# minimgui

Experimental immediate-mode GUI without IDs.

# Libraries

- [stb_image](https://github.com/nothings/stb/blob/master/stb_image.h)
- [stb_truetype](https://github.com/nothings/stb/blob/master/stb_truetype.h)

# Scope And Purpose

This is mostly just a proof-of-concept. It's not intended to be used for serious work yet.
There's currently just a software backend, so no accelerated graphics yet.
Currently, only Linux + X11 is supported.

IMGUIs typically come in two forms:
    - Dear ImGui-like: functions either explicitly accept an ID argument or use
      static arguments (like labels) to generate an ID. The obvious problems
      are that the user has to manually make sure the IDs are unique, since
      using the same ID multiple times will cause issues. Serious
      implementations use an ID stack to mitigate this, however, it can still
      cause issues:
      [Dear ImGui FAQ](https://github.com/ocornut/imgui/blob/master/docs/FAQ.md#q-about-the-id-stack-system)
    - Unity-like: Unity's IMGUI implicitly assigns incremental IDs that reset every frame.
      This fixes the problem of always needing a unique value and simplifies the API.
      However, IDs are still used, it's just largely opaque to the user.
      Because of the per-frame incremental nature of IDs, aliasing can happen dynamically
      depending on which code path is executed, which is very annoying to debug and fix,
      since you have to increase the ID counter by the exact amount necessary
      to make up for the omitted GUI calls, which isn't always 1:1, since more complex calls
      might use multiple IDs.

The reason conventional IMGUIs use IDs is that they need to 1. remember
state across frames and 2. detect when one UI element hides another. The first
problem is trivially solved by pushing the responsibility of storing state onto
the user, so IDs aren't strictly necessary here. This might seem like more
work for the user, but in practice, anywhere there's state, the user's already
storing some data. For example, text-fields require the user to store the
string anyway, so using a state object as opposed to a string doesn't add
complexity for the user. The only difference is that he now needs to access the
field of a struct (or call a toString() method) to access the string, instead
of storing the string directly. The second problem is more subtle. Take the
following pseudocode:
```
rect = getSomeRect();
if (button("Button 1", rect))
    print("Button 1 pressed");
if (button("Button 2", rect))
    print("Button 2 pressed");
```
Both Button 1 and 2 are in the same position on the screen, but with back-to-front
rendering, Button 2 is drawn on top. However, the code for Button 1 executes first,
so the implementation can't just return true if the cursor is inside Button 1's
bounds. In practice, IMGUIs have some sort of `clicked_id` and `propagated_click_id`.
When the user clicks, the code for Button 1 runs, which sets `propagated_click_id`
to "Button 1", then the code for Button 2 runs, which sets `propagated_click_id`
to "Button 2". At the end of the frame, `clicked_id` is set to the last value of
`propagated_click_id` (in this case "Button 2"), and then, on the next frame,
`button("Button 2", rect)` will return true.

There is a related, more complex, aliasing/desync bug that mostly occurs when dealing
with text input fields/areas in Unity-like (incremental) IMGUIs:
Even when the user stores the states of input elements,
some level of arbitration between the inputs is necessary to avoid situations like
multiple input fields being focused simultaneously. So the library internally stores
the ID of the currently focused element, which leads to the aforementioned problems
with IDs changing depending on which code paths are taken, leading to focus changing
seemingly at random.

Minimgui completely eliminates IDs.
This is done by rendering front-to-back, instead of the usual back-to-front.
If we simply declare that elements will be rendered front-to-back, "Button 1"
can just return true (and set some internal `click_consumed` bool to inhibit
following elements from handling clicks), since it's the top-most element.
This has two benefits: Firstly and most obviously, we no longer need IDs. Secondly,
we no longer have a 1-frame delay, since we immediately know whether an element
was clicked. Of course, conventional IMGUIs can mitigate this in all
sorts of ways: Unity does multiple GUI passes, which also allows automatically managing
more complex layouts (though in practice this is difficult to work with). Some implementations
do a hit test on click-start and return the hit result on click-end, though of course
this complicates internals and reduces flexibility.

While front-to-back might seem awkward, at the end of the day it's just a different
convention, and all the weirdness from having to dispatch rendering commands
backwards is limited to low-level internal functions that most users will never
interact with. So the only thing that changes from an API point-of-view is that
the user no longer needs to worry about IDs or aliasing, and the mental model
of drawing one element on top of another is replaced by drawing one element
behind another.

# Roadmap

- [x] Figure out a way to have an imgui without IDs
- [x] Implement MVP
    - [x] Rectangle
    - [x] Image
    - [x] Click
    - [x] Drag and Drop
    - [x] Rudimentary Text
- [ ] Port to MS Windows
- [ ] Add OpenGL backend
- [ ] Clean up project
    - [ ] Separate input handling library from project
    - [ ] Separate window handling library from project
    - [ ] Isolate Backends
    - [ ] Remove example/testing app

# Build

Requires zig 0.15

## As Executable (and run)

```
git clone git.vandorp.lu/minimgui
cd minimgui
zig build -Demit-exe
zig-out/bin/minimgui
```

## As Library (C-ABI)

```
git clone git.vandorp.lu/minimgui
cd minimgui
zig build -Demit-lib
```

# Examples

See src/app/app.zig, bindings/main.c, and bindings/main.py

# Contributing

If you have any ideas or issues, send them to steven@vandorp.lu.

If you want to modify code, make your changes in a separate branch,
generate the patch(es) (`git format-patch master` from inside your branch)
and send the patch file(s) to steven@vandorp.lu.

# License

MIT License

Copyright (c) 2026 Steven Van Dorp

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.