da_polar_events.c

Description

da_polar_events.c is a source code file from the bpdemo application. It is not a standalone command-line tool. This file contains the event handler for the polar plot drawing area (DA_polar), which is one of the visualization windows in the GUI.

Its structure and purpose are very similar to da_main_events.c, but it is specifically tailored to handle user interactions within the polar plot widget.

Functionality

The file’s primary function, da_polar_events, is registered as the event handler for the DA_polar widget. It processes user input and windowing events that occur within that specific area.

Event Handling

The function handles the following X11 events:

  • Expose: This event is sent when the polar plot window needs to be redrawn. The handler calls expose_main() to refresh the display of this specific widget.

  • MotionNotify, ButtonPress, and ButtonRelease: These events manage mouse interactions.
    • Left-clicking and dragging (Button 1) allows the user to draw a “rubber band” selection box within the polar plot window.
    • Right-clicking (Button 3) opens a context-sensitive popup menu (da_polar_popup) specific to the polar plot, which provides different display options for the phasor diagrams (e.g., “SUM”, “Separate”).
  • KeyPress: This event captures keyboard presses. However, unlike the main event handler, the KeyPress section in this file contains empty cases for the keys that control the simulation (e.g., arrow keys, +, -). This means that while the polar plot window can receive keyboard focus, it does not directly modify the simulation parameters. Its role is focused on display and mouse-based interaction.