ViewClockDriver

The view clock of one document (field-presentation §FVG-6): the rule for when it runs, its monotonic time and the values that OPAL fixes.

In the namespace construct::rendering. Declared in src/libs/libconstruct/construct/rendering/ViewClockDriver.hpp.

Detailed description

One driver for each document (document::DocumentContext::viewClock()). Both viewports read it, the worker viewport (SceneWorkerWidget) and the inline one (SceneWidget): one behavior, two invocations (§XM-2b). Each viewport asks wantsToRun() for its 33 ms heartbeat, calls advance() on a tick while it shows, and gives the clock to the scene that draws. `construct.view.clock` reads and sets the same driver.

View state, never document state: nothing here writes the document, makes an undo step or marks the document modified.