Category: bugs

Fun with Flutter

Fun with Flutter

Posted on by David

So I upgraded Flutter to 3.35 and tried building an app for the Web. It failed with a weird error about the js package being deprecated. Errors a bit like this:

Target dart2js failed: ProcessException: Process exited abnormally with exit code 1:
Error: Couldn’t resolve the package ‘libphonenumber_web’ in ‘package:libphonenumber_web/libphonenumber_web.dart’.
.dart_tool/flutter_build/6872c759b3585597f59b4a698a13ca94/web_plugin_registrant.dart:9:8:
Error: Not found: ‘package:libphonenumber_web/libphonenumber_web.dart’
import ‘package:libphonenumber_web/libphonenumber_web.dart’;

I’d been experimenting with flutter_login package and it was in the projects pubspec.yaml.  I found this out by using this command:

flutter pub deps

Which provides a full and detailed tree of all package dependencies. Like this but 260 lines in total!

turfwar 1.0.0+1
|– badges 3.1.2
| ‘– flutter…
|– cupertino_icons 1.0.8
|– flutter 0.0.0
| |– characters 1.4.0
| |– collection 1.19.1
| |– material_color_utilities 0.11.1
| | ‘– collection…
| |– meta 1.16.0
| |– sky_engine 0.0.0
| ‘– vector_math 2.2.0
|– flutter_lints 6.0.0
| ‘– lints 6.0.0
|– flutter_test 0.0.0

js was used by libphonenumber which was part of flutter_login.  However despite removing that from pubspec.yaml and removing the package files, the flutter build web command was still complaining about it.

The trick to solving that is just to delete the .dart_tool folder. It’s regenerated by the flutter build command so is safe to delete.

Flutter project screenshot

There’s a new feature now, you can add –wasm on the end of the flutter build web command to have it use wasm. More on this official flutter wasm page which includes a link to a neat demo project called wonderous that is worth a look; the source to that is available on GitHub as well..

Great mysteries – number 1

Great mysteries – number 1

Posted on by David

Hyper-v that refuses to become fullscreen!I run Ubuntu in a hyper-V session.  It works very well and handy for getting screenshots. I’ve been using a 24.04 LTS for a while and decided I needed another one to test CyberPanel. i already have Webmin on my main one so wanted a clean Ubuntu so as not to mess Webmin.  It took ten minutes to setup then another 20 minutes to install 300+ updates.

Then I edited Grub to give me a fullscreen- 1920 x 1080.  You just edit /etc/default/grub with an editor run under sudo. I use Gedit but nano will do. Just change the line to this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video=hyperv_fb:1920x1080"

followed by

sudo update-grub

and that should be it. Only it didn’t work in my new Ubuntu 24.04 LTS VM. I installed ifconfig from net-tools, connected to it from my Windows PC and copied grub across. I did the same with my older 24.04 LTS VM and compared the two grub files. Both identical yet one works fullscreen and the newer one doesn’t. Any ideas?

Rust on Windows – problem with sdl2.lib

Rust on Windows – problem with sdl2.lib

Posted on by David

I’m currently unable to compile Rust programs that use SDL2 on Windows. No problems on Ubuntu or Raspberry Pi OS, just Windows 11.
Compiling an SDL2 app (in Rust) on WindowsAlthough it says cannot open input file SDL2.lib, I think the problem is a parameter passed into Link.exe.

The text from the image above is listed below- I’ve broken it to make it readable as it’s displayed preformatted and unmodified it is all on a single very wide line!

 = note: "C:\\Program Files\\Microsoft Visual Studio\22\\Community\\VC\\Tools\\MSVC\.43.34808\\bin\\HostX64\\x64\\link.exe" 
"/NOLOGO" "C:\\Users\\dhbol\\AppData\\Local\\Temp\\rustcA1PhoK\\symbols.o" "<70 object files omitted>" 
"D:\\development\\rustapps\\choice\\target\\debug\\deps/{libsdl2-f8d94d30d19bed49.rlib,libsdl2_sys-325e30d8e9547ff4.rlib,
libbitflags-d15393d08e2f31fc.rlib,liblazy_static-c28c0e13093a4168.rlib,liblibc-851e0bf801239f69.rlib}.rlib" 
"<sysroot>\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib/{libstd-*,libpanic_unwind-*,libwindows_targets-*,
librustc_demangle-*,libstd_detect-*,libhashbrown-*,librustc_std_workspace_alloc-*,libunwind-*,libcfg_if-*,liballoc-*,
librustc_std_workspace_core-*,libcore-*,libcompiler_builtins-*}.rlib" "SDL2.lib" "SDL2_image.lib" "SDL2_ttf.lib" 
"legacy_stdio_definitions.lib" "kernel32.lib" "kernel32.lib" "advapi32.lib" "ntdll.lib" "userenv.lib" "ws2_32.lib" 
"dbghelp.lib" "/defaultlib:msvcrt" "/NXCOMPAT" "/OUT:D:\\development\\rustapps\\choice\\target\\debug\\deps\\choice.exe" 
"/OPT:REF,NOICF" "/DEBUG" "/PDBALTPATH:%_PDB%" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\intrinsic.natvis" 
"/NATVIS:<sysroot>\\lib\\rustlib\\etc\\liballoc.natvis" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\libcore.natvis" 
"/NATVIS:<sysroot>\\lib\\rustlib\\etc\\libstd.natvis"
= note: some arguments are omitted. use `--verbose` to show all linker arguments
= note: LINK : fatal error LNK1181: cannot open input file 'SDL2.lib'␍

But if you try running part of it like the first line
“C:\\Program Files\\Microsoft Visual Studio\\2022\\Community\\VC\\Tools\\MSVC\\14.43.34808\\bin\\HostX64\\x64\\link.exe”
“/NOLOGO” “C:\\Users\\dhbol\\AppData\\Local\\Temp\\rustcA1PhoK\\symbols.o”

Well the path to link..exe is correct, but there’s no  rustcA1PhoK\symbols.o in that temp folder. Any suggestions welcomed…

I just solved it.

I’ve left this in, in case anyone else has this problem.

You need to add an environment variable LIB with the address of the SDL .lib files including ttf, image and mixer. Make sure they’re all in this folder:

C:\Users\dhbol\.rustup\toolchains\stable-x86_64-pc-windows-msvc\lib

The bold part of the path will be different on you PC.

In File Explorer, right-click on This PC then click Properties on the popup menu.

File Explorer - This PC,.

 

 

 

It’ll open Settings – About, and you need to click Advanced system settings.

settings_about

This opens System Properties and on that you click Environment variables.

System properties on Windows

Environment variables popup on Windows

 

 

 

 

 

 

 

 

Now just click New and add Lib and that path It should look something like mine. Now reopen Visual Studio and your SDL2 Rust app should now build and run.

Interesting bug with controllermap

Interesting bug with controllermap

Posted on by David

Running a Rust program to show gamepad controls

So I’ve been playing with a Rust program that uses the config string generated by controllermap. It shows all the keys and the text of a particular button turns green when you press it and it shows PRESSED/RELEASED.

But it got A and B buttons mixed up and also X and Y. I’d press A, it highlighted B etc.

I checked my code, it wasn’t there. I ran controllermap again and it generated a similar config string.

I then went back to the Pi version of Asteroids, put it on a Pi, started debugging it, pressed the fire button and it hit the line of code for the A button. D’oh.

The only conclusion I can come up with is that controllermap gets it wrong for my gamepad. I had somehow missed it when I added gamepad control for the Asteroid Pi.

It’s quite easy to fix.  This is what the full text in gamepad.txt look like.

030000001008000001e5000010010000,usb gamepad,platform:Linux,crc:417e,a:b2,b:b1,x:b3,y:b0,back:b8,start:b9,leftshoulder:b4,rightshoulder:b5,leftx:a0,lefty:a1,

but we’re only interesed in the button mappings for a,b, x and y which are in bold.

a:b2,b:b1,x:b3,y:b0,

Just swap the a b mappings and the x and y so it looks like

a:b1,b:b2,x:b0,y,b3

Then save the file and it now works correctly.

 

Yet another fix

Yet another fix

Posted on by David

But no AI generated image this time.

The problem seems to be with Electron which is the technology that drives VS Code.

Normally I use code or code . when I’ve opened a terminal and done a cd to the folder containing the project.

What fiuxes the VS Code crash with Error 5 is adding this on the end of the command

--js-flags="--nodecommit_pooled_pages"

so use either of these.

code --js-flags="--nodecommit_pooled_pages" or 

code . --js-flags="--nodecommit_pooled_pages"

I’ve tested it with my Pi 4 and it has been rock solid. The bug report and the fix are here on GitHub.

So I bought a Raspberry PI 5 and VS Code crashes!

So I bought a Raspberry PI 5 and VS Code crashes!

Posted on by David

Crash on VS Code running on a Reaspberry Pi 5.

And the first thing I did after assembling it, was install VS Code and Rust.  And irritatingly, there’s some kind of a bug with the current version of VS Code. 1.97.

Open a project- say for a Rust application and view the source code. After a few seconds or so it crashes with a The window terminated unexpectedly (reason: ‘crashed’, code 5).

I also updated my Raspberry Pi 4B, installed Rust and got the same crash with it.

Thankfully Raspis come with grim which lets you do screenshots on Wayland.

Want to know if your system is running Wayland? From a terminal run this command:

echo “$XDG_SESSION_TYPE”

And you’ll either get wayland or x11.

So I hope the VS Code issue gets fixed soon.

So I found the fix

So I found the fix

Posted on by David

It's fixed text on a technology backgroundWell actually I asked Microsoft’s CoPilot AI and it sorted it!

This is what you need in the dependencies section in cargo.toml

[dependencies]
sdl2-sys = "*"
sdl2 = { version = "0.37", features = ["image","ttf"] }

It compiled with no problems after saving that.

A slight problem with SDL2 and Rust

A slight problem with SDL2 and Rust

Posted on by David

VS Code Rust SDL Copikle problemThis is on Ubuntu 24.04 LTS. I’ve installed the dev versions of SDL2, including images and TTF.  You can read how to install them in this tutorial.

Once that’s done you add them to the rust project with commands like this

cargo add sdl2

You can see these instruction in the relevant crates pages. For instance SDL2 crate, SDL2 Image and SDL2 TTF.

So far so good. The cargo add added the crates into cargo.toml as expected but when I compiled it. Not a compile error as such but a version of dll hell.

The text in that image says:

Updating crates.io index
error: failed to select a version for `sdl2-sys`.
... required by package `sdl2_image v0.25.0`
... which satisfies dependency `sdl2_image = "^0.25.0"` of package `sdl1 v0.1.0 (/home/david/rust/sdl1)`
versions that meet the requirements `^0.25.0` are: 0.25.0

the package `sdl2-sys` links to the native library `SDL2`, but it conflicts with a previous package which links to `SDL2` as well:
package `sdl2-sys v0.37.0`
... which satisfies dependency `sdl2-sys = "^0.37.0"` of package `sdl1 v0.1.0 (/home/david/rust/sdl1)`
Only one package in the dependency graph may specify the same links value. This helps ensure that only one copy of a native library is linked in the final binary. Try to adjust your dependencies so that only one package uses the `links = "SDL2"` value. For more information, see https://doc.rust-lang.org/cargo/reference/resolver.html#links.

failed to select a version for `sdl2-sys` which could resolve this conflict

The problem appears to be a clash between sdl-sys and sdl2-ttf or sdl2-image. If anyone knows a fix…

 

Yet another curious bug

Yet another curious bug

Posted on by David

MatchThree latest version with a bugI’m aware that C is notorious for unexpected behaviour (UB). Let me describe this bug:

My second game in C + SDL for my newest eBook is Match Three and compiled with Clang-11 on my Raspberry Pi 4B. I’m getting a weird bug that doesn’t occur when I compile it on Windows under MSVC; the only differences between the source code on the PI and Windows are the paths to SDL and the sn._s calls but there aren’t many of those. Also I compiled it with clang-14 on Ubuntu 22.04 LTS on a Hyper-VM and that behaves properly.

 

Each piece is held a struct in a 10 x 10 array. One field is  called size. It’s 0 normally but if it is set to a value, typically  64 then it counts down, one per frame and the piece is drawn rotated by 8 degrees each frame. When it reaches 0 the piece is removed. This is my “down the plughole” way of removing pieces. It takes exactly 64/60 seconds to vanish. I use the size field to draw it when size is non-zero so it shrinks as it rotates It’s a nice effect.

 

The bug though is that when it starts up, several pieces start rotating and keep rotating. The size field stays at 63. There’s no code that explains this behaviour and it only happens on the Raspberry Pi, not on Windows or on Ubuntu. Is it a compiler bug or some weird UB on the PI version. It’s an interesting bug and I’ve only wasted a week of evenings on it so far!

How to debug programs using SDL

How to debug programs using SDL

Posted on by David

Terminal fprintf outputThere’s nothing worse than a program halting with a simple “Segmentation fault” and no idea where or why. It happened to me today working on the 2nd eBook (for Raspberry Pi) and I had to figure out where it was going wrong.

In the end it was a really silly bug, I was trying to load masks but had left the masks/ folder out of the filename.

How did I find it? I sprinkled a few fprintf(stderr,”message”); throughout the program changing “message” to something appropriate and launched it from a terminal. I’d thought it was in a function LoadTextures() so added a call before and after but you can see that worked and the segmentation fault happened after LoadTextures().

So I added it before and after LoadMasks() and my second run it happened before it reached the After LoadMasks message.

Note, I used stderr as the output path because, unlike stdout which is buffered and can be cleared, anything sent to stderr appears immediately.  More about this in this offsite article.

The using SDL part of the title is just to show that you can find bugs even in programs that use SDL.