of possibilities for regressions.
All of these are examples of situation-dependent (or object-dependent) commands. Let's jointly call them state-dependent commands. You could picture handling the in-game menu by somehow dynamically changing the global list of commands available. But then the global bit becomes problematic - not all players are in the same menu at the same time. So you'll then have to start to track who has which list of commands available to them. And what happens when a state ends? How do you get back to the previous state - a state which may itself be different from the "default" state (like clearing your dizzy state while still being in darkness)? This means you have to track the previous few states and ...
+All of these are examples of situation-dependent (or object-dependent) commands. Let's jointly call them state-dependent commands. You could picture handling the in-game menu by somehow dynamically changing the global list of commands available. But then the global bit becomes problematic - not all players are in the same menu at the same time. So you'll then have to start to track who has which list of commands available to them. And what happens when a state ends? How do you get back to the previous state - a state which may itself be different from the "default" state (like clearing your dizzy state while still being in darkness)? This means you have to track the previous few states and ...
A few iterations of such thinking lead to what Evennia now uses: a non-global command set system. A command set (cmdset) is a structure that looks pretty much like a mathematical set. It can contain any number of (unique) command objects, and a particular command can occur in any number of command sets.
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The last point is the most interesting aspect of cmdsets. The ability to merge cmdsets allows you to develop your game states in isolation. You then just merge them in dynamically whenever the game state changes. So to implement the dark example above, you would define two types of "look" (the dark version probably being a child of the normal version). Normally you use your "default cmdset" containing the normal look. But once you end up in a dark room the system (or more likely the room) "merges" the dark cmdset with the default one on the player, replacing same-named commands with new ones. The dark cmdset contains the commands that are different (or new) to the dark condition - such as the look command and the changed inventory command. Becoming dazed just means yet another merger - merging the dazed set on top of the other two. Since all merges are non-destructive, you can later remove either of the sets to rebuild a new "combined" set only involving the remaining ones in any combination.
-Similarly, the menu becomes very simple to create in isolation (in Evennia it's actually an optional contrib). All it needs to do is define the required menu-commands in its own cmdset. Whenever someone triggers the menu, that cmdset is loaded onto the player. All relevant commands are then made available. Once the menu is exited, the menu-cmdset is simply removed and the player automatically returns to whichever state he or she was in before.
+Similarly, the menu becomes very simple to create in isolation (in Evennia it's actually an optional contrib). All it needs to do is define the required menu-commands in its own cmdset. Whenever someone triggers the menu, that cmdset is loaded onto the player. All relevant commands are then made available. Once the menu is exited, the menu-cmdset is simply removed and the player automatically returns to whichever state he or she was in before.
Final words
-The combination of commands-as-classes and command sets has proved to very flexible. It's not as easy to conceptualize as is the simple functions in a list, but so far it seems people are not having too much trouble. I also think it makes it pretty easy to both create and, importantly, expand a game with interesting new forms of gameplay without drastically rewriting old systems.
+The combination of commands-as-classes and command sets has proved to very flexible. It's not as easy to conceptualize as is the simple functions in a list, but so far it seems people are not having too much trouble. I also think it makes it pretty easy to both create and, importantly, expand a game with interesting new forms of gameplay without drastically rewriting old systems.