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"Open Source" is a broad spectrum, with various axes. The following is an attempt to describe various ways to look at openness to aid project leaders in determining what they want their project to look like. I originally wrote this for my colleagues at Google, but the concepts apply widely and I figured they might be of use for others. In practice, every project is a unique snowflake and there are exceptions to every rule. A project can be proprietary but use and contribute back to some open source library. An open source project can have undocumented proprietary protocols. A team can intend to fall in one category, but by their actions fall in another. The descriptions below should be seen merely as a high-level description of some possible ways projects can be configured, not as a comprehensive guide to the taxonomy of openness. Additionally, the examples I give below refer to the state of those products as of the time of writing. As projects evolve, these may become less...
a year ago

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More from Hixie's Natural Log

When complaints are a good sign

When you build something, you have to pick some design goals and priorities. Ideally you do so explicitly, but even if you don't, you're still implicitly doing so based on your design choices. These choices are trade-offs. If you want to write a quiet song, it won't be loud. If you are writing a software tool and you want to prioritize speed over simplicity, then it won't be as simple as if you'd prioritized simplicity over speed. There are two main signs that you've succeeded at your goals. The first, and more pleasant, is that you get compliments about how your thing is like you wanted it to be. "I love that song, it's so quiet!" "Your tool is so fast!" Why thank you, that's exactly what I was going for. The second sign, though, is that you will get complaints. Specifically, people will complain that your thing does not achieve the things you didn't set out to achieve. "I wish this song was louder", "this tool is so hard to use". That you are receiving complaints at all means that people are aware of your creation; that they are complaining about what you specifically set out to make a non-goal is a side-effect of the fact that you made that trade-off. The worst thing to do, when you receive such complaints, is take them to heart and try to fix them. This is because by definition you wanted these complaints. They are a sign that the thing you built is built as you wanted to build it. The people complaining want something different, they don't want your thing. It's just that your thing is so good that it's the thing they're compelled towards even though it doesn't prioritize the things they care about most. If you try to fix these complaints, you will, again by definition, be compromising on your goals. If you make the song have a loud part, then it's no longer a quiet song. You wanted a quiet song. Now it's a song that's quiet in parts and loud in parts. It probably still doesn't satisfy the needs of the people who want a loud song, and now it also doesn't satisfy the needs of the people who wanted your original quiet song. If you make your tool easier to use by compromising on the speed, then now you have a tool that's both not as fast as it could be and not as usable as it could have been if you'd started with that as a goal. It's important, therefore, to separate out complaints into those that are complaints you expect based on your design goals (which you should acknowledge but not fix), vs complaints that are either orthogonal to your goals (which you can fix without compromising your goals), or that are in line with your goals (which you should prioritize, since that's what you said to yourself was most important in the first place).

9 months ago 22 votes
Power dynamics in web specifications

My involvement in web standards started with the CSS working group. One of the things that we struggled with as a working group was that we would specify how the technology should work, but the browser vendors' implementations weren't exactly what we intended, and web authors would then write web pages that worked with those browsers, even though that meant the web pages themselves were also not doing things like the specifications said they should. The folks I worked with at the W3C (especially the academics and people working for organizations that did not themselves implement browsers) would frequently bemoan this state of affairs, expressing surprise at how they, the people in charge of the standards, were not being respected by the people implementing the standards. One of the key insights I had very early on in my work, before working on HTML5, which really influenced the WHATWG and its work, is the realization that the power dynamics at work were not at all the power dynamics that the folks at the W3C described. The reality of the situation was that the power lay entirely in the hands of the users. The users chose browsers. A browser vendor that ignored what the users wanted would lose market share. Market share is everything in this space. Browser vendors want users because they can convert users into dollars (in various ways, but they typically boil down to someone showing them ads and paying the browser vendors for the privilege). In turn, the browser vendors had more power than the specifications. What they implement is, by definition, what the technology is. The specification can say in absolute clarity that the keyword "marigold" should look yellow, but if a browser vendor makes it look red, then no web author is going to use it to mean yellow, and many will use it to mean red. There is a feedback loop here: if one browser implements "marigold" to mean red, and some important web site (or many unimportant web sites) rely on it, and say something like "best viewed in ThisOrThat browser!" because that's the one they use and in that browser it looks red and red is what looks best, then the other browser vendors are incentivised to make sure that the web page looks good in their browser too. Regardless of what the specification says, therefore, they are going to make "marigold" look red and not yellow. When I realized this, I also realized a corollary: if you have two competing specifications that both claim to define the same technology, but one matches what the browsers already do while the other one does not, the browser vendors are going to find it more useful to follow the one that matches what they do. This is because they can trust that implementing that specification will get them more market share. It means they won't have to stop and think at every step, "will following this specification cause me to lose users?". It is easier for them to use a specification that takes into account their needs in this way. We actually tried to explain this to the W3C membership. There was a big meeting in 2004 at Adobe in San Jose, the "W3C Workshop on Web Applications and Compound Documents". We tried to convey the above (I didn't quite understand it in the stark "power dynamic" terms yet, or at least, I didn't really express it in those terms, but if you read our position paper you can see this insight starting to crystalize). At this meeting, we made a pitch for the W3C to continue to maintain HTML and to care about what the browser vendors wanted. Representatives from Microsoft and Sun (in many ways arch enemies at the time) supported us. I seem to recall Apple being more quiet about it at the meeting but also essentially supporting the principles. The W3C membership resoundly rejected this whole concept. One of the W3C staff even explicitly said something along the lines of "if you want to do this you should do it elsewhere". That's what led to the WHATWG being founded a few weeks later.  The WHATWG was founded on this core principle — the specifications need to actually specify reality. When the browsers disagree with the spec, the spec is by definition incorrect and needs to change, regardless of how much technically superior the design in the spec is. Naturally, when you provide browser vendors with something that valuable, they will follow. You end up with a weird inverted power dynamic. The spec writer (when they follow this principle) has all the power, but only within the space that the browser vendors are themselves willing to play; and the browser vendors have all the power, but only within the space that the users are willing to put up with. It's very easy to appear to be in control when you tell people to do the thing they were going to do anyway (or at least, one of the things they were willing to do if they were to think about it). There is a (probably apocryphal) quote supposedly by Alexandre Auguste Ledru-Rollin that is often cited in mockery of bad leadership, but that perfectly matches the power dynamic here: "There go my people; I must find out where they are going so I can lead them". (Thanks to Leonard Damhorst for prompting me to write this post.)

a year ago 35 votes
How big is the Flutter team?

I often get asked how many people contribute to Flutter. It's a hard question to answer because "contribute" is a very vague concept. There's tens of thousands of packages on pub.dev, all of which are written by contributors to the community. There's over 100,000 of issues filed in our issue database, filed by more than 35,000 people over the years (the exact number is hard to pin down because people sometimes delete their GitHub accounts; about 700 issues have been filed by people who have since deleted their account). Many more people still have used the "thumbs-up" reaction to indicate that an issue matters to them, with almost 165,000 thumbs up from about 45,000 people. All of these people are valuable contributors to Flutter. Usually, when pressed, people try to clarify by asking about "the core team". Again though it's hard to say exactly what that means, but let's assume they mean "people with commit access". That is, people we trust enough to have added to the GitHub repo as collaborators. This includes people who work on Flutter for companies like Google, Canonical, or Nevercode, and it includes people like me who are self-employed and/or contribute to Flutter on a volunteer basis. Currently that's about 280 people. So is that the answer? Well, no, not really. Some people have commit access but aren't active (maybe they got access because of their employer, but were then reassigned to work on another project, and the bureaucracy hasn't caught up with them yet — we only audit the membership occasionally because it's rather tedious to do). Some people have been very active recently but don't have commit access (e.g. because they were just laid off and a bot automatically removed their access; they might even resume working on Flutter in the future, as a volunteer or funded by another company). So what's the answer? I recently drilled down through our data to see if I could answer this. I will caveat the following numbers by saying that this changes all the time. We added a new team member just today (hi Nate!) who is not counted as a team member in the following numbers because we collected the data a few weeks ago (it takes literally days to scrape all the data from GitHub, and then hours to explore the resulting very large and very slow spreadsheet). Also, some of my definitions are a bit arbitrary, and slightly tweaking the limits would probably change the numbers noticeably. First, I collected a list of everyone who has ever created an issue, commented on an issue, put an emoji reaction on the first comment of an issue, or submitted a PR, excluding bots and people who deleted their GitHub account. (Actually Piinks did the actual data collection. Thanks!) I limited this to a subset of the GitHub repos of the flutter org that is relatively inclusive but does not count everything (we have a lot of historical repositories and so forth). This finds about 94,357 people. (So there you go. The Flutter team is about a hundred thousand people!) To avoid padding the numbers with people who left the project long ago, and to avoid counting "drive-by" contributors who came, did a bunch of work, and then left, I then limited the data set to people who contributed over a period of more than 180 days, and who last contributed sometime in 2024. Because of the definition of "contributed" described above, that means that someone who added a thumbs-up to an issue in December 2020 and then filed an issue in January 2024, and did nothing else, is included, but someone who submitted two PRs in March 2024 is not. Like I said, this is a bit arbitrary. Anyway, that leaves 3,839 people, of which 182 currently have commit access, 27 once had commit access but don't currently (these are mainly people who either got laid off recently and had their commit access revoked by an automated process, or people who were once team members, left, lost access from inactivity long ago, and then later came to comment on issues or file new issues — it's surprisingly common for people who once worked on Flutter full time to stick around even when their employment changes), and about 3,627 people who have never had commit access. Of those who have never had commit access, 2,407 have filed at least one issue or submitted at least one PR (accounting for a total of 12,383 issues and 2,613 PRs). Of those, 341 have filed 5 to 9 issues (2,242 issues total), and 296 have filed 10 or more issues in their lifetime (7,021 total issues). Similarly, of the "never had commit access" cohort, 73 people have sent 5 to 9 pull requests in their lifetime (458 total PRs) and 47 have sent 10 or more (1,321 PRs total). (For context, 4,663 people have ever submitted a pull request, and 429 have ever submitted more than 10 PRs.) Of the people who currently have commit access, 98 people have submitted more than one PR every 3 weeks on average since they first got involved (accounting for 49,173 PRs), 75 people have closed at least one issue every 3 weeks (accounting for 48,490 total issue closures), of which 10 are not in the first group (mostly that's our triage team), and 150 people have commented at least once every 3 weeks. A follow-up question a lot of people ask is "do they all work for Google?". This is a surprisingly hard question to answer. There are a lot of weird edge cases. For example, one person worked on Flutter for a company that Google hired to work on Flutter, but then quit that company, asked for their commit privileges to be removed, but continued to be active in the community. Several people who have quit Google (such as myself), or been laid off by Google, have continued to be active in one sense or another (I think I submit more code to Flutter now than I did in my last year at Google). It's also hard to answer because a lot more people at Google contribute to Flutter than just those on Google's Flutter team, and a lot of people on Google's Flutter team contribute in ways that don't show up on GitHub (e.g. product management, marketing, developer relations, internal tooling). Of the 98 people who have commit access, have been active for more than 180 days, have contributed at least once this year, and have submitted more than one PR every 3 weeks on average for the entire time they've been contributing, I estimate (based on what I know of people's employment and so forth) that about 85% are Googlers or somehow get their funding from Google, and about 15% are currently independent of Google. (This is by no means the entirety of the Google team contributing to Flutter; as I mentioned earlier, many folks at Google working on Flutter don't appear in these statistics.) I'm not sure what conclusion to draw from this; it's both more people than I expected to see funded by Google, which is great, and fewer people that aren't funded by Google, which is less great. On the other hand, it's still a significant number of non-Google-funded people. Is it enough? I think that really depends on what your goals are. I think if your goal is for Flutter to be an order of magnitude better than other UI frameworks, then frankly no, it's not enough. There is a ton of work to be done to get there. We know what it would take, but we don't have the people to do it today. On the other hand if your goal is to be a great framework, on par with others, then it's probably adequate. It would certainly be difficult to continue to be great with fewer people today. Of course, that may change as we complete big efforts, or as we take on new ones, or as the landscape changes, it's all hard to predict. That said, I would love to see more direct contributions from non-Google sources, if for no other reason but to end this silly "will Google cancel Flutter" line of questioning that has followed the project since its inception. It's a dumb question. Flutter's an open source UI framework. It will never die. It will become old and something else will shine brighter one day, just as happens with literally every other UI framework ever. That's just how our industry works. There's no reason to believe that'll happen any time soon though, and certainly no reason for it to happen earlier for Flutter than any other modern UI framework.

a year ago 31 votes
The Future is Flutter

Despite my departure from Google, I am not leaving Flutter — the great thing about open source and open standards is that the product and the employer are orthogonal. I've had three employers in my career, and in all three cases when I left my employer I continued my job. With Netscape I was a member of the team before my internship, during my internship, and after my internship. With Opera Software, I joined while working on standards, kept working on standards, and left while working on the same standard that I then continued to work on at Google. So this is not a new thing for me. Flutter is amazingly successful. It's already the leading mobile app development framework, and I think we're close to having the table stakes required to make it the obvious default choice for desktop development as well (it's already there for some use cases). It's increasingly used in embedded scenarios. And Flutter is extremely well positioned to be the first truly usable Wasm framework as the web transitions to the more powerful, lower-level Wasm-based model over the next few years. In the coming month I will prepare our roadmap for 2024 (in consultation with the rest of the team). For me personally, however, my focus will probably be on fixing fun bugs, and on making progress on blankcanvas, my library for making it easy to build custom widget sets. I also expect I will be continuing to work on package:rfw, the UI-push library, as there has been increasing interest from teams using Flutter and wanting ways to present custom interfaces determined by the server at runtime without requiring the user to download an updated app.

a year ago 28 votes
Reflecting on 18 years at Google

I joined Google in October 2005, and handed in my resignation 18 years later. Last week was my last week at Google. I feel very lucky to have experienced the early post-IPO Google; unlike most companies, and contrary to the popular narrative, Googlers, from the junior engineer all the way to the C-suite, were genuinely good people who cared very much about doing the right thing. The oft-mocked "don't be evil" truly was the guiding principle of the company at the time (largely a reaction to contemporaries like Microsoft whose operating procedures put profits far above the best interests of customers and humanity as a whole). Many times I saw Google criticised for actions that were sincerely intended to be good for society. Google Books, for example. Much of the criticism Google received around Chrome and Search, especially around supposed conflicts of interest with Ads, was way off base (it's surprising how often coincidences and mistakes can appear malicious). I often saw privacy advocates argue against Google proposals in ways that were net harmful to users. Some of these fights have had lasting effects on the world at large; one of the most annoying is the prevalence of pointless cookie warnings we have to wade through today. I found it quite frustrating how teams would be legitimately actively pursuing ideas that would be good for the world, without prioritising short-term Google interests, only to be met with cynicism in the court of public opinion. Charlie's patio at Google, 2011. Image has been manipulated to remove individuals. Early Google was also an excellent place to work. Executives gave frank answers on a weekly basis, or were candid about their inability to do so (e.g. for legal reasons or because some topic was too sensitive to discuss broadly). Eric Schmidt regularly walked the whole company through the discussions of the board. The successes and failures of various products were presented more or less objectively, with successes celebrated and failures examined critically with an eye to learning lessons rather than assigning blame. The company had a vision, and deviations from that vision were explained. Having experienced Dilbert-level management during my internship at Netscape five years earlier, the uniform competence of people at Google was very refreshing. For my first nine years at Google I worked on HTML and related standards. My mandate was to do the best thing for the web, as whatever was good for the web would be good for Google (I was explicitly told to ignore Google's interests). This was a continuation of the work I started while at Opera Software. Google was an excellent host for this effort. My team was nominally the open source team at Google, but I was entirely autonomous (for which I owe thanks to Chris DiBona). Most of my work was done on a laptop from random buildings on Google's campus; entire years went by where I didn't use my assigned desk. In time, exceptions to Google's cultural strengths developed. For example, as much as I enjoyed Vic Gundotra's enthusiasm (and his initial vision for Google+, which again was quite well defined and, if not necessarily uniformly appreciated, at least unambiguous), I felt less confident in his ability to give clear answers when things were not going as well as hoped. He also started introducing silos to Google (e.g. locking down certain buildings to just the Google+ team), a distinct departure from the complete internal transparency of early Google. Another example is the Android team (originally an acquisition), who never really fully acclimated to Google's culture. Android's work/life balance was unhealthy, the team was not as transparent as older parts of Google, and the team focused on chasing the competition more than solving real problems for users. My last nine years were spent on Flutter. Some of my fondest memories of my time at Google are of the early days of this effort. Flutter was one of the last projects to come out of the old Google, part of a stable of ambitious experiments started by Larry Page shortly before the creation of Alphabet. We essentially operated like a startup, discovering what we were building more than designing it. The Flutter team was very much built out of the culture of young Google; for example we prioritised internal transparency, work/life balance, and data-driven decision making (greatly helped by Tao Dong and his UXR team). We were radically open from the beginning, which made it easy for us to build a healthy open source project around the effort as well. Flutter was also very lucky to have excellent leadership throughout the years, such as Adam Barth as founding tech lead, Tim Sneath as PM, and Todd Volkert as engineering manager. We also didn't follow engineering best practices for the first few years. For example we wrote no tests and had precious little documentation. This whiteboard is what passed for a design doc for the core Widget, RenderObject, and dart:ui layers. This allowed us to move fast at first, but we paid for it later. Flutter grew in a bubble, largely insulated from the changes Google was experiencing at the same time. Google's culture eroded. Decisions went from being made for the benefit of users, to the benefit of Google, to the benefit of whoever was making the decision. Transparency evaporated. Where previously I would eagerly attend every company-wide meeting to learn what was happening, I found myself now able to predict the answers executives would give word for word. Today, I don't know anyone at Google who could explain what Google's vision is. Morale is at an all-time low. If you talk to therapists in the bay area, they will tell you all their Google clients are unhappy with Google. Then Google had layoffs. The layoffs were an unforced error driven by a short-sighted drive to ensure the stock price would keep growing quarter-to-quarter, instead of following Google's erstwhile strategy of prioritising long-term success even if that led to short-term losses (the very essence of "don't be evil"). The effects of layoffs are insidious. Whereas before people might focus on the user, or at least their company, trusting that doing the right thing will eventually be rewarded even if it's not strictly part of their assigned duties, after a layoff people can no longer trust that their company has their back, and they dramatically dial back any risk-taking. Responsibilities are guarded jealously. Knowledge is hoarded, because making oneself irreplaceable is the only lever one has to protect oneself from future layoffs. I see all of this at Google now. The lack of trust in management is reflected by management no longer showing trust in the employees either, in the form of inane corporate policies. In 2004, Google's founders famously told Wall Street "Google is not a conventional company. We do not intend to become one." but that Google is no more. Much of these problems with Google today stem from a lack of visionary leadership from Sundar Pichai, and his clear lack of interest in maintaining the cultural norms of early Google. A symptom of this is the spreading contingent of inept middle management. Take Jeanine Banks, for example, who manages the department that somewhat arbitrarily contains (among other things) Flutter, Dart, Go, and Firebase. Her department nominally has a strategy, but I couldn't leak it if I wanted to; I literally could never figure out what any part of it meant, even after years of hearing her describe it. Her understanding of what her teams are doing is minimal at best; she frequently makes requests that are completely incoherent and inapplicable. She treats engineers as commodities in a way that is dehumanising, reassigning people against their will in ways that have no relationship to their skill set. She is completely unable to receive constructive feedback (as in, she literally doesn't even acknowledge it). I hear other teams (who have leaders more politically savvy than I) have learned how to "handle" her to keep her off their backs, feeding her just the right information at the right time. Having seen Google at its best, I find this new reality depressing. There are still great people at Google. I've had the privilege to work with amazing people on the Flutter team such as JaYoung Lee, Kate Lovett, Kevin Chisholm, Zoey Fan, Dan Field, and dozens more (sorry folks, I know I should just name all of you but there's too many!). In recent years I started offering career advice to anyone at Google and through that met many great folks from around the company. It's definitely not too late to heal Google. It would require some shake-up at the top of the company, moving the centre of power from the CFO's office back to someone with a clear long-term vision for how to use Google's extensive resources to deliver value to users. I still believe there's lots of mileage to be had from Google's mission statement (to organize the world’s information and make it universally accessible and useful). Someone who wanted to lead Google into the next twenty years, maximising the good to humanity and disregarding the short-term fluctuations in stock price, could channel the skills and passion of Google into truly great achievements. I do think the clock is ticking, though. The deterioration of Google's culture will eventually become irreversible, because the kinds of people whom you need to act as moral compass are the same kinds of people who don't join an organisation without a moral compass.

a year ago 32 votes

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15 hours ago 3 votes
Get in losers, we're moving to Linux!

I've never seen so many developers curious about leaving the Mac and giving Linux a go. Something has really changed in the last few years. Maybe Linux just got better? Maybe powerful mini PCs made it easier? Maybe Apple just fumbled their relationship with developers one too many times? Maybe it's all of it. But whatever the reason, the vibe shift is noticeable. This is why the future is so hard to predict! People have been joking about "The Year of Linux on the Desktop" since the late 90s. Just like self-driving cars were supposed to be a thing back in 2017. And now, in the year of our Lord 2025, it seems like we're getting both! I also wouldn't underestimate the cultural influence of a few key people. PewDiePie sharing his journey into Arch and Hyprland with his 110 million followers is important. ThePrimeagen moving to Arch and Hyprland is important. Typecraft teaching beginners how to build an Arch and Hyprland setup from scratch is important (and who I just spoke to about Omarchy). Gabe Newell's Steam Deck being built on Arch and pushing Proton to over 20,000 compatible Linux games is important. You'll notice a trend here, which is that Arch Linux, a notoriously "difficult" distribution, is at the center of much of this new engagement. Despite the fact that it's been around since 2003! There's nothing new about Arch, but there's something new about the circles of people it's engaging. I've put Arch at the center of Omarchy too. Originally just because that was what Hyprland recommended. Then, after living with the wonders of 90,000+ packages on the community-driven AUR package repository, for its own sake. It's really good! But while Arch (and Hyprland) are having a moment amongst a new crowd, it's also "just" Linux at its core. And Linux really is the star of the show. The perfect, free, and open alternative that was just sitting around waiting for developers to finally have had enough of the commercial offerings from Apple and Microsoft. Now obviously there's a taste of "new vegan sees vegans everywhere" here. You start talking about Linux, and you'll hear from folks already in the community or those considering the move too. It's easy to confuse what you'd like to be true with what is actually true. And it's definitely true that Linux is still a niche operating system on the desktop. Even among developers. Apple and Microsoft sit on the lion's share of the market share. But the mind share? They've been losing that fast. The window is open for a major shift to happen. First gradually, then suddenly. It feels like morning in Linux land!

10 hours ago 2 votes
All about Svelte 5 snippets

Snippets are a useful addition to Svelte 5. I use them in my Svelte 5 projects like Edna. Snippet basics A snippet is a function that renders html based on its arguments. Here’s how to define and use a snippet: {#snippet hello(name)} <div>Hello {name}!</div> {/snippet} {@render hello("Andrew")} {@render hello("Amy")} You can re-use snippets by exporting them: <script module> export { hello }; </script> {@snippet hello(name)}<div>Hello {name}!</div>{/snippet} Snippets use cases Snippets for less nesting Deeply nested html is hard to read. You can use snippets to extract some parts to make the structure clearer. For example, you can transform: <div> <div class="flex justify-end mt-2"> <button onclick={onclose} class="mr-4 px-4 py-1 border border-black hover:bg-gray-100" >Cancel</button > <button onclick={() => emitRename()} disabled={!canRename} class="px-4 py-1 border border-black hover:bg-gray-50 disabled:text-gray-400 disabled:border-gray-400 disabled:bg-white default:bg-slate-700" >Rename</button > </div> into: {#snippet buttonCancel()} <button onclick={onclose} class="mr-4 px-4 py-1 border border-black hover:bg-gray-100" >Cancel</button > {/snippet} {#snippet buttonRename()}...{/snippet} To make this easier to read: <div> <div class="flex justify-end mt-2"> {@render buttonCancel()} {@render buttonRename()} </div> </div> snippets replace default <slot/> In Svelte 4, if you wanted place some HTML inside the component, you used <slot />. Let’s say you have Overlay.svelte component used like this: <Overlay> <MyDialog></MyDialog> </Overlay> In Svelte 4, you would use <slot /> to render children: <div class="overlay-wrapper"> <slot /> </div> <slot /> would be replaced with <MyDialog></MyDialog>. In Svelte 5 <MyDialog></MyDialog> is passed to Overlay.svelte as children property so you would change Overlay.svelte to: <script> let { children } = $props(); </script> <div class="overlay-wrapper"> {@render children()} </div> children property is created by Svelte compiler so you should avoid naming your own props children. snippets replace named slots A component can have a default slot for rendering children and additional named slots. In Svelte 5 instead of named slots you pass snippets as props. An example of Dialog.svelte: <script> let { title, children } = $props(); </script> <div class="dialog"> <div class="title"> {@render title()} </div> {@render children()} </div> And use: {#snippet title()} <div class="fancy-title">My fancy title</div> {/snippet} <Dialog title={title}> <div>Body of the dialog</div> </Dialog> passing snippets as implicit props You can pass title snippet prop implicitly: <Dialog> {#snippet title()} <div class="fancy-title">My fancy title</div> {/snippet} <div>Body of the dialog</div> </Dialog> Because {snippet title()} is a child or <Dialog>, we don’t have to pass it as explicit title={title} prop. The compiler does it for us. snippets to reduce repetition Here’s part of how I render https://tools.arslexis.io/ {#snippet row(name, url, desc)} <tr> <td class="text-left align-top" ><a class="font-semibold whitespace-nowrap" href={url}>{name}</a> </td> <td class="pl-4 align-top">{@html desc}</td> </tr> {/snippet} {@render row("unzip", "/unzip/", "unzip a file in the browser")} {@render row("wc", "/wc/", "like <tt>wc</tt>, but in the browser")} It saves me copy & paste of the same HTML and makes the structure more readable. snippets for recursive rendering Sometimes you need to render a recursive structure, like nested menus or file tree. In Svelte 4 you could use <svelte:self> but the downside of that is that you create multiple instances of the component. That means that the state is also split among multiple instances. That makes it harder to implement functionality that requires a global view of the structure, like keyboard navigation. With snippets you can render things recursively in a single instance of the component. I used it to implement nested context menus. snippets to customize rendering Let’s say you’re building a Menu component. Each menu item is a <div> with some non-trivial children. To allow the client of Menu customize how items are rendered, you could provide props for things like colors, padding etc. or you could allow ultimate flexibility by accepting an optional menuitem prop that is a snippet that renders the item. You can think of it as a headless UI i.e. you provide the necessary structure and difficult logic like keyboard navigation etc. and allow the client lots of control over how things are rendered. snippets for library of icons Before snippets every SVG Icon I used was a Svelte component. Many icons means many files. Now I have a single Icons.svelte file, like: <script module> export { IconMenu, IconSettings }; </script> {#snippet IconMenu(arg1, arg2, ...)} <svg>... icon svg</svg> {/snippet}} {#snippet IconSettings()} <svg>... icon svg</svg> {/snippet}}

yesterday 2 votes
Logical Quantifiers in Software

I realize that for all I've talked about Logic for Programmers in this newsletter, I never once explained basic logical quantifiers. They're both simple and incredibly useful, so let's do that this week! Sets and quantifiers A set is a collection of unordered, unique elements. {1, 2, 3, …} is a set, as are "every programming language", "every programming language's Wikipedia page", and "every function ever defined in any programming language's standard library". You can put whatever you want in a set, with some very specific limitations to avoid certain paradoxes.2 Once we have a set, we can ask "is something true for all elements of the set" and "is something true for at least one element of the set?" IE, is it true that every programming language has a set collection type in the core language? We would write it like this: # all of them all l in ProgrammingLanguages: HasSetType(l) # at least one some l in ProgrammingLanguages: HasSetType(l) This is the notation I use in the book because it's easy to read, type, and search for. Mathematicians historically had a few different formats; the one I grew up with was ∀x ∈ set: P(x) to mean all x in set, and ∃ to mean some. I use these when writing for just myself, but find them confusing to programmers when communicating. "All" and "some" are respectively referred to as "universal" and "existential" quantifiers. Some cool properties We can simplify expressions with quantifiers, in the same way that we can simplify !(x && y) to !x || !y. First of all, quantifiers are commutative with themselves. some x: some y: P(x,y) is the same as some y: some x: P(x, y). For this reason we can write some x, y: P(x,y) as shorthand. We can even do this when quantifying over different sets, writing some x, x' in X, y in Y instead of some x, x' in X: some y in Y. We can not do this with "alternating quantifiers": all p in Person: some m in Person: Mother(m, p) says that every person has a mother. some m in Person: all p in Person: Mother(m, p) says that someone is every person's mother. Second, existentials distribute over || while universals distribute over &&. "There is some url which returns a 403 or 404" is the same as "there is some url which returns a 403 or some url that returns a 404", and "all PRs pass the linter and the test suites" is the same as "all PRs pass the linter and all PRs pass the test suites". Finally, some and all are duals: some x: P(x) == !(all x: !P(x)), and vice-versa. Intuitively: if some file is malicious, it's not true that all files are benign. All these rules together mean we can manipulate quantifiers almost as easily as we can manipulate regular booleans, putting them in whatever form is easiest to use in programming. Speaking of which, how do we use this in in programming? How we use this in programming First of all, people clearly have a need for directly using quantifiers in code. If we have something of the form: for x in list: if P(x): return true return false That's just some x in list: P(x). And this is a prevalent pattern, as you can see by using GitHub code search. It finds over 500k examples of this pattern in Python alone! That can be simplified via using the language's built-in quantifiers: the Python would be any(P(x) for x in list). (Note this is not quantifying over sets but iterables. But the idea translates cleanly enough.) More generally, quantifiers are a key way we express higher-level properties of software. What does it mean for a list to be sorted in ascending order? That all i, j in 0..<len(l): if i < j then l[i] <= l[j]. When should a ratchet test fail? When some f in functions - exceptions: Uses(f, bad_function). Should the image classifier work upside down? all i in images: classify(i) == classify(rotate(i, 180)). These are the properties we verify with tests and types and MISU and whatnot;1 it helps to be able to make them explicit! One cool use case that'll be in the book's next version: database invariants are universal statements over the set of all records, like all a in accounts: a.balance > 0. That's enforceable with a CHECK constraint. But what about something like all i, i' in intervals: NoOverlap(i, i')? That isn't covered by CHECK, since it spans two rows. Quantifier duality to the rescue! The invariant is equivalent to !(some i, i' in intervals: Overlap(i, i')), so is preserved if the query SELECT COUNT(*) FROM intervals CROSS JOIN intervals … returns 0 rows. This means we can test it via a database trigger.3 There are a lot more use cases for quantifiers, but this is enough to introduce the ideas! Next week's the one year anniversary of the book entering early access, so I'll be writing a bit about that experience and how the book changed. It's crazy how crude v0.1 was compared to the current version. MISU ("make illegal states unrepresentable") means using data representations that rule out invalid values. For example, if you have a location -> Optional(item) lookup and want to make sure that each item is in exactly one location, consider instead changing the map to item -> location. This is a means of implementing the property all i in item, l, l' in location: if ItemIn(i, l) && l != l' then !ItemIn(i, l'). ↩ Specifically, a set can't be an element of itself, which rules out constructing things like "the set of all sets" or "the set of sets that don't contain themselves". ↩ Though note that when you're inserting or updating an interval, you already have that row's fields in the trigger's NEW keyword. So you can just query !(some i in intervals: Overlap(new, i')), which is more efficient. ↩

2 days ago 5 votes
The missing part of Espressif’s reset circuit

In the previous article, we peeked at the reset circuit of ESP-Prog with an oscilloscope, and reproduced it with basic components. We observed that it did not behave quite as expected. In this article, we’ll look into the missing pieces. An incomplete circuit For a hint, we’ll first look a bit more closely at the … Continue reading The missing part of Espressif’s reset circuit → The post The missing part of Espressif’s reset circuit appeared first on Quentin Santos.

2 days ago 3 votes