ra8_app_nav_t Struct Reference

A bounded back-stack of app ids layered over a registry (zero-heap). More...

#include <ra8_app.h>

Collaboration diagram for ra8_app_nav_t:

Data Fields
ra8_app_registry_t *	reg
	Registry the navigation drives (non-NULL).
uint16_t *	stack
	Caller storage: back-stack of app ids.
uint16_t	cap
	Capacity of stack.
uint16_t	depth
	Number of ids currently on the back-stack.

Detailed Description

A bounded back-stack of app ids layered over a registry (zero-heap).

The registry tracks only the currently focused app. A chrome/shell that lets the user drill in (library -> reader -> settings) and then press "back" needs the trail it came from. ra8_app_nav_t is that trail: ra8_app_nav_go focuses an app and remembers the one it left, and ra8_app_nav_back returns to the most recently remembered app. The history is a caller-owned uint16_t array of app ids – nothing is allocated (NASA Rule 3). The registry's own focus lifecycle (on_leave -> on_enter) still fires under every move, so a navigation layer composes ra8_app_launch rather than reimplementing it.

Invariant

depth <= cap.

stack[0 .. depth) hold app ids the user can go back through, oldest at index 0, most recent at depth - 1.

Example:

ra8_app_nav_t nav;
uint16_t     trail[4];
ra8_app_nav_init(&nav, &reg, trail, 4U);
ra8_app_nav_go(&nav, k_app_reader);   // focus reader (trail empty)
ra8_app_nav_go(&nav, k_app_settings); // focus settings (reader pushed)
bool popped = false;
ra8_app_nav_back(&nav, &popped);      // back to reader (trail empty again)

See also

ra8_app_launch The lower-level focus switch this layer composes.

Since

0.1.0

Definition at line 485 of file ra8_app.h.

Field Documentation

cap

uint16_t ra8_app_nav_t::cap

Capacity of stack.

Definition at line 488 of file ra8_app.h.

Referenced by ra8_app_nav_go(), and ra8_app_nav_init().

depth

uint16_t ra8_app_nav_t::depth

Number of ids currently on the back-stack.

Definition at line 489 of file ra8_app.h.

Referenced by ra8_app_nav_back(), ra8_app_nav_depth(), ra8_app_nav_go(), and ra8_app_nav_init().

reg

ra8_app_registry_t* ra8_app_nav_t::reg

Registry the navigation drives (non-NULL).

Definition at line 486 of file ra8_app.h.

Referenced by ra8_app_nav_back(), ra8_app_nav_go(), ra8_app_nav_go_index(), and ra8_app_nav_init().

stack

uint16_t* ra8_app_nav_t::stack

Caller storage: back-stack of app ids.

Definition at line 487 of file ra8_app.h.

Referenced by ra8_app_nav_back(), ra8_app_nav_go(), and ra8_app_nav_init().

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The documentation for this struct was generated from the following file:

• libs/ra8_app/inc/ra8_app.h