feat(display-server): add DisplayServer<F: Framebuffer> with protocol, mock adapter, and tests

crates/servers/display-server/src/protocol.rs

@@ -0,0 +1,76 @@
+use server_framework::{Decode, Encode};
+
+#[derive(Debug, PartialEq)]
+pub enum DisplayRequest {
+    DrawRect { x: u16, y: u16, w: u16, h: u16, color: u32 },
+    Clear { color: u32 },
+    Flush,
+    GetDimensions,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum DisplayResponse {
+    Ok,
+    Dimensions { width: u16, height: u16 },
+    Error,
+}
+
+impl Encode for DisplayRequest {
+    fn encode(&self) -> [usize; 4] {
+        match self {
+            DisplayRequest::DrawRect { x, y, w, h, color } => {
+                let xy = (*x as usize) | ((*y as usize) << 16);
+                let wh = (*w as usize) | ((*h as usize) << 16);
+                [0, xy, wh, *color as usize]
+            }
+            DisplayRequest::Clear { color } => [1, *color as usize, 0, 0],
+            DisplayRequest::Flush => [2, 0, 0, 0],
+            DisplayRequest::GetDimensions => [3, 0, 0, 0],
+        }
+    }
+}
+
+impl Decode for DisplayRequest {
+    fn decode(words: [usize; 4]) -> Option<Self> {
+        match words[0] {
+            0 => {
+                let x = (words[1] & 0xFFFF) as u16;
+                let y = ((words[1] >> 16) & 0xFFFF) as u16;
+                let w = (words[2] & 0xFFFF) as u16;
+                let h = ((words[2] >> 16) & 0xFFFF) as u16;
+                let color = words[3] as u32;
+                Some(DisplayRequest::DrawRect { x, y, w, h, color })
+            }
+            1 => Some(DisplayRequest::Clear { color: words[1] as u32 }),
+            2 => Some(DisplayRequest::Flush),
+            3 => Some(DisplayRequest::GetDimensions),
+            _ => None,
+        }
+    }
+}
+
+impl Encode for DisplayResponse {
+    fn encode(&self) -> [usize; 4] {
+        match self {
+            DisplayResponse::Ok => [0, 0, 0, 0],
+            DisplayResponse::Dimensions { width, height } => {
+                [1, *width as usize, *height as usize, 0]
+            }
+            DisplayResponse::Error => [2, 0, 0, 0],
+        }
+    }
+}
+
+impl Decode for DisplayResponse {
+    fn decode(words: [usize; 4]) -> Option<Self> {
+        match words[0] {
+            0 => Some(DisplayResponse::Ok),
+            1 => Some(DisplayResponse::Dimensions {
+                width: words[1] as u16,
+                height: words[2] as u16,
+            }),
+            2 => Some(DisplayResponse::Error),
+            _ => None,
+        }
+    }
+}