add experimental null char handling

src/cli.rs

@@ -22,6 +22,11 @@ pub struct Cli {
         help = "Set default log level lower. You can also change this via the RUST_LOG environment variable."
     )]
     pub verbose: bool,
+    #[arg(
+        long,
+        help = "When receiving a null byte as a char in the CharGridCommand, do not overwrite any pixels instead of clearing all pixels."
+    )]
+    pub experimental_null_char_handling: bool,
 }
 
 #[derive(Parser, Debug)]

src/command_executor.rs

@@ -22,6 +22,7 @@ pub struct CommandExecutionContext<'t> {
     luma: &'t RwLock<BrightnessGrid>,
     cp437_font: Cp437Font,
     font_renderer: FontRenderer8x8,
+    experimental_null_char_handling: bool,
 }
 
 #[must_use]
@@ -193,20 +194,30 @@ impl CommandExecute for CharGridCommand {
         for char_y in 0usize..grid.height() {
             for char_x in 0usize..grid.width() {
                 let char = grid.get(char_x, char_y);
-                trace!("drawing {char}");
-
+                let mut bitmap_window = {
                     let pixel_x = (char_x + x) * TILE_SIZE;
                     let pixel_y = (char_y + y) * TILE_SIZE;
-
-                if let Err(e) = context.font_renderer.render(
-                    char,
-                    &mut display
+                    display
                         .window_mut(
                             pixel_x..pixel_x + TILE_SIZE,
                             pixel_y..pixel_y + TILE_SIZE,
                         )
-                        .unwrap(),
-                ) {
+                        .unwrap()
+                };
+
+                if char == '\0' {
+                    if context.experimental_null_char_handling {
+                        trace!("skipping {char:?}");
+                    } else {
+                        bitmap_window.fill(false);
+                    }
+                    continue;
+                }
+
+                trace!("drawing {char}");
+                if let Err(e) =
+                    context.font_renderer.render(char, &mut bitmap_window)
+                {
                     error!(
                         "stopping drawing text because char draw failed: {e}"
                     );
@@ -256,12 +267,14 @@ impl<'t> CommandExecutionContext<'t> {
         display: &'t RwLock<Bitmap>,
         luma: &'t RwLock<BrightnessGrid>,
         font_renderer: FontRenderer8x8,
+        experimental_null_char_handling: bool,
     ) -> Self {
         CommandExecutionContext {
             display,
             luma,
             font_renderer,
             cp437_font: Cp437Font::default(),
+            experimental_null_char_handling,
         }
     }
 }

src/main.rs

@@ -39,7 +39,12 @@ fn main() {
         .font
         .map(FontRenderer8x8::from_name)
         .unwrap_or_else(FontRenderer8x8::default);
-    let context = CommandExecutionContext::new(&display, &luma, font_renderer);
+    let context = CommandExecutionContext::new(
+        &display,
+        &luma,
+        font_renderer,
+        cli.experimental_null_char_handling,
+    );
     let mut udp_server = UdpServer::new(
         cli.bind,
         stop_udp_rx,