imgui

A Dear ImGui binding for hica. Immediate-mode GUI backed by Dear ImGui + SDL2 + OpenGL3, with the Inter font and the Ilseon dark theme bundled out of the box. Includes ImPlot for 2-D plotting.

Installation

1. Install SDL2

brew install sdl2                   # macOS
# sudo apt install libsdl2-dev      # Linux

2. Add the package

hica add imgui
hica fetch

This records the dependency in hica.hml and downloads the package.

3. Download the pre-built static library

hica fetch downloads the hica source files; the compiled C++ backend must be obtained separately (it contains native code that cannot be distributed as plain hica):

mkdir -p vendor/imgui/lib

# macOS Apple Silicon:
curl -L https://github.com/cladam/imgui/releases/latest/download/libimgui_hica-macos-arm64.a \
     -o vendor/imgui/lib/libimgui_hica.a

# Linux x86-64:
# curl -L https://github.com/cladam/imgui/releases/latest/download/libimgui_hica-linux-x86_64.a \
#      -o vendor/imgui/lib/libimgui_hica.a

Alternatively, build from source (requires clang++ and SDL2 dev headers):

cd vendor/imgui && ./build.sh

4. Configure hica.hml

Add the linker flags to your project's hica.hml. Run sdl2-config --libs to find the SDL2 lib path on your machine.

macOS:

@koka {
    flags: "--cclinkopts=-L./vendor/imgui/lib --cclinkopts=-L/opt/homebrew/opt/sdl2/lib --cclib=imgui_hica --cclib=SDL2 --cclinkopts=-lc++ --cclinkopts=-framework --cclinkopts=OpenGL"
}

Linux:

@koka {
    flags: "--cclinkopts=-L./vendor/imgui/lib --cclib=imgui_hica --cclib=SDL2 --cclib=GL"
}

5. Import

import "imgui"

Quick start

import "imgui"

fun main() {
  var count = 0

  gui_window("My App", 520, 360, () => {
    gui_text("Counter: " + show(count))
    if gui_button("Increment") {
      count = count + 1
    }
  })
}

gui_window opens the OS window, runs the event loop, and calls your lambda every frame. Close the window to exit.

API

Window

Function	Signature	Purpose
gui_window	(title: string, w: int, h: int, frame: () -> ()) -> ()	Open window and run the frame loop

gui_window handles gui_init, gui_begin_frame / gui_end_frame, and gui_shutdown for you. Call the low-level lifecycle functions directly only if you need custom control.

Lifecycle (low-level)

Function	Signature	Purpose
gui_init	(title: string, w: int, h: int) -> ()	Open window, init SDL2 + OpenGL + ImGui
gui_begin_frame	() -> bool	Start frame; returns false when window is closed
gui_end_frame	() -> ()	Render and swap buffers
gui_shutdown	() -> ()	Tear down ImGui, SDL2, OpenGL

Widgets

All widgets must be called between gui_begin_frame() and gui_end_frame() — or inside the gui_window lambda.

Function	Signature	Purpose
gui_text	(s: string) -> ()	Static text label
gui_text_colored	(s: string, r: float, g: float, b: float, a: float) -> ()	Text in an RGBA colour (channels 0.0–1.0)
gui_text_wrapped	(s: string) -> ()	Text that wraps at the window edge
gui_bullet_text	(s: string) -> ()	Bullet point + text
gui_button	(label: string) -> bool	Button; returns true on the click frame
gui_checkbox	(label: string, checked: bool) -> bool	Toggle; returns current state
gui_slider_int	(label: string, min: int, max: int, default: int) -> int	Integer slider; returns current value
gui_slider_float	(label: string, min: float, max: float, default: float) -> float	Float slider; returns current value
gui_drag_int	(label: string, min: int, max: int, default: int, speed: float) -> int	Click-drag int control; speed ≈ change per pixel
gui_drag_float	(label: string, min: float, max: float, default: float, speed: float) -> float	Click-drag float control
gui_input_text	(label: string, capacity: int) -> string	Single-line text input; returns current content
gui_input_int	(label: string, default: int) -> int	Integer input field with +/- buttons
gui_input_float	(label: string, default: float) -> float	Float input field
gui_radio_button	(label: string, active: bool) -> bool	Radio button; returns true when clicked (caller manages which is selected)
gui_selectable	(label: string, selected: bool) -> bool	Clickable row; returns current selected state (widget owns state)
gui_combo	(label: string, items: string, default: int) -> int	Dropdown; items is newline-separated ("A\nB\nC"); returns selected index
gui_progress_bar	(fraction: float, overlay: string) -> ()	Horizontal bar filled 0.0–1.0; overlay="" shows default XX% label

Layout helpers

Function	Signature	Purpose
gui_separator	() -> ()	Horizontal rule
gui_same_line	() -> ()	Place next widget on the same line
gui_new_line	() -> ()	Undo a same_line; move to the next line
gui_spacing	() -> ()	Extra vertical gap
gui_dummy	(w: float, h: float) -> ()	Invisible spacer of exact pixel size
gui_indent	() -> ()	Push indent (shift subsequent widgets right)
gui_unindent	() -> ()	Pop indent

Panels

Function	Signature	Purpose
gui_begin_panel	(label: string) -> bool	Start a collapsible section; returns true when expanded
gui_end_panel	() -> ()	End the collapsible section

Call gui_end_panel() only when gui_begin_panel() returns true:

if gui_begin_panel("Settings") {
  gui_slider_int("Volume", 0, 100, 80)
  gui_end_panel()
}

Containers & structure

Helper	Signature	Purpose
gui_child	(id: string, w: float, h: float, content: () -> ()) -> ()	Scrollable child region
gui_tree	(label: string, content: () -> ()) -> ()	Collapsible tree node
gui_with_item_width	(w: float, content: () -> ()) -> ()	Constrain next widget width in pixels
gui_tab_bar	(id: string, content: () -> ()) -> ()	Tab bar container
gui_tab	(label: string, content: () -> ()) -> ()	One tab inside a gui_tab_bar

Tooltips

Function	Signature	Purpose
gui_tooltip	(text: string) -> ()	Show a text tooltip when the previous widget is hovered
gui_set_tooltip	(text: string) -> ()	Raw version (same behaviour)
gui_begin_tooltip	() -> bool	Start a custom-content tooltip region
gui_end_tooltip	() -> ()	End the tooltip region

Popups

Helper	Signature	Purpose
gui_open_popup	(id: string) -> ()	Schedule a popup to open next frame
gui_popup	(id: string, content: () -> ()) -> ()	Non-blocking popup window
gui_modal	(id: string, content: () -> ()) -> ()	Blocking modal dialog
gui_close_popup	() -> ()	Dismiss the current popup from within its block

if gui_button("Options") { gui_open_popup("opts") }
gui_popup("opts", () => {
  if gui_menu_item("Reset") { ... }
  if gui_button("Close")   { gui_close_popup() }
})

Menu bar

Helper	Signature	Purpose
gui_main_menu	(content: () -> ()) -> ()	Top-level OS menu bar
gui_menu	(label: string, content: () -> ()) -> ()	Drop-down menu inside a bar or another menu
gui_menu_item	(label: string) -> bool	Clickable item; returns true when clicked

gui_main_menu(() => {
  gui_menu("File", () => {
    if gui_menu_item("Save") { save() }
    if gui_menu_item("Quit") { }
  })
})

Tables

Function	Signature	Purpose
gui_begin_table	(id: string, columns: int, flags: int) -> bool	Start a table; returns true when visible
gui_end_table	() -> ()	End the table
gui_table_setup_column	(label: string) -> ()	Define a column header label
gui_table_headers_row	() -> ()	Emit the header row from setup columns
gui_table_next_row	() -> ()	Advance to the next row
gui_table_next_column	() -> ()	Advance to the next cell

Common flag values (combine with +):

Value	Meaning
0	Plain table, no decorations
1	Inner cell borders
2	Outer border
3	Both borders
64	Alternating row background
67	Borders + alternating rows (most common)

if gui_begin_table("##scores", 3, 67) {
  gui_table_setup_column("Player")
  gui_table_setup_column("Score")
  gui_table_setup_column("Level")
  gui_table_headers_row()
  gui_table_next_row()
  gui_table_next_column()  // cell [0,0]
  gui_text("Alice")
  gui_table_next_column()  // cell [0,1]
  gui_text("1024")
  gui_table_next_column()  // cell [0,2]
  gui_text("12")
  gui_end_table()
}

Widget state

Sliders, checkboxes, and text inputs manage their own persistent state keyed by label string. Read the return value each frame to get the current value, the hica var bindings work naturally:

var volume = 80
var muted  = false

gui_window("Player", 400, 200, () => {
  volume = gui_slider_int("Volume", 0, 100, volume)
  muted  = gui_checkbox("Mute", muted)
  if muted {
    gui_text("  (audio muted)")
  }
})

Examples

See examples/hello-gui in this repo for a full widget showcase, and examples/chart for ImPlot.

To run the examples from a clone of this repo:

./build.sh                                # build libimgui_hica.a (once)
hica run examples/hello-gui/hello-gui.hc
hica run examples/chart/chart.hc

Building the C backend

Requirements

macOS:

brew install sdl2

Linux (Debian/Ubuntu):

sudo apt install libsdl2-dev libgl-dev

Build

cd lib/imgui
./build.sh

This compiles Dear ImGui, the SDL2 + OpenGL3 backends, the C glue layer, and archives everything into lib/libimgui_hica.a. The Inter font and Ilseon theme are baked in – no runtime assets needed.

Theme and font

The bundled defaults are:

• Font: Inter Regular 16px, HiDPI-aware (scales with display pixel density)
• Theme: Ilseon, an OLED-focused dark palette with organic muted accents, sourced from the hica standard library

Project structure

backend/
  imgui_glue.h        # Plain-C API: hk_gui_* functions
  imgui_glue.cpp      # C++ implementation — Dear ImGui + SDL2 + OpenGL3
  kk_imgui.c          # Koka FFI trampolines (compiled by Koka)
  inter_font.h        # Inter-Regular.ttf embedded as a C array
src/
  imgui.kk            # Koka module: pub extern gui_* functions + gui_window
vendor/
  imgui/              # Dear ImGui source (cloned by build.sh)
  fonts/
    Inter-Regular.ttf
examples/
tests/
build.sh              # Builds libimgui_hica.a
lib/
  libimgui_hica.a     # Pre-built static library (after ./build.sh)

License

MIT