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Reactive vs. Quiet Figures

There are also two modes for figures: reactive (or interactive) mode and quiet mode.

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// Reactive mode
auto f = figure(false);
auto ax = f->gca();
auto p = ax->plot(ax, x, y);   // draws once
p->color("red").line_width(2); // draws twice more
show();                        // pause console

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// Quiet mode
auto f = figure(true);
auto ax = f->gca();
auto p = ax->plot(x,y);        // does not draw
p->color("red").line_width(2); // does not draw
f->show();                     // draw only once and pause console

Figures in reactive mode are updated whenever any of their child objects change. This happens through the touch function, that gets called on any child object when it changes its appearance. This creates an interactive mode in which figures are updated as soon as we adjust their properties. If we combine interactive figures with free-standing functions, we have a "Matlab-like style" for plots. This is a coding pattern where the figure registry works as a stream for plots. The problem with this coding style is that the user might unnecessarily create useless intermediary plots.

Figures in quiet mode are updated by calling the functions draw() or show() (Section Reactive Figures). Unless these functions are called, nothing changes in the figure. The combination of the object-oriented coding style and quiet mode is the "OO-Matplotlib-like style" for plots. This is a coding style in which the user explicitly decides when the plot is shown or updated. This is beneficial to applications that cannot waste computational resources on intermediary figures that might not be valuable to the application.

We generally use free-standing functions with reactive mode and the object-oriented interface with quiet mode. By default, new figures are in reactive mode, unless it is using an non-interactive backend. One can turn this reactive mode on and off with:

  • ion() or ioff() free-standing functions
  • reactive(bool) or quiet(bool) function on the figure object
  • figure(true) or figure(false) when explicitly creating a new figure

For convenience, the examples in Section Examples use the reactive mode. The show function pauses the console until the user interacts with the plot window. If the backend is based on process pipes, because these are unidirectional, closing the window is not enough to resume. The user needs to use the console to unblock execution. A similar example is quiet mode would be

In this example, the figure is only updated once. The user could replace the show function with the draw function, but the window would close as soon as execution completes. It is important to use show() with caution. These functions are meant for some particular executables so that an interactive plot does not close before the user can see it. It is probably unreasonable to call these functions inside a library because the user would have to manually interfere with the execution to continue.