Boost basics

The smallest end-to-end dasImgui v2 program. One window, one slider, one button. The slider drives a float (VOLUME.value) and the button accumulates a click counter (BUMP_BTN.click_count). Both pieces of state are auto-generated daslang globals; nothing is stored inside Dear ImGui.

Source: examples/tutorial/boost_basics.das.

Walkthrough

options gen2

require imgui
require imgui_app
require glfw/glfw_boost
require opengl/opengl_boost
require live/glfw_live
require live/live_api
require live/live_commands
require live/live_vars
require live/opengl_live
require live_host
require imgui/imgui_live
require imgui/imgui_boost_runtime
require imgui/imgui_boost_v2
require imgui/imgui_widgets_builtin
require imgui/imgui_containers_builtin
require imgui/imgui_visual_aids

// =============================================================================
// TUTORIAL: boost_basics — the smallest dasImgui v2 program.
//
// One window. One slider drives a float. One button increments a counter.
// State lives in daslang globals (@live by default, so values survive reload).
//
// STANDALONE: daslang.exe modules/dasImgui/examples/tutorial/boost_basics.das
// LIVE:       daslang-live modules/dasImgui/examples/tutorial/boost_basics.das
//
// DRIVE (when running live):
//   curl -X POST -d '{"name":"imgui_snapshot"}' localhost:9090/command
//   curl -X POST -d '{"name":"imgui_set","args":{"target":"BASICS_WIN/VOLUME","value":0.75}}' \
//        localhost:9090/command
//   curl -X POST -d '{"name":"imgui_click","args":{"target":"BASICS_WIN/BUMP_BTN"}}' \
//        localhost:9090/command
// =============================================================================

[export]
def init() {
    live_create_window("dasImgui boost basics", 640, 320)
    live_imgui_init(live_window)
    var io & = unsafe(GetIO())
    io.FontGlobalScale = 1.5
}

[export]
def update() {
    if (!live_begin_frame()) return
    begin_frame()

    ImGui_ImplOpenGL3_NewFrame()
    ImGui_ImplGlfw_NewFrame()
    apply_synth_io_override()
    NewFrame()

    SetNextWindowSize(ImVec2(560.0, 240.0), ImGuiCond.Always)
    window(BASICS_WIN, (text = "Boost basics", closable = false,
                        flags = ImGuiWindowFlags.None)) {
        // Slider — VOLUME state lives in a generated daslang global.
        VOLUME.bounds = (0.0f, 1.0f)
        slider_float(VOLUME, (text = "Volume"))
        text("volume = {VOLUME.value}")

        spacing(BB_SP_1)

        // Button — BUMP_BTN.click_count is updated on every click.
        if (button(BUMP_BTN, (text = "Bump"))) {
            print("bump clicked\n")
        }
        text("bumps = {BUMP_BTN.click_count}")
    }

    end_of_frame()
    Render()
    var w, h : int
    live_get_framebuffer_size(w, h)
    glViewport(0, 0, w, h)
    glClearColor(0.10f, 0.10f, 0.12f, 1.0f)
    glClear(GL_COLOR_BUFFER_BIT)
    ImGui_ImplOpenGL3_RenderDrawData(GetDrawData())

    live_end_frame()
}

[export]
def shutdown() {
    live_imgui_shutdown()
    live_destroy_window()
}

[export]
def main() {
    init()
    while (!exit_requested()) {
        update()
    }
    shutdown()
}

Requires

The require block pulls in:

The C++-bound Dear ImGui surface (imgui, imgui_app).
The GLFW backend + OpenGL renderer + live-reload host glue (glfw/..., opengl/..., live/...).
The dasImgui v2 boost layer: imgui_live (lifecycle), imgui_boost_runtime (state structs), imgui_boost_v2 (macros), imgui_widgets_builtin (the actual widget implementations), imgui_containers_builtin (the window(...) block-arg container and its siblings), imgui_visual_aids (the synth-IO override hook used by the recording driver — see Recording APNGs).

Init and shutdown

init() opens a 640x320 GLFW window via live_create_window and hands its handle to live_imgui_init so the ImGui context, fonts, and GL backend get wired up. shutdown() reverses the pair in shutdown order.

The frame loop

update() is what runs every frame. The pattern, line by line:

live_begin_frame() — return early if the window is closing.
begin_frame() — boost-side per-frame setup (registry, command dispatch).
ImGui_ImplOpenGL3_NewFrame / ImGui_ImplGlfw_NewFrame / apply_synth_io_override / NewFrame — the ImGui backend prologue. apply_synth_io_override lets synthetic mouse/keyboard events from live-commands win against the GLFW backend’s per-frame poll (needed for tutorial recordings).
The widget block (see below).
end_of_frame() / Render() — boost-side bookkeeping, then ImGui composes the draw list.
glViewport / glClear / ImGui_ImplOpenGL3_RenderDrawData — paint.
live_end_frame() — swap buffers, advance live-reload housekeeping.

The window container

The window(NAME, ...) { ... } macro is the boost-layer wrapper around ImGui’s Begin/End pair:

SetNextWindowSize(ImVec2(560.0, 240.0), ImGuiCond.Always)
window(BASICS_WIN, (text = "Boost basics", closable = false,
                    flags = ImGuiWindowFlags.None)) {
    // ... widgets ...
}

Three things to notice:

The block runs the body once per frame between Begin and End — no manual End() to forget.
BASICS_WIN is a daslang identifier — the macro auto-emits a WindowState global named that, and pushes BASICS_WIN onto the boost registry path. Every leaf widget registers under BASICS_WIN/<ident>.
Per-call config goes in the named-tuple — text is the title, closable controls whether the X-button shows, flags are the raw ImGuiWindowFlags bits.

SetNextWindowSize / SetNextWindowPos are the same raw ImGui calls you’d use without the boost layer — they affect the next Begin (the one the macro emits) just like before.

Widgets

Two boost macros do the actual work:

VOLUME.bounds = (0.0f, 1.0f)
slider_float(VOLUME, (text = "Volume"))
Text("volume = {VOLUME.value}")

The macro form slider_float(VOLUME, ...) declares a module global VOLUME : SliderStateFloat the first time it expands. Telemetry registers it under the path-prefixed name BASICS_WIN/VOLUME (every widget inside window(BASICS_WIN, ...) inherits the prefix); the bounds line is plain assignment to the struct field.

if (button(BUMP_BTN, (text = "Bump"))) {
    print("bump clicked\n")
}
Text("bumps = {BUMP_BTN.click_count}")

button(BUMP_BTN, ...) returns true on the frame the click registers; the underlying ButtonState keeps click_count updated for later assertions (e.g. from imgui_playwright).

Standalone vs live

main() runs the loop directly when invoked as daslang.exe boost_basics.das. Under daslang-live the host calls init / update / shutdown itself; main is ignored. The slider and button states preserve across live reloads because every boost-generated global carries @live by default.

Driving from outside

When run live, the boost layer exposes the standard live-command surface at localhost:9090. Mutate the slider:

curl -X POST -d '{"name":"imgui_set","args":{"target":"BASICS_WIN/VOLUME","value":0.75}}' \
     localhost:9090/command

…and VOLUME.value jumps to 0.75 on the next frame. Note the BASICS_WIN/ prefix — the window container pushes its identifier onto the registry path, so external drivers target the path-qualified name.

Next steps

The next tutorial walks the full common-widget surface — text input, slider, checkbox, combo, color, button — on a single panel.