8.19.20. Modal popups

popup_modal is the blocking sibling of popup: ImGui dims the parent window, absorbs every click outside the modal, and routes ESC to the close path. The wrapper’s signature:

popup_modal(IDENT, (text = "title",
                    closable = bool,
                    flags = ImGuiWindowFlags....)) {
    // body — runs only while ImGui has the modal open
}

Lifecycle is identical to popup — OpenPopup + BeginPopupModal + EndPopup, driven by state.pending_open / pending_close. The differences are entirely visual + input-blocking, both handled by ImGui.

closable=true adds an X-button on the title bar wired to state.open. The wrapper feeds &state.open to BeginPopupModal’s p_open parameter, so an X-click sets state.open=false and ImGui closes the modal on the next frame.

Source: modules/dasImgui/examples/tutorial/popup_modal.das.

8.19.20.1. Walkthrough

options gen2
options _comment_hygiene = true
options gc

require imgui
require imgui_app
require opengl/opengl_boost
require live/glfw_live
require live/live_api
require live/live_commands
require live/live_vars
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: popup_modal — blocking modal dialog with optional X-button.
//
//   popup_modal(IDENT, (text = "title", closable = bool,
//                       flags = ImGuiWindowFlags....)) { body }
//
// Lifecycle is identical to popup() — OpenPopup + BeginPopupModal/EndPopup,
// driven by state.pending_open / pending_close — but ImGui ALSO:
//
//   1. Dims the parent window — visual backdrop says "deal with this first".
//   2. Blocks input outside the modal — clicks elsewhere are absorbed, not
//      passed through. ESC closes the modal (vanilla ImGui behavior).
//   3. With closable=true, renders an X-button wired to state.open.
//
// The boost wrapper threads three control surfaces through state.pending_*:
//   - app code        — `MODAL_X.pending_open = true`
//   - live commands   — imgui_open / imgui_close
//   - close-button    — ImGui flips state.open when X clicked or ESC pressed
//
// STANDALONE: daslang.exe modules/dasImgui/examples/tutorial/popup_modal.das
// LIVE:       daslang-live modules/dasImgui/examples/tutorial/popup_modal.das
//
// DRIVE (when running live):
//   curl -X POST -d '{"name":"imgui_open","args":{"target":"PM_WIN/CONFIRM_MODAL"}}' \
//        localhost:9090/command
// =============================================================================

var private CONFIRM_RESULT : string = "(no answer yet)"

[export]
def init() {
    live_create_window("dasImgui popup_modal tutorial", 720, 480)
    live_imgui_init(live_window)
    let io & = unsafe(GetIO())
    GetStyle().FontScaleMain = 1.4
}

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

    ImGui_ImplGlfw_NewFrame()
    apply_synth_io_override()
    NewFrame()

    SetNextWindowPos(ImVec2(20.0f, 20.0f), ImGuiCond.Always)
    SetNextWindowSize(ImVec2(680.0f, 440.0f), ImGuiCond.Always)
    window(PM_WIN, (text = "popup_modal tutorial", closable = false,
                    flags = ImGuiWindowFlags.None)) {

        text("Two modals - a Yes/No confirm and a closable settings dialog.")
        separator()

        // ---- A: trigger the confirm modal ----
        if (button(OPEN_CONFIRM, (text = "Delete file..."))) {
            CONFIRM_MODAL.pending_open = true
        }
        same_line((spacing = 12.0f))
        if (button(OPEN_SETTINGS, (text = "Open settings (X-button)"))) {
            SETTINGS_MODAL.pending_open = true
        }

        separator()
        text(STATUS_LINE, (text = "Last confirm answer: {CONFIRM_RESULT}"))
        text("SETTINGS_MODAL.open (closable) = {SETTINGS_MODAL.open}")

        // ---- Modal A: Yes/No confirm ----

        // closable=false → no X-button; Yes/No buttons + ESC close it (ESC is an
        // ImGui built-in — to disable it the app must intercept the key before
        // NewFrame()).
        popup_modal(CONFIRM_MODAL, (text = "Confirm delete",
                                    closable = false,
                                    flags = ImGuiWindowFlags.AlwaysAutoResize)) {
            text("Are you sure you want to delete the selected file?")
            separator()
            if (button(CONFIRM_YES, (text = "Yes"))) {
                CONFIRM_RESULT = "Yes"
                CONFIRM_MODAL.pending_close = true
            }
            same_line((spacing = 12.0f))
            if (button(CONFIRM_NO, (text = "No"))) {
                CONFIRM_RESULT = "No"
                CONFIRM_MODAL.pending_close = true
            }
        }

        // ---- Modal B: closable settings ----
        // closable=true → X-button on the title bar wired to state.open.
        popup_modal(SETTINGS_MODAL, (text = "Settings",
                                     closable = true,
                                     flags = ImGuiWindowFlags.AlwaysAutoResize)) {
            text("Background tasks")
            separator()
            checkbox(S_AUTOSAVE, (text = "Auto-save every 5 minutes"))
            checkbox(S_TELEMETRY, (text = "Send anonymous telemetry"))
            S_MAX_FPS.bounds = (30, 240)
            slider_int(S_MAX_FPS, (text = "Max FPS cap"))
            separator()
            if (button(S_APPLY, (text = "Apply"))) {
                SETTINGS_MODAL.pending_close = true
            }
        }
    }

    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)
    live_imgui_render()

    live_end_frame()
}

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

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

8.19.20.1.1. Requires

Already in the baseline boost layer:

imgui/imgui_containers_builtin — popup_modal plus window.
imgui/imgui_widgets_builtin — button, checkbox, slider_int, text.

8.19.20.1.2. Confirm dialog (non-closable)

The classic “Yes/No before destructive action”:

popup_modal(CONFIRM_MODAL, (text = "Confirm delete",
                            closable = false,
                            flags = ImGuiWindowFlags.AlwaysAutoResize)) {
    text("Are you sure you want to delete the selected file?")
    separator()
    if (button(CONFIRM_YES, (text = "Yes"))) {
        CONFIRM_RESULT = "Yes"
        CONFIRM_MODAL.pending_close = true
    }
    same_line()
    if (button(CONFIRM_NO, (text = "No"))) {
        CONFIRM_RESULT = "No"
        CONFIRM_MODAL.pending_close = true
    }
}

closable=false means there’s no X-button — but ESC still closes the modal (ImGui’s built-in popup keybinding, unaffected by closable or any ImGuiWindowFlags bit). The body’s Yes/No buttons are the explicit answer paths: both write to CONFIRM_RESULT and set pending_close. To make the modal truly non-dismissable, the app must intercept the ESC key before NewFrame() and avoid issuing any pending_close from app code — outside the scope of this tutorial.

The AlwaysAutoResize flag (passed via flags) sizes the modal to its content — saves the caller from picking width/height by hand.

8.19.20.1.5. Pending-flag channels

Three control surfaces converge on the same state:

App code — MODAL.pending_open = true from a button handler or any event.
Live commands — imgui_open / imgui_close against the registered path.
Close button / ESC (closable only) — ImGui flips state.open, the next frame’s wrapper applies the close.

The wrapper bridges them: pending_open=true triggers OpenPopup, pending_close=true triggers CloseCurrentPopup inside the active modal body, X-click flips open=false and the wrapper closes on next frame.

8.19.20.1.6. Standalone vs live

Same convention as the other tutorials.

8.19.20.1.7. Driving from outside

The walkthrough above opens each modal by clicking its trigger button and dismisses it by clicking Yes / No / Apply — every gesture is a real click, self-verified by the modal body appearing or vanishing. The live commands below drive the same lifecycle directly, for remote or scripted control:

curl -X POST -d '{"name":"imgui_open","args":{"target":"PM_WIN/CONFIRM_MODAL"}}' \
     localhost:9090/command
curl -X POST -d '{"name":"imgui_click","args":{"target":"PM_WIN/CONFIRM_MODAL/CONFIRM_YES"}}' \
     localhost:9090/command
curl -X POST -d '{"name":"imgui_close","args":{"target":"PM_WIN/CONFIRM_MODAL"}}' \
     localhost:9090/command

The path for body widgets composes off the modal IDENT — clicks against PM_WIN/CONFIRM_MODAL/CONFIRM_YES resolve correctly only while the modal is open (the body’s widgets aren’t in the registry otherwise).