remove screen tearing

kernel/src/abi.rs

@@ -1,13 +1,19 @@
-use abi_sys::{DrawIterAbi, GetKeyAbi, PrintAbi, SleepAbi};
+use core::sync::atomic::Ordering;
+
+use abi_sys::{DrawIterAbi, GetKeyAbi, LockDisplay, PrintAbi, SleepAbi};
 use embassy_rp::clocks::clk_sys_freq;
 use embedded_graphics::{Pixel, draw_target::DrawTarget, pixelcolor::Rgb565};
 use shared::keyboard::KeyEvent;
 
-use crate::{KEY_CACHE, display::FRAMEBUFFER};
+use crate::{
+    KEY_CACHE,
+    display::{FB_PAUSED, FRAMEBUFFER},
+};
 
 // ensure the abi and the kernel fn signatures are the same
 const _: PrintAbi = print;
 const _: SleepAbi = sleep;
+const _: LockDisplay = lock_display;
 const _: DrawIterAbi = draw_iter;
 const _: GetKeyAbi = get_key;
 
@@ -24,6 +30,10 @@ pub extern "Rust" fn sleep(ms: u64) {
     }
 }
 
+pub extern "Rust" fn lock_display(lock: bool) {
+    FB_PAUSED.store(lock, Ordering::Relaxed);
+}
+
 // TODO: maybe return result
 pub extern "Rust" fn draw_iter(pixels: &[Pixel<Rgb565>]) {
     unsafe { FRAMEBUFFER.draw_iter(pixels.iter().copied()).unwrap() }

kernel/src/display.rs

@@ -1,3 +1,5 @@
+use core::sync::atomic::{AtomicBool, Ordering};
+
 use crate::framebuffer::AtomicFrameBuffer;
 use embassy_rp::{
     Peri,
@@ -24,6 +26,7 @@ pub const SCREEN_WIDTH: usize = 320;
 pub const SCREEN_HEIGHT: usize = 320;
 
 pub static mut FRAMEBUFFER: AtomicFrameBuffer = AtomicFrameBuffer::new();
+pub static FB_PAUSED: AtomicBool = AtomicBool::new(false);
 
 pub async fn init_display(
     spi: Spi<'static, SPI1, Async>,
@@ -48,20 +51,16 @@ pub async fn init_display(
     display
 }
 
-pub fn clear_fb() {
-    unsafe {
-        FRAMEBUFFER.clear(Rgb565::WHITE).unwrap();
-    }
-}
-
 #[embassy_executor::task]
 pub async fn display_handler(mut display: DISPLAY) {
     loop {
-        unsafe {
-            FRAMEBUFFER
-                .partial_draw_batched(&mut display)
-                .await
-                .unwrap()
+        if !FB_PAUSED.load(Ordering::Acquire) {
+            unsafe {
+                FRAMEBUFFER
+                    .partial_draw_batched(&mut display)
+                    .await
+                    .unwrap()
+            }
         }
 
         Timer::after_millis(32).await; // 30 fps

kernel/src/elf.rs

@@ -54,6 +54,7 @@ pub async unsafe fn load_binary(name: &ShortFileName) -> Result<EntryFn, &str> {
         let entries: &[(CallAbiTable, usize)] = &[
             (CallAbiTable::Print, abi::print as usize),
             (CallAbiTable::Sleep, abi::sleep as usize),
+            (CallAbiTable::LockDisplay, abi::lock_display as usize),
             (CallAbiTable::DrawIter, abi::draw_iter as usize),
             (CallAbiTable::GetKey, abi::get_key as usize),
         ];

kernel/src/main.rs

@@ -29,7 +29,6 @@ use crate::{
     ui::{SELECTIONS, clear_selection, ui_handler},
 };
 use abi_sys::EntryFn;
-use alloc::string::String;
 use embedded_graphics::{
     pixelcolor::Rgb565,
     prelude::{DrawTarget, RgbColor},

kernel/src/ui.rs

@@ -1,15 +1,16 @@
 use crate::{
-    BINARY_CH, display::FRAMEBUFFER, elf::load_binary, peripherals::keyboard, storage::FileName,
+    BINARY_CH,
+    display::{FB_PAUSED, FRAMEBUFFER},
+    elf::load_binary,
+    peripherals::keyboard,
+    storage::FileName,
 };
 use alloc::{str::FromStr, string::String, vec::Vec};
+use core::sync::atomic::Ordering;
 use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, mutex::Mutex};
-use embassy_time::Timer;
 use embedded_graphics::{
     Drawable,
-    mono_font::{
-        MonoTextStyle,
-        ascii::{FONT_9X15, FONT_10X20},
-    },
+    mono_font::{MonoTextStyle, ascii::FONT_10X20},
     pixelcolor::Rgb565,
     prelude::{Dimensions, Point, Primitive, RgbColor, Size},
     primitives::{PrimitiveStyle, Rectangle},
@@ -81,6 +82,8 @@ async fn draw_selection() {
     const NO_BINS: &str = "No Programs found on SD Card. Ensure programs end with '.bin', and are located in the root directory";
     let no_bins = String::from_str(NO_BINS).unwrap();
 
+    FB_PAUSED.store(true, Ordering::Release); // ensure all elements show up at once
+
     if file_names.is_empty() {
         TextBox::new(
             &no_bins,
@@ -124,6 +127,7 @@ async fn draw_selection() {
     }
 
     guard.changed = false;
+    FB_PAUSED.store(false, Ordering::Release); // ensure all elements show up at once
 }
 
 #[derive(Clone)]