From the specification, almost everything in the layout algorithm is defined, but this item seems to be missing.
Paragraph 9.4.7: https://www.w3.org/TR/css-flexbox-1/#algo-cross-item - says:
"Determine the hypothetical cross size of each item by performing
layout with the used main size and the available space, treating auto
as fit-content."
However "performing layout" is undefined -- it's what this paragraph is supposed to define, and instead it just ... recursively defines itself?
By contrast, the previous section (for Main Size) explicitly defines the algorithm for "perform layout". But the algorithms for Main and Cross must necessarily (almost by definition?) be (at least slightly!) different.
I'm debugging some detailed Flexbox code, and questions over "what, exactly, is the correct behaviour for cross-size layout?" are proving difficult to answer when I can't find an unambiguous section of the spec for this.
Ultimately, and with extensive testing in browsers, I came to the conclusion it means something like:
Do the undefined, arbitrary, parts of this specification, in whatever way you - the implementer - think is 'good'
i.e. there isn't a specification here. (officially: 'whatever the browsers do' is correct, but of course: what they do changes over time, and has its own bugs)
In particular: there's a big hole in CSS spec, which is "what is the size of an element?"; it's explicitly unexplicit, with 'suggestions' offered for what the sizes of various elements 'might' be. e.g. a PNG image could, perhaps, use its raw pixel width and height (but should you be following retina sizes, real sizes, points vs pixels, etc? And what should an SVG do? There's several arguably-correct answers to each of these).
... which I think is why the spec leaves this space blank.
Ultimately I found the best results by implementing a sensible set of heuristics for intrinsic sizes for elements, then using them here with the available meta info, constraints, etc. This fit most closely with what browsers were doing, and gives good results.
What are the syntactical features of current languages that prove problematic for screen readers or braille readers? What symbols and constructs are annoying to hear or feel? To the blind programmers out there, if you were to design a programming language which was easier for other blind people to work with, what would it be like?
Although it is a very interesting question, it is highly a matter of personal preferences and likings, so I'll answer as if you asked me personally.
Note: My working system is Windows, so I'll focus on it. I can write cross-platform apps, of course, but I do that on a Windows machine.
Indentation, White Spaces
All indentation-related things are more or less annoying, especially if the indentation is made with multiple spaces, not tabs (yes yes, I know the whole "holy war" around it!). Python did teach me to indent code properly even in languages that don't require it, but it still hurts me to write proper Python because of these spaces. Why so? The answer is simple: my screen reader tells me the number of spaces, and the actual nesting level is four times less. Each such operation (20 spaces, aha, dividing by 4, it is fifth nesting level) brings some overhead to my mind and makes me spend my inner "CPU" resources that I could free for debugging or other fancy stuff. It is a wee little thing, you'd say, and you'd be right, but this overhead is on each and single line of my (or another person's!) code I must read or debug! This is quite a lot.
Tabs are much better: 5 tabs, fifth nesting level, nice and well. Braille display here would be also a problem because, as you probably know, a Braille display (despite the name) is a single line of text, usually 14 to 40 characters long. I.e., imagine a tiny monitor with one single line of text that you pan (i.e., scroll), and nothing besides that. If 20 chars are spaces, you stay with only 20 chars left for the code. A bit more, if you read in Grade 2 Braille, but I don't know whether it would be appropriate for coding, I mostly use speech for it, except some cases.
Yet more painful are some code styling standards where you have to align code in the line. For instance, this was the case with tests in moment.js. There the expected values and messages should match their line position so, for example, the opening quote would be in column 55 on every line (this is beautiful to see, I admit). I couldn't get my pull request accepted for more than a week until I finally understood what Iskren (thank him for his patience with me!), one of the main developers, was trying to tell me. As you can guess, this would be completely obvious for a sighted person.
Block Endings
A problem adjacent to the previous one: for me personally it is very nifty when I know that a particular code block ends. A right brace (as in C) or the word end (as in Ruby) are good, indentation level change (as in Python) is not: still some overhead on getting knowing that the nesting level has abruptly changed.
IDEs
Sorry to admit it, but there is virtually no comfortable IDE for the blind. The closest to such an IDE is Microsoft Visual Studio, especially the latest version (gods bless Jenny Lay-Flurrie!), Android Studio seems also moving towards accessibility starting with version 2. However, these are not as usable, nifty and comfortable as they are for the sighted users. So, for instance, I use text editors and command-line tools to write, compile and debug my code, as do many blind people around me.
Ballad of the snake_case, or Another Holy War
Yet another thing to blame Python about: camelCase is far more comfortable to deal with then snake_case or even PascalCase. Usually screen readers separate words written in camelCase as if they were separated with spaces, so I get no pain readingThisPartOfSentence.
When you write code, you have to turn your punctuation on, otherwise you'll miss something really tiny and "unimportant", such as a quote, a semicolon or a parenthesis. Then, if your punctuation is on, and you read my_very_cool_descriptive_variable_name, you hear the following: "my underline very underline cool underline.... underline underline underline!!!" (bad language and swears censored). I tried even to replace underlines with sounds (yes, my screen reader gives such an opportunity), but the sounds can't be so well synchronized because of the higher speech rate I use. And it is quite a nightmare when dealing with methods and properties like __proto__ (aha, there are two underscores on both sides, not one, not three - well, got it right, I think!), __repr__ and so on, and so forth. Yes, you might say, I can replace the word "underline" with something really short like "un" (this is also possible), but some overhead is still here, as with white spaces and code nesting.
PascalCase is far better but it implies a bit more concentration, also, since we need to remember putting the first capital letter (oh, I'm too fastidious now, let it be PascalCase, but not those under... oh well, you got it already). This was the reason I gave up with Rust, btw.
Searching for Functions
As I have already told you, IDEs are not good for us, so text editor is our best friend. and then, you need to search for functions and methods, as well as for classes and code blocks. In certain languages (not Python this time), there are no keyword that would start a function (see, for example, C or Java code). Searching for functions in these conditions becomes quite painful if, for example, you do know that you have a logical error somewhere in the third or fourth function in the file, but you don't exactly remember its name, or you skim through someone's code... well, you know, there are lots of reasons to do that. In this particular context, Python is good, C is not.
Multiple Repeating and Alike Characters
This is not a problem per se, but a circumstance that complicates debugging, for example, regular expressions or strongly nested operations like ((((a + ((b * c) - d) ** e) / f) + g) - h. this particular example is really synthetic, but you get what I mean: nested ternary operators (that I love, btw!), conditional blocks, and so on. And regular expressions, again.
The Ideal Language
The closest to the ideal blind-friendly language as for me is the D language. The only drawback it has is absence of the word function except for anonymous functions. PHP and Javascript are also good, but they have tons of other, blind-unrelated drawbacks, unfortunately.
Update about Go
In one of his talks Rob Pike, the main developer of the Go language said that no one likes the code style imposed by the Gofmt utility. Probably, no one — except me! I like it, I love it so much, every file in Go is so concise and good to read, I'm really excited about the language because of that. The only slightly annoying thing for a blind coder is when a function has several pairs of parentheses in its definition, like if it is actually a struct method. the <- channel operator still gives me moments to think about what I'm doing, sending or receiving, but I believe it's a matter of habit.
Update about Visual Studio Code
Believe it or not, when I was writing this answer and the first update to it, I wasn't working as a full-time developer — now I am. So many circumstances went favorably for accessibility and me in particular! Slack, that virtually every business uses, became accessible, and so became Microsoft Visual Studio Code (again, gods bless Jenny and her team!). Now I use it as my primary code editor. Yes, it's not an IDE per se, but it's sufficient for my needs. And yes, I had to rework my punctuation reading: now I have shorter and often artificial names for many punctuation signs.
So, calling from end of January 2021, I definitely recommend Visual Studio Code as the coding editor for blind people and their colleagues. What is even more amazing is that LiveShare, their pair programming service, is also accessible! Yes, it does have some quirks (for now you can't tell what line in the file your colleague is editing if you're blind), but still it's an extremely huge step forward.
In a css file, how much difference is there between a file where the properties are in the same order for all selectors and one where they are randomly ordered, when considering the compressed output provided a process such as GZip.
Has anyone investigated this with some real examples and numbers they could share?
As order of bits always make a difference with compression, it will make a difference. But not as you could say one is better than the other. It's more like random (for us developers) which one will result in some bits more or less. But I think you will spent more time on finding the optimal solution than it would change something.
But remember, that some old IE had a functional difference considering the order of elements. As I remember, there was something that position had to be set before you want to set top, left, right, bottom and z-index (so attributes that only work when you have position).
I would just mind readability. This saves the most time (and by that money) during development :)
What are the parameters/factors that a QR detector need to detect/check before(during) decoding the QR code itself.
From what I know:
1. it need to find/locate three finder patterns
2. need to locate alignment patterns (if there is any)
3. need to check luminance
Is there anything else that need to be determined/checked?
I suppose that there are many ways to detect a QR code, and it's not required to do it one particular way or the other as long as the detection succeeds. There is a reference algorithms in the QR code specification, though in my opinion it is too slow to be practical, though it's quite thorough.
I can tell you how zxing does it. Yes, it first locates the three finder patterns. This is done by looking for 1:1:3:1:1 black/white/black/white/black crossings horizontally and vertically. It figures out which one is which by looking at the vectors between them.
Then it needs a fourth point since four points are needed to correct for perspective distortion. It uses the location of the 3 finder patterns to guess about where it is and scans for it similarly (looking for 1:1:1:1:1). You don't need to find all alignment patterns, though doing so would allow you to correct for warping in the QR code, which is very rare.
Then you can sample the image to get the black/white modules by computing the perspective transform and reversing it. Then the decoding proceeds, the processing of those black/white modules, which is a fair bit of work too but nothing to do with detection or image processing anymore.
Looking at luminance is really a step before all this, so you even have a notion of black and white in the image to begin with. That's different.
I'm writing some children's Math Education software for a class.
I'm going to try and present problems to students of varying skill level with randomly generated math problems of different types in fun ways.
One of the frustrations of using computer based math software is its rigidity. If anyone has taken an online Math class, you'll know all about the frustration of taking an online quiz and having your correct answer thrown out because your problem isn't exactly formatted in their form or some weird spacing issue.
So, originally I thought, "I know! I'll use an expression parser on the answer box so I'll be able to evaluate anything they enter and even if it isn't in the same form I'll be able to check if it is the same answer." So I fire up my IDE and start implementing the Shunting Yard Algorithm.
This would solve the problem of it not taking fractions in the smallest form and other issues.
However, It then hit me that a tricky student would simply be able to enter most of the problems into the answer box and my expression parser would dutifully parse and evaluate it to the correct answer!
So, should I not be using an expression parser in this instance? Do I really have to generate a single form of the answer and do a string comparison?
One possible solution is to note how many steps your expression evaluator takes to evaluate the problem's original expression, and to compare this to the optimal answer. If there's too much difference, then the problem hasn't been reduced enough and you can suggest that the student keep going.
Don't be surprised if students come up with better answers than your own definition of "optimal", though! I was a TA/grader for several classes, and the brightest students routinely had answers on their problem sets that were superior to the ones provided by the professor.
For simple problems where you're looking for an exact answer, then removing whitespace and doing a string compare is reasonable.
For more advanced problems, you might do the Shunting Yard Algorithm (or similar) but perhaps parametrize it so you could turn on/off reductions to guard against the tricky student. You'll notice that "simple" answers can still use the parser, but you would disable all reductions.
For example, on a division question, you'd disable the "/" reduction.
This is a great question.
If you are writing an expression system and an evaluation/transformation/equivalence engine (isn't there one available somewhere? I am almost 100% sure that there is an open source one somewhere), then it's more of an education/algebra problem: is the student's answer algebraically closer to the original expression or to the expected expression.
I'm not sure how to answer that, but just an idea (not necessarily practical): perhaps your evaluation engine can count transformation steps to equivalence. If the answer takes less steps to the expected than it did to the original, it might be ok. If it's too close to the original, it's not.
You could use an expression parser, but apply restrictions on the complexity of the expressions permitted in the answer.
For example, if the goal is to reduce (4/5)*(1/2) and you want to allow either (2/5) or (4/10), then you could restrict the set of allowable answers to expressions whose trees take the form (x/y) and which also evaluate to the correct number. Perhaps you would also allow "0.4", i.e. expressions of the form (x) which evaluate to the correct number.
This is exactly what you would (implicitly) be doing if you graded the problem manually -- you would be looking for an answer that is correct but which also falls into an acceptable class.
The usual way of doing this in mathematics assessment software is to allow the question setter to specify expressions/strings that are not allowed in a correct answer.
If you happen to be interested in existing software, there's the open-source Stack http://www.stack.bham.ac.uk/ (or various commercial options such as MapleTA). I suspect most of the problems that you'll come across have also been encountered by Stack so even if you don't want to use it, it might be educational to look at how it approaches things.