This helpfile is part of a GUI tutorial.
SuperCollider provides some useful classes to automate processes. Some of them are associated to a Clock: mainly Routine and Task.
Qt rendering system is unavailable within the context of clock associated threads. In other words, you cannot 'directly' modify a widget within a Routine or a Task.
Instead, you need to defer the modification by encapsulating it in a deferred function, that will be executed once SuperCollider resume its main context, see Function: -defer. Doing otherwise will crash the program:
This remark mostly concerns debugging and understanding issues. Since Qt is a third-party library integrated within SuperCollider, some of its limitations are unrelated to SuperCollider itself.
As an example, at the time of writing this, Qt QImage has a strict pixel limit and cannot exceed 32767x32767 pixels. This 'issue' being only related to Qt, it is documented on Qt sources/forums, but not on SuperCollider sources/forums. In other words, working with Qt within the context of SuperCollider might also include using Qts documentation directly.
The Pen class allows the user to define a custom drawFunc to a View.
Pen usage is a two-steps process: the user first 'describes' the shape they want to draw (using methods such as fillRect or lineTo), then renders the shape, using either fill, stroke, or fillStroke.
Depending on the hardware, when drawing very complex shapes (for a example a million lines), some issues might arise:
Drawing instructions are cached until they are drawn. This means that calling lineTo a million times before calling stroke might saturate the computers RAM before the stroke instruction effectively takes place and frees the cached instructions.
On the other hand, calling successively lineTo then stroke a million time might be time inefficient as several lineTo could have been grouped together before being drawn on screen.
The best solution in this case would be to test several configurations to balance RAM/CPU usage in the most efficient way.