Improve directory redirects and strict entry-file handling for root folders and VFS

[triuk]

Summary

This PR improves directory redirect and fallback behavior when serving UI content from either a root folder or a VFS. It also adds default arguments to the C++ show(), show_browser(), and start_server() APIs.

The main change is in the resolution logic for directory requests, including nested subdirectories.

---

Core

Redirects / fallback / err404 now work consistently for any directory depth across all modes (server / vfs) combination.

If a custom entry file is defined, for example:

• start_server("custom.html")
• show("custom.html")
• show_browser("custom.html", ...)

then requests such as:

• /
• /sub
• /sub/foo

with or without a trailing slash, resolve to:

• /custom.html
• /sub/custom.html
• /sub/foo/custom.html

Trailing-slash redirects are normalized, so paths such as /sub/ and /sub/foo/ do not generate double slashes in Location.

If no custom filename is defined:

• start_server()
• show()
• show_browser()

WebUI falls back to the hardcoded index list in this order:

1. index.html
2. index.htm
3. index.ts
4. index.js

This also works for nested subdirectories.

If an explicit filename does not exist, for example:

• start_server("not_exists.html")
• show("not_exists.html")
• show_browser("not_exists.html", ...)

then the request remains strict and returns Resource Not Available.
This avoids implicit "magic" behavior and keeps the intent explicit:

• use an explicit filename when an exact file is required
• use an empty argument when fallback behavior is desired

---

API usage

C server mode

Explicit custom entry file:

(void)webui_start_server(window, "custom.html");

Fallback mode using the hardcoded index.* list:

(void)webui_start_server(window, "");

C normal mode

Explicit custom entry file:

webui_show(window, "custom.html");
webui_show_browser(window, "custom.html", AnyBrowser);

Fallback mode using the hardcoded index.* list:

webui_show(window, "");
webui_show_browser(window, "", AnyBrowser);

C++ server mode

Explicit custom entry file:

window_.start_server("custom.html");

Fallback mode using the hardcoded index.* list:

window_.start_server();

C++ normal mode

Explicit custom entry file:

window_.show("custom.html");
window_.show_browser("custom.html");

Fallback mode using the hardcoded index.* list:

window_.show();
window_.show_browser();

In C++, show_browser() now defaults to AnyBrowser when no browser is specified.

---

Examples

This PR adds dedicated test_index_redirect examples for both C and C++.
The test binaries accept --server and --vfs, so the redirect behavior can be checked across all relevant combinations.

Do not forget to change set_root_folder path according to your situation when using non-vfs mode.

This PR also updates the VFS example generators:

• all example vfs.py scripts were unified to the same v2.0 generator format
• generation of the default index list inside vfs.py was removed
• all corresponding vfs.h files were regenerated

---

Notes

The redirect / fallback / err404 behavior was verified for:

• root-folder mode / VFS mode | server / non-server
• custom entry file present / empty argument fallback / custom entry file non-existent
• nested subdirectories
• trailing slash variants
• Linux / Windows

---

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: a868e13168

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Split custom index paths with Windows separators

When deriving the per-folder custom entry filename, the code only looks for '/' via strrchr(user_index, '/'). On Windows, callers commonly pass paths like sub\custom.html; this leaves filename as the full sub\custom.html, so a request to /sub probes ...\sub\sub\custom.html instead of ...\sub\custom.html and fails to redirect. This breaks the new nested-directory custom-entry behavior for backslash-formatted paths.

Useful? React with 👍 / 👎.

[AlbertShown]

Not sure, is request her refer to browser url request, or to path in arguments?

[AlbertShown]

Thank you @triuk for the PR, looks like you solved the puzzle. I will re-test it again after merge, but look like we have some examples build error that prevent it from margin.

[triuk]

Yes, I'll look at those automatic suggestions and build errors. I've only tested it on my Win/Lin setup and did the PR at 2 am :)
The merging probably not fails due to failed builds, but from failed "resolve" of those automatic Chatgpt codex suggestions, as I have it active for PR - I'll address it tomorrow. After that, I think it should merge.
@AlbertShown meanwhile you could check it using my fork: https://github.com/triuk/webui/tree/main

[AlbertShown]

I think the build issue is due to the missing Makefile and GNUmakefile in examples/C/test_index_redirect

[AlbertShown]

examples/C++/test_index_redirect as well