C/C++ :: Setting Resolution On Screen
Mar 29, 2015
Just reading some code and come across a section where its setting the resolution on a screen
so like
image->sizeX=640;
image->sizeY = 480;
size = image->sizeX * image->sizeY *3;
float sizeLog = ceil(log((float)image->sizeX) / log(2.F)));
So yea, my understanding of this code is that firstly there is member access and that a resolution is being set.
And then its like 640 * 480 * 3
and then the log of 640 *480*3 ...being divided by something else and being rounded up by ceil
is this the right way to look at it?
and also what is the log(2.F) - i don't really understand that.
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Feb 21, 2013
I have done alot of googling for the scope resolution operator and Ive gained a bit of an understanding as to what it does i know it can distinguish between global and local variables, but I see it used to access methods/members of classes such as this example, why not just use a dot instead to access it?:
sql:: Driver *driver;
Why is the scope resolution operator being used here?
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Apr 23, 2013
I have a global var (m) with an initial value 5.
I have a template class (A) that derives from a either a base class that has a member (_A1.m) or not (_A0), based upon it's template parameter. class (A) has a member function (fn) returns the value of (m) as it understands what (m) is.
However, this gives different results compared with a non-template class in a similar scenario. I'm expecting that if derived from _A1, that m should be taken from the base class scope and if derived from _A0, it should be taken from the global one.
Here is the code for your amusement:
int m = 5;
class _A0 {
public:
_A0(int) {
[Code] ....
This compiled using g++ 4.5.3 and 4.6.3 with the same results:
Global value of m is: 5
B0 class has no internal m member. Object resolves m internally with value 5
B1 class has internal m member. Object resolves m internally with value 3
A<_A0> class has no internal m member. Object resolves m internally with value 5
A<_A1> class has internal m member. Object resolves m internally with value 5
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Jan 2, 2014
I'm trying to learn how to use variadic templates, and I decided a great example would be serializing a series of types into a stringstream:
Code:
// Send a fully constructed message.
virtual void send(ostringstream &msg) = 0;
// Construct a message from the arguments and send it.
// This is the usual entry point.
template <typename ...Args>
void send(Args ...args {
[Code] ....
This works fine, so far as I can tell. However, I decided to see if I could specialize the way certain types are serialized. I tried using a Google Protocol Buffer object as an example, and added this:
Code:
// Handle a protocol buffer type while constructing a message.
template <typename ...Args>
void send(ostringstream &msg,
const google::protobuf::MessageLite &protobuf, Args ...args) {
std::string msg_str = protobuf.SerializeAsString();
msg << msg_str;
send(msg,args...);
}
I would expect this overload to be preferred over the generic T overload when a protobuf object (which always inherits from MessageLite) is passed into send() anywhere in the list. However, this is not happening. I am getting an error message to the effect that << doesn't know how to deal with my concrete type, pointing at the T overload.
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Mar 25, 2013
I have an mfc dialog of size 1280 X 1024 and when i change the resolution to 800 X 600, after adding scroll bar, it don't show the entire dialog contents, Seems like it clips the 800 X 600 portion.
I have handled VScroll and HScroll. It works fine for higher resolutions!
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Dec 6, 2012
I have written a program to capture signal from machine and display it on screen in the form of sinosoidal wave. I have print buffer for 256 X 400 pixel strip chart. This prints fine if I set page size A4 and resolution 600 DPI. If anyone changes print parameters , there is problem. I can resize the printer buffer and interpolate the stored signal.
My problem is , how to find the printer resolution from GetDeviceCaps ? how to know the Print Type Normal / Draft etc in mFC.
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Aug 25, 2014
What is the limit of a VGA with 256k VRAM, running 1bpp monochrome graphics? How high can the display resolution go?
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Jun 13, 2014
I stumbled upon an unexpected difference between GCC and VisualStudio: Different overloaded functions are called in the following example:
// -------- can assume this is located in 'tool.h' file --------------
// Fwd declaration support foo( const int& ) gets called as expected by both compilers
// void foo( const int& n );
template< typename T >
void foo( const T& n ) {
[Code] ....
What happens: I expected that by calling bar(1) compiler will notice both versions of foo() and call the best match, in this case foo(const int&). That is not the case.
Note that overloaded foo(const int&) is below bar(). It seems that at that point GCC does not see overloaded version, and happily calls template version. Visual studio on the other hand has no problem finding them both.
If I introduce a forward declaration of foo( const int& ) before bar(), both compilers call that version correctly. Unfortunately, that is not a solution for my problem here.
Template version is part of a library while overloaded is part of the user code. Both would be located in different (header) files and I would not like to impose #include order to the users or to be dependant on it.
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Mar 14, 2013
Need a free image library that can handle png xresolution and yresolution. I need it to be compatible with visual studio 6.0
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Mar 1, 2014
i am writing this bank accounts program using structures. i haven't implemented the function before that i want to check if the data is being read and printed. When i build and run the program in visual studio it gives me the following error. "No constructor could take the source type, or constructor overload resolution was ambiguous". Now whats wrong in this program?
/* Bank Accounts Program */
#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>//needed to use system() function
using namespace std;
const int MAX_NUM = 50;
struct Name{
[code]....
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Jun 14, 2013
Are there any situations to explicitly use the scope resolution operator with global scope? I can imagine a situation like:
#include <cmath>
class IntWrapper{
public:
IntWrapper& pow(char);
IntWrapper(char);
private:
int m_int;
[Code] ....
But then I would think that the writer should have used a different name, and that using the scope resolution operator in the constructor body is still pointless...
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Mar 1, 2013
Lets say i have an array with the values 1, 5, 9, and 3. is there anyway to make this so i can have an int with the value 1593 based on those numbers in the array?
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Feb 22, 2013
I want to set limit on cin for example
int i;
cout<<"Please enter 4 digits id: ";
cin>>i
If user enter more then 4 digits it must give an error
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Apr 5, 2014
This function below takes a pointer as an argument. What I expect to happen is, since expr++ has higher precedence than *expr, that is, the primary expression operators have higher precedence than the unary operators, pointer arithmetic should occur where we increment to the second address pointed to by dbuf, and then we should dereference the value at that address. Given that logiv, when i print dbuf[3] it should print the value pointed to at the 4th address in dbuf. However, the value it returns is 0x0 not 0x3. Why doesn't it dereference the value 0x3?
Code: void dfill(unsigned char *dbuf)
{
dbuf = (unsigned char*)malloc(4);
memset(dbuf, 0, 4);
*dbuf = 0x0;
*dbuf++ = 0x1;
*dbuf++ = 0x2;
*dbuf++ = 0x3;
printf("dbuf val: 0x%x
", dbuf[3]);
}
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Oct 18, 2013
I am trying to create the lparam for the WM_KEYDOWN message. I know this is the C programming forum, but my code is standard enough to apply here. According to Microsoft, the lparam must be formatted like this : lParam The repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown following. Bits Meaning 0-15 The repeat count for the current message. The value is the number of times the keystroke is autorepeated as a result of the user holding down the key. If the keystroke is held long enough, multiple messages are sent.
However, the repeat count is not cumulative. 16-23 The scan code. The value depends on the OEM. 24 Indicates whether the key is an extended key, such as the right-hand ALT and CTRL keys that appear on an enhanced 101- or 102-key keyboard. The value is 1 if it is an extended key; otherwise, it is 0. 25-28 Reserved; do not use. 29 The context code. The value is always 0 for a WM_KEYDOWN message. 30 The previous key state.
The value is 1 if the key is down before the message is sent, or it is zero if the key is up. 31 The transition state. The value is always 0 for a WM_KEYDOWN message. ( WM_KEYDOWN message (Windows) )^ I'm troubled by setting it into the 32-bit value, and I get confused about what exactly happens when the logical or and the bitshift operators are used. I tried to use them below in my code by looking at Stack Overflow for setting a bit. I also don't know how to test for the endianess of my system, and how to handle it if it's big endian or little endian. Here is my code so far :
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
[Code].....
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Oct 27, 2013
I have the following situation:
Code:
void myFun(float *pfMyPtr) {
float Val[] = {0.234, 0,432, 0.322, 0762, 0.984};
pfMyPtr = Val;
}
int main() {
float *pfPtr;
pfPtr = (float*) calloc (5,sizeof(float));
myFun(pfPtr);
}
I would like pfPtr to contain the values of array Val. What am I missing here?
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Oct 29, 2014
I need to set a function to a variable of some kind. Then later in the program it needs to run the function that is set to the variable. The variable doesn't need to change after it is set to a function, it just needs to be able to be set to a function. So maybe I don't need a variable? What do I do? :3 Is this even possible? :o
Example:
if (PosRampYes == 0)
{
SomeVariableOrSomething = FirstFunction();
}
else
{
SomeVariableOrSomething = SecondFunction();
}
//later:
SomeVariableOrSomething; //so if PosRampYes is set to 0 then this line would run FirstFunction()
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Oct 8, 2013
I am trying to find a quicker way of setting the variables for text. here is my code:
sf::Text set_text_values(sf::Text text, sf::Font font) {
text.setFont(font);
text.setCharacterSize(50);
text.setColor(sf::Color::White);
return text;
[Code] ....
And I have tried it like this
void set_text_values(sf::Text text, sf::Font font) {
text.setFont(font);
text.setCharacterSize(50);
text.setColor(sf::Color::White);
[Code] ....
The code compiles and runs but it won't show the text on the screen like it did when i did it manually like this:
int main() {
Hull.setFont(font);
Hull.setCharacterSize(50);
Hull.setColor(sf::Color::White);
}
What is wrong with it?
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Sep 18, 2013
I'm trying to set all the elements of my array to 0 but nothing seems to be working.
.h
#ifndef ServerGroup_h
#define ServerGroup_h
class ServerGroup {
public:
ServerGroup(const int&);
[Code] .....
I want to set each element of the array in servers to 0 based on what is passed into size by numArray.
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Feb 20, 2013
I declared a pointer in main with value 0, so I want to change its value so that it points to other variable from a function, I guess the function creates a copy of my pointer that's why whatever I do within function doesn't change the real direction of the pointer in main. I've been trying something like this:
#include <stdio.h>
void redirectionate(char *str, char *ptrCopy);
int main()
{
[Code]....
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Apr 3, 2015
I would like to know how can i set a constant attribute in the constructor. This attribute is an int value that cannot be changed.
For instance:
class Test {
public:
const int x;
public:
Test(const int val);
[code].....
With this code i get compile error!
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Jun 23, 2014
I created a WinForm app in C# using VS 2013 Express.
I added code to create a Global Hot Key on the main form. This works fine. My hot key is Ctrl-T. I can press the hot key and make the main form show and hide.
Then I created a second form (ChecklistForm) and now I want to press ctrl-T and make that form show and hide. I do not need the main form to do this any more. I just used the main form to test my Global Hot Key code.
So I'm having trouble getting the second form to respond to the hot key. When I put a break on the WndProc(), there is no break.
namespace ChecklistFSX {
public partial class MainForm : Form {
[DllImport("user32.dll")]
public static extern IntPtr FindWindow(String sClassName, String AppName);
private IntPtr thisWindow;
private GlobalHotKeys hotkey;
public MainForm()
[code]....
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Feb 7, 2013
Basically the whole purpose of this program is to prompt the user to use a calculator. Choices 1-6 are valid, but I want to set it up where selecting any other number outside of 1-6 to be Invalid, and will display an 'Invalid Choice' message, and then go back to the main menu.... The main program does work properly, it's the 'Invalid' setup that is giving me problems
Code:
#include <iostream>
#include <iomanip>
using namespace std;
[Code].....
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Aug 12, 2013
I am having trouble setting up SFML 2.1 to run with the eclipse IDE for c++ development. I use MinGW for my compiler.
When I link my include folder, lib folder and dll's it will not run a simple SFML program.
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Jun 27, 2013
I am trying to find out when using float in a calculation how to set the number of decimal places. For example my code below
Code:
#include stdio.h>
int main()
{
float x=123.0;
[Code]....
This returns an answer 8487.0000 I would like it not to show all the decimal places. However if the sum has decimal places I would like to select the number of decimal places shown.
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Dec 18, 2013
How do I set all of these string and double value(s) to 0?
Code:
#define MAXcharacters 12
#define MAXaccounts 100
struct Records {
char userid[MAXcharacters + 1];
char password[MAXcharacters + 1];
double balance;
};
[code]...
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