examples/rust: Add basic Slint example

Summary:
- Added a basic Slint example to demonstrate Rust integration with NuttX
- Includes a simple UI with a timer and text display
- Implements a software renderer for Slint targeting the STM32F746G-DISCO board
- Adds touch input handling via FFI to NuttX touchscreen driver

Impact:
- Provides a reference implementation for Rust GUI development on NuttX
- Demonstrates how to integrate Slint's software renderer with NuttX's framebuffer
- Shows FFI usage for hardware interaction (touchscreen)
- Enables future GUI application development using Rust and Slint on NuttX

Signed-off-by: Huang Qi <[email protected]>

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"] }
+
+[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::boxed::Box;
+use std::rc::Rc;
+
+use slint::platform::software_renderer::{LineBufferProvider, Rgb565Pixel};
+
+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 {
+    let ui = AppWindow::new().expect("Failed to load UI");
+
+    ui
+}
+
+#[no_mangle]
+pub extern "C" fn slint_main() {
+    // -------- Setup the Slint backend --------
+    let window = slint::platform::software_renderer::MinimalSoftwareWindow::new(Default::default());
+    window.set_size(slint::PhysicalSize::new(480, 272));
+
+    slint::platform::set_platform(Box::new(NuttXPlatform {
+        window: window.clone(),
+    }))
+    .unwrap();
+
+    // -------- Configure the UI --------
+    // (need to be done after the call to slint::platform::set_platform)
+    let _ui = create_slint_app();
+
+    // Map framebuffer memory, this is a hardcoded address for the stm32f746g-disco, need to be
+    // refactored to use a generic way to get the framebuffer address
+    let fb_ptr = 0xc0000000 as *mut Rgb565Pixel;
+    let fb_size = (480 * 272) as usize;
+    let framebuffer = unsafe { std::slice::from_raw_parts_mut(fb_ptr, fb_size) };
+
+    loop {
+        slint::platform::update_timers_and_animations();
+        window.draw_if_needed(|renderer| {
+            struct FrameBuffer<'a> {
+                frame_buffer: &'a mut [Rgb565Pixel],
+                stride: usize,
+            }
+            impl<'a> LineBufferProvider for FrameBuffer<'a> {
+                type TargetPixel = Rgb565Pixel;
+                fn process_line(
+                    &mut self,
+                    line: usize,
+                    range: std::ops::Range<usize>,
+                    render_fn: impl FnOnce(&mut [Self::TargetPixel]),
+                ) {
+                    let mut line_buffer = [Rgb565Pixel(0); 480];
+                    render_fn(&mut line_buffer);
+                    let offset = line * self.stride;
+                    self.frame_buffer[offset..offset + range.end - range.start]
+                        .copy_from_slice(&line_buffer[range]);
+                }
+            }
+            renderer.render_by_line(FrameBuffer {
+                frame_buffer: framebuffer,
+                stride: 480,
+            });
+        });
+    }
+}