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It probably gets even crazier in .Net 3 and above as managed threads are generally serviced by a central threadPool, and you just get the next one to stick up it's hand and admit to not doing any work at the moment. It will then start when it is ready. If the pool is empty the framework just extends the pool, calls a party and a whole load more threads become available... Not unlike the highfliers of the hollywood party scene.
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Did that actually happen in 3.0? I was under the impression 3.0 and 3.5 didn't change anything to what already existed in 2.0, it just added functionality. It would be more likely to hold true since 4.0 but I haven't observed (nor tested or analyzed) these aspects, I just have known all along it was going to happen someday, as it is in MSDN doc since day 1.
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Depends.
3.0 introduced the ThreadPool but you could still do it the same old way if you wanted. Not sure about 4.0.
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Threads can be expected to start and threads can be expected to stop(maybe). All other assumptions are not thread safe.
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Yeah, I figured... and honestly I am not surprised, especially now days with the progression from simple clock allocation over to physical core style allocation.
Just makes me wonder if REAL multi-threading, outside of the typical ‘I just want to be able to do a few things at a time to help increase efficiency’ is really used today except for some very time-critical systems.
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.NET 3.5
At loading of the map of a TIFF-file compressed by a JPEG algorithm in class Bitmap according to a code:
<br />
string sFileName = "C:\Test.tif"; <br />
FileStream m_WorkFileStream = new FileStream (sFileName, FileMode. Open, FileAccess. Read, FileShare. ReadWrite | FileShare. Delete); <br />
Bitmap m_pBitMap = new Bitmap (m_WorkFileStream);<br />
There is an elimination on the last line «Parameter is not valid». How it is necessary to load the map from a TIFF-file contracted by a JPEG-compression?
File example on http://ifolder.ru/19301311
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GDI+ doesn't support JPEG compressed (LZW) TIFF files.
You'll have to use a third party library to handles images of this type.
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Hi. I'm using an embed windows media player in a windows form in vb.net.
The Media Player has the uiMode = none. The Media Player Control has a fixede size of width = 480 and height =320
The videos plays fine, but when i pause a video(with a button of my form) the windows media player change its size without any reason. it happens sometimes when the video starts too. Does Anybody know why this is happening and how can i fix it?.
Please forgive my english. I need help. Any suggestions or article you know about this topic.
Thanks.
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For a side project I am working on, I want to write a layout engine for a very simplified, light-weight mark-up language that will be used for writing hypernovels, also known as interactive fiction (read a page, click on one of the links on the page, and follow the story depending on where the link leads.) For flexibility, I would rather try and write my own engine rather than rely on HTML or XSL transformation.
The mark-up of the page text has <p>, <strong>, <em> and <hr/> tags, which work just like HTML. I am also adding a <high> (highlight) tag which will normally underline text, and a <link> tag to replace the HTML <a> tag (to avoid confusion over very different attributes.) Right now, I am only interested in finding a technique for doing the layout, but eventually the reader will be able to set preferences such as font family, font size and color.
The approach I am working on now is to parse the text into blocks with various rendering styles, use DrawString to write the blocks onto a custom control out one by one, then make a note as to the location of where the last block ended to be the starting location of the next block. The pages would be pre-validated before the book file is created, so I don't need to worry about missing or misaligned tags.
I have tracked down some open source materials, such as the Gecko engine used in Firefox. Unfortunately, the source code has all been complete browser implementations, and I don't really have the time to go through and try to separate the layout engine from JavaScript support, managing plug-ins and gracefully handling cantankerous web servers that have been running for 20 years. What can I say, I'm lazy like that.
Any suggestions as to technique, books, web sites, etc. that present the theory and practice of laying out and rendering marked-up text would be much appreciated. I have a strong preference for VB.Net or C# code, but anything that I can translate into .Net will be welcome, as would materials discussing the theory without the practice.
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Gregory.Gadow wrote: use DrawString to write the blocks onto a custom control out one by one
I would try a RichTextBox first -- Gregory.Gadow wrote: I'm lazy like that
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I have considered using a RichTextBox, but I figured that would mean translating the page into RTF first, which paints me into a corner I would rather avoid.
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Creating an HTML document and feeding it to a WebBrowser would be easier than creating RTF.
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That may be what I end up doing. I was particularly keen on creating a custom link tag; if I write the project in HTML then I will have to have each and every page -- potentially hundreds of them for a full novel -- as separate page files, and managing the network of links becomes unwieldy. My own mark-up would let me design a tag that could pull a page out of a compiled data store, and other tags to efficiently encode meta-data.
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You could have virtual HTML pages by using an embedded web server; in such scheme your browser gets a page from the built-in server, which does whatever it takes to generate the HTML page on the spot; there is no need to have all the HTML pages ready beforehand.
I've done this, based on the ideas from a CodeProject article, unfortunately the link does no longer work: http://www.codeproject.com/KB/IP/CSHTTPServer.asxp[^]. Search for embedded HTTP server I'd say.
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The ultimate idea is to have a single desktop or mobile application and a library of hypernovel files, much like a ebook reader and a collection of .epub files. The challenge I am looking to solve is that readers load the entire file, while I want to load a single arbitrary page. If there is a server, it would be built into the reader app.
The virtual HTML idea sounds promising, though; I will do some research in that direction. Thanks.
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The control does that for you.
(Easier than trying to draw on something.)
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Bold text? Italics? Links that will change the cursor on hover and take the user to a different page when clicked?
I'm pretty sure I cannot do that just by writing text to a rich text control.
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Sure, if you do it right.
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It is possible that I am the only person in the world who didn't already know this , but there is one very important difference between the behavior of a For Each loop that iterates through an array (or an array of Structures, which was the context that has just bitten me!) and the corresponding For Next loop. When you use For Each, the item that is passed into the loop is effectively passed by Value. Any assignment that you make to it within the loop is lost as soon as you leave it. If you put exactly the same code within an equivalent For Next loop, the assignments "stick".
The following very short Console Application demonstrates this:
Module Module1
Dim intArray(10) As Integer
Sub Main()
Dim intI As Integer
For intI = 0 To 10 ' fill the array
intArray(intI) = intI
Next
For Each item In intArray ' show that the data has been stored
Console.Write(item.ToString & ", ")
Next
Console.Write(vbCrLf)
intI = 10
For Each item In intArray ' fill it again in reverse order
item = intI
Console.Write(item.ToString & ", ") ' show that contents of the "local" copy of the array element has been changed
intI -= 1
Next
Console.Write(vbCrLf)
For Each item In intArray
Console.Write(item.ToString & ", ") ' but the contents of the actual array have not!
Next
Console.Write(vbCrLf)
Console.ReadLine()
End Sub
End Module
I was (eventually) able to find documentation of this behavior in the VB .Net docs (ms-help://MS.VSCC.v90/MS.MSDNQTR.v90.en/dv_vbalr/html/ebce3120-95c3-42b1-b70b-fa7da40c75e2.htm), but I could not find any explicit mention of it in any of the books I have or in any other on-line resources, even though all of the latter do only show For Each being used in ways that work. I am hoping that this note may help others to avoid the head-scratching that I went through before if figured out why my code was not working.
modified on Monday, September 13, 2010 11:27 AM
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I'm not sure I ever used a For Each in VB.NET; however the same is true in C#, and there the compiler would not even let you modify the variable, so I was surprised to see VB.NET lets you do item = intI at all.
BTW: I trust the snippet is just an example of the phenomenon. If you want to turn an array upside down, you could as well use Array.Reverse()
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Yes, it was just an intentionally trivial example. I wouldn't have minded (much ), and I certainly wouldn't have wasted the time I ended up spending on the issue, if the compiler had flagged the assignment as an error.
I don't see why this restriction should be imposed (presumably) by the compiler writers. For an array of substantial structures, it would seem to add complexity and cycles (copying everything instead of passing pointers) to no good purpose.
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There is no willful copying. If it were an array of Forms, you'd get a reference to each Form in turn; as it is an array of ints, you get each int in turn (and not a pointer to an array element). It would be exactly the same if the body of your foreach loop were a separate method, value types get passed by value, reference types get also passed by value, i.e. you get their reference (not a pointer to their reference). That works fine, except for large value types (but then you are always given the advice not to come up with big structs).
I'm not absolutely sure why the languages were designed like that; I realize the collection (the array in your example) could be virtual and could be read-only; all foreach requires is something that is enumarable, so arays, lists, an anything implementing IEnumerable should do. Elements of some of those would not be modifiable by sending a new value through some pointer.
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If I were calling a Sub, I would find it natural (and well-documented!) that I was getting a Value rather than a Reference in the Sub (and I could explicitly change that, if I wanted to). I think that is the in-line nature of and the almost exact parallel between the For Each and For Next syntax and operation, except for this one important detail, that makes the former's behavior feel wrong.
For a simple, one-dimensional, array of any simple value or object type, you are right - the "pass by value" approach will result in no increase in code size or complexity - but even for an array of relatively small structs, a lot of copying will be necessary to (in effect) pass each struct item by value.
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Peter R. Fletcher wrote: a lot of copying will be necessary to (in effect) pass each struct item by value.
And that makes me think it is the reason why C# does not accept any changes to it: they probably don't copy but use the real stuff, which is fine if they disallow any code to change it.
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Actually, they do make a copy, even in the optimized code.
In fact, two copies are made, at least in the code I tested.
See here:
shl rcx,4
mov eax,dword ptr [rbx+rcx+10h]
mov dword ptr [rsp+20h],eax
mov eax,dword ptr [rbx+rcx+14h]
mov dword ptr [rsp+24h],eax
mov eax,dword ptr [rbx+rcx+18h]
mov dword ptr [rsp+28h],eax
mov eax,dword ptr [rbx+rcx+1Ch]
mov dword ptr [rsp+2Ch],eax
lea rcx,[rsp+20h]
mov rax,qword ptr [rcx]
mov qword ptr [rsp+40h],rax
mov rax,qword ptr [rcx+8]
mov qword ptr [rsp+48h],rax
lea rax,[rsp+40h]
movss xmm5,dword ptr [rax]
The C# code:
static void Normalize(Float3[] array)
{
Float3 x = new Float3();
foreach (Float3 f in array)
{
x = f.Normalize();
}
if (array.Length != 0)
throw new Exception(x.ToString());
}
edit: made a slight mistake here, whatever.
If you change "the foreach value" (indirectly, of course), the second copy is affected but not the first. The first copy is never used again.
For primitive types, the code is actually sane.
modified on Monday, September 13, 2010 5:39 PM
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