Possibility to register a shared native display

examples/app.rs

@@ -3,6 +3,10 @@ use embedded_graphics::prelude::*;
 use embedded_graphics_simulator::{OutputSettingsBuilder, SimulatorDisplay, Window};
 use lvgl;
 use lvgl::display::Display;
+use lvgl::widgets::Label;
+use parking_lot::Mutex;
+use std::cell::RefCell;
+use std::sync::Arc;
 
 type ColorSpace = Rgb565;
 
@@ -15,7 +19,15 @@ fn main() {
     let output_settings = OutputSettingsBuilder::new().scale(2).build();
     let mut window = Window::new("App Example", &output_settings);
 
+    let mut shared_native_display = Arc::new(Mutex::new(embedded_graphics_display));
+
     // LVGL usage
     lvgl::init();
-    Display::register(embedded_graphics_display).unwrap();
+    let display = Display::register_shared(&shared_native_display).unwrap();
+    let label = Label::new().unwrap();
+
+    {
+        let mut val = shared_native_display.lock();
+        val.draw_pixel(Pixel::default()).unwrap();
+    }
 }

lvgl/src/display.rs

@@ -3,12 +3,17 @@ use crate::Box;
 use crate::{disp_drv_register, disp_get_default, get_str_act};
 use crate::{Color, Obj};
 use core::marker::PhantomData;
-use core::mem::MaybeUninit;
 use core::ptr::NonNull;
 use core::{ptr, result};
 use embedded_graphics::drawable;
 use embedded_graphics::prelude::*;
 
+#[cfg(feature = "alloc")]
+use parking_lot::Mutex;
+
+#[cfg(feature = "alloc")]
+use alloc::sync::Arc;
+
 // TODO: Make this an external configuration
 const REFRESH_BUFFER_LEN: usize = 2;
 // Declare a buffer for the refresh rate
@@ -23,7 +28,9 @@ pub enum DisplayError {
 
 type Result<T> = result::Result<T, DisplayError>;
 
-#[derive(Copy, Clone)]
+#[cfg(feature = "alloc")]
+pub type SharedNativeDisplay<T> = Arc<Mutex<T>>;
+
 pub struct Display {
     pub(crate) disp: NonNull<lvgl_sys::lv_disp_t>,
 }
@@ -33,11 +40,23 @@ impl Display {
         Self { disp }
     }
 
-    pub fn register<C>(embedded_graphics_display: impl DrawTarget<C>) -> Result<Self>
+    // pub fn register<T, C>(native_display: T) -> Result<Self>
+    // where
+    //     T: DrawTarget<C>,
+    //     C: PixelColor + From<Color>,
+    // {
+    //     let mut display_diver = DisplayDriver::new(DisplayBuffer::new(), native_display);
+    //     Ok(disp_drv_register(&mut display_diver)?)
+    // }
+
+    #[cfg(feature = "alloc")]
+    pub fn register_shared<T, C>(shared_native_display: &SharedNativeDisplay<T>) -> Result<Self>
     where
+        T: DrawTarget<C>,
         C: PixelColor + From<Color>,
     {
-        let mut display_diver = DisplayDriver::new(DisplayBuffer::new(), embedded_graphics_display);
+        let mut display_diver =
+            DisplayDriver::new_shared(DisplayBuffer::new(), Arc::clone(shared_native_display));
         Ok(disp_drv_register(&mut display_diver)?)
     }
 
@@ -62,37 +81,36 @@ impl DefaultDisplay {
     }
 }
 
-#[derive(Copy, Clone)]
 pub struct DisplayBuffer {
-    disp_buf: lvgl_sys::lv_disp_buf_t,
+    disp_buf: Box<lvgl_sys::lv_disp_buf_t>,
 }
 
 impl DisplayBuffer {
     pub fn new() -> Self {
-        let disp_buf = unsafe {
-            let mut disp_buf = MaybeUninit::uninit();
+        let disp_buf = {
+            let mut disp_buf = Box::new(lvgl_sys::lv_disp_buf_t::default());
             let refresh_buffer = Box::new([lvgl_sys::lv_color_t::default(); BUF_SIZE]);
-
-            lvgl_sys::lv_disp_buf_init(
-                disp_buf.as_mut_ptr(),
-                Box::into_raw(refresh_buffer) as *mut cty::c_void,
-                ptr::null_mut(),
-                lvgl_sys::LV_HOR_RES_MAX * REFRESH_BUFFER_LEN as u32,
-            );
-            disp_buf.assume_init()
+            unsafe {
+                lvgl_sys::lv_disp_buf_init(
+                    disp_buf.as_mut() as *mut _,
+                    Box::into_raw(refresh_buffer) as *mut cty::c_void,
+                    ptr::null_mut(),
+                    lvgl_sys::LV_HOR_RES_MAX * REFRESH_BUFFER_LEN as u32,
+                );
+            }
+            disp_buf
         };
 
         Self { disp_buf }
     }
 }
 
-#[derive(Copy, Clone)]
 pub struct DisplayDriver<T, C>
 where
     T: DrawTarget<C>,
     C: PixelColor + From<Color>,
 {
-    pub(crate) disp_drv: lvgl_sys::lv_disp_drv_t,
+    pub(crate) disp_drv: Box<lvgl_sys::lv_disp_drv_t>,
     phantom_display: PhantomData<T>,
     phantom_color: PhantomData<C>,
 }
@@ -102,25 +120,29 @@ where
     T: DrawTarget<C>,
     C: PixelColor + From<Color>,
 {
-    pub fn new(display_buffer: DisplayBuffer, native_display: T) -> Self {
-        let mut disp_drv = unsafe {
-            let mut disp_drv = MaybeUninit::uninit();
-            lvgl_sys::lv_disp_drv_init(disp_drv.as_mut_ptr());
-            disp_drv.assume_init()
-        };
+    #[cfg(feature = "alloc")]
+    pub fn new_shared(
+        display_buffer: DisplayBuffer,
+        shared_native_display: SharedNativeDisplay<T>,
+    ) -> Self {
+        let mut disp_drv = Box::new(lvgl_sys::lv_disp_drv_t::default());
+        unsafe {
+            lvgl_sys::lv_disp_drv_init(disp_drv.as_mut() as *mut _);
+        }
 
         // We need to add to a `Box`, so it's copied to a memory location in the "heap" (LVGL statically allocated heap).
-        let disp_buf = Box::new(display_buffer.disp_buf);
-        disp_drv.buffer = Box::into_raw(disp_buf) as *mut lvgl_sys::lv_disp_buf_t;
+        disp_drv.buffer = Box::into_raw(display_buffer.disp_buf) as *mut lvgl_sys::lv_disp_buf_t;
 
-        let native_display = Box::new(DisplayUserData {
-            display: native_display,
+        let native_display = Box::new(SharedDisplayUserData {
+            display: shared_native_display,
             phantom: PhantomData,
         });
         disp_drv.user_data =
             Box::into_raw(native_display) as *mut _ as lvgl_sys::lv_disp_drv_user_data_t;
 
-        disp_drv.flush_cb = Some(disp_flush_trampoline::<T, C>);
+        // Sets trampoline pointer to the function implementation using the types (T, C) that
+        // are used in this instance of `DisplayDriver`.
+        disp_drv.flush_cb = Some(shared_disp_flush_trampoline::<T, C>);
 
         // We do not store any memory that can be accidentally deallocated by on the Rust side.
         Self {
@@ -131,16 +153,18 @@ where
     }
 }
 
-pub(crate) struct DisplayUserData<T, C>
+#[cfg(feature = "alloc")]
+pub(crate) struct SharedDisplayUserData<T, C>
 where
     T: DrawTarget<C>,
     C: PixelColor + From<Color>,
 {
-    display: T,
+    display: SharedNativeDisplay<T>,
     phantom: PhantomData<C>,
 }
 
-unsafe extern "C" fn disp_flush_trampoline<T, C>(
+#[cfg(feature = "alloc")]
+unsafe extern "C" fn shared_disp_flush_trampoline<T, C>(
     disp_drv: *mut lvgl_sys::lv_disp_drv_t,
     area: *const lvgl_sys::lv_area_t,
     color_p: *mut lvgl_sys::lv_color_t,
@@ -150,7 +174,7 @@ unsafe extern "C" fn disp_flush_trampoline<T, C>(
 {
     let display_driver = *disp_drv;
     if !display_driver.user_data.is_null() {
-        let user_data = &mut *(display_driver.user_data as *mut DisplayUserData<T, C>);
+        let user_data = &mut *(display_driver.user_data as *mut SharedDisplayUserData<T, C>);
         let x1 = (*area).x1;
         let x2 = (*area).x2;
         let y1 = (*area).y1;
@@ -174,7 +198,10 @@ unsafe extern "C" fn disp_flush_trampoline<T, C>(
             })
             .flatten();
 
-        let _ = user_data.display.draw_iter(pixels);
+        let _ = user_data
+            .display
+            .try_lock()
+            .map(move |mut display| display.draw_iter(pixels));
     }
 }
 

lvgl/src/functions.rs

@@ -16,9 +16,7 @@ type Result<T> = result::Result<T, CoreError>;
 pub fn disp_drv_register<C: PixelColor + From<Color>, T: DrawTarget<C>>(
     disp_drv: &mut DisplayDriver<T, C>,
 ) -> Result<Display> {
-    let disp_ptr = unsafe {
-        lvgl_sys::lv_disp_drv_register(&mut disp_drv.disp_drv as *mut lvgl_sys::lv_disp_drv_t)
-    };
+    let disp_ptr = unsafe { lvgl_sys::lv_disp_drv_register(disp_drv.disp_drv.as_mut() as *mut _) };
     Ok(Display::from_raw(
         NonNull::new(disp_ptr).ok_or(CoreError::OperationFailed)?,
     ))