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• OpenCV: Getting and Setting Camera Settings

  - by jhaip

  I have been searching around and can't find an example of how to get and set the camera capturing settings. For example the capturing resolution, fps, color balance, etc. I have only seen examples of how to change the settings when saving the captured video but I want to be able to find all the camera's capturing modes and choose which one I want. For example, I am using the PS3eye webcam and in the test program it allows you to change the settings (320x240 at 15,30,60,120 fps, 640x480 at 15,30,60,75 fps). So is there a function in OpenCV for getting all the camera's capture modes and choosing one? I remember in OpenFrameworks there was a function to change these settings but I would like to know how to do it in OpenCV. Here is the code for OpenFrameworks with OpenCV that does sort of what I want: vidGrabber.setDeviceID( 4 ); vidGrabber.setDesiredFrameRate( 30 ); //I want this vidGrabber.videoSettings(); vidGrabber.setVerbose(true); vidGrabber.initGrabber(320,240); //And this

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• Which isolation level should I use for the following insert-if-not-present transaction?

  - by Steve Guidi

  I've written a linq-to-sql program that essentially performs an ETL task, and I've noticed many places where parallelization will improve its performance. However, I'm concerned about preventing uniquness constraint violations when two threads perform the following task (psuedo code). Record CreateRecord(string recordText) { using (MyDataContext database = GetDatabase()) { Record existingRecord = database.MyTable.FirstOrDefault(record.KeyPredicate()); if(existingRecord == null) { existingRecord = CreateRecord(recordText); database.MyTable.InsertOnSubmit(existingRecord); } database.SubmitChanges(); return existingRecord; } } In general, this code executes a SELECT statement to test for record existance, followed by an INSERT statement if the record doesn't exist. It is encapsulated by an implicit transaction. When two threads run this code for the same instance of recordText, I want to prevent them from simultaneously determining that the record doesn't exist, thereby both attempting to create the same record. An isolation level and explicit transaction will work well, except I'm not certain which isolation level I should use -- Serializable should work, but seems too strict. Is there a better choice?

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• Modify existing struct alignment in Visual C++

  - by Crend King

  Is there a way to modify the member alignment of an existing struct in Visual C++? Here is the background: I use an 3rd-party library, which uses several structs. To fill up the structs, I pass the address of the struct instance to some functions. Unfortunately, the functions only returns unaligned buffer, so that data of some members are always wrong. /Zp is out of choice, since it breaks the other parts of the program. I know #pragma pack modifies the alignment of the following struct, but I do not want to copy the structs into my code, for the definitions in the library might change in the future. Sample code: test.h: struct am_aligned { BYTE data1[10]; ULONG data2; }; test.cpp: include "test.h" // typedef alignment(1) struct am_aligned am_unaligned int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) { char buffer[20] = {}; for (int i = 0; i < sizeof(unaligned_struct); i++) { buffer[i] = i; } am_aligned instance = *(am_aligned*) buffer; return 0; } instance.data2 is 0x0f0e0d0c, while 0x0d0c0b0a is desired. The commented line does not work of course. Thanks for help!

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• Problem with .release behavior in file_operations

  - by Yannick

  Hello, I'm dealing with a problem in a kernel module that get data from userspace using a /proc entry. I set open/write/release entries for my own defined /proc entry, and manage well to use it to get data from userspace. I handle errors in open/write functions well, and they are visible to user as open/fopen or write/fwrite/fprintf errors. But some of the errors can only be checked at close (because it's the time all the data is available). In these cases I return something different than 0, which I supposed to be in some way the value 'close' or 'fclose' will return to user. But whatever the value I return my close behave like if all is fine. To be sure I replaced all the release() code by a simple 'return(-1);' and wrote a program that open/write/close the /proc entry, and prints the close return value (and the errno). It always return '0' whatever the value I give. Behavior is the same with 'fclose', or by using shell mechanism (echo "..." /proc/my/entry). Any clue about this strange behavior that is not the one claimed in many tutorials I found? BTW I'm using RHEL5 kernel (2.6.18, redhat modified), on a 64bit system. Thanks. Regards, Yannick

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• iPhone shooter game bullet physics!

  - by user298261

  Hello, Making a new shooter game here in the vein of "Galaga" (my fav shooter game growing up). Here's the code I have for bullet physics: -(IBAction)shootBullet:(id)sender{ imgBullet.hidden = NO; timer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(fireBullet) userInfo:Nil repeats:YES]; } -(void)fireBullet{ imgBullet.center = CGPointMake(imgBullet.center.x + bulletVelocity.x , imgBullet.center.y + bulletVelocity.y); if(imgBullet.center.y <= 0){ imgBullet.hidden = YES; imgBullet.center = self.view.center; [timer invalidate]; } } Anyway, the obvious issue is that once the bullet leaves the screen, its center is being reset, so I'm reusing the same bullet for each press of the "fire" button. Ideally, I would like the user to be able to spam the "fire" button without causing the program to crash. How would I tinker this existing code so that a bullet object would spawn on the button press each time, and then despawn after it exits the screen, or collides with an enemy? Thank you for any assistance you can offer!

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• problem finding a header with a c++ makefile

  - by Max

  Hi. I've started working with my first makefile. I'm writing a roguelike in C++ using the libtcod library, and have the following hello world program to test if my environment's up and running: #include "libtcod.hpp" int main() { TCODConsole::initRoot(80, 50, "PartyHack"); TCODConsole::root->printCenter(40, 25, TCOD_BKGND_NONE, "Hello World"); TCODConsole::flush(); TCODConsole::waitForKeypress(true); } My project directory structure looks like this: /CppPartyHack ----/libtcod-1.5.1 # this is the libtcod root folder --------/include ------------libtcod.hpp ----/PartyHack --------makefile --------partyhack.cpp # the above code (while we're here, how do I do proper indentation? Using those dashes is silly.) and here's my makefile: SRCDIR = . INCDIR = ../libtcod-1.5.1/include CFLAGS = $(FLAGS) -I$(INCDIR) -I$(SRCDIR) -Wall CC = gcc CPP = g++ .SUFFIXES: .o .h .c .hpp .cpp $(TEMP)/%.o : $(SRCDIR)/%.cpp $(CPP) $(CFLAGS) -o $@ -c $< $(TEMP)/%.o : $(SRCDIR)/%.c $(CC) $(CFLAGS) -o $@ -c $< CPP_OBJS = $(TEMP)partyhack.o all : partyhack partyhack : $(CPP_OBJS) $(CPP) $(CPP_OBJS) -o $@ -L../libtcod-1.5.1 -ltcod -ltcod++ -Wl,-rpath,. clean : \rm -f $(CPP_OBJS) partyhack I'm using Ubuntu, and my terminal gives me the following errors: max@max-desktop:~/Desktop/Development/CppPartyhack/PartyHack$ make g++ -c -o partyhack.o partyhack.cpp partyhack.cpp:1:23: error: libtcod.hpp: No such file or directory partyhack.cpp: In function ‘int main()’: partyhack.cpp:5: error: ‘TCODConsole’ has not been declared partyhack.cpp:6: error: ‘TCODConsole’ has not been declared partyhack.cpp:6: error: ‘TCOD_BKGND_NONE’ was not declared in this scope partyhack.cpp:7: error: ‘TCODConsole’ has not been declared partyhack.cpp:8: error: ‘TCODConsole’ has not been declared make: * [partyhack.o] Error 1 So obviously, the makefile can't find libtcod.hpp. I've double checked and I'm sure the relative path to libtcod.hpp in INCDIR is correct, but as I'm just starting out with makefiles, I'm uncertain what else could be wrong. My makefile is based off a template that the libtcod designers provided along with the library itself, and while I've looked at a few online makefile tutorials, the code in this makefile is a good bit more complicated than any of the examples the tutorials showed, so I'm assuming I screwed up something basic in the conversion. Thanks for any help.

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• How do you use stl's functions like for_each?

  - by thomas-gies

  I started using stl containers because they came in very handy when I needed functionality of a list, set and map and had nothing else available in my programming environment. I did not care much about the ideas behind it. STL documentations were only interesting up to the point where it came to functions, etc. Then I skipped reading and just used the containers. But yesterday, still being relaxed from my holidays, I just gave it a try and wanted to go a bit more the stl way. So I used the transform function (can I have a little bit of applause for me, thank you). From an academic point of view it really looked interesting and it worked. But the thing that boroughs me is that if you intensify the use of those functions, you need 10ks of helper classes for mostly everything you want to do in your code. The hole logic of the program is sliced in tiny pieces. This slicing is not the result of god coding habits. It's just a technical need. Something, that makes my life probably harder not easier. And I learned the hard way, that you should always choose the simplest approach that solves the problem at hand. And I can't see what, for example, the for_each function is doing for me that justifies the use of a helper class over several simple lines of code that sit inside a normal loop so that everybody can see what is going on. I would like to know, what you are thinking about my concerns? Did you see it like I do when you started working this way and have changed your mind when you got used to it? Are there benefits that I overlooked? Or do you just ignore this stuff as I did (and will go an doing it, probably). Thanks. PS: I know that there is a real for_each loop in boost. But I ignore it here since it is just a convenient way for my usual loops with iterators I guess.

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• BinaryFormatter in C# a good way to read files?

  - by mr-pac

  I want to read a binary file which was created outside of my program. One obvious way in C# to read a binary file is to define class representing the file and then use a BinaryReader and read from the file via the Read* methods and assign the return values to the class properties. What I don't like with the approach is that I manually have to write code that reads the file, although the defined structure represents how the file is stored. I also have to keep the order correct when I read. After looking a bit around I came across the BinaryFormatter which can automatically serialize and deserialze object in binary format. One great advantage would be that I can read and also write the file without creating additional code. However I wonder if this approach is good for files created from other programs on not just serialized .NET objects. Take for example a graphics format file like BMP. Would it be a good idea to read the file with a BinaryFormatter or is it better to manually and write via BinaryReader and BinaryWriter? Or are there any other approaches which suit better? I'am not looking for concrete examples but just for an advice what is the best way to implement that.

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• Goldbach theory in C

  - by nofe

  I want to write some code which takes any positive, even number (greater than 2) and gives me the smallest pair of primes that sum up to this number. I need this program to handle any integer up to 9 digits long. My aim is to make something that looks like this: Please enter a positive even integer ( greater than 2 ) : 10 The first primes adding : 3+7=10. Please enter a positive even integer ( greater than 2 ) : 160 The first primes adding : 3+157=160. Please enter a positive even integer ( greater than 2 ) : 18456 The first primes adding : 5+18451=18456. I don't want to use any library besides stdio.h. I don't want to use arrays, strings, or anything besides for the most basic toolbox: scanf, printf, for, while, do-while, if, else if, break, continue, and the basic operators (<,, ==, =+, !=, %, *, /, etc...). Please no other functions especially is_prime. I know how to limit the input to my needs so that it loops until given a valid entry. So now I'm trying to figure out the algorithm. I thought of starting a while loop like something like this: #include <stdio.h> long first, second, sum, goldbach, min; long a,b,i,k; //indices int main (){ while (1){ printf("Please enter a positive integer :\n"); scanf("%ld",&goldbach); if ((goldbach>2)&&((goldbach%2)==0)) break; else printf("Wrong input, "); } while (sum!=goldbach){ for (a=3;a<goldbach;a=(a+2)) for (i=2;(goldbach-a)%i;i++) first = a; for (b=5;b<goldbach;b=(b+2)) for (k=2;(goldbach-b)%k;k++) sum = first + second; } }

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• Simple average calculation

  - by sasquatch90

  I'm trying to write program calculating average of given numbers stored in an array. Amount of numbers should be not more than 100, and user should input them until a !int variable is given : #include <iostream> #include <conio.h> using namespace std; double average(int tab[], int i){ int sum=0; for(int j=0; j<i; ++j){ sum+=tab[j]; } return (double)sum/i; } int main() { int tab[100]; int n=0; int number=0; do { if(n < 100){ cout << "Give " << n+1 << " number : "; cin >> number; tab[n]=number; number=0; ++n; } else{ break; } } while( !isdigit(number) ); cout << average(tab, n) << endl; getch(); return 0; } Why after giving char, it prints me 'Give n number:' for all empty cells of my array ? It should end and use only given numbers.

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• How to call Java code from Javascript and assign a value to a JSP page?

  - by Frank

  I have the following "form.jsp" program, it generates a drop down list, below the list is a textarea to show the display_name of a selected item, now when user selected a item, it shows the selected item id in the textarea, how to call the DB from my code and get the display_name in the javascript so the result display_name will be shown in the textarea ? <%@ taglib prefix="s" uri="/struts-tags"%> <script type="text/javascript"> function callme(Display_Name) { alert('callme : Display_Name = '+Display_Name); var v=document.getElementById('hiddenValue').value; alert('hiddenValue : v = '+v); document.getElementById('defaultDisplayName').value=Display_Name; } </script> <s:hidden id="pricelist.id" name="pricelist.id" value="%{pricelist.id}"/> <div class="dialog"> <table> <tbody> <s:if test="%{enableProductList}"> <tr class="prop"> <td valign="top" class="name required"><label for="description">Product:</label></td> <td valign="top"> <s:select id="productPrice.product" name="productPrice.product" headerKey="0" headerValue="-- Select Product --" list="products" listKey="id" listValue="name" value="productPrice.product.id" theme="simple" displayName1='value' onchange="callme(value)" /> <s:hidden id="hiddenValue" name="hiddenValue" value="123"/> </td> </tr> </s:if> <tr class="prop"> <td valign="top" class="name"><label for="description">Default Display Name:</label></td> <td valign="top"><s:textarea id="defaultDisplayName" name="defaultDisplayName" theme="simple" readonly="true"/></td> </tr> See attached image for details, in the DB, a product table has the product Id and display_name, I know the Id, how to use Java to get the display_name and plug it into the jsp ?

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• Scope of the c++ using directive

  - by ThomasMcLeod

  From section 7.3.4.2 of the c++11 standard: A using-directive specifies that the names in the nominated namespace can be used in the scope in which the using-directive appears after the using-directive. During unqualified name lookup (3.4.1), the names appear as if they were declared in the nearest enclosing namespace which contains both the using-directive and the nominated namespace. [ Note: In this context, “contains” means “contains directly or indirectly”. —end note ] What do the second and third sentences mean exactly? Please give example. Here is the code I am attempting to understand: namespace A { int i = 7; } namespace B { using namespace A; int i = i + 11; } int main(int argc, char * argv[]) { std::cout << A::i << " " << B::i << std::endl; return 0; } It print "7 7" and not "7 18" as I would expect. Sorry for the typo, the program actually prints "7 11".

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• PHP driven site needs password change.

  - by Drea

  I have inherited a website that needs the password changed that accesses the database. I can see that there are two tables within the database but neither of them have username or password info. The previous web guy moved out of the country and can't be reached. I am not up-to-speed enough to figure this out. I have gone through all the files to try and find the answer but can't get it. It's hosted by goDaddy.com and I have changed the passwords there but it didn't change this login info. www.executivehomerents.com/cpanel <-this brings up the prompt for the username & password which I won't give out but the page only gives you 5 choices and none of them deal with changing the password. They are simply to change the data in the tables. If you go to: http://www.websitedatabases.com/ <=this is the company that the PHPMagic program was purchased from-- They have no contact number. Here is another page that might help: http://www.executivehomerents.com/cpanel/dbinput/setup.php I don't think I'll get an answer to this but it's worth a try... thanks.

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• Why does the output look like this?

  - by cjk

  I have a c program below, I would like to send out a 32 bit message in a particular order Eg.0x00000001. #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <stdint.h> struct test { uint16_t a; uint16_t b; }; int main(int argc, char const *argv[]) { char buf[4]; struct test* ptr=(struct test*)buf; ptr->a=0x0000; ptr->b=0x0001; printf("%x %x\n",buf[0],buf[1]); //output is 0 0 printf("%x %x\n",buf[2],buf[3]); //output is 1 0 return 0; } Then I test it by print out the values in char array. I got output in the above comments. Shouldn't the output be 0 0 and 0 1? since but[3] is the last byte? Is there anything I missed? Thanks!

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• Storing strings from a text file/scanner. Array or built-in?

  - by Flowdorio

  This code snippet is to to read a text file, turn the lines into objects through a different public (non changeable) class(externalClass). The external class does nothing but turn strings (lines from the .txt through nextLine) into objects, and is fully functional. The scanner(scanner3) is assigned to the text file. while (scanner3.hasNext()) { externalClass convertedlines = new externalClass(scanner3.nextLine()); I'm not new to programming, but as I'm new to java, I do not know if this requires me to create an array, or if the returned objects are sorted in some other way. i.e is the "importedlines" getting overwritten with each run of the loop(and I need to introduce an array into the loop), or are the objects stored in some way? The question may seem strange, but with the program I am making it would be harder (but definitely not impossible) if I used an array. Any help would be appreciated. As requested, externalClass: public class exernalClass { private String line; externalClass(String inLine){ line = inLine; } public String giveLine() { return line; } }

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• MVVM and avoiding Monolithic God object

  - by bufferz

  I am in the completion stage of a large project that has several large components: image acquisition, image processing, data storage, factory I/O (automation project) and several others. Each of these components is reasonably independent, but for the project to run as a whole I need at least one instance of each component. Each component also has a ViewModel and View (WPF) for monitoring status and changing things. My question is the safest, most efficient, and most maintainable method of instantiating all of these objects, subscribing one class to an Event in another, and having a common ViewModel and View for all of this. Would it best if I have a class called God that has a private instance of all of these objects? I've done this in the past and regretted it. Or would it be better if God relied on Singleton instances of these objects to get the ball rolling. Alternatively, should Program.cs (or wherever Main(...) is) instantiate all of these components, and pass them to God as parameters and then let Him (snicker) and His ViewModel deal with the particulars of running this projects. Any other suggestions I would love to hear. Thank you!

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• Haskell Cons Operator (:)

  - by Carson Myers

  I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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• Pascals Triangle by recursion

  - by Olpers

  Note : My Class Teacher gave me this question as an assignment... I am not asked to do it but please tell me how to do it with recursion Binomial coefficients can be calculated using Pascal's triangle: 1 n = 0 1 1 1 2 1 1 3 3 1 1 4 6 4 1 n = 4 Each new level of the triangle has 1's on the ends; the interior numbers are the sums of the two numbers above them. Task: Write a program that includes a recursive function to produce a list of binomial coefficients for the power n using the Pascal's triangle technique. For example, Input = 2 Output = 1 2 1 Input = 4 Output = 1 4 6 4 1 done this So Far but tell me how to do this with recursion... #include<stdio.h> int main() { int length,i,j,k; //Accepting length from user printf("Enter the length of pascal's triangle : "); scanf("%d",&length); //Printing the pascal's triangle for(i=1;i<=length;i++) { for(j=1;j<=length-i;j++) printf(" "); for(k=1;k<i;k++) printf("%d",k); for(k=i;k>=1;k--) printf("%d",k); printf("\n"); } return 0; }

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• java gui image problem : doesn't display in the background

  - by thegamer

  Hello, i have a query about why is my image not being displayed in my background of my program. I mean i did all the steps necessary and still it would'nt be displayed. The code runs perfectly but without having the image displayed. The directory is written in the good location of the image. I am using java with gui. If anyone could help me solve my problem, i would appreciate :) here is the code below: import java.awt.*; import java.awt.event.*; import javax.swing.*; public class hehe extends JPanel{ public hehe(){ setOpaque(false); setLayout(new FlowLayout()); } public static void main (String args[]){ JFrame win = new JFrame("yooooo"); // it is automaticcally hidden JPanel mainPanel = new JPanel(new BorderLayout()); win.add(mainPanel); JLabel titleLabel = new JLabel("title boss"); titleLabel.setFont(new Font("Arial",Font.BOLD,18)); titleLabel.setForeground(Color.blue); mainPanel.add(titleLabel,BorderLayout.NORTH); win.setSize(382,269); // the dimensions of the image win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); win.setVisible(true); } public void paint(Graphics g) { Image a = Toolkit.getDefaultToolkit().getImage("C:\\Users\\andrea\\Desktop\\Gui\\car"); // car is the name of the image file and is in JPEG g.drawImage(a,0,0,getSize().width,getSize().height,this); super.paint(g); } }

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• Does everything after my try statement have to be encompassed in that try statement to access variab

  - by Mithrax

  I'm learning java and one thing I've found that I don't like, is generally when I have code like this: import java.util.*; import java.io.*; public class GraphProblem { public static void main(String[] args) { if (args.length < 2) { System.out.println("Error: Please specify a graph file!"); return; } FileReader in = new FileReader(args[1]); Scanner input = new Scanner(in); int size = input.nextInt(); WeightedGraph graph = new WeightedGraph(size); for(int i = 0; i < size; i++) { graph.setLabel(i,Character.toString((char)('A' + i))); } for(int i = 0; i < size; i++) { for(int j = 0; j < size; j++) { graph.addEdge(i, j, input.nextInt()); } } // .. lots more code } } I have an uncaught exception around my FileReader. So, I have to wrap it in a try-catch to catch that specific exception. My question is does that try { } have to encompass everything after that in my method that wants to use either my FileReader (in) or my Scanner (input)? If I don't wrap the whole remainder of the program in that try statement, then anything outside of it can't access the in/input because it may of not been initialized or has been initialized outside of its scope. So I can't isolate the try-catch to just say the portion that intializes the FileReader and close the try statement immediately after that. So, is it the "best practice" to have the try statement wrapping all portions of the code that are going to access variables initialized in it? Thanks!

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• Qt/C++ Error handling

  - by ShiGon

  I've been doing a lot of research about handling errors with Qt/C++ and I'm still as lost as when I started. Maybe I'm looking for an easy way out (like other languages provide). One, in particular, provides for an unhandled exception which I use religiously. When the program encounters a problem, it throws the unhandled exception so that I can create my own error report. That report gets sent from my customers machine to a server online which I then read later. The problem that I'm having with C++ is that any error handling that's done has to be thought of BEFORE hand (think try/catch or massive conditionals). In my experience, problems in code are not thought of before hand else there wouldn't be a problem to begin with. Writing a cross-platform application without a cross-platform error handling/reporting/trace mechanism is a little scary to me. My question is: Is there any kind of Qt or C++ Specific "catch-all" error trapping mechanism that I can use in my application so that, if something does go wrong I can, at least, write a report before it crashes?

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• Trying to make a plugin system in C++

  - by Pirate for Profit

  I'm making a task-based program that needs to have plugins. Tasks need to have properties which can be easily edited, I think this can be done with Qt's Meta-Object Compiler reflection capabilities (I could be wrong, but I should be able to stick this in a QtPropertyBrowser?) So here's the base: class Task : public QObject { Q_OBJECT public: explicit Task(QObject *parent = 0) : QObject(parent){} virtual void run() = 0; signals: void taskFinished(bool success = true); } Then a plugin might have this task: class PrinterTask : public Task { Q_OBJECT public: explicit PrinterTask(QObject *parent = 0) : Task(parent) {} void run() { Printer::getInstance()->Print(this->getData()); // fictional emit taskFinished(true); } inline const QString &getData() const; inline void setData(QString data); Q_PROPERTY(QString data READ getData WRITE setData) // for reflection } In a nutshell, here's what I want to do: // load plugin // find all the Tasks interface implementations in it // have user able to choose a Task and edit its specific Q_PROPERTY's // run the TASK It's important that one .dll has multiple tasks, because I want them to be associated by their module. For instance, "FileTasks.dll" could have tasks for deleting files, making files, etc. The only problem with Qt's plugin setup is I want to store X amount of Tasks in one .dll module. As far as I can tell, you can only load one interface per plugin (I could be wrong?). If so, the only possible way to do accomplish what I want is to create a FactoryInterface with string based keys which return the objects (as in Qt's Plug-And-Paint example), which is a terrible boilerplate that I would like to avoid. Anyone know a cleaner C++ plugin architecture than Qt's to do what I want? Also, am I safely assuming Qt's reflection capabilities will do what I want (i.e. able to edit an unknown dynamically loaded tasks' properties with the QtPropertyBrowser before dispatching)?

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• Creating many polygons with OpenGL is slow?

  - by user146780

  I want to draw many polygons to the screen but i'm quickly noticing that it slows down quickly. As a test I did this: for(int i = 0; i < 50; ++i) { glBegin( GL_POLYGON); glColor3f( 0.0f, 1, 0.0f ); glVertex2f( 500.0 + frameGL.GetCameraX(), 0.0f + frameGL.GetCameraY()); glColor3f( 0.0f, 1.0f, 0.0f ); glVertex2f( 900.0 + frameGL.GetCameraX(), 0.0f + frameGL.GetCameraY()); glColor3f( 0.0f, 0.0f, 0.5 ); glVertex2f(900.0 + frameGL.GetCameraX(), 500.0f + frameGL.GetCameraY() + (150)); glColor3f( 0.0f, 1.0f, 0.0f ); glVertex2f( 500 + frameGL.GetCameraX(), 500.0f + frameGL.GetCameraY()); glColor3f( 1.0f, 1.0f, 0.0f ); glVertex2f( 300 + frameGL.GetCameraX(), 200.0f + frameGL.GetCameraY()); glEnd(); } This is only 50 polygons and already it's gtting slow. I can't upload them directly to the card because my program will allow the user to reshape the verticies. My question is, how can I speed this up. I'm not using depth. I also know it's not my GetCamera() functions because if I create 500,000 polygons spread apart t's fine, it just has trouble showing them in the view. If a graphics card can support 500,000,000 on screen polygons per second, this should be easy right? Thanks

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• Organizing a String based on maxlength of each field

  - by pringlesinn

  I've made a program that makes my life easier by reading a class and creating methods like these below: //Ferramentas Parâmetros acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Pesquisa", "ppaParametrosList", null, TipoAcessoBean.TELA)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Gravar", "ppaParametrosHome", "persist", TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Atualizar Dados", "ppaParametrosHome", "update", TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Leitura", "ppaParametrosHome", "find", TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Excluir", "ppaParametrosHome", "remove", TipoAcessoBean.ACAO)); Don't worry about the language. It won't make it harder to understand what I need to make. I want to organize it to be shown like this: //Ferramentas Parâmetros acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Pesquisa" , "ppaParametrosList", null , TipoAcessoBean.TELA)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Gravar" , "ppaParametrosHome", "persist", TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Atualizar Dados", "ppaParametrosHome", "update" , TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Leitura" , "ppaParametrosHome", "find" , TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Excluir" , "ppaParametrosHome", "remove" , TipoAcessoBean.ACAO)); I'm reading the whole class with Scanner, but once I read, I save only the things I want in a Collection containing this things above. How can I make a method to complete with blank to make it organized?

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• Parsing: How to make error recovery in grammars like " a* b*"?

  - by Lavir the Whiolet

  Let we have a grammar like this: Program ::= a* b* where "*" is considered to be greedy. I usually implement "*" operator naively: Try to apply the expression under "*" to input one more time. If it has been applied successfully then we are still under current "*"-expression; try to apply the expression under "*" one more time. Otherwise we have reached next grammar expression; put characters parsed by expression under "*" back into input and proceed with next expression. But if there are errors in input in any of "a*" or "b*" part such a parser will "think" that in position of error both "a*" and "b*" have finished ("let's try "a"... Fail! OK, it looks like we have to proceed to "b*". Let's try "b"... Fail! OK, it looks like the string should have been finished...). For example, for string "daaaabbbbbbc" it will "say": "The string must end at position 1, delete superflous characters: daaaabbbbbbc". In short, greedy "*" operator becomes lazy if there are errors in input. How to make "*" operator to recover from errors nicely?

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