From 854140850478860f6ce5a2726a90cfcd77da4c98 Mon Sep 17 00:00:00 2001
From: Simen Svale <simen@sanity.io>
Date: Tue, 30 Dec 2025 04:12:15 +0100
Subject: [PATCH] Fix DisplayGet: add ensureStopped, response type, correct
 body parsing
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- Add ensureStopped() before DisplayGet to ensure VICE is ready
- Add ResponseType.DisplayGet (0x84) to types
- Fix response parsing: FL(4)+DW(2)+DH(2)+XO(2)+YO(2)+IW(2)+IH(2)+BP(1)+BL(4)+BD
- Width/height are 16-bit not 32-bit per VICE docs

🤖 Generated with [Claude Code](https://claude.ai/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
---
 src/protocol/client.ts | 31 ++++++++++++++++++-------------
 src/protocol/types.ts  |  1 +
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/src/protocol/client.ts b/src/protocol/client.ts
index 042ed49..5e5cb31 100644
--- a/src/protocol/client.ts
+++ b/src/protocol/client.ts
@@ -726,26 +726,31 @@ export class ViceClient {
     innerHeight: number;
     pixels: Buffer;
   }> {
+    // Ensure VICE is stopped before display capture
+    await this.ensureStopped();
+
     // Body: useVicii(1) + format(1)
     // Format: 0 = indexed 8-bit
     const body = Buffer.alloc(2);
     body[0] = useVicii ? 1 : 0;
     body[1] = 0; // 8-bit indexed
 
-    const response = await this.sendCommand(Command.DisplayGet, body);
+    // Response type is 0x84 (same as command)
+    const response = await this.sendCommand(Command.DisplayGet, body, ResponseType.DisplayGet);
 
-    // Parse response
-    // Response: length(4) + width(4) + height(4) + bpp(1) + offsetX(4) + offsetY(4) +
-    //           innerWidth(4) + innerHeight(4) + pixels...
-    const dataLength = response.body.readUInt32LE(0);
-    const width = response.body.readUInt32LE(4);
-    const height = response.body.readUInt32LE(8);
-    const bitsPerPixel = response.body[12];
-    const offsetX = response.body.readUInt32LE(13);
-    const offsetY = response.body.readUInt32LE(17);
-    const innerWidth = response.body.readUInt32LE(21);
-    const innerHeight = response.body.readUInt32LE(25);
-    const pixels = response.body.subarray(29, 29 + dataLength);
+    // Parse response per VICE docs:
+    // FL(4) + DW(2) + DH(2) + XO(2) + YO(2) + IW(2) + IH(2) + BP(1) + BL(4) + BD(BL)
+    // FL = length of fields before display buffer (should be 17)
+    // const fieldsLength = response.body.readUInt32LE(0); // Not used but documented
+    const width = response.body.readUInt16LE(4);          // DW - debug width
+    const height = response.body.readUInt16LE(6);         // DH - debug height
+    const offsetX = response.body.readUInt16LE(8);        // XO - x offset
+    const offsetY = response.body.readUInt16LE(10);       // YO - y offset
+    const innerWidth = response.body.readUInt16LE(12);    // IW - inner width
+    const innerHeight = response.body.readUInt16LE(14);   // IH - inner height
+    const bitsPerPixel = response.body[16];               // BP - bits per pixel
+    const bufferLength = response.body.readUInt32LE(17);  // BL - buffer length
+    const pixels = response.body.subarray(21, 21 + bufferLength); // BD - display buffer
 
     return {
       width,
diff --git a/src/protocol/types.ts b/src/protocol/types.ts
index ed12a4c..998fc22 100644
--- a/src/protocol/types.ts
+++ b/src/protocol/types.ts
@@ -77,6 +77,7 @@ export enum ResponseType {
   Undump = 0x42,
   ResourceGet = 0x51,
   ResourceSet = 0x52,
+  DisplayGet = 0x84,
 
   // Async event codes (sent by VICE unprompted)
   JAM = 0x61,                // CPU jam event