First step in removing dependency on alloc crate

examples/Cargo.toml

@@ -10,6 +10,9 @@ lvgl = { path = "../lvgl" }
 lvgl-sys = { path = "../lvgl-sys" }
 embedded-graphics = "0.6"
 embedded-graphics-simulator = "0.2.0"
+heapless = "0.5.5"
+cstr_core = { version = "0.2.0" }
+typenum = "1.12.0"
 
 [[example]]
 name = "demo"

examples/demo.rs

@@ -1,3 +1,4 @@
+use cstr_core::{CStr, CString};
 use embedded_graphics::pixelcolor::Rgb565;
 use embedded_graphics::prelude::*;
 use embedded_graphics_simulator::{
@@ -44,7 +45,7 @@ fn main() -> Result<(), LvError> {
     style_time.set_text_color(State::DEFAULT, Color::from_rgb((255, 255, 255)));
     time.add_style(Part::Main, style_time)?;
     time.set_align(&mut screen, Align::Center, 0, 0)?;
-    time.set_text("20:46")?;
+    time.set_text(CString::new("20:46").unwrap().as_c_str())?;
     time.set_width(240)?;
     time.set_height(240)?;
 
@@ -52,15 +53,29 @@ fn main() -> Result<(), LvError> {
     bt.set_width(50)?;
     bt.set_height(80)?;
     bt.set_recolor(true)?;
-    bt.set_text("#5794f2 \u{F293}#")?;
+    bt.set_text(CString::new("#5794f2 \u{F293}#").unwrap().as_c_str())?;
     bt.set_label_align(LabelAlign::Left)?;
     bt.set_align(&mut screen, Align::InTopLeft, 0, 0)?;
 
+    fn set_text<S>(text: S) -> Result<(), ()>
+    where
+        S: AsRef<cstr_core::CStr>,
+    {
+        let _v: *const i8 = text.as_ref().as_ptr();
+        Ok(())
+    }
+
+    let mut t: heapless::String<heapless::consts::U8> = heapless::String::from("test");
+    t.push('\0').unwrap();
+    set_text(CStr::from_bytes_with_nul(t.as_bytes()).unwrap()).unwrap();
+    set_text(CStr::from_bytes_with_nul("test\0".as_bytes()).unwrap()).unwrap();
+    set_text(cstr_core::CString::new("test").unwrap().as_c_str()).unwrap();
+
     let mut power = Label::new(&mut screen)?;
     power.set_recolor(true)?;
     power.set_width(80)?;
     power.set_height(20)?;
-    power.set_text("#fade2a 20%#")?;
+    power.set_text(CString::new("#fade2a 20%#").unwrap().as_c_str())?;
     power.set_label_align(LabelAlign::Right)?;
     power.set_align(&mut screen, Align::InTopRight, 0, 0)?;
 
@@ -83,7 +98,8 @@ fn main() -> Result<(), LvError> {
         if i > 59 {
             i = 0;
         }
-        time.set_text(format!("21:{:02}", i).as_str())?;
+        let val = format!("21:{:02}", i);
+        time.set_text(CString::new(val.as_str()).unwrap().as_c_str())?;
         i = 1 + i;
 
         sleep(Duration::from_secs(1));

lvgl-codegen/src/lib.rs

@@ -19,7 +19,7 @@ lazy_static! {
         ("i32", "i32"),
         ("u8", "u8"),
         ("bool", "bool"),
-        ("* const cty :: c_char", "&str"),
+        ("* const cty :: c_char", "_"),
     ]
     .iter()
     .cloned()
@@ -259,18 +259,12 @@ impl LvArg {
     }
 
     pub fn get_processing(&self) -> TokenStream {
-        let ident = self.get_name_ident();
         // TODO: A better way to handle this, instead of `is_sometype()`, is using the Rust
         //       type system itself.
-        if self.typ.is_str() {
+
-            quote! {
-                let #ident = cstr_core::CString::new(#ident)?;
-            }
-        } else {
         // No need to pre-process this type of argument
         quote! {}
     }
-    }
 
     pub fn get_value_usage(&self) -> TokenStream {
         let ident = self.get_name_ident();
@@ -339,7 +333,7 @@ impl Rusty for LvType {
         match TYPE_MAPPINGS.get(self.literal_name.as_str()) {
             Some(name) => {
                 let val = if self.is_str() {
-                    quote!(&str)
+                    quote!(&cstr_core::CStr)
                 } else {
                     let ident = format_ident!("{}", name);
                     quote!(#ident)
@@ -573,8 +567,8 @@ mod test {
 
         let code = label_set_text.code(&parent_widget).unwrap();
         let expected_code = quote! {
-            pub fn set_text(&mut self, text: &str) -> crate::LvResult<()> {
+
-                let text = cstr_core::CString::new(text)?;
+            pub fn set_text(&mut self, text: &cstr_core::CStr) -> crate::LvResult<()> {
                 unsafe {
                     lvgl_sys::lv_label_set_text(
                         self.core.raw()?.as_mut(),
@@ -583,6 +577,7 @@ mod test {
                 }
                 Ok(())
             }
+
         };
 
         assert_eq!(code.to_string(), expected_code.to_string());

lvgl/Cargo.toml

@@ -17,6 +17,8 @@ cty = "0.2.1"
 embedded-graphics = "0.6.2"
 cstr_core = { version = "0.2.0", default-features = false, features = ["alloc"] }
 bitflags = "1.2.1"
+heapless = "0.5.5"
+typenum = "1.12.0"
 
 [build-dependencies]
 quote = "1.0.7"

lvgl/src/display.rs

@@ -19,23 +19,21 @@ impl DisplayDriver {
             // Declare a buffer for the refresh rate
             // TODO: Make this an external configuration
             const REFRESH_BUFFER_LEN: usize = 2;
-            let refresh_buffer1 = vec![
+            const BUF_SIZE: usize = lvgl_sys::LV_HOR_RES_MAX as usize * REFRESH_BUFFER_LEN;
-                Color::from_rgb((0, 0, 0)).raw;
-                lvgl_sys::LV_HOR_RES_MAX as usize * REFRESH_BUFFER_LEN
-            ];
 
-            let refresh_buffer2 = vec![
+            let refresh_buffer1: [lvgl_sys::lv_color_t; BUF_SIZE] =
-                Color::from_rgb((0, 0, 0)).raw;
+                [Color::from_rgb((0, 0, 0)).raw; BUF_SIZE];
-                lvgl_sys::LV_HOR_RES_MAX as usize * REFRESH_BUFFER_LEN
+
-            ];
+            let refresh_buffer2: [lvgl_sys::lv_color_t; BUF_SIZE] =
+                [Color::from_rgb((0, 0, 0)).raw; BUF_SIZE];
 
             // Create a display buffer for LittlevGL
             let mut display_buffer = MaybeUninit::<lvgl_sys::lv_disp_buf_t>::uninit();
             // Initialize the display buffer
             lvgl_sys::lv_disp_buf_init(
                 display_buffer.as_mut_ptr(),
-                Box::into_raw(refresh_buffer1.into_boxed_slice()) as *mut cty::c_void,
+                Box::into_raw(Box::new(refresh_buffer1)) as *mut cty::c_void,
-                Box::into_raw(refresh_buffer2.into_boxed_slice()) as *mut cty::c_void,
+                Box::into_raw(Box::new(refresh_buffer2)) as *mut cty::c_void,
                 lvgl_sys::LV_HOR_RES_MAX * REFRESH_BUFFER_LEN as u32,
             );
             let display_buffer = Box::new(display_buffer.assume_init());

lvgl/src/support.rs

@@ -12,6 +12,8 @@ pub enum LvError {
     InvalidReference,
     Uninitialized,
     InvalidNulByteString,
+    StringSizeTooShort,
+    StringCannotAppendNulByte,
     AlreadyInUse,
 }