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: 89 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.
Custom 3D background (OpenGL)¶
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
Power save when idle¶
When nothing happens, Hello ImGui lowers the frame rate to spare the CPU: watch the FPS and the spinner slow down.
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Move the mouse, and they speed up again. The slider sets fps_idle (0 means full speed), and the checkbox turns idling off, for example during an animation.
Uses: spinners
Chinese and other non-Latin fonts¶
The bundled fonts cover Latin, Greek and Cyrillic only: other scripts show up as ???.
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The fix: load a font that has the glyphs you need, first, so that it becomes the default font. This demo shows how, with Noto Sans SC: download it, and the demo’s sample lines come alive.
Desktop only
Command palette¶
A searchable list of commands, as in VS Code: press Ctrl+Shift+P (Cmd+Shift+P on macOS).
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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¶
Three windows: the Dear ImGui demo, the ImGui Test Engine panel, and a few buttons that run tests.
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Watch a test drive the mouse and the keyboard: it opens tree nodes, clicks buttons, types text, and checks the results. See the test engine doc.
Desktop only
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.
Run code alongside the GUI (async)¶
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 yields with await asyncio.sleep(0) to share the event loop. See async support.
Desktop only
Python: Code