Signature and structures

Now that we have box_mover.c in our box_mover folder, we can finally start programming.

Model Struct

To make our lives easier, let's define all the information we need to encode for rendering our app:

• A point to render our box at, consisting of:
  • an x coordinate
  • and a y coordinate

Pretty simple! We'll do that by declaring a BoxMoverModel struct that holds that information.

box_mover/box_mover.c

typedef struct {
    int x;
    int y;
} BoxMoverModel;

Application Struct

Now that we're able to encode the information we need, let's create a struct that will hold all of the necessary variables and structures for our entire application.

This might seem a little odd at this point, but the benefits will show soon. This type of program structure is idiomatic with the rest of Flipper Zero's applications and will allow you to more easily transfer into other GUI Paradigms later down the line.

typedef struct {
    BoxMoverModel* model;
} BoxMover;

For now, it'll just hold a pointer to our model.

Allocating and freeing functions

Now, let's write two functions that will allocate and free an instance of our BoxMover struct. Let's call them box_mover_alloc and box_mover_free

Allocation

BoxMover* box_mover_alloc(){
    BoxMover* instance = malloc(sizeof(BoxMover));
    instance->model = malloc(sizeof(BoxMoverModel));
    instance->model->x = 10;
    instance->model->y = 10;
    
    return instance;
}

Our box_mover_alloc will allocate space for a BoxMover instance and subsequent model instance, and then initialize the model with some data. We return the instance at the end for our caller to use later.

Freeing

void box_mover_free(BoxMover* instance){
    free(instance->model);
    free(instance);
}

Since all we've done in our box_mover_alloc is allocate memory for our structs, we just need to use free to release that memory back.

Main Signature

The function that will run our plugin's code will follow a simple signature, complying with the other applications:

#include <furi.h>

// --snip--

int32_t box_mover_app(void* p){
    BoxMover* box_mover = box_mover_alloc();

    box_mover_free(box_mover);
    return 0;
}

This is how all applications are declared within Flipper Zero firmware, and it is common practice to append the name with _app.

info

To avoid unused errors, call UNUSED(p).

Unsure of your code?

Check out the code so far for this section!