Internal Design#
pw_console: Multi-purpose pluggable interactive console for dev & manufacturing
Threads and Event Loops#
In ptpython and IPython all user repl code is run in the foreground. This
allows interrupts like Ctrl-C and functions like print() and
time.sleep() to work as expected. Pigweed’s Console doesn’t use this
approach as it would hide or freeze the prompt_toolkit user interface while
running repl code.
To get around this issue all user repl code is run in a dedicated thread with stdout and stderr patched to capture output. This lets the user interface stay responsive and new log messages to continue to be displayed.
Here’s a diagram showing how pw_console threads and asyncio tasks are
organized.
flowchart LR
classDef eventLoop fill:#e3f2fd,stroke:#90caf9,stroke-width:1px;
classDef thread fill:#fffde7,stroke:#ffeb3b,stroke-width:1px;
classDef plugin fill:#fce4ec,stroke:#f06292,stroke-width:1px;
classDef builtinFeature fill:#e0f2f1,stroke:#4db6ac,stroke-width:1px;
%% Subgraphs are drawn in reverse order.
subgraph pluginThread [Plugin Thread 1]
subgraph pluginLoop [Plugin Event Loop 1]
toolbarFunc-->|"Refresh<br/>UI Tokens"| toolbarFunc
toolbarFunc[Toolbar Update Function]
end
class pluginLoop eventLoop;
end
class pluginThread thread;
subgraph pluginThread2 [Plugin Thread 2]
subgraph pluginLoop2 [Plugin Event Loop 2]
paneFunc-->|"Refresh<br/>UI Tokens"| paneFunc
paneFunc[Pane Update Function]
end
class pluginLoop2 eventLoop;
end
class pluginThread2 thread;
subgraph replThread [Repl Thread]
subgraph replLoop [Repl Event Loop]
Task1 -->|Finished| Task2 -->|Cancel with Ctrl-C| Task3
end
class replLoop eventLoop;
end
class replThread thread;
subgraph main [Main Thread]
subgraph mainLoop [User Interface Event Loop]
log[[Log Pane]]
repl[[Python Repl]]
pluginToolbar([User Toolbar Plugin])
pluginPane([User Pane Plugin])
class log,repl builtinFeature;
class pluginToolbar,pluginPane plugin;
end
class mainLoop eventLoop;
end
class main thread;
repl-.->|Run Code| replThread
pluginToolbar-.->|Register Plugin| pluginThread
pluginPane-.->|Register Plugin| pluginThread2