Hello ImGui: the app runner. It creates the window and the rendering backend, and runs the loop, on desktop, mobile and the web.
Around Dear ImGui, it adds what an app needs: dockable windows and layouts, a menu and a status bar, fonts and icons, assets, DPI awareness, themes, power saving when idle, and the user’s settings.
Start with hello_imgui.run(gui_function); for more control, fill a RunnerParams. immapp.run does the same, and
also sets up the add-ons (ImPlot, markdown, the node editor...): most apps of the bundle use it.
Docs: https://
Upstream repository · The book’s page
Modules¶
In imgui_bundle (from imgui_bundle import hello_imgui):
hello_imgui: 97 functions, 30 classes, 15 enums · the C++ viewhello_imgui_nb: 4 functions, 0 classes, 0 enums
Demos using it¶
The demos of the catalog that use it (the pictures link to their code and to the playground).
Assets and add-ons¶
Load images and icons from your assets folder, and use two add-ons: markdown and ImPlot.
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A markdown editor with a live preview, and a pie chart whose values you can drag. Tick More info under each part to see how it is done. The add-ons are activated with immapp.AddOnsParams.
Uses: ImPlot
A full app: docking, fonts, logs¶
A template for a real application, built with Hello ImGui: copy it and start from there.
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Dockable windows with several layouts, colored fonts and emojis, a log window, a status bar, toolbars, menus and a theme chooser. Your settings are saved, and restored at the next start. The code is heavily commented.
Power save when idle¶
When nothing happens, Hello ImGui lowers the frame rate to spare the CPU: after 3 seconds, the live plot and the spinner become choppy.
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Content that changes on its own says so with hello_imgui.set_item_is_live(), and keeps the full speed while it is visible. The idling settings are global.
Uses: ImPlot, toggles, spinners
Command palette¶
A searchable list of commands, as in VS Code: press Ctrl+Shift+P (Cmd+Shift+P on macOS), or its button.
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Type a few letters to filter it. One command changes the theme in two steps, another writes to the log below. Learn how to register commands and their callbacks with imgui
Uses: command palette
Test engine¶
Watch a ImGui Test Engine drive the mouse and the keyboard: it clicks buttons, types text, etc., and checks the results.
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For scripted runs on top of it (automated tests, pictures, an AI agent at the mouse), see the immapp.testing demo. See the test engine doc.
Themes and theme tweaking¶
Pick a complete look for your app, then fine-tune its colors, rounding and spacing.
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The complete looks come from Hello ImGui.
Async: compute beside the GUI¶
The GUI runs as an asyncio task, while a Python loop keeps computing.
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The window shows both rates: the GUI’s frames per second, and the loop’s computations per second. The loop works in short slices, and yields between them with await asyncio.sleep(...) to share the event loop. See async support.
3D sea in OpenGL (desktop)¶
Draw anything behind your GUI with OpenGL: here, an animated sea whose waves and colors you can tune.
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The Seascape shader is by Alexander Alekseev (TDM, 2014). Hello ImGui calls runner_params.callbacks.custom_background at each frame, before the GUI: that is where it draws, with OpenGL (PyOpenGL in Python).
Desktop only
Uses: OpenGL