examples/rust: Add basic Slint example

Summary:
- Added a new Rust example demonstrating the integration of Slint UI framework with NuttX
- Includes CMake build configuration, Kconfig options, and Makefile support
- Implements a basic UI application with a timer counter display
- Provides framebuffer rendering support for NuttX using RGB565 format
- Includes touch input handling implementation (currently not integrated with UI)

Impact:
- Demonstrates Rust UI development capabilities on NuttX
- Provides a foundation for building more complex Rust-based UI applications
- Enables future integration of touch input with Slint UI components
- Shows how to use Rust's FFI capabilities to interface with NuttX system calls
- Adds support for software rendering of Slint UI on embedded systems

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

examples/rust/slint/.gitignore

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+target

examples/rust/slint/CMakeLists.txt

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+# ##############################################################################
+# apps/examples/rust/slint/CMakeLists.txt
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more contributor
+# license agreements.  See the NOTICE file distributed with this work for
+# additional information regarding copyright ownership.  The ASF licenses this
+# file to you under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License.  You may obtain a copy of
+# the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations under
+# the License.
+#
+# ##############################################################################
+
+if(CONFIG_EXAMPLES_RUST_SLINT)
+
+  # Build the Rust crate using nuttx_add_rust
+  nuttx_add_rust(CRATE_NAME slint CRATE_PATH ${CMAKE_CURRENT_SOURCE_DIR})
+
+  nuttx_add_application(
+    NAME ${CONFIG_EXAMPLES_RUST_SLINT_PROGNAME} STACKSIZE
+    ${CONFIG_EXAMPLES_RUST_SLINT_STACKSIZE} PRIORITY
+    ${CONFIG_EXAMPLES_RUST_SLINT_PRIORITY})
+
+endif() # CONFIG_EXAMPLES_RUST_SLINT

examples/rust/slint/Cargo.toml

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+[package]
+name = "slint"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+crate-type = ["staticlib"]
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+lto = true
+codegen-units = 1
+opt-level = 'z'
+
+[dependencies]
+libc = "0.2"
+slint = { version = "1.9", default-features = false, features = ["compat-1-2", "renderer-software", "libm", "unsafe-single-threaded"] }
+nuttx = { git = "https://github.com/no1wudi/nuttx-rs.git", branch = "master" }
+
+[build-dependencies]
+slint-build = { version = "1.9" }

examples/rust/slint/Kconfig

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+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+config EXAMPLES_RUST_SLINT
+	tristate "Slint Basic Example"
+	default n
+	---help---
+		Enable the basic Slint example.
+
+if EXAMPLES_RUST_SLINT
+
+config EXAMPLES_RUST_SLINT_PROGNAME
+	string "Program name"
+	default "slint"
+	---help---
+		This is the name of the program that will be used when the
+		program is installed.
+
+config EXAMPLES_RUST_SLINT_PRIORITY
+	int "Task priority"
+	default 100
+
+config EXAMPLES_RUST_SLINT_STACKSIZE
+	int "Stack size"
+	default DEFAULT_TASK_STACKSIZE
+
+endif

examples/rust/slint/Make.defs

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+############################################################################
+# apps/examples/rust/slint/Make.defs
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+include $(APPDIR)/tools/Rust.mk
+
+ifneq ($(CONFIG_EXAMPLES_RUST_SLINT),)
+CONFIGURED_APPS += $(APPDIR)/examples/rust/slint
+EXTRA_LIBS += $(call RUST_GET_BINDIR,slint,$(APPDIR)/examples/rust)
+endif

examples/rust/slint/Makefile

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+############################################################################
+# apps/examples/rust/slint/Makefile
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+include $(APPDIR)/Make.defs
+
+PROGNAME  = $(CONFIG_EXAMPLES_RUST_SLINT_PROGNAME)
+PRIORITY  = $(CONFIG_EXAMPLES_RUST_SLINT_PRIORITY)
+STACKSIZE = $(CONFIG_EXAMPLES_RUST_SLINT_STACKSIZE)
+MODULE    = $(CONFIG_EXAMPLES_RUST_SLINT)
+
+context::
+	$(call RUST_CARGO_BUILD,slint,$(APPDIR)/examples/rust)
+
+clean::
+	$(call RUST_CARGO_CLEAN,slint,$(APPDIR)/examples/rust)
+
+include $(APPDIR)/Application.mk

examples/rust/slint/build.rs

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+// ##############################################################################
+// examples/rust/slint/build.rs
+//
+// Licensed to the Apache Software Foundation (ASF) under one or more contributor
+// license agreements.  See the NOTICE file distributed with this work for
+// additional information regarding copyright ownership.  The ASF licenses this
+// file to you under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License.  You may obtain a copy of
+// the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+// License for the specific language governing permissions and limitations under
+// the License.
+//
+// ##############################################################################
+
+fn main() {
+    slint_build::compile_with_config(
+        "ui/app.slint",
+        slint_build::CompilerConfiguration::new()
+            .embed_resources(slint_build::EmbedResourcesKind::EmbedForSoftwareRenderer),
+    )
+    .unwrap();
+}

examples/rust/slint/src/lib.rs

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+// ##############################################################################
+// examples/rust/slint/src/lib.rs
+//
+// Licensed to the Apache Software Foundation (ASF) under one or more contributor
+// license agreements.  See the NOTICE file distributed with this work for
+// additional information regarding copyright ownership.  The ASF licenses this
+// file to you under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License.  You may obtain a copy of
+// the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+// License for the specific language governing permissions and limitations under
+// the License.
+//
+// ##############################################################################
+
+use std::rc::Rc;
+use std::{cell::RefCell, ffi::CStr};
+
+use slint::platform::software_renderer::{LineBufferProvider, Rgb565Pixel};
+
+use nuttx::video::fb::*;
+
+slint::include_modules!();
+
+struct NuttXPlatform {
+    window: Rc<slint::platform::software_renderer::MinimalSoftwareWindow>,
+}
+
+impl slint::platform::Platform for NuttXPlatform {
+    fn create_window_adapter(
+        &self,
+    ) -> Result<Rc<dyn slint::platform::WindowAdapter>, slint::PlatformError> {
+        Ok(self.window.clone())
+    }
+    fn duration_since_start(&self) -> std::time::Duration {
+        std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap()
+    }
+}
+
+fn create_slint_app() -> AppWindow {
+    AppWindow::new().expect("Failed to load UI")
+}
+
+#[derive(Debug, Clone)]
+struct NuttXRenderer {
+    frame_buffer: *mut u8,
+    line_buffer: Rc<RefCell<Vec<Rgb565Pixel>>>,
+    stride: usize,
+    lines: usize,
+}
+
+impl LineBufferProvider for NuttXRenderer {
+    type TargetPixel = Rgb565Pixel;
+    fn process_line(
+        &mut self,
+        line: usize,
+        range: std::ops::Range<usize>,
+        render_fn: impl FnOnce(&mut [Self::TargetPixel]),
+    ) {
+        let fb_size = self.stride * self.lines;
+        let frame = unsafe {
+            std::slice::from_raw_parts_mut(self.frame_buffer as *mut Rgb565Pixel, fb_size)
+        };
+        let mut buffer = self.line_buffer.borrow_mut();
+        render_fn(&mut buffer[range.clone()]);
+        let offset = line * self.stride;
+        frame[offset..offset + range.end - range.start].copy_from_slice(&buffer[range]);
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn slint_main() {
+    // Open the framebuffer device and get its information
+    let fbdev = match FrameBuffer::new(CStr::from_bytes_with_nul(b"/dev/fb0\0").unwrap()) {
+        Ok(fb) => fb,
+        Err(_) => {
+            println!("Failed to open framebuffer device");
+            return;
+        }
+    };
+
+    let planeinfo = fbdev.get_plane_info().unwrap();
+    let videoinfo = fbdev.get_video_info().unwrap();
+
+    println!("Plane info: {:?}", planeinfo);
+    println!("Video info: {:?}", videoinfo);
+
+    if videoinfo.fmt != Format::RGB565 as u8 {
+        println!("Unsupported pixel format, only RGB565 is supported for now");
+        return;
+    }
+
+    // Setup the Slint backend
+    let window = slint::platform::software_renderer::MinimalSoftwareWindow::new(Default::default());
+    window.set_size(slint::PhysicalSize::new(
+        videoinfo.xres.into(),
+        videoinfo.yres.into(),
+    ));
+
+    // Set the platform
+    slint::platform::set_platform(Box::new(NuttXPlatform {
+        window: window.clone(),
+    }))
+    .unwrap();
+
+    // Configure the UI
+    let _ui = create_slint_app();
+
+    // Create the renderer for NuttX
+    let nxrender = NuttXRenderer {
+        frame_buffer: planeinfo.fbmem as *mut u8,
+        line_buffer: Rc::new(RefCell::new(vec![
+            Rgb565Pixel::default();
+            videoinfo.xres as usize
+        ])),
+        stride: videoinfo.xres.into(),
+        lines: videoinfo.yres.into(),
+    };
+
+    loop {
+        slint::platform::update_timers_and_animations();
+        window.draw_if_needed(|renderer| {
+            renderer.render_by_line(nxrender.clone());
+        });
+    }
+}