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• C#, WinForms: What would prevent KeyDown events from chaining up from focused control up to main For

  - by blak3r

  As i understand it, when a keyboard button is pressed it should invoke the KeyDown event for the control which has focus. Then, the KeyDown for the parent control, so on and so forth until it reaches main form. UNLESS - along the chain one of the EventHandlers did: e.SuppressKeyPress = true; e.Handled = true; In my case, KeyDown events never get to the main form. I have Form - Panel - button for example. Panel doesn't offer a KeyDown Event, but it shouldn't stop it from reaching the main form right? Right now as a work around I set every single control to call an event handler I wrote. I'm basically trying to prevent Alt-F4 from closing the application and instead minimize it.

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• make mouse pointer invisible on idle

  - by Joseph

  Is there a way to make the mouse pointer disappear when the computer goes idle? If the solution could work in both XP and 7, that would be great.

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• Windows 8 black screen with mouse pointer after login

  - by Sagar Juneja

  I restarted my system today and after logging in, i could see see nothing but a black screen with mouse pointer. I can start task manager via alt+ctrl+del, Task manager and msconfig show fine but when i try to run 'explorer' nothing happens. In safe mode everything seems fine. I do not have any system restore points and repair options from the DVD show "this option is not available for the selected OS" I've also updated my graphic drivers. Didn't help

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• How to debug lost events posted from non-GUI thread in Qt?

  - by gp

  As the subject says, I'm posting events from non-GUI thread (some GStreamer thread, to be precise). Code looks like this: GstBusSyncReply on_bus_message(GstBus* bus, GstMessage* message, gpointer data) { bool ret = QMetaObject::invokeMethod(static_cast<QObject*>(data), "stateChanged", Qt::QueuedConnection); Q_ASSERT(ret); return GST_BUS_PASS; } The problem is, stateChanged (doesn't matter whether it is a slot or signal) is not called. I've stepped into QMetaObject::invokeMethod with debugger, followed it till it called PostMessage (it is Qt 4.6.2 on Windows, by the way) – everything seemed to be OK. Object pointed to by data lives in GUI thread, I've double-checked this. How can I debug this problem? Or, better, maybe sidestep it altogether?

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• delete pointer to 2d array c ++

  - by user1848054

  i have this pointer to 2d array of Robot class Robot ***rob; and this is here the code for the constructor !! and the program works fine !!! but now i am trying to build a destructor to delete this pointer !! and it keeps on crashing the program !! my question is , how to delete this pointer to 2d array of robots ? RobotsWorld::RobotsWorld(int x , int y) { X=x;Y=y; // returns the limitation of the matrix rob = new Robot**[x]; for(int i = 0; i < x; i++) { rob[i] = new Robot*[y]; for(int j = 0; j < y; j++) { rob[i][j] = NULL; } } }

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• pointer reference type

  - by Codenotguru

  I am trying to write a function that takes a pointer argument, modifies what the pointer points to, and then returns the destination of the pointer as a reference. I am gettin the following error: cannot convert int***' toint*' in return| Code: #include <iostream> using namespace std; int* increment(int** i) { i++; return &i;} int main() { int a=24; int *p=&a; int *p2; p2=increment(&p); cout<<p2; } Thanks for helping!

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• Handling pointer while updating a key value in rpgle

  - by abhinav singh

  my code goes like this femp uf e k disk dvar1 s 5p 0 c *loval setll emp c read emp c dow not %eof(emp) C eval ecode = ecode + 10 c eval var1=ecode c update recemp c var1 setgt emp c read emp c enddo c eval *inlr=*on here is a file named emp with record format name recemp with ecode as the key ...now when i am reading the file and then updating the ecode without using setgt ..the pointer is not moving ahead it is updating the same ecode value many time ...now when i use set gt pointer picks the next record but it dint work when two ecode values are same ...else also it will not be working with descending key values...is there any solution so that i can set pointer regardless of the fact whether the values are same or ascending or descending .......thanks

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• Does copy_from_user modify the user pointer?

  - by Michael

  Does the copy_from_user function, declared in uaccess.h, modify the (void __user *)from pointer? The pointer isn't declared as const in the function declaration, only the contents it points to. The reason I ask is that I want to use copy_from_user twice, with the second copy_from_user copying from the place where the first one finished. I was planning on doing something like this, is it guaranteed to work? //buf is a user pointer that is already defined copy_from_user(my_first_alloced_region, buf, some_size); //do stuff copy_from_user(my_second_alloced_region, buf + some_size, some_other_size); Thanks in advance.

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• Double pointer as Objective-C block parameter

  - by George WS

  Is it possible (and if so, safe) to create/use a block which takes a double pointer as an argument? For instance: - (void)methodWithBlock:(void (^)(NSError **error))block; Additional context, research, and questions: I'm using ARC. When I declare the method above and attempt to call it, XCode autocompletes my method invocation as follows: [self methodWithBlock:^(NSError *__autoreleasing *error) {}]; What does __autoreleasing mean here and why is it being added? I presume it has something to do with ARC. If this is possible and safe, can the pointer still be dereferenced in the block as it would be anywhere else? In general, what are the important differences between doing what I'm describing, and simply passing a double pointer as a method parameter (e.g. - (void)methodWithDoublePointer:(NSError **)error;)? What special considerations, if any, should be taken into account (again assuming this is possible at all)?

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• Malloc to a CGPoint Pointer throwing EXC_BAD_ACCESS when accessing

  - by kdbdallas

  I am trying to use a snippet of code from a Apple programming guide, and I am getting a EXC_BAD_ACCESS when trying to pass a pointer to a function, right after doing a malloc. (For Reference: iPhone Application Programming Guide: Event Handling - Listing 3-6) The code in question is really simple: CFMutableDictionaryRef touchBeginPoints; UITouch *touch; .... CGPoint *point = (CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch); if (point == NULL) { point = (CGPoint *)malloc(sizeof(CGPoint)); CFDictionarySetValue(touchBeginPoints, touch, point); } Now when the program goes into the if statement it assigns the 'output' of malloc into the point variable/pointer. Then when it tries to pass point into the CFDictionarySetValue function it crashes the application with: Program received signal: “EXC_BAD_ACCESS”. Someone suggested not doing the malloc and pass the point var/pointer as: &point, however that still gave me a EXC_BAD_ACCESS. What I am (and it looks like Apple) doing wrong??? Thanks in advance.

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• Add C pointer to NSMutableArray

  - by Georges Oates Larsen

  I am writing an Objective-C program that deals with low level image memory. I am using ANSI-C structs for my data storage -- Full blown objects seem overkill seeing as the data I am storing is 100% data, with no methods to operate on that data. Specifically, I am writing a customizable posterization algorithm which relies on an array of colors -- This is where things get tricky. I am storing my colors as structs of three floats, and an integer flag (related to the posterization algorithm specifically). Everyhting is going well, except for one thing... [actual question] I can't figure out how to add pointers to an NSMutableArray! I know how to add an object, but adding a pointer to a struct seems to be more difficult -- I do not want NSMutableArray dereferencing my pointer and treating the struct as some sort of strange object. I want NSMutableArray to add the pointer its self to its collection. How do I go about doing this? Thanks in advance, G

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• Pointer-based binary heap implementation

  - by Derek Chiang

  Is it even possible to implement a binary heap using pointers rather than an array? I have searched around the internet (including SO) and no answer can be found. The main problem here is that, how do you keep track of the last pointer? When you insert X into the heap, you place X at the last pointer and then bubble it up. Now, where does the last pointer point to? And also, what happens when you want to remove the root? You exchange the root with the last element, and then bubble the new root down. Now, how do you know what's the new "last element" that you need when you remove root again?

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• rewrite a function using only pointer increment/decrement

  - by Richard Nguyen

  can anyone help me rewrite the function i wrote below using only points and pointer increment/decrement? I dont have much experience with pointer so I dont know what to do. void reverse(char * s) { int i, l = strlen(s); char c; for(i = 0; i < (l >> 1); i++) { c = s[i]; s[i] = s[l - i - 1]; s[l - i - 1] = c; } } do not use pointer arithmetic or array notation. any help or hint on how to rewrite the function above is appriciated. Thanks!

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• Returning new base class when the parent class shared pointer is the return type

  - by Ben Dol

  Can you have a parent class shared pointer return type of a function and then return a new child class without it being a shared pointer? I'm not sure how shared pointers work in these situations, do they act like a regular pointer? Here is my example: BaseEventPtr Actions::getEvent(const std::string& nodeName) { if(asLowerCaseString(nodeName) == "action") return new ActionEvent(&m_interface); return nullptr; } ActionEvent is the subclass of BaseEvent in this situation. Cheers!

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• C pointer array scope and function calls

  - by juvenis

  I have this situation: { float foo[10]; for (int i = 0; i < 10; i++) { foo[i] = 1.0f; } object.function1(foo); // stores the float pointer to a const void* member of object } object.function2(); // uses the stored void pointer Are the contents of the float pointer unknown in the second function call? It seems that I get weird results when I run my program. But if I declare the float foo[10] to be const and initialize it in the declaration, I get correct results. Why is this happening?

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• Passing a pointer to a function that doesn't match the requirements of the formal parameter

  - by Andreas Grech

  int valid (int x, int y) { return x + y; } int invalid (int x) { return x; } int func (int *f (int, int), int x, int y) { //f is a pointer to a function taking 2 ints and returning an int return f(x, y); } int main () { int val = func(valid, 1, 2), inval = func(invalid, 1, 2); // <- 'invalid' does not match the contract printf("Valid: %d\n", val); printf("Invalid: %d\n", inval); /* Output: * Valid: 3 * Invalid: 1 */ } At the line inval = func(invalid, 1, 2);, why am I not getting a compiler error? If func expects a pointer to a function taking 2 ints and I pass a pointer to a function that takes a single int, why isn't the compiler complaining? Also, since this is happening, what happens to the second parameter y in the invalid function?

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• Alternates to C++ Reference/Pointer Syntax

  - by Jon Purdy

  What languages other than C and C++ have explicit reference and pointer type qualifiers? People seem to be easily confused by the right-to-left reading order of types, where char*& is "a reference to a pointer to a character", or a "character-pointer reference"; do any languages with explicit references make use of a left-to-right reading order, such as &*char/ref ptr char? I'm working on a little language project, and legibility is one of my key concerns. It seems to me that this is one of those questions to which it's easy for a person but hard for a search engine to provide an answer. Thanks in advance!

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• Alternatives to C++ Reference/Pointer Syntax

  - by Jon Purdy

  What languages other than C and C++ have explicit reference and pointer type qualifiers? People seem to be easily confused by the right-to-left reading order of types, where char*& is "a reference to a pointer to a character", or a "character-pointer reference"; do any languages with explicit references make use of a left-to-right reading order, such as &*char/ref ptr char? I'm working on a little language project, and legibility is one of my key concerns. It seems to me that this is one of those questions to which it's easy for a person but hard for a search engine to provide an answer. Thanks in advance!

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• C++ deleting a pointer

  - by eSKay

  On this page, its written that One reason is that the operand of delete need not be an lvalue. Consider: delete p+1; delete f(x); Here, the implementation of delete does not have a pointer to which it can assign zero. Adding a number to a pointer shifts it forward in memory by those many number of sizeof(*p) units. So, what is the difference between delete p and delete p+1, and why would making the pointer 0 only be a problem with delete p+1?

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• Size of a class with 'this' pointer

  - by psvaibhav

  The size of a class with no data members is returned as 1 byte, even though there is an implicit 'this' pointer declared. Shouldn't the size returned be 4 bytes(on a 32 bit machine)? I came across articles which indicated that 'this' pointer is not counted for calculating the size of the object. But I am unable to understand the reason for this. Also, if any member function is declared virtual, the size of the class is now returned as 4 bytes. This means that the vptr is counted for calculating the size of the object. Why is the vptr considered and 'this' pointer ignored for calculating the size of object?

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• Boost Shared Pointer: Simultaneous Read Access Across Multiple Threads

  - by Nikhil

  I have a thread A which allocates memory and assigns it to a shared pointer. Then this thread spawns 3 other threads X, Y and Z and passes a copy of the shared pointer to each. When X, Y and Z go out of scope, the memory is freed. But is there a possibility that 2 threads X, Y go out of scope at the exact same point in time and there is a race condition on reference count so instead of decrementing it by 2, it only gets decremented once. So, now the reference count newer drops to 0, so there is a memory leak. Note that, X, Y and Z are only reading the memory. Not writing or resetting the shared pointer. To cut a long story short, can there be a race condition on the reference count and can that lead to memory leaks?

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• Call function by pointer and set parametrs in memory block

  - by Ellesmess Glain

  Hi, I've little problem : I'm solving problem with calling function by pointer and passing to it parameters in continuous memory block. My goal is to have function named e.g CallFunc(void * func,void *params, unsigned int param_length); that I'll send function pointer, pointer to function's parameters and eventually parameters length and this calling function will call passed function with it's parameters. I will like write this in C/C++, but if somebody has idea, how this resolve in other language, that supports DLL generation and exportet functions, it will be fine too. Thanks for answers, Ellesmess P.S. I'm sorry about my English, but I'm Czech, thanks :o)

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• Add 64 bit offset to a pointer

  - by Novox

  In F#, there's the NativePtr module, but it seems to only support 32 bit offsets for its’ add/get/set functions, just like System.IntPtr does. Is there a way to add a 64 bit offset to a native pointer (nativeptr<'a) in F#? Of course I could convert all addresses to 64 bit integers, do normal integer operations and then convert the result again to nativeptr<'a, but this would cost additional add and imul instructions. I really want the AGUs to perform the address calculations. For instance, using unsafe in C# you could do something like void* ptr = Marshal.AllocHGlobal(...).ToPointer(); int64 offset = ...; T* newAddr = (T*)ptr + offset; // T has to be an unmanaged type Well actually you can't, because there is no "unmanaged" constraint for type parameters, but at least you can do general pointer arithmetic in a non-generic way. In F# we finally got the unmanaged constraint; but how do I do the pointer arithmetic?

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• FullCalendar and events: function

  - by Ernest

  I am trying to display my events from a MySQL database. I'm using the events function. My XML file being returned is pretty basic. I've looked at all of the FullCalendar questions and most of them talk about JSON and point to the documentation for JSON. I can't use JSON. I have to go XML. Can you tell me where I'm off. Here is a sample of what my xml looks like: Grow Your Business on the Web 2010-06-05T9:30 2010-06-05T12:30 O The whole file is prefaced with a tag and closed with a tag. My jquery is as follows: $(document).ready(function() { $('#calendar').fullCalendar({ height: 550, theme: true, header: { left: 'prev,next today', center: 'title', right: 'month,agendaWeek,agendaDay' }, editable: true, events: function(start, end, callback) { $.ajax({ url: 'ncludeFiles/sbdp-cal-xml.php', dataType: 'xml', data: { // our hypothetical feed requires UNIX timestamps start: Math.round(start.getTime() / 1000), end: Math.round(end.getTime() / 1000) }, success: function(doc) { var events = []; $(doc).find('event').each(function() { events.push({ title: $(this).attr('title'), start: $(this).attr('start'), end: $(this).attr('end'), className: $(this).attr('className'), url: $(this).attr('url') }); }); callback(events); } }); } }); }); I'd appreciate any help you could give me. Thanks!

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• Updates to fullcalendar events (through updateEvent) not maintaining across ajax month changes

  - by user549615

  Hey there. I have the calendar configured to allow me to edit and add (drag/drop) calendar events. I use .fullCalendar('updateEvent', theEvent) to edit an event, and it immediately updates on the page. Excellent. If I move to another month and then move back (get via ajax), that change is undone. By contrast, if I add a new event by drag/drop using: .fullCalendar('renderEvent', newEventObject, true); it appears on the calendar, and if I move to another month, and move back, it maintains. If I edit this newly added event object, and move to another month and back, the updates are retained! So the "stickiness" of edits seem to work on newly added events, but not events that were pulled via ajax (since it just pulls a fresh version via ajax when the month changes). My calendar config is: $('#calendar').fullCalendar({ theme: true, header: { left: "prev,next today", center: 'title', right: "today prev,next" }, selectable: true, selectHelper: true, select: calendarSelect, droppable: true, drop: calendarDrop, events:getCalendarData, eventClick:calendarEventClicked }); I tried setting editable: true, as well, but no dice. I noticed that if I view "event.source" on one of the ajax pulled events, it shows me a function, and if i read the source attribute on one of the "added" events, it reads [object]. So I tried setting the event.source of the event being added, to that same event object: curCalendarEvent.source = curCalendarEvent But no dice. It sets, but when I move back month forward again, it returns to the function as a source. I tried adding lazyFetching: false to my calendar config, but that didn't help. I even tried a .fullCalendar('renderEvent', curCalendarEvent, true); on the existing "edited" event to see if I could get "stick" to work, and it didn't help. The only thing I can think of doing is deleting the event flat out and recreating it. Any help would be appreciated. -Brian

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