From 4a7f1259da03ee30c4b30df8b8229d7dc8f55fb7 Mon Sep 17 00:00:00 2001
From: EmacsConf <emacsconf-org@gnu.org>
Date: Sat, 2 Dec 2023 13:00:19 -0500
Subject: Automated commit

---
 ...diagnostics-with-overlays--jeff-trull--main.vtt | 1319 ++++++++++++++++++++
 1 file changed, 1319 insertions(+)
 create mode 100644 2023/captions/emacsconf-2023-overlay--improving-compiler-diagnostics-with-overlays--jeff-trull--main.vtt

(limited to '2023/captions/emacsconf-2023-overlay--improving-compiler-diagnostics-with-overlays--jeff-trull--main.vtt')

diff --git a/2023/captions/emacsconf-2023-overlay--improving-compiler-diagnostics-with-overlays--jeff-trull--main.vtt b/2023/captions/emacsconf-2023-overlay--improving-compiler-diagnostics-with-overlays--jeff-trull--main.vtt
new file mode 100644
index 00000000..9c948e2b
--- /dev/null
+++ b/2023/captions/emacsconf-2023-overlay--improving-compiler-diagnostics-with-overlays--jeff-trull--main.vtt
@@ -0,0 +1,1319 @@
+WEBVTT captioned by sachac, checked by sachac
+
+NOTE Introduction
+
+00:00.000 --> 00:00:04.897
+Hi, I'm Jeff Trull, and today I'm going to talk to you
+
+00:00:04.898 --> 00:00:08.460
+about improving C++ compiler diagnostics
+
+00:08.460 --> 00:13.600
+using overlays and other features from Emacs.
+
+00:13.600 --> 00:15.840
+First an overview of my talk.
+
+00:15.840 --> 00:00:17.656
+I'm going to cover what overlays are
+
+00:00:17.657 --> 00:00:19.325
+and how you can use them in code,
+
+00:00:19.326 --> 00:00:21.478
+then I'm going to talk about C++
+
+00:00:21.479 --> 00:00:24.480
+and why its compiler errors can be so onerous.
+
+00:24.480 --> 00:00:26.750
+Finally, we'll take that information
+
+00:00:26.751 --> 00:00:28.447
+and build a new minor mode
+
+00:00:28.448 --> 00:00:33.560
+using overlays and other Emacs features.
+
+NOTE Overlays and what they can do
+
+00:33.560 --> 00:35.520
+First of all, overlays.
+
+00:35.520 --> 00:36.680
+What are they?
+
+00:36.680 --> 00:00:39.124
+They are objects consisting of a buffer range
+
+00:00:39.125 --> 00:00:40.400
+and a set of properties.
+
+00:40.400 --> 00:43.120
+That means that they cover a region in a buffer.
+
+00:43.120 --> 00:00:45.533
+The properties can be a certain set
+
+00:00:45.534 --> 00:00:47.344
+of special property names,
+
+00:00:47.345 --> 00:00:50.288
+in which case they can be used to cause
+
+00:00:50.289 --> 00:00:52.569
+special effects in the buffer,
+
+00:00:52.570 --> 00:00:55.660
+but they never change the underlying text.
+
+00:55.660 --> 00:59.900
+You can use them for things like hiding things.
+
+00:59.900 --> 00:01:02.886
+So, for example, overlays are working right now
+
+00:01:02.887 --> 00:01:04.660
+in this window. `org-present`,
+
+00:01:04.661 --> 00:01:07.595
+the technology I'm using for this presentation,
+
+00:01:07.596 --> 00:01:10.031
+is hiding the asterisk before every headline,
+
+00:01:10.032 --> 00:01:12.520
+as well as the things called emphasis markers;
+
+00:01:12.521 --> 00:01:16.269
+that is, those things that make things look
+
+00:01:16.270 --> 00:01:20.700
+monospaced for verbatim, or italic, or bold.
+
+01:20.700 --> 00:01:24.421
+The special characters we use to mark off those sections
+
+00:01:24.422 --> 00:01:28.940
+are also hidden by `org-present` using overlays.
+
+01:28.940 --> 00:01:30.601
+But those things are still in the buffer
+
+00:01:30.602 --> 00:01:31.980
+and they're still visible to code.
+
+01:31.980 --> 00:01:34.921
+So if I run this little snippet of code down here,
+
+00:01:34.922 --> 00:01:37.403
+it's going to go up to the headline "Overlays
+
+00:01:37.404 --> 00:01:40.051
+and what they can do," and it's going to tell us
+
+00:01:40.052 --> 00:01:41.540
+what's there in the buffer.
+
+01:41.540 --> 01:45.100
+Let's go down and run this.
+
+01:45.100 --> 00:01:48.957
+So according to this code, the contents of the buffer
+
+00:01:48.958 --> 00:01:51.990
+to the left of the headline is a star in a space,
+
+00:01:51.991 --> 00:01:55.204
+which means that even though we can't see that star,
+
+00:01:55.205 --> 00:01:58.220
+it's still there, because it's hidden by an overlay.
+
+01:58.220 --> 02:02.500
+And that's kind of the essence of what overlays are.
+
+NOTE Simple overlay example - creating an overlay
+
+02:02.500 --> 02:04.780
+Let's do a simple overlay example.
+
+02:04.780 --> 00:02:06.719
+We have some text on the right here,
+
+00:02:06.720 --> 00:02:09.340
+which is a famous poem by William Carlos Williams,
+
+02:09.340 --> 02:12.180
+which has been the subject of many memes.
+
+02:12.180 --> 02:17.860
+Let's create an overlay that covers it.
+
+02:17.860 --> 02:20.700
+I'll go down here and use this snippet of code here.
+
+02:20.700 --> 00:02:25.918
+We'll go up to the top, and we'll mark everything
+
+00:02:25.919 --> 00:02:29.540
+between `#+BEGIN_VERSE` and `#+END_VERSE`.
+
+02:29.540 --> 00:02:33.276
+You can see we've created an overlay
+
+00:02:33.277 --> 00:02:35.700
+from position 74 to 224.
+
+NOTE Adding properties
+
+02:35.700 --> 00:02:38.063
+Now we can take that overlay that we already created
+
+00:02:38.064 --> 00:02:41.211
+and add a property, in this case a `face` property,
+
+00:02:41.212 --> 00:02:43.540
+to change the appearance of the text.
+
+02:43.540 --> 00:02:46.279
+This is a poem, and it's currently using
+
+00:02:46.280 --> 00:02:48.083
+a face that is monospaced,
+
+00:02:48.084 --> 00:02:50.491
+and so it looks like a computer program,
+
+00:02:50.492 --> 00:02:51.900
+even though it's a poem.
+
+02:51.900 --> 00:02:54.585
+I think it would be nicer to use something
+
+00:02:54.586 --> 00:02:57.980
+with variable-width font, maybe with some serifs.
+
+02:57.980 --> 03:01.140
+So let's give that a try.
+
+03:01.140 --> 03:03.700
+Now you can see that the poem looks quite a bit different.
+
+03:03.700 --> 03:10.940
+It looks more like what we'd see in a book.
+
+NOTE Deleting an overlay
+
+03:10.940 --> 03:13.100
+We can also delete overlays.
+
+03:13.100 --> 03:15.140
+So I've named this one.
+
+03:15.140 --> 00:03:17.765
+So we can just go down and run `delete-overlay`
+
+00:03:17.766 --> 00:03:20.048
+and get rid of it, and it'll go back to
+
+00:03:20.049 --> 00:03:22.660
+the appearance it had before.
+
+03:22.660 --> 03:23.660
+And there it is.
+
+03:23.660 --> 03:24.660
+It's back to normal.
+
+NOTE Setting fonts the right way
+
+03:24.660 --> 00:03:28.473
+Now, if you're interested in changing all of the verses
+
+00:03:28.474 --> 00:03:31.108
+inside an Org Mode file to a different face
+
+00:03:31.109 --> 00:03:32.785
+or a different font family,
+
+00:03:32.786 --> 00:03:35.060
+this isn't the way you'd really do it.
+
+03:35.060 --> 03:37.520
+I'll just show you that real quick.
+
+03:37.520 --> 00:03:43.471
+The right way is probably to change the `org-verse` face,
+
+00:03:43.472 --> 00:03:48.868
+which is the face used for all of the verse blocks
+
+00:03:48.869 --> 00:03:51.620
+inside your Org Mode file.
+
+03:51.620 --> 03:55.100
+And so this is how you do it here:
+
+03:55.100 --> 03:56.100
+`face-remap-add-relative`.
+
+03:56.100 --> 03:58.340
+Let's give it a try.
+
+03:58.340 --> 03:59.340
+It worked!
+
+NOTE More properties
+
+03:59.540 --> 00:04:01.805
+There are more advanced things that you can do
+
+00:04:01.806 --> 00:04:03.300
+other than just changing fonts.
+
+04:03.300 --> 00:04:05.543
+There's a whole long list of them in the manual,
+
+00:04:05.544 --> 00:04:12.580
+but let's talk about the ones we're going to use today.
+
+NOTE Visibility
+
+04:12.580 --> 04:17.380
+You can make text invisible, just like `org-present` did.
+
+04:17.380 --> 04:21.820
+The simplest way is to set the `invisible` property to true,
+
+04:21.820 --> 04:24.500
+so here's a code snippet that will do that.
+
+04:24.500 --> 00:04:26.159
+What we're going to do is
+
+00:04:26.160 --> 00:04:28.966
+go and find the word "plums" inside the poem,
+
+00:04:28.967 --> 00:04:31.284
+and then we're going to make it invisible
+
+00:04:31.285 --> 00:04:33.436
+by creating an overlay that covers it,
+
+00:04:33.437 --> 00:04:36.820
+and then setting the invisible property to true.
+
+04:36.820 --> 04:37.940
+Boom!
+
+04:37.940 --> 04:38.940
+It's gone.
+
+04:38.940 --> 04:39.940
+We've eaten the plums.
+
+04:39.940 --> 04:42.180
+Visibility is a huge topic and very complicated.
+
+04:42.180 --> 04:44.220
+There are powerful mechanisms for using it.
+
+04:44.220 --> 00:04:46.626
+I suggest reading the manual
+
+00:04:46.627 --> 00:04:49.780
+if you'd like to know more about that.
+
+NOTE Adding text
+
+04:49.780 --> 00:04:52.117
+Another thing we can do with properties
+
+00:04:52.118 --> 00:04:54.980
+is to add text either before or after an overlay.
+
+04:54.980 --> 00:04:57.347
+Since we've made the word "plums" invisible,
+
+00:04:57.348 --> 00:05:00.574
+or anything that you make invisible in the buffer,
+
+00:05:00.575 --> 00:05:02.662
+if you add text then afterwards,
+
+00:05:02.663 --> 00:05:05.700
+it looks like you've replaced the original words
+
+05:05.700 --> 05:08.220
+with new words.
+
+05:08.220 --> 00:05:12.046
+So let's add a property, a `before-string` property,
+
+00:05:12.047 --> 00:05:14.193
+to the overlay that we used before
+
+00:05:14.194 --> 00:05:17.137
+to make it seem as though we're eating cherries
+
+00:05:17.138 --> 00:05:18.180
+instead of plums.
+
+05:18.180 --> 05:19.180
+Boom!
+
+05:19.580 --> 05:22.020
+There it is.
+
+05:22.020 --> 05:27.820
+So that's how you can replace words using overlays.
+
+NOTE Custom properties
+
+05:27.820 --> 00:05:29.760
+You can also have custom properties
+
+00:05:29.761 --> 00:05:31.700
+that you name and then use yourself.
+
+05:31.700 --> 05:35.320
+For example, you can use it to mark regions in the buffer.
+
+05:35.320 --> 00:05:38.008
+You can also use it to add information
+
+00:05:38.009 --> 00:05:41.180
+to regions in the buffer for your own tracking
+
+05:41.180 --> 05:45.380
+in a minor mode or something like that, which we will use.
+
+NOTE Notes on properties
+
+05:45.380 --> 05:49.620
+Finally, two notes on properties.
+
+05:49.620 --> 00:05:51.950
+We've been talking about overlay properties,
+
+00:05:51.951 --> 00:05:54.540
+but there's also something called text properties.
+
+05:54.540 --> 05:57.460
+Text properties are attached to text in a buffer.
+
+05:57.460 --> 06:00.900
+When you copy that text, the properties come along with it.
+
+06:00.900 --> 00:06:03.056
+If you modify the properties,
+
+00:06:03.057 --> 00:06:05.500
+the buffer is considered modified.
+
+06:05.500 --> 06:08.460
+Org Mode makes heavy use of text properties,
+
+06:08.460 --> 00:06:11.677
+as we can see by running this little code snippet here,
+
+00:06:11.678 --> 00:06:14.060
+which is going to tell us the properties
+
+06:14.060 --> 00:06:16.565
+and the string attached
+
+00:06:16.566 --> 00:06:20.740
+to the "Some poetry" headline on the right.
+
+06:20.740 --> 06:23.660
+There's also some controversy regarding performance.
+
+06:23.660 --> 00:06:25.520
+It may be that text properties
+
+00:06:25.521 --> 00:06:27.860
+perform better than overlay properties,
+
+06:27.860 --> 00:06:28.892
+so do some research
+
+00:06:28.893 --> 00:06:31.060
+if you're going to make heavy use of them.
+
+06:31.060 --> 06:36.100
+I prefer overlays because they're just easier to use.
+
+NOTE Improving C++ compiler output
+
+06:36.100 --> 06:37.540
+C++ compiler output.
+
+06:37.540 --> 00:06:41.170
+So my day job is C++ programmer,
+
+00:06:41.171 --> 00:06:46.560
+and although I've been an Emacser for many years,
+
+00:06:46.561 --> 00:06:52.860
+it can be a little bit of a chore dealing with errors.
+
+06:52.860 --> 00:06:55.680
+The error messages that come out of the compiler
+
+00:06:55.681 --> 00:06:57.580
+can be pretty hard to understand.
+
+06:57.580 --> 00:07:00.537
+This has often been a barrier,
+
+00:07:00.538 --> 00:07:04.640
+particularly for people who are new to C++.
+
+07:04.640 --> 07:09.040
+So let's see what that's like.
+
+07:09.040 --> 00:07:10.559
+I have an example
+
+00:07:10.560 --> 00:07:14.780
+which is generously supplied by Ben Deane of Intel.
+
+07:14.780 --> 00:07:17.082
+So let's see what it looks like
+
+00:07:17.083 --> 00:07:19.313
+when you compile a C++ program
+
+00:07:19.314 --> 00:07:24.400
+that has a difficult error in it.
+
+07:24.400 --> 07:27.400
+Okay.
+
+07:28.400 --> 07:31.400
+Okay.
+
+07:31.400 --> 07:35.680
+So you see we have a lot of fairly verbose messages.
+
+07:35.680 --> 07:39.400
+The most verbose one I think is probably here.
+
+07:39.400 --> 07:41.000
+This one here.
+
+07:41.000 --> 07:42.000
+These are pretty bad.
+
+07:42.000 --> 07:43.000
+I think there might be bigger ones.
+
+07:43.000 --> 00:07:43.720
+Oh, yeah. Here we go.
+
+00:07:43.721 --> 00:07:44.960
+Here's my favorite one.
+
+00:07:44.961 --> 00:07:51.063
+You can see... Let's look for specialization... Basically,
+
+00:07:51.064 --> 00:07:55.178
+this whole section of the buffer here,
+
+00:07:55.179 --> 00:07:58.228
+that is specifying the specific types
+
+00:07:58.229 --> 00:08:02.000
+that a function template was instantiated with.
+
+08:02.000 --> 08:04.000
+And it's a lot there.
+
+08:04.000 --> 00:08:05.473
+So if you're trying to figure out
+
+00:08:05.474 --> 00:08:06.817
+what's wrong with your program
+
+00:08:06.818 --> 00:08:08.884
+and you're looking at something like this,
+
+00:08:08.885 --> 00:08:11.000
+it can be really, really hard to understand.
+
+08:11.000 --> 08:12.000
+Okay.
+
+08:12.000 --> 08:17.680
+Back to our presentation.
+
+NOTE The problem with C++ error messages
+
+08:17.680 --> 00:08:20.063
+So it's often this way in C++
+
+00:08:20.064 --> 00:08:23.400
+because we compose types from other types.
+
+08:23.400 --> 00:08:26.216
+They can be long to begin with,
+
+00:08:26.217 --> 00:08:30.240
+but then a couple of other factors come into play.
+
+NOTE Many standard class templates have defalut arguments
+
+08:30.240 --> 08:33.280
+First of all, we can have default template arguments.
+
+08:33.280 --> 00:08:35.363
+These are arguments you didn't write,
+
+00:08:35.364 --> 00:08:37.008
+but that are implicitly there
+
+00:08:37.009 --> 00:08:38.325
+and can sometimes refer
+
+00:08:38.326 --> 00:08:40.300
+to the arguments that you did write,
+
+00:08:40.301 --> 00:08:42.440
+which causes them to get a bit bigger,
+
+00:08:42.441 --> 00:08:47.520
+such as these allocator arguments here and here.
+
+NOTE Some types are aliases for longer things, too
+
+08:47.520 --> 08:49.360
+Then there are type aliases.
+
+08:49.360 --> 00:08:54.014
+For example, `std::string` here expands to
+
+00:08:54.015 --> 00:08:58.320
+a type with three template arguments.
+
+08:58.320 --> 00:09:01.940
+So you can imagine, when we combine
+
+00:09:01.941 --> 00:09:04.733
+those two things together,
+
+00:09:04.734 --> 00:09:09.763
+our simple vector of maps from strings to ints
+
+00:09:09.764 --> 00:09:14.257
+becomes this humongous thing here, which...
+
+00:09:14.258 --> 00:09:17.360
+Let's run the comparison.
+
+09:18.360 --> 09:20.960
+Yeah.
+
+NOTE Reporting type information accurately means long lines
+
+09:20.960 --> 00:09:24.924
+So in summary, to properly understand an error
+
+00:09:24.925 --> 00:09:27.370
+when you're a C++ programmer
+
+00:09:27.371 --> 00:09:29.718
+requires knowing the exact types
+
+00:09:29.719 --> 00:09:32.280
+that were supplied to your function.
+
+09:32.280 --> 00:09:34.430
+And types are built recursively,
+
+00:09:34.431 --> 00:09:36.646
+and therefore the types can--
+
+00:09:36.647 --> 00:09:40.513
+the correct exact name for the type
+
+00:09:40.514 --> 00:09:42.776
+can just be really huge
+
+00:09:42.777 --> 00:09:46.360
+and have many levels and layers to it.
+
+09:46.360 --> 00:09:48.113
+So when I was trying to understand
+
+00:09:48.114 --> 00:09:49.466
+the things I'd done wrong,
+
+00:09:49.467 --> 00:09:52.401
+especially when I was a newer C++ programmer,
+
+00:09:52.402 --> 00:09:54.570
+but honestly still even recently,
+
+00:09:54.571 --> 00:09:57.440
+if I was having a really intractable problem,
+
+09:57.440 --> 00:10:00.123
+I would just copy the entire error message out,
+
+00:10:00.124 --> 00:10:01.735
+stick it in the scratch buffer,
+
+00:10:01.736 --> 00:10:03.649
+and then manually reformat it
+
+00:10:03.650 --> 00:10:05.563
+so I could see what it was telling me
+
+00:10:05.564 --> 00:10:07.261
+I'd actually called the function
+
+00:10:07.262 --> 00:10:09.320
+or whatever it was with, the exact type.
+
+10:09.320 --> 00:10:11.311
+I had to sit there
+
+00:10:11.312 --> 00:10:13.240
+and go through the whole thing.
+
+10:13.240 --> 10:15.240
+But there's a better way.
+
+10:15.240 --> 10:18.240
+Now, anyway.
+
+NOTE Emacs can help - Treat C++ type names as just another kind of balanced expression
+
+10:18.240 --> 10:23.960
+So what can Emacs do to help us with this problem?
+
+10:23.960 --> 00:10:28.870
+First of all, if you think about a type name,
+
+00:10:28.871 --> 00:10:33.080
+it's a lot like what we call S-expressions
+
+10:33.080 --> 10:35.480
+or balanced expressions.
+
+10:35.480 --> 10:38.400
+Lisp code itself is an S-expression.
+
+10:38.400 --> 00:10:41.464
+It's basically things with parentheses
+
+00:10:41.465 --> 00:10:44.214
+and little atoms or symbols in it,
+
+00:10:44.215 --> 00:10:46.520
+or strings or numbers.
+
+10:46.520 --> 00:10:50.231
+But parenthesized balanced expressions
+
+00:10:50.232 --> 00:10:55.800
+are things that Emacs was actually built to deal with.
+
+10:55.800 --> 00:10:58.944
+They were... I found an old manual from 1981,
+
+00:10:58.945 --> 00:11:02.160
+and the two major modes that they recommended
+
+11:02.160 --> 00:11:05.765
+or that they actually documented in the manual were
+
+00:11:05.766 --> 00:11:08.400
+one, assembly language, and two, Lisp.
+
+11:08.400 --> 00:11:10.652
+They mentioned that there were other modes,
+
+00:11:10.653 --> 00:11:12.700
+but they didn't say anything about them.
+
+11:12.700 --> 00:11:14.625
+So Lisp is something
+
+00:11:14.626 --> 00:11:17.440
+with a really long history with Emacs.
+
+11:17.440 --> 00:11:19.976
+Balanced expressions and manipulating them
+
+00:11:19.977 --> 00:11:21.434
+and doing them efficiently
+
+00:11:21.435 --> 00:11:24.155
+is just a thing that Emacs knows how to do,
+
+00:11:24.156 --> 00:11:25.640
+and Emacs is good at it.
+
+11:25.640 --> 00:11:27.705
+There's just a legacy
+
+00:11:27.706 --> 00:11:31.320
+of algorithms and functions for doing it.
+
+11:31.320 --> 00:11:33.182
+So we take types,
+
+00:11:33.183 --> 00:11:37.839
+and we take the angle brackets in the types,
+
+00:11:37.840 --> 00:11:40.840
+and we get the symbols right.
+
+11:40.840 --> 00:11:41.814
+Then we can treat them
+
+00:11:41.815 --> 00:11:44.312
+as though they were balanced expressions or S-expressions,
+
+00:11:44.313 --> 00:11:49.320
+the same kind that Emacs is really good at handling.
+
+NOTE Add overlays to improve readability
+
+11:49.320 --> 00:11:51.979
+Secondly, we can use overlays
+
+00:11:51.980 --> 00:11:55.260
+to improve the readability of errors.
+
+11:55.260 --> 00:11:58.012
+We can take long lines and break and indent them
+
+00:11:58.013 --> 00:12:00.160
+using `before-string`s, so the same thing
+
+12:00.200 --> 12:03.440
+I used to add "cherries" into the poem.
+
+12:03.440 --> 00:12:06.611
+We can use that to insert new lines
+
+00:12:06.612 --> 00:12:08.725
+followed by indentation
+
+00:12:08.726 --> 00:12:15.160
+and produce a much nicer-looking listing of a type.
+
+12:15.160 --> 00:12:19.641
+We can also use the `invisible` property
+
+00:12:19.642 --> 00:12:22.400
+to hide unwanted detail.
+
+NOTE Create a minor mode that runs during compilation
+
+12:22.400 --> 12:24.960
+Last of all, we can create a minor mode.
+
+12:24.960 --> 00:12:27.854
+When we're compiling things in Emacs,
+
+00:12:27.855 --> 00:12:30.140
+we often use `compilation-mode`.
+
+12:30.140 --> 00:12:32.097
+`compilation-mode` allows you to install
+
+00:12:32.098 --> 00:12:33.553
+compilation filters that run
+
+00:12:33.554 --> 00:12:36.434
+when the compiler is producing output,
+
+00:12:36.435 --> 00:12:39.980
+and at that time, then, we can add our overlays.
+
+12:39.980 --> 00:12:42.868
+We can also add in minor-mode commands
+
+00:12:42.869 --> 00:12:45.757
+that do whatever we want to the keymap.
+
+00:12:45.758 --> 00:12:48.321
+In this case, we're going to show and hide
+
+00:12:48.322 --> 00:12:50.176
+lower-level details interactively
+
+00:12:50.177 --> 00:12:53.906
+so that we can see a simplified version
+
+00:12:53.907 --> 00:12:59.500
+or a more detailed version of a type, depending on our needs.
+
+NOTE Parsing types as balanced expressions
+
+12:59.500 --> 13:03.980
+First of all, parsing types as balanced expressions.
+
+13:03.980 --> 00:13:05.686
+We need to be able to quickly locate
+
+00:13:05.687 --> 00:13:07.162
+the boundaries and the contents
+
+00:13:07.163 --> 00:13:08.500
+of parenthesized expressions,
+
+13:08.500 --> 13:12.100
+or in this case, expressions in angle brackets.
+
+13:12.100 --> 00:13:14.995
+We use a syntax table inside Emacs
+
+00:13:14.996 --> 00:13:18.800
+to allow movement functions like `forward-list`
+
+00:13:18.801 --> 00:13:21.100
+to jump between matching angle brackets.
+
+13:21.100 --> 13:23.460
+By default, they're just parentheses.
+
+13:23.460 --> 13:25.900
+First of all, let's look at our syntax table.
+
+13:25.900 --> 00:13:29.189
+We're going to add here syntax entries
+
+00:13:29.190 --> 00:13:33.900
+to handle angle brackets as though they were parentheses.
+
+13:33.900 --> 00:13:37.247
+Then we have a lot of types
+
+00:13:37.248 --> 00:13:42.980
+that have colons in them, and those are namespaces in C++.
+
+13:42.980 --> 00:13:45.766
+By default, Emacs does not recognize them
+
+00:13:45.767 --> 00:13:49.134
+as parts of symbols, so we're going to tell Emacs
+
+00:13:49.135 --> 00:13:52.839
+that a colon is something called a symbol constituent,
+
+00:13:52.840 --> 00:13:54.860
+that it can be part of a name.
+
+13:54.860 --> 00:13:57.613
+Once we do that, then we can use our functions
+
+00:13:57.614 --> 00:13:59.442
+like `forward-list`, `backward-word`,
+
+00:13:59.443 --> 00:14:03.288
+all of the navigation and movement functions that we have
+
+00:14:03.289 --> 00:14:06.623
+that do things, that do more complicated things
+
+00:14:06.624 --> 00:14:08.707
+like S-expressions and so on,
+
+00:14:08.708 --> 00:14:11.485
+can be used now with our angle brackets
+
+00:14:11.486 --> 00:14:16.100
+and inside of our types.
+
+NOTE Indent and fill with overlays - Use ancient "pretty printing" algorithms"
+
+14:16.100 --> 00:14:18.462
+The next thing we can do is
+
+00:14:18.463 --> 00:14:21.540
+perform indent and fill with overlays.
+
+14:21.540 --> 00:14:23.735
+We're going to use `before-string` properties
+
+00:14:23.736 --> 00:14:25.630
+to break lines and create indentation
+
+00:14:25.631 --> 00:14:28.900
+to make the output look a little better.
+
+14:28.900 --> 14:35.320
+Today, we fill mostly text and we indent mostly code.
+
+14:35.320 --> 00:14:37.307
+We fill text in order to prevent it
+
+00:14:37.308 --> 00:14:39.902
+from running off the side of the right margin,
+
+00:14:39.903 --> 00:14:43.940
+and we indent code to line up syntactic elements.
+
+14:43.940 --> 14:47.080
+Back in the day, they had algorithms that could do both.
+
+14:47.080 --> 14:52.260
+Those are what we're going to leverage.
+
+NOTE Overlays can mimic line breaks and indentation
+
+14:52.260 --> 00:14:54.582
+We can use the `before-string` property
+
+00:14:54.583 --> 00:14:57.760
+to insert a new line in the correct number of spaces
+
+14:57.760 --> 15:00.240
+to emulate indentation.
+
+15:00.240 --> 00:15:03.525
+As a simplified example, here's some code
+
+00:15:03.526 --> 00:15:07.280
+that will indent 4 upon each open angle bracket.
+
+15:07.280 --> 15:14.520
+Let's give it a try.
+
+NOTE Hiding details - Marking depths with overlays
+
+15:14.520 --> 15:18.280
+The next thing we're going to need to do is hide details.
+
+15:18.280 --> 00:15:22.688
+So we have nested types, and the user is going to want to
+
+00:15:22.689 --> 00:15:27.371
+be able to reveal lower-level or hide lower-level parts
+
+00:15:27.372 --> 00:15:30.131
+of the nested type interactively
+
+00:15:30.132 --> 00:15:35.480
+once we've already reformatted the error messages.
+
+15:35.480 --> 15:40.440
+Let's see how we can do that using invisible properties.
+
+15:40.440 --> 00:15:43.992
+The first thing we're going to do is
+
+00:15:43.993 --> 00:15:46.680
+mark depths within the type.
+
+15:46.680 --> 00:15:49.328
+When we're originally analyzing and formatting
+
+00:15:49.329 --> 00:15:51.920
+and doing the indentation and the line breaks,
+
+15:51.920 --> 00:15:55.071
+at the same time, we're going to go through
+
+00:15:55.072 --> 00:15:58.817
+and mark the nested levels inside the type names,
+
+00:15:58.818 --> 00:16:00.840
+just as this diagram shows.
+
+16:00.840 --> 00:16:03.573
+So depth 1, for example, will be everything
+
+00:16:03.574 --> 00:16:06.120
+inside the first level of angle brackets.
+
+16:06.120 --> 00:16:09.038
+Depth 2 will be everything inside the second level,
+
+00:16:09.039 --> 00:16:09.600
+and so on.
+
+16:09.760 --> 00:16:12.070
+And then later on, when the users request it,
+
+00:16:12.071 --> 00:16:16.303
+we can go and look at the depth that they've selected
+
+00:16:16.304 --> 00:16:19.360
+and then mark those sections invisible.
+
+16:19.360 --> 16:20.520
+Let's see how that might work.
+
+16:20.520 --> 00:16:24.022
+First of all, let's delete the overlays
+
+00:16:24.023 --> 00:16:28.400
+that we already have that created the indentation.
+
+16:28.400 --> 00:16:32.419
+Now we're going to go and do that marking
+
+00:16:32.420 --> 00:16:35.740
+with the custom depth properties here.
+
+16:35.740 --> 00:16:38.760
+To prove that I didn't pull a fast one,
+
+00:16:38.761 --> 00:16:42.082
+let's go and see what `describe-char` tells us
+
+00:16:42.083 --> 00:16:44.660
+about the depths inside here.
+
+16:44.660 --> 16:46.460
+Let's start here.
+
+16:46.460 --> 16:52.820
+Okay, so inside this part here, `std::string`,
+
+16:52.820 --> 16:54.980
+There are two overlays.
+
+16:54.980 --> 00:16:57.780
+One of them is of depth 1, and the other is of depth 2,
+
+00:16:57.781 --> 00:17:00.601
+which makes sense, because depth 1 is going to be
+
+00:17:00.602 --> 00:17:02.011
+from about here to here,
+
+00:17:02.012 --> 00:17:07.660
+and depth 2 is going to be from about here to this area.
+
+17:07.660 --> 00:17:10.829
+So it's reasonable that there should be two,
+
+00:17:10.830 --> 00:17:12.660
+and that's what we expect.
+
+NOTE Hiding to a target depth
+
+17:12.660 --> 00:17:17.353
+Now that we've marked the nested types with their depths,
+
+00:17:17.354 --> 00:17:21.380
+let's experiment with hiding details.
+
+17:21.380 --> 00:17:26.773
+This fragment of code takes a user-supplied depth,
+
+00:17:26.774 --> 00:17:29.085
+in this case 2, and will hide,
+
+00:17:29.086 --> 00:17:30.875
+based on those markings
+
+00:17:30.876 --> 00:17:33.932
+that we've already made on the overlays,
+
+00:17:33.933 --> 00:17:36.020
+the custom depth properties.
+
+17:36.020 --> 17:40.020
+We'll take those and apply your requested level of detail.
+
+17:40.020 --> 17:42.020
+So let's try it out.
+
+17:42.020 --> 17:43.020
+Depth 2.
+
+17:43.020 --> 00:17:46.005
+All right, that hid everything under the `std::map`,
+
+00:17:46.006 --> 00:17:47.260
+so the deepest level.
+
+17:47.260 --> 17:52.140
+If we make it 1, we should get a level higher than that.
+
+17:52.140 --> 17:54.540
+So now level 1 and below are hidden.
+
+17:54.540 --> 17:59.660
+Now if we put it back to 3, it should reveal everything.
+
+17:59.660 --> 18:04.900
+So that's what we're going to use in our minor mode.
+
+NOTE Demo
+
+18:04.900 --> 18:05.900
+Let's have a demo.
+
+18:05.900 --> 00:18:08.538
+We're going to revisit the initial example
+
+00:18:08.539 --> 00:18:10.380
+with the minor mode installed.
+
+18:10.380 --> 00:18:12.101
+Now we're going to have a compilation filter
+
+00:18:12.102 --> 00:18:13.593
+that will run on every chunk of output
+
+00:18:13.594 --> 00:18:15.780
+produced by the compiler.
+
+18:15.780 --> 00:18:17.849
+It's going to add those overlays
+
+00:18:17.850 --> 00:18:20.420
+with the line breaks and the indentation.
+
+18:20.420 --> 00:18:22.206
+It's also going to add overlays
+
+00:18:22.207 --> 00:18:23.880
+that mark up the nested types
+
+00:18:23.881 --> 00:18:26.220
+with the depths for each region.
+
+18:26.220 --> 18:31.580
+Let's add the hook for `tspew-mode`.
+
+18:31.580 --> 18:37.220
+And now we can compile again.
+
+18:38.220 --> 00:18:41.503
+All right, we can already see
+
+00:18:41.504 --> 00:18:47.195
+that these things are formatted a little bit better
+
+00:18:47.196 --> 00:18:49.180
+than they were before.
+
+18:49.180 --> 18:50.180
+They're not all on one line.
+
+18:50.180 --> 18:53.580
+Things are getting kind of lined up here.
+
+18:53.580 --> 19:05.620
+Here's a good example.
+
+19:05.620 --> 00:19:08.637
+And here's our big ugly one from before
+
+00:19:08.638 --> 00:19:10.900
+with all the characters in it.
+
+19:10.900 --> 19:14.500
+Let's try hiding some of this information.
+
+19:14.500 --> 00:19:17.431
+We'll just slowly decrease the level of detail
+
+00:19:17.432 --> 00:19:19.740
+and you can see how it works.
+
+19:19.740 --> 00:19:22.333
+Over here, where there's these ellipses
+
+00:19:22.334 --> 00:19:25.460
+next to string constant, the "..." there,
+
+19:25.460 --> 00:19:30.386
+that's where we are starting to hide information
+
+00:19:30.387 --> 00:19:32.900
+and go to the next level.
+
+19:32.900 --> 19:36.460
+Hiding more, hiding more, hiding more.
+
+19:36.460 --> 19:38.220
+Now we can go back and start adding it back.
+
+19:38.220 --> 00:19:42.736
+You can see here now we just have about four layers,
+
+00:19:42.737 --> 00:19:45.540
+which is a lot easier to understand.
+
+19:45.540 --> 00:19:47.733
+And if we start understanding what it is
+
+00:19:47.734 --> 00:19:52.180
+and we need more detail, we can just increase detail again.
+
+19:52.180 --> 00:19:55.402
+And every time we increase or decrease detail,
+
+00:19:55.403 --> 00:19:58.900
+it reformats so it still stays kind of consolidated
+
+19:58.900 --> 19:59.900
+and nice looking.
+
+19:59.900 --> 20:01.980
+Let's increase it a little bit more.
+
+20:02.060 --> 20:04.540
+Okay, so you can see how that worked.
+
+20:04.540 --> 20:08.340
+Let's go back to our presentation.
+
+20:08.340 --> 20:10.220
+All right.
+
+NOTE Conclusion
+
+20:10.220 --> 00:20:12.996
+In conclusion, we saw how we could solve
+
+00:20:12.997 --> 00:20:15.367
+a real problem for C++ programmers
+
+00:20:15.368 --> 00:20:18.534
+by combining several Emacs features: overlays,
+
+00:20:18.535 --> 00:20:20.489
+compilation mode extensions,
+
+00:20:20.490 --> 00:20:25.700
+and balanced expression navigation using syntax tables.
+
+20:25.700 --> 00:20:27.978
+Emacs is often compared unfavorably
+
+00:20:27.979 --> 00:20:31.460
+to newer IDEs and editors with slicker user interfaces.
+
+20:32.220 --> 00:20:36.386
+What Emacs has that they don't is powerful abstractions,
+
+00:20:36.387 --> 00:20:38.862
+tons of libraries, and decades of work
+
+00:20:38.863 --> 00:20:42.100
+by some of the luminaries in the field of software.
+
+20:42.100 --> 00:20:45.343
+I think that this project would have been much harder to do
+
+00:20:45.344 --> 00:20:48.020
+in a prettier but less powerful environment.
+
+20:48.020 --> 20:50.860
+In short, there's plenty of hope for Emacs.
+
+20:50.860 --> 20:51.220
+Thank you.
-- 
cgit v1.2.3