Revising the public API for better flexibility

examples/app.rs

@@ -0,0 +1,26 @@
+use embedded_graphics::pixelcolor::Rgb565;
+use embedded_graphics::prelude::*;
+use embedded_graphics_simulator::{OutputSettingsBuilder, SimulatorDisplay, Window};
+use lvgl;
+use lvgl::display::{Display, DisplayBuffer, DisplayDriver};
+
+type ColorSpace = Rgb565;
+
+fn main() {
+    let mut embedded_graphics_display: SimulatorDisplay<ColorSpace> = SimulatorDisplay::new(
+        Size::new(lvgl_sys::LV_HOR_RES_MAX, lvgl_sys::LV_VER_RES_MAX),
+    );
+
+    let output_settings = OutputSettingsBuilder::new().scale(2).build();
+    let mut window = Window::new("App Example", &output_settings);
+
+    // LVGL usage
+    lvgl::init();
+
+    let mut display_diver: DisplayDriver<ColorSpace> =
+        DisplayDriver::new(DisplayBuffer::new(), |pixels| {
+            // Here we draw to the external display
+            let _ = embedded_graphics_display.draw_iter(pixels);
+        });
+    let _display = lvgl::disp_drv_register(&mut display_diver).unwrap();
+}

lvgl-sys/build.rs

@@ -114,6 +114,7 @@ fn main() {
     let bindings = bindgen::Builder::default()
         .header(shims_dir.join("lvgl_sys.h").to_str().unwrap())
         .generate_comments(false)
+        .derive_default(true)
         .layout_tests(false)
         .use_core()
         .rustfmt_bindings(true)

lvgl/Cargo.toml

@@ -32,6 +32,11 @@ lvgl-sys = { version = "0.5.2", path = "../lvgl-sys" }
 embedded-graphics-simulator = "0.2.1"
 heapless = "0.5.5"
 
+[[example]]
+name = "app"
+path = "../examples/app.rs"
+required-features = ["alloc"]
+
 [[example]]
 name = "demo"
 path = "../examples/demo.rs"

lvgl/src/display.rs

@@ -0,0 +1,150 @@
+use crate::{Color, LvError, LvResult, Obj};
+use core::marker::PhantomData;
+use core::mem::{ManuallyDrop, MaybeUninit};
+use core::ptr;
+use core::ptr::NonNull;
+use embedded_graphics::drawable;
+use embedded_graphics::prelude::*;
+
+// TODO: Make this an external configuration
+const REFRESH_BUFFER_LEN: usize = 2;
+// Declare a buffer for the refresh rate
+pub(crate) const BUF_SIZE: usize = lvgl_sys::LV_HOR_RES_MAX as usize * REFRESH_BUFFER_LEN;
+
+pub enum DisplayError {
+    FailedToRegister,
+    NotRegistered,
+}
+
+#[derive(Copy, Clone)]
+pub struct Display {
+    disp: NonNull<lvgl_sys::lv_disp_t>,
+}
+
+impl Display {
+    pub(crate) fn from_raw(disp: NonNull<lvgl_sys::lv_disp_t>) -> Self {
+        Self { disp }
+    }
+}
+
+#[derive(Copy, Clone)]
+pub struct DefaultDisplay {}
+
+impl DefaultDisplay {
+    pub fn get_screen_active() -> Result<Obj, DisplayError> {
+        Err(DisplayError::NotRegistered)
+    }
+}
+
+#[derive(Copy, Clone)]
+pub struct DisplayBuffer {
+    disp_buf: lvgl_sys::lv_disp_buf_t,
+}
+
+impl DisplayBuffer {
+    pub fn new() -> Self {
+        let disp_buf = unsafe {
+            let mut disp_buf = MaybeUninit::uninit();
+            let mut refresh_buffer = ManuallyDrop::new([lvgl_sys::lv_color_t::default(); BUF_SIZE]);
+
+            lvgl_sys::lv_disp_buf_init(
+                disp_buf.as_mut_ptr(),
+                refresh_buffer.as_mut_ptr() as *mut cty::c_void,
+                ptr::null_mut(),
+                lvgl_sys::LV_HOR_RES_MAX * REFRESH_BUFFER_LEN as u32,
+            );
+            disp_buf.assume_init()
+        };
+
+        Self { disp_buf }
+    }
+}
+
+#[derive(Copy, Clone)]
+pub struct DisplayDriver<C>
+where
+    C: PixelColor + From<Color>,
+{
+    pub(crate) disp_drv: lvgl_sys::lv_disp_drv_t,
+    phantom: PhantomData<C>,
+}
+
+impl<C> DisplayDriver<C>
+where
+    C: PixelColor + From<Color>,
+{
+    pub fn new<I, F>(display_buffer: DisplayBuffer, callback: F) -> Self
+    where
+        I: IntoIterator<Item = drawable::Pixel<C>>,
+        F: FnMut(I) + 'static,
+    {
+        let mut disp_buf = ManuallyDrop::new(display_buffer.disp_buf);
+        let mut callback = ManuallyDrop::new(callback);
+        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()
+        };
+        disp_drv.buffer = &mut *disp_buf as *mut lvgl_sys::lv_disp_buf_t;
+        disp_drv.user_data = &mut callback as *mut _ as lvgl_sys::lv_disp_drv_user_data_t;
+        disp_drv.flush_cb = Some(disp_flush_trampoline::<C, I, F>);
+
+        Self {
+            disp_drv,
+            phantom: PhantomData,
+        }
+    }
+}
+
+// impl Default for DisplayDriver {
+//     fn default() -> Self {
+//         Self::new(DisplayBuffer::new())
+//     }
+// }
+
+pub struct DisplayDriverBuilder {
+    disp_buf: Option<DisplayBuffer>,
+}
+
+impl DisplayDriverBuilder {
+    pub fn with_callback() {}
+}
+
+unsafe extern "C" fn disp_flush_trampoline<C, I, F>(
+    disp_drv: *mut lvgl_sys::lv_disp_drv_t,
+    area: *const lvgl_sys::lv_area_t,
+    color_p: *mut lvgl_sys::lv_color_t,
+) where
+    C: PixelColor + From<Color>,
+    I: IntoIterator<Item = drawable::Pixel<C>>,
+    F: FnMut(I) + 'static,
+{
+    let display_driver = *disp_drv;
+    if !display_driver.user_data.is_null() {
+        let callback = &mut *(display_driver.user_data as *mut F);
+        let x1 = (*area).x1;
+        let x2 = (*area).x2;
+        let y1 = (*area).y1;
+        let y2 = (*area).y2;
+
+        let ys = y1..=y2;
+        let xs = (x1..=x2).enumerate();
+        let x_len = (x2 - x1 + 1) as usize;
+
+        // We use iterators here to ensure that the Rust compiler can apply all possible
+        // optimizations at compile time.
+        let pixels = ys
+            .enumerate()
+            .map(|(iy, y)| {
+                xs.clone().map(move |(ix, x)| {
+                    let color_len = x_len * iy + ix;
+                    let lv_color = unsafe { *color_p.add(color_len) };
+                    let raw_color = Color::from_raw(lv_color);
+                    drawable::Pixel(Point::new(x as i32, y as i32), raw_color.into())
+                })
+            })
+            .flatten();
+
+        callback(pixels);
+    }
+}

lvgl/src/functions.rs

@@ -0,0 +1,16 @@
+use crate::display::{Display, DisplayDriver, DisplayError};
+use crate::Color;
+use core::ptr::NonNull;
+use embedded_graphics::drawable;
+use embedded_graphics::prelude::*;
+
+pub fn disp_drv_register<C: PixelColor + From<Color>>(
+    disp_drv: &mut DisplayDriver<C>,
+) -> Result<Display, DisplayError> {
+    let disp_ptr = unsafe {
+        lvgl_sys::lv_disp_drv_register(&mut disp_drv.disp_drv as *mut lvgl_sys::lv_disp_drv_t)
+    };
+    Ok(Display::from_raw(
+        NonNull::new(disp_ptr).ok_or(DisplayError::FailedToRegister)?,
+    ))
+}

lvgl/src/lib.rs

@@ -31,6 +31,8 @@ use ::alloc::boxed::Box;
 #[cfg(feature = "lvgl_alloc")]
 mod allocator;
 
+pub mod display;
+mod functions;
 mod support;
 mod ui;
 #[macro_use]
@@ -47,6 +49,7 @@ pub(crate) mod mem;
 #[cfg(not(feature = "lvgl_alloc"))]
 use crate::mem::Box;
 
+pub use functions::*;
 pub use lv_core::*;
 pub use support::*;
 pub use ui::*;
@@ -56,7 +59,7 @@ use core::sync::atomic::{AtomicBool, Ordering};
 // Initialize LVGL only once.
 static LVGL_INITIALIZED: AtomicBool = AtomicBool::new(false);
 
-pub(crate) fn lvgl_init() {
+pub fn init() {
     if LVGL_INITIALIZED
         .compare_exchange(false, true, Ordering::Relaxed, Ordering::Relaxed)
         .is_ok()

lvgl/src/ui.rs

@@ -1,7 +1,7 @@
 use crate::Box;
 use crate::{Color, Event, LvError, LvResult, Obj, Widget};
 use core::marker::PhantomData;
-use core::mem::MaybeUninit;
+use core::mem::{ManuallyDrop, MaybeUninit};
 use core::ptr;
 use core::ptr::NonNull;
 use core::sync::atomic::{AtomicBool, Ordering};
@@ -47,7 +47,7 @@ where
             .compare_exchange(false, true, Ordering::Relaxed, Ordering::Relaxed)
             .is_ok()
         {
-            crate::lvgl_init();
+            crate::init();
             Ok(Self {
                 _not_sync: PhantomData,
                 display_data: None,
@@ -80,10 +80,13 @@ where
             // Basic initialization of the display driver
             lvgl_sys::lv_disp_drv_init(disp_drv.as_mut_ptr());
             let mut disp_drv = Box::new(disp_drv.assume_init());
-            // Assign the buffer to the display
+            // Assign the buffer to the display, the memory "leaks" here since
+            // the `disp_drv` is dropped in the end of this method. This is not a problem
+            // since this should live for the whole lifetime of the program anyways.
             disp_drv.buffer = Box::into_raw(Box::new(disp_buf.assume_init()));
             // Set your driver function
             disp_drv.flush_cb = Some(display_callback_wrapper::<T, C>);
+            // The memory of `display_data` is kept because of the reference in `self`
             disp_drv.user_data = &mut self.display_data as *mut _ as *mut cty::c_void;
             // We need to remember to deallocate the `disp_drv` memory when dropping UI
             lvgl_sys::lv_disp_drv_register(Box::into_raw(disp_drv));
@@ -110,7 +113,7 @@ where
         }
     }
 
-    pub fn event_send<W>(&mut self, obj: &mut W, event: Event<W::SpecialEvent>) -> LvResult<()>
+    pub fn event_send<W>(&self, obj: &mut W, event: Event<W::SpecialEvent>) -> LvResult<()>
     where
         W: Widget,
     {