Sci Cloj Meetings, 23 Dec 2020

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From YouTube: Skija graphics library for the JVM - Nikita Prokopov - Scicloj meeting 18

Description

In this meeting, Nikita Prokopov presented Skija -- a new graphics library for the JVM, wrapping Skia.
https://tonsky.me/blog/skija/
https://github.com/JetBrains/skija

Moderator:
Kannan Ramamoorthy

Text chat:
https://tinyurl.com/ya8tqpou

Also, see this recent live demo by Nikita:
https://tonsky.me/blog/skija/

A

Hi everyone welcome to psychloge and good evening or good morning, based on the time zone that you're in and uh today we'll be discussing about uh schedule. uh 2D, graphics, library, tackle around jvm and with us we have nikita uh is an interesting gig with the various dimensions, so he has around 40 plus forecasts on his name and also a lot of focus, contribution and lot of interesting uh contribution he has done and uh for the people from closure background he's the one who has designed the logo for a famous babashika library.

A

So uh that's a brief about nikita and uh so uh with respect to this talk we'll be having this talk for uh uh closer to us. So this talk has been organized into multiple topics, starting from the intro to comparison and scope of development. That's that'll be in the future plan for this library, so in between each topics will have time for qas.

A

So any questions that you have on whatever nikita's discussing with us so uh feel free to post your questions in the chat so uh I'll be compiling the questions and uh we'll be raising it uh uh in between each sections and, uh if possible, feel free to turn on your videos. So it'll be more interactive and uh yeah.

A

That's it uh feel, free to interact and feel free to raise questions and uh will also be interested in knowing uh your current background, so either you are from java or closure so and if at all, you are not into closure too much and if at all you are not getting, what we are discussing feel free to raise it so that we'll see what we can do about it. So uh nikita.

B

I think you can uh hi everyone uh welcome to this kj introduction um yeah. uh Let me start just by saying that it's so um yeah, uh so this this kija is a library, uh it's a gvm library. So basically it has java api for in for graphics, right, 2d, graphics. Basically, that's it.

B

The idea is that and it's basically it's just a wrapper around skia library, which is a completely different thing, not completely different thing like but uh yeah. Let me just make myself a little bigger, so this kia library yeah, uh this is uh the library written by google and it's quite uh popular and many well-known projects are based on it. So chrome is based on it and flutter is based on it. So basically they use uh skia, not skidra, to draw all the pixels to the screen right.

B

So all the ui of the board that share those slides- I don't know whatever images uh flutter also uses it uh and in the bottom row there are like submarine, which is uh microsoft, bot uh valonia, which is ui4.net so basically submarine and avalonia.net things, and they have wrappers around skia for c-sharp.

B

Firefox doesn't use kia for the main page, but it uses for canvas. So when you instantiate the canvas in webpage and drawing it in firefox, you will be drawing into skier uh through ski and libreoffice. Is this uh black logo is libreoffice and starting from version seven? I think they also switched the rendering to skier. So it's a quite capable quiet library for doing 2d, graphics, you doing ui, graphics, right and the only problem was that it was cpos plus library which is okay, for I don't know for cpus plus programmers for chrome.

B

I guess and for not fundraising- and I wanted something to draw graphics on jvm, eventually enclosure but like building a wrapper just for closure seems short-sighted, probably, and for any language that cost it on juvia right.

B

So that's how skijo was born and skija is just a very thin layer that grabs c, plus plus skier library in java bindings- that's that's all it does. uh Whatever skier can do. Skedger can do as well through drawing, and the name is just like one extra letter j. uh So it's like, like most java libraries, do um that's what what it is. Okay, it's! It's also became later.

B

It became a problem because it's really easy to confuse the two names and people sometimes even don't understand that I'm talking about two different things when I talk about them, but that's that's! That's very small problem um yeah. So let me also explain a little bit uh about the scope of what what what graphics library does right. So this is not a complete ui solution like it's not the ui frameworks, it doesn't have buttons or check boxes or even windows and window events.

B

All it does is it puts pixels on a screen so basically stuff like lines, rectangles, gradients shadows.

B

It can draw them into screen into a bitmap yeah. So that was so. uh Let me okay I'll try to do this so I'll. I I draw a stack here. So here sorry, there's dryers! Oh, I can move this as well. Okay, so drivers, it's like bottom layers. It talks to hardware. Then there is opengl right which, like wraps drivers and skier and skija by extension, can work with opengl metal vulcan, and I think it has software render as well so rendering the bitmaps or something like that. uh It has, except it has many renderers.

B

Actually it can even render to pdf, but um what we are interested in is like hardware, accelerated, graphics, so opengl metal or welcome so yeah. I don't have examples for that yet, but uh it is certainly possible uh when we're working on examples.

B

Then there is a window management us os integration and stuff like create a window uh handle user events stuff like that, and this stuff is not covered by schedule right.

B

So this many many solutions exist in javaspace, so there is lwg, which I use for most of my examples: there's j, o g, l, uh j, r, a w t, not a w t but j r, a w t and they all handle the problem of creating a window in initializing, opengl context and stuff like that and hang these events so then don't have to, and then there is like here is graphics right.

B

So graphics is when you put lines rectangles on the screen, and this is what kia does and what skija does through through this kia. So it expects that you created the window somehow and expects that you created texture to rendering and then it can work. Finally right, but.

C

B

C

So sorry to interrupt, I just realized something about the recording.

C

uh I think, if you would share your screen, it will appear better on the youtube video eventually because it is recording like as a gallery of every all the little windows. So if you can somehow share your screen, if it is not a trouble.

B

I can let me I probably will have to restart zoom but yeah. It asks me to start zoom. Let me do it real, quick.

C

Yeah, I'm so sorry for that. We never had this special way of presentation that you are using and I should have thought about it.

B

Is there a way to put me in spotlight or something like that? No, oh.

C

uh Yeah but I'm not sure about the recording setup, I will try I'm trying to look for moments at the recording setup and maybe we can make it work uh yeah. So um if you are still with this slide, then you may just keep talking for a few more minutes and then why I will update if I find a way to make it work.

C

We you are on spotlight for the audience, but I'm not sure about the recording, so I will try to set it up.

B

I think if you, if you put me in speaker view it should be okay, yeah.

C

But recording is on the cloud and there is I'm set up there to to record the gallery. So um so maybe maybe um you can forget about me for a few minutes and I will come back maybe with okay. So exactly.

B

If you don't find anything, tell me I'll, restart and show your screen no problem. uh So I was talking about the graphics, so graphics is like this green layer and on top of it, usually people build like widget library, ui library controls, like buttons panels, scroll views lists. I don't know that thing that is not in schedule as well, not not in sketchup. uh We have uh jetpack compose for desktop android brains which is based on schedule and which solves this problem. So it's like the next layer so visit. You can create a whole application.

B

You can create widgets, buttons and stuff like that, but schedule it like handles low level, graphics, stuff, just putting pixels on the screen. If you want to compare it with java swing or javafx, they cover all three layers right. So if you use swing, for example, you have window management, built-in, graphics, building and widgets and all together in one single package on in case of skidra, we, this is decoupled into different layers, a single responsibility for each library.

B

So you can swap in and swap out different parts as you like, basically how we, like things, enclosure right. Decoupled not bundled together, libraries, not frameworks, so that's approach uh works for skij as well. Okay,.

C

So yeah, I'm sorry! I will stop you again, so you will have to show.

B

C

Just in case just to be sure, yeah.

B

But I will, I will reconnect.

C

Yeah, thank you, yeah, sorry, everybody. I should have thought about it and in a moment we will be fine.

A

Yeah, actually, uh it's good that you noticed it.

C

Yeah, the thing is that we just cannot know how the recording may turn out, because I know we are just recording the gallery unless screen is shared, so we will see in a moment.

B

Okay, I'm back.

B

Let me share screen, stop one.

B

Okay, so all my tricks about the camera will now not work, but okay, I I can use like this. I guess I wish I could hide stuff, but I can't but anyways okay. At least you can see me now right and um okay, okay, okay, okay, okay, now, let's go um so this! I was talking about it. So let me say yeah, so this is that tells us about what sketch does what it doesn't uh it's place so, basically, graphics, and even though it's not a complete ui solution, it's still useful.

B

I believe it's still useful well. First of all, you can use it as a basis for like widgets and controls like um like we do in compose right, but then you can do also visualizations, like I don't know, scientific visualizations, like graphics and especially interactive graphics, uh charts with with many data points, for example, if you need high performance graphics for some reason, uh you you can do that the problem the as long as it's 2d. So there is no 3d stuff just flat um and then you can build.

B

I guess games, I guess 2d games probably should be possible should be no problem for it as well, and then I have actually. I wanted to show you how what what type of graphics schedule supports, and for that I have a demo application here. So it's a little demo time, we'll just cycle through many examples and just show the basics, so the most basic stuff.

B

Is graphics, primitives like points lines, polygons, bezier, curves, arcs, gradients, different types of fields clips?

B

I don't know stuff like that right. This is there. Then there are some effects like lighting shadows and distortions, different types blowers.

B

uh There is very sophisticated, uh like path effects when you can put different shapes on the pass and fill paths with different shapes stuff like that, which also might be useful for some reason very sophisticated pass library. uh Basically, everything that you can expect from vector, graphics, editor, like figma or sketch. It's sketcher probably can do that as well.

B

uh Then there are there's text. Oh, this is still all different types of effects. There's also text, like I don't know, text layouting, uh complex text layouts, including emojis, bi-directional text and stuff, like that multiple fonts phones fall backs. So it does all that very good right. So it's very high quality implementation because uh because chrome is based on it and android is based on it and they need it to be good. So that's why it's also good in ski as well. So it's not it's something if it works in chrome.

B

It probably works correctly here as well. uh This is svg different, so it can render svg. You can render gradients shadows as it, though, so this is interesting. We implemented java dvd 2d graphics uh in skidra. It's not completely implemented, yet there are some bugs, but especially in this site, it's called.

B

I forget how it's called, but the the oldest style for swing uh it. uh It can render spin components but not going to java 2d instead going to schedule, but the same components. Yeah, there's text effects.

B

Scales and stuff like that, this also different bitmap effects like stretch of glass, black and white stuff, like that, you can do that uh clips images. uh This is uh like figma ui, but it's kids.

B

You cannot draw here with just static picture, but everything here is drawn with kj, including icons, so this all are vector. Icons.

B

Different types of text, rendering so there's also sophisticated text, rendering with many knobs to control that supports variable, fonts, open type features, also modern stuffs with browsers support supports as well. um Let me go back to where to here. Yes, so this is what uh skj is good for: okay uh boom, okay! Next next part, I don't have many slides, so I think it's best.

B

If we handle questions at the end, I will go through them quickly, probably quick enough, and then we can answer all the questions and have a discussion. So the next thing I wanted to show you how schedule works and, as I said, it is yeah. It is java api.

B

It is java api uh like you, go to, for example, canvas.java, and here uh you can, I don't know, draw polygon right, so you call it draw polygon plus, coordinates, plus paint, which is another object that has color and stuff like that and and yeah it will appear on the screen um yeah. So the the tricky part in implementing this so scheduler is not an automatically generated buildings for skier.

B

So when I started this project, there existed two two after generated buildings, which were pretty bad they're, really hard to use they're, confusing and stuff like that, so uh we decided to build a library that is uh like handcrafted, but it's also feels like normal java api. So things make sense, sometimes for some things you need to be using native objects behind the java object. Sometimes you are good with just java objects. Sometimes there is like stream in c plus, for example, or in students.

B

Keys key implements its own streams for reading files, but in java we have input streams, so you need to build a breach so that java users will use input streams which they used to instead of like some weird wrapper, around c plus plus library, which is like implemented in ski and stuff like that. So where things make sense, we use native java classes native java idioms.

B

We use iterators instead of ski iterators, for example stuff, like that, and I think it's much more pleasant to use and existing solutions. uh It also handles memory management for you, so c, plus plus it means you have to manage your memory. If you allocate cpus plus object, you have to free it at some point right, and this is not what java programmers are used to do. So we do a special wrapper. So all the skeda classes are extending managed class which handles memory management for you.

B

Basically it it is wrapper around cpus, plus pointer and when java object gets garbage collected and simple splash pointer gets freed. So you don't do memory management when using skija, because it's java library java does it for you. You don't bother.

B

Don't worry about it, but behind the scenes everything gets located and freed in simplest past correctly and reliably.

B

And that's the beauty of it. There is a method called close. So if you want to for some heavy weight resources, you can freeze them manually from java. So if you allocate, I don't know typeface or texture or something like that, it's probably a good idea to get rid of it as soon as possible, instead of waiting for garbage collector. So you can do that too, but it is optional right, so you can call it. You can not call it whatever you do.

B

The result will be at some point. The native object will be freed and closed correctly. So this was a pretty interesting problem to solve, but it seems to work okay, so far, yeah and then there are just lots: lots of classes uh this on the left, all the classes uh that schedule have to drop in one way and or another uh different c plus bus class.

B

This is about implementation, okay and about closure.

B

So closure is not native to skidra, but I had it in mind so because of jvm library you can use jvm um you, you can use it for enclosure and probably it would be better if there was a closure wrapper around it because something's a little trickier to use but anyways it totally works. I have an example that works in closure.

B

I think here and yeah. So the color creation was tricky because the color colors are integers in java and it's hard to create 32-bit integer enclosure. It always tries to create long instead.

B

So this is long and we need integer and they're not easily transformable. So yeah this function, I wrote and then there's draw. So basically it is paint set. Color translate on canvas, canvases, kids class paint, the schedule, class reactive schedule class right. So this and then there is some uh lj vga alerts whatever to create a window.

B

There is a rental loop and it's in the center of it. You clear, canvas and draw on kind of so yeah. I can show you that it works. If you go, I hope it works.

B

Maybe I need yeah change version.

B

Here, no, it doesn't work.

B

Oh yeah yeah, because I need to change this sorry, but the examples are set up to work with local built version, not with a maven version.

B

Yeah- and there is your window, you can even I think you can change. Let me see, I think there is something for yeah red color, so we are in.

B

Let me let me just show you so we have this, and maybe I have reset apps, but anyway you can. You can have interactive development while how you normally do enclosure.

B

B

B

Okay, let's see if yeah so it changes should have it prepared, but.

B

Yeah so, um and the idea actually is a global plan- is eventually that eventually having this library for uh graphics for jvm, I would build some ui library for closure, because I think closure is best suited for ui development because of ripple and interactivity and from there you can, we can like develop desktop applications.

B

The way closure script developers develop the browser applications with live reload and instant feedback and stuff like that. That would be awesome. I think, yeah, what else it also does. Okay, let me switch back to here.

B

uh Performance performance is, I have about different stuff about it? The performance is pretty good for some pretty bad for not not bad, so performance for skedja is pretty good and solid for most of the tasks that I can think of that I tried uh it is sometimes slower than javafx and some in some tasks. For example, this is uh the repo I built for testing performance of javafx and scheduler and awt.

B

Eventually, maybe right now just does two so the results, for example the feeling screen with circles javafx, does it faster than than skija, but teacher? Does it reasonably fast as well, but something like clipping or drawing shadows? Javafx is very, very slow while skj is is okay, it's it's it's doing pretty good and I think it's well.

B

I didn't try to do anything, fancy just the stuff that you would expect from user interface like clips for button shapes or I know, check, boxes or gradients for buttons backgrounds or shadows again, the stuff that you commonly see in user interfaces or text stuff like that uh yeah and uh it's it's pretty solid. It's not like fastest in the world. Again, sometimes javafx is faster, uh but it's pretty solid and I think.

A

Yeah uh one quick question: uh whatever you mentioned less than one uh is it in.

B

So this is uh pretty interesting, so let me show you: this is a benchmark where I draw the circles, but then don't draw any circles they're drawn as clipping rectangles. So basically it's a rectangle that has a clipping mask of the shape of the donut right. So, for example, if you're drawing something like this, you would probably need to clip on the on the border. So you don't overdraw to the uh stuff. That's out of your button so anyway, so clipping is sometimes is important in user interface.

B

So this is what skij does and who does it print reasonably well, for some reason, javafx cannot do clipping at all. So if I try to do it, it will be very, very slow, so it can draw like four or six or eight clipping masks with like tens, uh 10 fps, or something like that. If I do this much it, it basically goes to zero it. It needs multiple seconds to render this picture. For some reason. It also cannot draw a doughnut with clipping mask.

B

I know why I didn't like research deeply, why it is, but it was pretty bad. The same goes with shadow shadows, also pretty low performance performer in javafx, so the unit that.

A

You have mentioned, there is frames per second. Is it.

B

Frames per second: yes, oh okay, okay, yeah uh yeah! This is about performance, so I think if it's uh those are my my uh judgment is if it's good for chrome- and this is good for android- it's probably will be good for your application as well uh and finally, comparisons with between java and skeeja and javafx.

B

So one yeah. So it's not that I want to compare this to specifically, but um with any existing java solutions right, so there's awt there's swings, there are javafx, and now there is new graphics library. So what's the point, so uh there are many many problems.

B

First of all, as I mentioned, javafx and swing are complete solution for ui schedule. Only does part of that. So it's not probably fair comparison, but we can compare on the graphics side and exclude everything else and from the graphics side I have. I have at least somewhere yeah here. I think so. What I I like about.

B

The skija is, it gives you high quality, high fidelity with, like super uh detailed control over details of what you're pushing drawing on the screen. So awt and javafx do a decent job, but they are very basic. So basically, you can do basic things, but if you dedicated to do uh very, I don't know how high quality and very specific things. If you like, pixel, perfect sync, they might not be powerful enough. The api might be not powerful enough or wide enough to do what you want. So skidget just has much much broader api surface.

B

It can do much more things. It has much more control over what you're doing, um and that was important for me right. So so one of the things so two two things actually that I missed uh when I evaluated javafx for as a as a graphics backend for compose jpeg compose and for any potential uh closure. Ui library, if it ever happens, uh was color management, which is, as far as I know, doesn't exist in javafx or nor in awt.

B

uh Also, the code and typography right so text rendering so color management is a thing that becomes more and more important, especially for graphics application, and the problem is before I don't know like five years ago. Probably I don't remember exactly five fish years ago. Most of the displays that we had were srgb and so color management problem didn't exist, at least for showing pictures on the screen for computer screens. uh You just render srgb picture and you're fine.

B

Now apple started to selling wide gamut displays, so all the modern macbooks and the pro display hdr display, or it's called uh white gamut. They can show more colors than rgb, and this is a problem, because if you ignore that fact, you will probably be rendering slightly around colors on this displays. So if you just rendering srgb your your, uh how they say it so color management in a pro it's a problem that cannot be ignored. You have to deal with it.

B

Otherwise, you're just doing like ironic thing, and there are no control for color management for white gamma displays or stuff like that called conversions in javafx.

B

Unfortunately, and then the typography is uh and yeah about color management, and then there are hdr displays, of course, which also have like uh uh the different variety of them, but again they're becoming more and more popular, and you have to work with color differently when draining pictures for them. So it just the point: is it becomes a problem that cannot be ignored anymore, unfortunately, and if we're playing for building something for the future, we probably have this somehow foundation for this solved right now.

B

The second problem is typography right, so the text we live in, uh like in a world where there exists, left to right languages right to left languages where emoji exists and uh utf-8 or etfs etf 16 are not enough for everything. There are multiple fonts and fold fontful backs. There's there's also a text rendering which is pretty hard problem uh to do correctly, and all that also is very important for ui right.

B

You cannot build the ui if you cannot render like right to left text correctly or if you cannot render an emoji, uh and all this is, I would say, underwhelming in javafx, so I did some quick tests yesterday.

B

I had for some reason, even just putting text on the screen, renders it much bolder than the rest of mac os. So bottom is kidra. This is text edit, so native macos, macos text, rendering they're more or less the same javafx. For some reason does much bull renders much bolder text than it should.

B

Then I learned there are still unsolved problems about this, which is uh lcd text, rendering which shouldn't be enabled on mac os at all, but javafx enables it and if it end and then does their own job. So as far as understand you shouldn't see this type of colors, this saturated colors in lcd, anti layers text and then there's also for some reason.

B

It it two pixels white, I'm not sure why it should be one pixel, the color color binding should be for one pixel or two, but anyway uh yeah and these problems, and then I try to render text with emoji. uh So this is skija on the in the bottom, on the bottom and on the top is javafx.

B

To be honest, there are two. There are two two ways to render text right. You can create a text. Node and if you're, using javafx as a ui library, you're, probably not drawing drawing to the canvas directly you're using text, nodes and text, node knows how render itself. Maybe it works better. I didn't test it. This is uh like using graphics, like graphics, graphics context, so it's basically canvas which I put pixels to.

B

But even if text nodes work better, it's still not perfect. I think that.

B

It uses some apis that you don't have access to right. I I prefer to have access to all the apis that the library itself uses uh yeah then there's like high dpi support fractional scaling like vsync, and this uh this all stuff. That uh javafx has problems with and yeah, and this is the last problem with it is that javafx is a single single thing. You you need to use it all together. You cannot use like window management from javafx and throw away the rest.

B

You can't use graphics from javafx and should always rest it's not decoupled. So if, for example, I don't like the ui library of javafx, I I can't write my own, I have to work with what they offer and it's it's not the best, uh so yeah. So this is why I think the graphics library is.

B

Is needed. This is why I think it's needed on jvm. uh Well, because I work in java company right and we we have most our code, expertise in jvm. I work in two brains right now and they sponsor this development and plan to use it for java as well, and then uh I think closure is perfect for ui building and it's a shame. It still doesn't have any ui framework in closure. We do have we do have, but I think we can do better. That's that's all.

B

uh We have a javafx wrapper, for example, but that brings the whole of javafx, which is not not optimal uh yeah, but that's for the future right. So in the future, maybe somehow we'll solve window management, ui library, probably in different libraries, so I don't want to put that all into schedule. I want skidget to stay just graphics and you have a choice of which window management you choose, which your library chooses and stuff like that uh yeah yeah. I think that's, that's it! That's all.

B

I have to say I would be glad to answer any questions if anyone has them, but.

A

Let's, for the moment, uh we haven't received any questions from the audience yet, but uh uh as a user of uh swing in the past, I have certain questions.

A

So uh the first thing is like uh in so I remember using uh html rendering from swing so do we have support for that in schedule.

B

No, no, no! No, um I think the the it's it's like it's! It's the wrong level to to solve this problem, so this kj is pretty damp and low level. Just draws what you tell it it doesn't uh doesn't have it doesn't come with all the stuff that that you might actually need. So in that sense, it's pretty limited. I guess in its users it's it's like foundation for other stuff, including html, rendering, okay, okay,.

A

Yeah uh yeah and the next question is like so, as you have mentioned, we have a lot of advantages with schedule and there.

B

Are certain things which is available.

A

In the existing java ecosystem, which is safe to be implemented in skija, so, given this scenario, uh do we have? Is there a possibility of uh so developing? So uh so is it possible to combine skija and existing java effects or swing together so that they complement each other in a single application? Things like that.

B

uh It is, it is possible.

B

uh It is possible, but you you have to work on it yeah. So one example I can give you we have. uh We have jpeg compose for desktop and it's also the brains, library which, uh which basically it's japak compose, which is android library but ported for desktop to building desktop applications and it uses kidra and uh folks that are working on it. I right now they're working working on integration with swing, and this is two-way integration.

B

I I know that they can render a ski surface in a swing application, and now they very recently they also learned to draw swing components inside uh ski surface. So it is, let me show you actually, I think it's in uh in a public channel, so I can probably show you.

B

Here yeah, so uh this is like swing window or awt window, this awt buttons or panels on the on the border inside this clock. Wall of clocks is uh scheduler, rendered graphics right and inside inside it. uh There are two buttons which are also swing components. So it's like three layered cake. The swing then skija then swing again uh and it seems to work yeah. Now there are yeah, it works.

B

Okay, it's tricky to set up, but it works here. Okay,.

A

Yeah and we have a question from audience now so uh so that's from daniel, so uh he's saying like it would be great to hear more about the solution for handling c, plus plus memory release on garbage collection.

A

It is something that we need in closure currently uh using a nice library called egg.resource curious to hear about any challenges you have run into when taking care of them. So uh you'd like to know more about uh the garbage collection and uh yeah, absolutely any interesting issues that you would like to share. Yeah.

B

It is, you can always go to github. I don't know, I didn't, show the github. So the github is this: the brain, slash skija, and here, if you find it's called managed class.

B

Yeah and make it bigger so so the idea is very simple: you you store a native pointer in in a java class, as is long it's actually. Let me switch here.

B

So this is native class. It has a long which is just a pointer to simplesplus object right and it's stored as java field, then in managed there is some machinery which is based on this cleaner, which is, I think, something like jvm solution for, um like they used to have finalizers.

B

Now it's like there's different api called cleaner, or something like that. So the idea is you, you put your object in the cleaning queue and when garbage collector decides to kill your object to collect your object, you get a chance to do something at that point in time, so there's cleaner time they are sunk.

B

I pass a pointer and finalizer so and then the cleaner sonic goes into native method and calls this finalizer, which is also pointer and my monitor, for example, if I show you something simple like paint java right, so it's a managed object. So it has like this pointer and a.

B

Simple plus pointer, and then we go to c plus plus version of the paint. uh So this is the constructor that creates new paint on zippo's plus side. uh It creates new paint uh c, plus plus object, sets anti-alias and returns the say there is a pointer casted to j long okay, then there is finalizer that just calls delete and we take pointer to the function and we also pass it back to the java. So java now has this pointer to the object and this pointer to this function actually to this function.

B

So then, when garbage collector hits it calls it calls. This delete, pane passes the pointer to it and it gets deleted. So it's pretty straightforward.

B

One interesting thing that I learned is actually quite recently this week. Actually is that java can be pretty eager to collect your object, uh even if you're, like currently in the native method. So there is, we had a race uh when you're in a native madness, working with pointers and java decides to delete your object. You are working with, and that was maybe expected, because java is multi-threaded. Of course it has garbage characters threat and, of course it can hit at any time.

B

uh But what I didn't expect is that, while you're in a java method here, for example right so it's a it's, not static method, it's a paint method. It can collect the paint itself so, while you're in the object method, it can collect this.

B

It's method is not finished yet, but if java sees that for the rest of it, you don't use this anymore. It can collect it. So this was kind of unexpected. So here you can see. I have reachability fence that guards this. So until this native method finishes, please, please don't collect itself, otherwise it will erase here uh but yeah. That's that's basic, uh the gist of it.

A

Yeah- and we have a couple of more interesting questions and discussion to me so uh another question from uh story on- uh I hope I spelled the name right. So the question is like uh nikita: do you have any plans to do live coding session, uh something like writing a simple game using skija?

A

So I assume that the intention is uh to get a hands-on feel for both the audience and you.

B

I actually wanted to do that yeah. I I used to do some live coding uh some time ago, but yeah when I was like, I had data, I have data scripts streams. I think I have ram streams uh now yeah. It would totally make sense. I would probably even do it in closure, because I I don't think live coding in java is much fun uh and I also want to try how it feels to use it from closure.

B

Even even writing, like this small example gives gave me some insights into what closure wrapper should be uh so yeah. Probably if you follow me on twitter, you'll probably be you you can subscribe to it or you can write to my youtube channel. I guess it's. It has a much um weirder link. It's something like something like this. No okay, I don't know which my youtube link is, but I have youtube channel. Oh they are uh no twitter is better, so the nickname is nikitansky yeah. Oh yes, I'm really awesome. Yeah yeah yeah.

A

Yeah, so uh I think the answer is uh sometimes we might have a session and uh next is an interesting question and we have vladislav and uh who is author of clj effects, so uh so he so the strategy is like due to its back end. I happen to know a lot about java effects. I wholeheartedly agree that javafx, being everything in one package makes me at mercy of the quality of building components.

A

I think it's fair to say that javafx is neither very bad nor very good it's somewhere in between, but for ui development. I usually need something higher level than shapes and text, so I would say it makes more sense to compare javafx to jetpack compose for the desktop. Can you provide comparison between those two? So uh so it's asking if there is any comparison between java effects and jpeg compose that you have.

B

Yeah, um I cannot provide you first of all, you're right. Absolutely right! Javafx is something that should be compared to something like just bug compose. Yes, they are complete ui solutions, both both of them right.

B

Then um the components are the components I think are tricky because they still it's still unclear. Even for android, which is like a upstream for desktop compose uh it's android compose and even there they don't yet know what components should be, but I think, if you, I think, most of them, if they're available in android they're, probably available in um desktop as well, because they should basically share most of the code base.

B

uh So you probably should go to something like just pack compose documentation. Jet pack compose.

B

For for android and see she's there, so I don't think um desktop does anything differently it. I think what it does differently is stuff around windows like I think they have components like window component or pop-up component stuff like that or dialogue, something like that which doesn't exist on android right, so they have to implement those about those. I don't think you have.

B

There is a good place to read, but everything inside the window is probably just straight from jetpack compose as for other comparisons, so well um they're using awt, I think jawt, which is uh a way to render open trail texture inside awt window. So they are sitting on awt event, kill awt window management um but render their own components inside um they use skedra instead of about twink uses java2d right, so they use kj.

B

Instead, this is a big difference and um or javafx uses its own thing, uh but other from that uh yeah they're, probably pretty similar. Well, it's not similar. So come! Okay! Sorry, sorry for uh it's just I have some so many things and I I struggle to say them in order.

B

uh So the biggest difference like if we move away from internals from the outside for the outsider's view, the biggest difference is that javafx is old-style, ui framework as the one which has, I think it's based on 2d, two two-way bindings right, so the properties and they have components that react to a change of property or if you change subject component, it gets propagated back back to the property, sometimes that they have like buildings. Observable properties stuff like that, um but others from that. I think it's also imperative like.

B

If you want to create a window, you just write, create a window and window appears. If you want to close it, you write window.close and it disappears. uh As far as I know, my I.

B

uh So and compose is like this uh new way of building ui, which is now it's called declarative, ui, which was pioneered by react, and the idea is that you build virtual, dom and then and the library itself behind the scenes, somehow synchronizes your state between the what you see on screen between persistent components and your virtual dom so in compose uh you don't retain references to windows and text boxes and stuff like that, you you don't have them. Instead, you just call function after function.

B

You instead, you basically write a render function that renders your whole ui as if it's rendered from the scratch every time, uh and then you call it over and over and uh but the engine underneath compares what what it has and what you're trying to do and only calculates diff and applies this div to the persistent tree.

B

And this approach that react pioneered that flutter took that swing ui. I think you are right. This thing ui took so and now there is jetpack compose. So I think that's the main players in this area. I I personally find it much much better way to develop uil, I loved react when it was out. I even wrote a closure library, core skip library for react, and it was a joy to use the fact that you don't have to manage state transitions and you only render ui from scratch every time uh it's.

B

It simplifies a lot of things and I'm glad that uh campus joined this train.

D

Very cool thanks uh for your answer, but now it makes me think that maybe it makes more sense to compare the pack compose to clj fix, which is a react-like wrapper of javafx. So they are really have the same uh semantics when it comes to defining components.

B

Yeah yeah, maybe uh you're, probably right- I I I haven't worked with it, so I couldn't say much, but uh if, if it does of this react style things, it's probably kind of doing the same thing. Yes,.

A

And uh the next question is like uh so so it's it's from uh glass lab. So uh the question is like uh in uh github of uh compose uh jb, uh I'm unable to find uh the built-in components. Is there a reference where I can find the components that is supported in compose.

B

Yeah, I I think I answered that. I think you should be.

B

You should be looking at this jetpack compose for android and look. I think they have some documentation somewhere, but I also need to mention that this is in alpha. So it's not out even for android, so stuff changes, it changes pretty significantly significantly every month. So it's it's pretty hard to keep.

B

Stay stay updated about it, everything changes but see, I think they, the google, they really committed to it. It seems like and they will probably have lots of documentation. I mentioned I hope so. I never work with google, but that's how I expect.

A

And the next question from daniel is: are you aware of any other interesting c, plus plus libraries in the ecosystem, around skia? uh That could be useful to uh build bridges for something for data visualization, for example?

A

So is there any c, plus first library uh which can be used uh used to uh build a rapid around it can be used for things like data should decision or things like that.

B

uh I'm not uh I yeah yeah, okay, so the answer is, I am not, but even the skier repo itself has pretty well has some right, so uh it has svg library which is uh actually in skija, so you can render svg in skija. They also have this koti, which is, I think, a format for svg animations or something like that. So for vector animations. I think it's I I I think vector editors can export it. Something like that um yeah, I'm, not sure what else is there, but something like that: mothers.

B

There is uh yeah. Well yeah. I think that's it! That's all I know, but they probably are. This kia has been around for pretty long time. I think I think it's 10 years at least 10 years, probably more. I think.

A

Okay, so uh that's all the questions that we have uh for the moment. So anyone have any questions, so we have a lot more time left. So uh probably, if you are interested to discuss something or anything that you are unclear of, I think we have time to have a detailed discussion. Of course,.

C

Can I ask something: maybe.

A

C

Ahead so again, thank you. Thank you for the brilliant talk really exciting. I think um there is something that we sometimes like to do after we have talks like this one, and that is to go and learn, and I wanted to ask people in the audience if anybody would be interested in meeting afterwards and trying to play with skija from closure or not from closure, so that we can learn together and try to use it for our needs.

C

So if anybody is interested, then let us talk after the meeting. You have our email and it would be great to talk. Thank you.

A

So the email is the one from which we got the invite right. That's what you were referring to right: okay, yeah.

A

So any other questions from audience or anything that you'd like to.

A

A

Okay, yeah, uh I think.

A

We don't have any more questions from the audience.

A

Yeah yeah thanks a lot nikita for for such a preparation and such a innovative presentation that you started with and we went on and thanks for the work uh that you are putting in for uh ski job and other libraries and podcasts that you are trying and if people here uh didn't know already so uh uh nikita is having an interesting blog in which he's posting his uh thoughts and the podcast that he's doing and the videos that he have so probably can follow that as well.

A

And I have also posted uh uh twitter handle of nikita a couple of uh comments back in the chat so yeah. I think we are good anything else that you uh we haven't discussed.

B

Yeah, I just want to say thank you for inviting me and it was my pleasure to talk to you, because I hope I wasn't too worrying and yeah.

A

uh It uh it uh so especially for me, uh since I have uh uh experience with java swing, uh so it gave a different perspective and uh especially to see closer in action. I was happy.

B

And yeah, if you, if you do experiments or start build something with kids, please let me know I would be happy to to know it, and probably I will put the link to this kj repo as well so yeah.

A

D

B

A

You thank everyone.

B

To visiting yeah, it was my pleasure thank.

A

You everyone thank you. Bye, bye, bye,.