C / C++ / MFC

Re: How to get current screen DPI?

28-Dec-07 22:58

IMHO you have to go through GetDeviceCaps [^] (it can return both logical screen dimensions and physical ones) and a small number of elementary math operations.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Mark Salsbery29-Dec-07 7:34

Mark Salsbery

29-Dec-07 7:34

In addition to CPallini's reply...

Note that many devices don't provide an accurate value when you call
GetDeviceCaps(LOGPIXELSn) - some displays aren't capable of it, some can
be stretched horizontally and vertically, etc..

If you need accuracy, you may need to provide some method of calibration.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: How to get current screen DPI?

grmanoj19-Dec-12 17:15

grmanoj

19-Dec-12 17:15

Now we can use the ID2D1Factory interface to get the desktop DPI directly as shown below.

ID2D1Factory* m_pDirect2dFactory;
D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &m_pDirect2dFactory);
FLOAT dpiX, dpiY;
m_pDirect2dFactory->GetDesktopDpi( &dpiX, &dpiY );

with regards,

Manoj G.R.
- "So far so good, but the best is yet to come."

Application Crash problem

Atul2328-Dec-07 18:10

Atul23

28-Dec-07 18:10

Hi ALL,

I am doing project in VC++ 6.0, When I run the application, application gets crash. Message box is display with 3 button as "Don't Send" ,"Ignore" and "send". I check all values in my function if there is any NULL value.In my code there is no NULL value is occured any object. Please send me solution to this problem if anybody have. Tell me the possibilities of application crash.

Thanks in Advance

Steve Echols28-Dec-07 19:26

Steve Echols

28-Dec-07 19:26

Have you tried debugging the program? Build, Start Debug, Go (or hit F5). Make sure you compile in debug mode (Build, Set Active Configuration to Win32 Debug). This should stop on the line of code that's causing the problem.

Otherwise, post some code.

- S
50 cups of coffee and you know it's on!

Atul2328-Dec-07 19:37

Atul23

28-Dec-07 19:37

Hi Steve,

I write code in CPageView class which is derived from CView class. My project is to create web page design tool. when I create page by using my code, as the page is open there is error ocuure. I write customize function to open web page. The error is occur after page is open and application gets crash with messgeBox having 3 buttons as Send Error,Don't sent error and ignore.

void CPageView::OpenWebSite(int nTabIndex)
{
if(nTabIndex > 0 && nTabIndex < nSize+1)

{
CString strPagePath = pFrame->m_selWebPagePaths.GetAt(nTabIndex-1);
theApp.OpenDocumentFile(strPagePath);
}
}

Thanks
Abm

Steve Echols28-Dec-07 19:53

Steve Echols

28-Dec-07 19:53

Potential problems I see:

1. pFrame is null
2. (nTabIndex - 1) is out of range of the array
3. nSize is not the actual size of the array being indexed

You're probably trying to access an element of m_selWebPagePaths that doesn't exist.

Put a breakpoint in there and check the value of nTabIndex and nSize. Make sure nSize is the same as m_selWebPagePaths.Count (or GetSize).

- S
50 cups of coffee and you know it's on!

Atul2328-Dec-07 21:33

Atul23

28-Dec-07 21:33

Hi Steve,

I check above all values by adding break point. There is no NULL value so OpenDocument() function called sucessfully and document is open. but after opening the document the application get crash. that is the main problem here. please give me some hint if know !!!

Thanks in Advance

abm

CPallini28-Dec-07 23:41

28-Dec-07 23:41

When you run the application is in debug mode, the IDE gives valuable info (see for instance call stack window) about the error occurred.
Try to detect the exactly the troublesome point and post the relevant code.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

string and xstring

Maxwell Chen28-Dec-07 4:51

28-Dec-07 4:51

In iostream library, <xstring> is the internal header file of <string>. But there is not #include <xstring> in file <string>. How do they build up the relationship??

Maxwell Chen

CPallini28-Dec-07 5:05

28-Dec-07 5:05

Maxwell Chen wrote:
In iostream library, <xstring> is the internal header file of <string>

How the above comes out (i.e I never heard before, please explain)?

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Maxwell Chen28-Dec-07 5:07

28-Dec-07 5:07

CPallini wrote:
How the above comes out (i.e I never heard before, please explain)?

// Visual C++ 2005
#include <string>
// ...
std::string str;

By right-clicking std::string and choosing [Go to definition], VC++2005 leads you to file <string>. And then by right-clicking basic_string and [Go to definition], you are lead to file <xstring>. In the beginning of <xstring>, it states that it is the internal header file of <string>.

(I am at home and do not have VC++ 2005 now. But it is something the like.)

Maxwell Chen

CPallini28-Dec-07 5:13

28-Dec-07 5:13

The target of my request was the <xstring>:
you said

Maxwell Chen wrote:
<xstring> is the internal header file of <string>

but I never heard about <xstring>. How can you affirm that?

Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Maxwell Chen28-Dec-07 5:18

28-Dec-07 5:18

I updated my previous reply. Smile | :)

Maxwell Chen

CPallini28-Dec-07 5:36

28-Dec-07 5:36

as far I can understand, there is a long nesting of includes, starting from <string> that includes <istream>, that includes <ostream>, that includes <ios>, ..., terminating with <stdexcept> that includes <xstring>.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Maxwell Chen28-Dec-07 5:48

28-Dec-07 5:48

I'm not sure, but I remember that <string> only includes <xmemory> ...
I do not have VC++2005 at home now. Let me check next week. Smile | :)

Maxwell Chen

Maxwell Chen2-Jan-08 1:02

(Solved) GDI+ and CDC::GetWindow()

2-Jan-08 1:02

CPallini wrote:
starting from <string> that includes <istream>, that includes <ostream>, that includes <ios>, ..., terminating with <stdexcept> that includes <xstring>.

Got it! Thanks! Big Grin | :-D

Maxwell Chen

bob1697228-Dec-07 4:00

28-Dec-07 4:00

(Update: Problem solved)

I'm trying to use CDC::GetWindow to get a pointer to a CWnd object to perform some tests but CDC::GetWindow() returns NULL. I'm trying to derive the CDC from the Graphics object passed into a function as follows...

void SomeFunction(Graphics& graphics)
{
	HDC hDC=graphics.GetHDC();
	CDC* pDC=CDC::FromHandle(hDC);

	if (pDC) {

		CWnd* pWnd=pDC->GetWindow();
		if (pWnd) {

			// Never gets here
		}
	}

	graphics.ReleaseHDC(hDC);
}

Can anyone tell me the folly of my ways?
thanks in advance

modified on Friday, December 28, 2007 11:17:40 AM

CPallini28-Dec-07 4:46

28-Dec-07 4:46

Why are you doing that (i.e. have you no control on Graphics object instance?)?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

bob1697228-Dec-07 5:03

28-Dec-07 5:03

I'm passing the graphics object around to drawing functions in classes that have no knowledge of who is using them. Those other classes, however, are interested in knowing whether the window the Graphics object is drawing to has the input focus so they can perform their drawing actions differently.

I'm just trying to minimize the number of parameters I'm passing around.

CPallini28-Dec-07 5:08

28-Dec-07 5:08

Well, I don't think that a Graphics object is a good transport medium for a CWnd one. Pass needed parameters packed in a struct.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

bob1697228-Dec-07 5:17

28-Dec-07 5:17

I realized what I was doing wrong.

I'm using a memDC so there is no window associated with the underlying DC.

Thanks for the response.
I apologize for my oversight. Blush | :O

bob1697228-Dec-07 5:29