Development question: PATHRELATIVE_OBJECT question

[coolcajun]

I am working on a Xar File parser at the moment in C# and I am having problems with the PATHRELATIVE_OBJECT record. I am to parse the data section of this record but I am having difficulty extracting that data. How exactly is this data stored? Is it stored differently in Xara X1 than Xara LX?
From the documentation it says that the first Unsigned 32 bit integer is the number of points but after that how are the coordinates stored? Is it a sequence of (X,Y) points?

Here is a code snippet of what I have tried so far. It fails on the next verb I try to grab(The verb value of 255 is invalid). Also I suspect that I am getting the wrong value in num points as I have create multiple bezier paths with different lengths and I still get the value of 6. Any help or insight would be appriciated.

using (BinaryReader tmpReader = new BinaryReader(new MemoryStream(record.Data)))
{
//Determine the number of points
_numPoints = tmpReader.ReadUInt32();

for (int i = 0; i < _numPoints; i++)
{
List<byte> xList = new List<byte>();
List<byte> yList = new List<byte>();
byte verb;
UInt32 x;
UInt32 y;
verb = tmpReader.ReadByte();
x = tmpReader.ReadUInt32();
y = tmpReader.ReadUInt32();

_verbs.Add(verb);
}
}

[fjgaude]

Have you tried asking your question on the dev email?

dev@xaraxtreme.org

This is where the programmers hang out.

frank

[coolcajun]

Frank,

Thanks for the email address.
rob

[GerryI]

There was an error in the documentation for these records that I thought had been fixed. You should try downloading a new copy of the file format spec. The record does not have a count of the number of points. This should be calculated from the size of the record by dividing it by 9 (there are 9 bytes per point in the path). The verbs and coordinates are stored interleaved. For each point you first read a BYTE which is the verb. Then you need to read the next 8 bytes and manipulate them as follows to get the x and y coord values.

BYTE b;
LONG x = 0;
LONG y = 0;
ReadBYTE(&b); x += (b << 24);
ReadBYTE(&b); y += (b << 24);
ReadBYTE(&b); x += (b << 16);
ReadBYTE(&b); y += (b << 16);
ReadBYTE(&b); x += (b << 8);
ReadBYTE(&b); y += (b << 8);
ReadBYTE(&b); x += (b << 0);
ReadBYTE(&b); y += (b << 0);

The first point simply uses this (x, y) coord directly but the following points are then relative to the previous point. When reading the second and subsequent points you must subtract the read value from the previous point, e.g.:

pCoord[i].x = pCoord[i-1].x - TempCoord.x;
pCoord[i].y = pCoord[i-1].y - TempCoord.y;

Hope this helps,
Gerry