Godot Debugging Techniques EVERY Dev Should Know

for the better part of my career I did most of my bug hunting by desperately printing messages to the console like a caveman cave person anyway it's time to quit using print and save yourself a bunch of time in the process let's [Music] go all right so I'm not actually suggesting you never use print again but there are some scenarios where print is underpowered the debugger or methods might be a little bit more effective for hunting down one of those pesky bugs in this video I'm going to use this Metroid Vania sooon prototype I've been fiddling with we're going to look at a couple of scenarios where I might need to debug this prototype let's take a look at this scene manager so this is actually an early version of what later became the scene manager video that I made I'll put that up in the corner now if you want to check that out the game when I run it will attempt to load this level two file and and let's just suppose for a second that I mistyped this and if I come down here I've got this check where if the resource it's trying to load doesn't exist it's going to dump out of it and it's going to print you know a message to that effect so if I run this you see nothing loads and I come down in here and yeah I do get this error showing you know does not exist you know it's kind of mixed in visually with all this other stuff that I've been outputting stuff that's probably less critical because none of this is forcing the game to fail to load you know I I can't click on this I can't really do anything useful with it and yeah maybe in this example I might just right here notice that oh it's that extra two but maybe I forgot where that's defined so the sort of next line of defense here is instead of using print I can use print err and if I run this I still get that same error stands out a little more but I'm not getting any new functionality out of this so instead of that we can use push error what you'll see now instead of showing up here with with all this other stuff it's actually gotten pushed over to the debugger where I can now actually expand it first of all and I can follow the logic okay the ready fired uh and then I got into the scene manager which called load scene and I can literally click on this move this to the side and it's going to take me right to that line and now I can investigate a little bit further and go okay so this failed in the scene manager let me scroll up oh yeah okay this is just a typo and now if I close this and rerun it it would be fixed there are actually quite a few different print functions and if you command click or control click on a PC it'll take you right to the definition and then you can scroll through and have a look at some of the other options that are [Music] available we could actually take that a step further cuz let's pretend for a second that this wasn't the error maybe following that thread into the scene manager got me closer but not all the way there the next line of defense is looking at some of these objects live um inspecting them so let's go up to editor editor settings and search for remote and then come down to debugger and check this always switch to remote scenry let me uncheck that real quick so you can see what this does when you run the game you get your window here and then here is my local view this is everything I did at edit time if I switch manually over to the remote view it's going to show me what's actually represented right here I've got the scene manager and Global these are my autol loads and then if I click Start it's going to take take us into well it's actually not going to take us in because that error is still there but what you would see is that level loaded you can see it already started doing some of that um but we're stuck because we haven't fixed that so if I come into editor settings and check this on now when I play this you see it automatically switches over to our remote view which generally from a debugging perspective is way more interesting and useful than your local view so I like to turn this on the other thing I like to turn on is under project settings with your advanced settings turned on you can search for always and then go to window and turn on always on top if I uncheck this and we run our game comes up automatically switches over to the remote but if I want to inspect one of these see as soon as I click it pushes that window to the background because it's lost Focus so with that turned on it switches to my remote view I can click on the scene man manager and look at the information in it I can click on all of these things and this is still going to stay front and center I find those to be to very helpful settings not just for debugging but for working on your game in general in a minute we're going to talk about how to use the debugger but before we do that I want to talk about how to use the remote tree to debug rather than having to use print statements so let me fire up this level one of the things in this game is that you can push more than one block at a time and so there's the sense of of the player strength and then the concept of the weight of the total objects that are being pushed so if I push this block up and try to push it again with the strength of one I can only push one block so this effectively is now solid because I can't move two at a time if I collect this strength object it should allow me to push both of these but it's not and this could be for a number of reasons it could be because the thing I collected is broken it could be that the logic behind tallying the total weight of the push is broken it could be a whole bunch of different things and I could go through my code and put print statements all over the place and try to figure out exactly where the error is but instead I can click over here onto my globals which is where I'm managing the player strength you can see it's set to one right now and now I can move my player around and I can collect this and I can see oh you know what player strength hasn't changed hang on a second so let me take a look at my strength upgrade oh well here's the issue I'm not adding one I'm adding zero so if I save this and play now when I collect this I can push one and oh now I can now I can push two great that's fixed not only can you inspect things at runtime but you can also edit them as a way to debug whether that's even the fix so let's say for example you know I push these and okay so my strength is one I'm trying to push two so of course of course that doesn't work let me click on globals and increase my strength to two now I can come back to the game and push and oh it works okay so the issue actually is the player strength it's not something else and then that might be where I go in and fix this but what if we're running into an issue we want to test that isn't represented in our scene tree how do we inspect that that's where the debugger can give you insight into things that the scene tree [Music] can't so let's jump over to our scene manager again this portion of code right here is where we're passing data from one level to the next so this is this data to pass packet is where we're defining a bunch of things like the door that the player came through and whether they're bringing a crate with them this doesn't exist in the scene tree it gets created by the level you're exiting and passed off to the level that you're entering so there isn't really an easy way to come into the scene to click on something and take a look so we can use the debugger by clicking in this margin here you see this little red dot when I click here it creates this little red dot which means that it's going to execute code up until that point and then it's going to stop before it continues and I can put as many of these as I want and I can walk through them and take a look into the variables and objects and other things in that moment in time before continuing on so if I run this now we're going to see it when I click Start because it's using that scene manager so you see it's paused that's why I have this little arrow in here and I don't know where to put this so with it paused I have a couple of options I can step through my code one line at a time um and we'll get into why you might do that in a second or I can click this little continue button which is just going to say all right just continue executing from here on out until you hit another break point so I'm going to click that because I don't actually want to inspect anything right now I'm going to keep clicking this until we get into our level and then what I actually want to do is I want to look at the data packet that I'm handing off oh actually got to move the blocks into place now the door is open and I can pass and now I'm going to hit that break point so we're we're right here and so this data to pass does exist and I can actually just scroll down here and you can see right here here's my data to pass and if I click on this it's going to open up in our properties window just like we're used to seeing when we're editing our game this is the departing door ID so we're exiting through East and when we enter into the next level we're entering through the west door so if I hit continue again my player gets positioned right here which is one unit to the right of the west door now granted this level is a placeholder and only has the one West door but if we had a North a South and an East door it's not going to know where to put the player unless I tell it where I came from but if for example I I came through this door actually here we can do this we can do this live so if I go to level two and click on my level Gateway here right you see over here I'm defining destination G Gateway West well maybe I duplicated this from another door in the room and then I forgot to change it maybe it said East if I play this again oops hang on oh this is actually a good opportunity to show you this so the reason it started Us in the level that we left from is that I'm actually in the middle of writing the save system and and it remembered that I was in that room when I quit and so it put me back there and that's not what I want during this test so an easy way to undo that is I can go into project open user data folder and it's going to bring up this it's my save file which I can just delete and now if I test this again and we're going to have to skip through this break point now we're in this level let me push my crates into place and now when I go through this door it's actually going to CRA well it's not going to crash let me continue through now you see I'm here and not here and that's because this is the default starting point I currently have in this temp level so let's do this one more time so we've got that breakpoint set up right now if I go through this now it pauses and I can come in here to the data to pass and go huh destination gate East well that's not right because I'm coming from the East so I have to end in the west so I can quit this and go back in here and you know reselect that and fix this issue here so you might be thinking well do you really need the break point can't you just come in here click on level Gateway and look at this and see that it's wrong yes you absolutely can do that this is a contrived example where we know the problem at a time if I had a much more complex game maybe it's procedurally generated stuff and you know it's harder for me to recreate exactly the scenario you know one uh I don't know where to look in the first place um that's what the break point might get you is that introspection but also maybe it just doesn't exist in a form like this because things are being generated on the fly so you know that's where using break points and inspecting your code uh one line at a time and looking at the objects as they exist in that moment uh can be really powerful getting back to the the different controls here in the debugger let's um let's uncheck that because we don't want to do that anymore and let's go over to our level objects and the way this system works is when the player presses a direction the request move fires and we check whether or not we're able to move into that space if we are then we attempt to move the tile and then when everything is done this move ended function fires and the turn is over let's say I've got an error somewhere in that chain of actions and I'm not exactly sure where it is I can put a break point here and this might be a kind of a janky game to check it on to test it on because we're going to get a lot of break points because the turns are short but you know if I press left you'll see it's attempting to move and now it's paused here and instead of hitting continue I might want to step through my code one line at a time and see how the variables change and in what order and you know where the logic breaks so I can actually I can press these two items down here will respectively step into a function or step over a function and both of them will move one line at a time so if I click this one what you see is going to happen is it's going to go to the next line and if I click it one more time it's going to go from line 11 to line 12 it still executed that function it's just not going to walk you line by line through it why is that important well in this case maybe I know that my check all moves function is perfectly fine you know if this were let me pause this for a second let's say there was a line here that was significantly more benign I know this is working so if I run this code and I start stepping through it I get to this and I'm like I don't need to granted that's one line but if this were a a larger function that I know to be sound I can step over that function instead of into it and I can actually verify okay here's X yeah okay X is four that's correct If This Were a really long function that I knew to be working I wouldn't want to jump into it and go through that line by line I just I want to continue through and you know look at other lines where I think the logic might be failing me so you know if I ran this again and I try to move and I hit my break point if I I step down to this and then into my check all moves function as an example by clicking the step into you see it's going to take me here check all moves and now I can either continue through the entirety of this or I can step through line by line and follow the breadcrumbs as I'm going and at any point if I go well if it's working up until this point let me just continue and it's going to you know you can see it's continued the execution and now it's actually waiting for input and if I move again we're going to hit that breakpoint again and everything's going to repeat so these two features step into and step over can be really helpful if you have a hunch for roughly where your error might be but you're not sure and you want to go through and kind of audit like okay let me run this one line check the variables does everything line up the way it's supposed to be you know what sometimes you'll find is you're trying to access something before it exists and so you step through your code one line at a time and you go oh this is undefined I was expecting this to be defined at this point so let me figure out why this thing isn't existing at the moment that I expected it [Music] to as you've probably noticed when I'm testing this I'm not actually seeing my Collision shapes and sometimes that can be an issue so here's my Ray Caster here's all the different triggers more or less these are area 2DS if I under debug I can actually turn on visual Collision shapes and various other things to give me that feedack back while I'm also testing so that I can see oh you know what I thought these two things were overlapping or they're not so for example you know now I can see my raycaster and let's say and actually it's helping me visualize when that Ray Caster is see that it turns red because it's it's colliding with something so maybe you know if I thought my Ray cter was long enough and it wasn't uh this would give me that visual feedback that oh you know what I just need to make this a little bit longer for what I'm using it for okay so you don't have to completely quit using print but I hope this gives you a couple extra techniques for hunting down bugs in your code and if you'd like some tips for writing fewer bugs in the first place check out this video right up here until next time be kind to yourself and be kind to others I'll see you in the next [Music] video

Channel: Bacon and Games

Views: 18,748

Keywords: godot4 debugger, godot debugger, godot 4 debug, show collision shapes godot, keep godot window on top, fix bugs godot, godot print to console, godot 4 print, how to use godot debugger, godot 4 breakpoints, debugging in godot, godot 4, debugging with breakpoints, godot 4 console, push_error godot, godot warnings, godot error, godot debug, debug godot, debug godot 4, godot 3.5 debugger, godot engine, godot, how to debug godot, godot tutorial, godot 4 tutorial

Id: P7AQLUU3xKk

Length: 16min 22sec (982 seconds)

Published: Sat Feb 03 2024