Why my file operations fail on the Mac

My first thought for why things fails is the the Environment.SpecialFolder don’t map, and thus I found this page talking about it

So I ran the code on my Windows XP box and got:

Desktop                 C:\Documents and Settings\spilgrim\Desktop
Programs                C:\Documents and Settings\spilgrim\Start Menu\Programs
Personal                C:\Documents and Settings\spilgrim\My Documents
Personal                C:\Documents and Settings\spilgrim\My Documents
Favorites               C:\Documents and Settings\spilgrim\Favorites
Startup                 C:\Documents and Settings\spilgrim\Start Menu\Programs\Startup
Recent                  C:\Documents and Settings\spilgrim\Recent
SendTo                  C:\Documents and Settings\spilgrim\SendTo
StartMenu               C:\Documents and Settings\spilgrim\Start Menu
MyMusic                 C:\Documents and Settings\spilgrim\My Documents\My Music
DesktopDirectory        C:\Documents and Settings\spilgrim\Desktop
MyComputer
Templates               C:\Documents and Settings\spilgrim\Templates
ApplicationData         C:\Documents and Settings\spilgrim\Application Data
LocalApplicationData    C:\Documents and Settings\spilgrim\Local Settings\Application Data
InternetCache           C:\Documents and Settings\spilgrim\Local Settings\Temporary Internet Files
Cookies                 C:\Documents and Settings\spilgrim\Cookies
History                 C:\Documents and Settings\spilgrim\Local Settings\History
CommonApplicationData   C:\Documents and Settings\All Users\Application Data
System                  C:\WINDOWS\system32
ProgramFiles            C:\Program Files
MyPictures              C:\Documents and Settings\spilgrim\My Documents\My Pictures
CommonProgramFiles      C:\Program Files\Common Files

and on my MacBook I get

Desktop                 /Users/parents/Desktop
Programs
Personal                /Users/parents
Favorites
Startup
Recent
SendTo
StartMenu
MyMusic                 /Users/parents/Music
DesktopDirectory        /Users/parents/Desktop
MyComputer
Templates
ApplicationData         /Users/parents/.config
LocalApplicationData    /Users/parents/.local/share
InternetCache
Cookies
History
CommonApplicationData   /usr/share
System
ProgramFiles
MyPictures              /Users/parents/Pictures
CommonProgramFiles

One question raised on that page is why are there two Personal values, and it’s because MyDocuments is the second Enumeration, but .ToString() only names the first in order of an enum set.

So the mystery deepens as I’m using Environment.SpecialFolder.Personal, and therefore it should work, but it seems to be failing to create the data directory, time to explore more…

After some a bit more playing around I found the file “SAVE/player.cha” in my Mac folder structure, and realised I was doing string concatenation with DOS slashes, etc. hard coded all over the place, so I refactored the code, and now it saves/loads files fine.

I then created a Mac .app bundle, so you can now just download form Google Code the Mac OS X version of the game, un-tar/gzip it, and as long as you have Mono installed, tada, instant game action. Albeit slow…

Only problem to solve is that the save files are case sensitive, in how they are searched and managed, and I’ve not got a standard schema in place. I may have to build some wrapper code to manage this, so odd DOS/Windows casing works fine on Mac/Linux systems.

Also I’ll have to make a Linux tar ball for those Linux/Mono people to test play with.

SafeArrayTypeMismatchException

We extended our legacy C++ DCOM application last week, and when the developer wrote the C#.Net end to call the new method, we were getting the error:

System.Runtime.InteropServices.SafeArrayTypeMismatchException

The developer that had added the method stated it work, and pointed to his Delphi test app that worked happily.

Reviewing the method code it all looked fine. Single stepping through the code there where no problems.

The help for this exception says:

The exception thrown when the type of the incoming SAFEARRAY does not match the type specified in the managed signature.

But as we are dynamically calling the method like this:

objAddType = Type.GetTypeFromProgID("DCOM_OBJECT_NAME.COMPANY_CLASS_A");
objAdd = Activator.CreateInstance(objAddType);

object[] input = {};

object result = objAddType.InvokeMember("MethodName", BindingFlags.InvokeMethod, null, objAdd, input);

There was no was no signature.

This is for this Method:

VARIANT CompanyClassAObject::MethodName(void)
{
    VARIANT vaResult;
    VariantInit(&vaResult);

    SAFEARRAY* sfa = GetSafeArray();

    vaResult.vt = VT_UI1 | VT_ARRAY;
    vaResult.parray = sfa;

    return vaResult;
}

with the body of GetSafeArray looked like:

    SAFEARRAYBOUND sfabounds[1];
    sfabounds[0].lLbound = 0;
    sfabounds[0].cElements = bytes_needed;
    SAFEARRAY *sfa = SafeArrayCreate(VT_I1, 1, sfabounds);
    if(sfa)
    {
        void *data;
        if(SafeArrayAccessData(sfa, &data) == S_OK)
        {
            memcpy(data, buffer, bytes_needed);
            SafeArrayUnaccessData(sfa);

            delete buffer;
            return sfa;
        }
    }

The problem ended up being that the SafeArray is created as VT_I1 type but when it is put into the variant type it was typed as VT_UI1.  So the .Net runtime was picking up the conflict and correctly complaining, and once you know what the error is, the exception message make sense.  Funny that!

Setting the SafeArrayCreate to use VT_UI1 and every thing worked.

Creating Palette based GIFs

A question was asked on the mailing list (ages ago) about creating 8-bit GIF files.  I proved this code for simple palette based GIFs, so here it is:

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;

namespace Project
{
    class ProjectMain
    {
        public static void Main()
        {
            GenerateBackgroundImage(Color.AliceBlue, Color.Beige, Color.Cyan, 10, 10, 10, @"c:\image.gif");
        }

        public static void GenerateBackgroundImage(Color leftColour, Color centerColour,
            Color rightColour, int leftWidth, int centerWidth, int rightWidth, string path)
        {

            int width = leftWidth + centerWidth + rightWidth + 2;
            int height = 10;

            using (Bitmap bitmap = new Bitmap(width, height, PixelFormat.Format8bppIndexed))
            {
                Color backColour = Color.White;
                byte idxBackground = 0;
                byte idxLeft = 1;
                byte idxCenter = 2;
                byte idxRight = 3;

                ColorPalette cp = bitmap.Palette;
                cp.Entries[idxBackground] = backColour;
                cp.Entries[idxLeft] = leftColour;
                cp.Entries[idxCenter] = centerColour;
                cp.Entries[idxRight] = rightColour;

                bitmap.Palette = cp;

                fillrect(idxBackground, bitmap, new Rectangle(0, 0, width, height));
                fillrect(idxLeft, bitmap, new Rectangle(0, 0, leftWidth, height));
                fillrect(idxCenter, bitmap, new Rectangle(leftWidth + 1, 0, centerWidth, height));
                fillrect(idxRight, bitmap, new Rectangle(leftWidth + 2 + centerWidth, 0, rightWidth, height));

                bitmap.Save(path, ImageFormat.Gif);
            }
        }

        static void fillrect(byte colorIndex, Bitmap b, Rectangle r)
        {
            BitmapData bmpData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.WriteOnly, b.PixelFormat);

            // Get the address of the first line.
            IntPtr ptr = bmpData.Scan0;

            // Declare an array to hold the bytes of the bitmap.
            // This code is specific to a bitmap with 8 bits index per pixels.
            int bytes = b.Width * b.Height;
            byte[] Values = new byte[bytes];

            // Copy the RGB values into the array.
            Marshal.Copy(ptr, Values, 0, bytes);

            for (int y = r.Top; y < r.Bottom; y++)
            {
                for (int x = r.Left; x < r.Right; x++)
                {
                    Values[(y * b.Width) + x] = colorIndex;
                }
            }

            // Copy the values back to the bitmap
            Marshal.Copy(Values, 0, ptr, bytes);

            // Unlock the bits.
            b.UnlockBits(bmpData);
        }
    }
}

I would change fillrect, to seperate out the locking, and Marshal calls, to CreateTempBuffer, FillTempBuffer, and WriteTempBuffer functions, if you were to use fillrect more than a couple times.  But as it stands, the code is correct after each call.

Loving the Visual Studio 2008 compiler

I have been finding lambda and extension methods really helpful in my game port.

Blobs of C styled single linked list code, when changed to generic lists boil down to one line.

like this:

Item item = player.itemsPtr;
while (item != null)
{
    Item next_item = item.next;

    if (item_type == item.type)
    {
        lose_item(item, player); // just removes from linked list.
    }
    item = next_item;
}

to this:

player.items.RemoveAll(item => item.type == item_type);

much nicer.

Microsoft UNPLUGGED – WPF & VS2008

I attended the November Unplugged WPF & VS2008 developer session on Tuesday.

JD’s talk was well balanced, and covered the basics of what WPF is, how the UI and UX work.  He avoided only showing the shiny demo screens and dug deeper into Command and RoutedEvents and how the UI and UX are decoupled.

WPF is so big, and a bit of a mind shift from VB6 drag and drop that I’m not sure there is much more that can be demoed to a general audience.

Kirk’s Visual Studio 2008 talk was fantastic.  Lots of keyboard short-cuts for tasks I’m currently doing via the  mouse, so I’m very pleased to learn the key combo’s.

I’m torn between Crtl + . and F8 being my absolute take-away gems, both will be used heavily.  Nice to see a talk about using the tools better.

There were some good give-away’s, an office 2007 license, a wireless mouse and a 22″ wide screen panel.  Of which I didn’t win any.

This has made me more keen to port CotAB to Silverlight, just for the experience of it.

Before the event I attended a MS feedback discussion group.  So funny to see who of the .Net CHCH scene turned-up.  It was good to talk about issues, impressions, and opinions.  I hope Microsoft guys got the value they were hoping to get.