Method decodeRect

systemvm/agent/noVNC/core/decoders/hextile.js:19–132

(x, y, width, height, sock, display, depth)

    }

    decodeRect(x, y, width, height, sock, display, depth) {
        if (this._tiles === 0) {
            this._tilesX = Math.ceil(width / 16);
            this._tilesY = Math.ceil(height / 16);
            this._totalTiles = this._tilesX * this._tilesY;
            this._tiles = this._totalTiles;
        }

        while (this._tiles > 0) {
            let bytes = 1;

            if (sock.rQwait("HEXTILE", bytes)) {
                return false;
            }

            let subencoding = sock.rQpeek8();
            if (subencoding > 30) {  // Raw
                throw new Error("Illegal hextile subencoding (subencoding: " +
                            subencoding + ")");
            }

            const currTile = this._totalTiles - this._tiles;
            const tileX = currTile % this._tilesX;
            const tileY = Math.floor(currTile / this._tilesX);
            const tx = x + tileX * 16;
            const ty = y + tileY * 16;
            const tw = Math.min(16, (x + width) - tx);
            const th = Math.min(16, (y + height) - ty);

            // Figure out how much we are expecting
            if (subencoding & 0x01) {  // Raw
                bytes += tw * th * 4;
            } else {
                if (subencoding & 0x02) {  // Background
                    bytes += 4;
                }
                if (subencoding & 0x04) {  // Foreground
                    bytes += 4;
                }
                if (subencoding & 0x08) {  // AnySubrects
                    bytes++;  // Since we aren't shifting it off

                    if (sock.rQwait("HEXTILE", bytes)) {
                        return false;
                    }

                    let subrects = sock.rQpeekBytes(bytes).at(-1);
                    if (subencoding & 0x10) {  // SubrectsColoured
                        bytes += subrects * (4 + 2);
                    } else {
                        bytes += subrects * 2;
                    }
                }
            }

            if (sock.rQwait("HEXTILE", bytes)) {
                return false;
            }