Why does GDI+ DrawString punch holes in the alpha channel? - C / C++ / MFC Discussion Boards

Fareed Rizkalla7-Apr-10 2:27

7-Apr-10 2:27

LPWSTR URL;
ComboBox_GetText(hComboBox, URL, sizeof URL);

I'm writing this app where the user enters a URL in a ComboBox.
When he presses OK, the text in the ComboBox is retrieved to start processing.
Using Unicode!

Every time I enter a URL the program breaks and starts the debugger.
Running Visual Studio 2010.

Any help appreciated. Blush | :O

modified on Wednesday, April 7, 2010 8:43 AM

Re: ComboBox / Win32

CPallini7-Apr-10 2:31

CPallini

7-Apr-10 2:31

And what is your trouble about?

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.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: ComboBox / Win32

Fareed Rizkalla7-Apr-10 2:38

Fareed Rizkalla

7-Apr-10 2:38

Every time I enter a URL the program breaks and starts the debugger.
Running Visual Studio 2010.

Re: ComboBox / Win32

CPallini7-Apr-10 2:50

CPallini

7-Apr-10 2:50

You didn't provide the required buffer (URL doesn't point to a valid memory buffer).
Try

LPTSTR  URL;
int len = ComboBox_GetTextLength(hComboBox);
URL = new TCHAR[len+1];
ComboBox_GetText(hComboBox, URL, len+1);
//.. use URL
delete [] URL;

Re: ComboBox / Win32

Fareed Rizkalla7-Apr-10 3:15

Fareed Rizkalla

7-Apr-10 3:15

It works, but something weird happened.

The GetText method requested URL to be LPWSTR.
LPTSTR is multibyte, not unicode.
Any pointers what was the trick in fixing it?

Re: ComboBox / Win32

CPallini7-Apr-10 3:18

CPallini

7-Apr-10 3:18

Actually the ComboBox_GetText macro accpts a LPTSTR as you may see in the documentation [^].
Is there something I missed?
Smile | :)

Re: ComboBox / Win32

Sauro Viti7-Apr-10 6:54

Sauro Viti

7-Apr-10 6:54

LPTSTR is defined as follow:

#ifdef UNICODE
typedef WCHAR *LPTSTR;
#else
typedef char *LPTSTR;
#endif

so it will be a pointer to a multibyte or unicode string depending on the project settings; if you choose "Use Unicode Character Set" on the General Tab of your project properties, then LPCSTR is a pointer to an unicode string.

Why does GDI+ DrawString punch holes in the alpha channel?

Code-o-mat7-Apr-10 2:24

Code-o-mat

7-Apr-10 2:24

Hello folks!

I got an annoying anomaly with GDI+ i just can't understand. I created a 32 bit bitmap in memory, did some drawing on it and used it to display a layered window. This all works well except for one thing. I use Gdipluss::Graphics::DrawString to render some text onto this bitmap which seems to erase the alpha channel on the bitmap everywhere where letters of the text are drawn. Here's the simplified code i use:

...
  Gdiplus::Graphics     Gx(MemDC);
  Gdiplus::SolidBrush   GxTextBrush(Gdiplus::Color(0, 0, 0));
  Gdiplus::Font         GxFont(MemDC, &LFont); //LFont is a LOGFONT and it is initialized to the default GUI font.

  Gdiplus::RectF TextRect;
  //... init textrect to the correct position...

  Gdiplus::StringFormat GxFormat;
  //... set GxFormat to the needed values...

  Gx.DrawString(text, textlength, &GxFont, TextRect, &GxFormat,  &GxTextBrush);
  ...

Changing the GxTextBrush's color by adding an alpha component of 254 "fixes" the problem, but adding 255 produces the holes again, also making the font bold (LFont.lfWeight = FW_BOLD) seems to fix the problem also... so could someone please tell me what's the logic behind this? For now i set the alpha to 254 and go on with it...
Thanks for any light-sheding attempts in advance.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Sometimes you just have to hate coding to do it well. <

Send request to open a http link

Pryabu7-Apr-10 1:23

Pryabu

7-Apr-10 1:23

Hi,

I want to send a request to execute a http link which is running in another machine.how to do this using?Is there any function in MFC or SDK? anyone please help me?

thanks,

Re: Send request to open a http link

eusto7-Apr-10 1:26

eusto

7-Apr-10 1:26

See CHttpConnection and the other classes that help you do this

Re: Send request to open a http link

Code-o-mat7-Apr-10 2:25

Code-o-mat

7-Apr-10 2:25

What do you mean by "execute"?

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Sometimes you just have to hate coding to do it well. <

Re: Send request to open a http link [modified]

Pryabu7-Apr-10 18:57

Pryabu

7-Apr-10 18:57

I want to send a request to another system to run a URL.I tried with following code. Its showing error like URL is invalid. But im able to open that URL from my machine.But not able to open that URL using this code.

CInternetSession objInetSession;
CHttpConnection *objhttp ;
CHttpFile *objFile;
char szURL[100];

while(1)
{

objhttp = objInetSession.GetHttpConnection ("http:////101.16.0.42/test/prelogin.aspx", INTERNET_FLAG_MAKE_PERSISTENT, INTERNET_INVALID_PORT_NUMBER,
NULL, NULL);

try
{
wsprintf(szURL,"%s","http:////101.16.0.242/test/prelogin.aspx");
CStdioFile* objStdFile = objInetSession.OpenURL(szURL,1,INTERNET_FLAG_TRANSFER_ASCII,NULL,0);
}
catch(CInternetException* exp)
{
exp->ReportError(MB_OK,0);
}

}

modified on Thursday, April 8, 2010 1:29 AM

Re: Send request to open a http link

eusto8-Apr-10 0:18

eusto

8-Apr-10 0:18

1. '/' is not an escape character so your url should be "http://101.16.0.42/..." not http:////...
2. Depending on what that the script at that url does, what you're trying to do might or might not work. Read about the HTTP protocolhere

in very simple terms, when using a http connection, you're making a request (that might contain some parameters - see GET/POST methods) and you receive a response - the html code that you see in your browser

I hope this helps Smile | :)

Re: Send request to open a http link

Pryabu8-Apr-10 21:10

Pryabu

8-Apr-10 21:10

thanks

enum in .c-file

LionAM7-Apr-10 1:06

LionAM

7-Apr-10 1:06

Hello!
I tried to compile a library with VC++ 2008.
However I get a compiler error which I don't understand - which only occurs in .c-Files:

struct MV_Vector_
{
    enum ref_type { ref = 1 };   //C2208
};

The enum leads to the error C2208 ('ref_type' : no members defined using this type).
What is wrong with the code? Any ideas how to work that around?

Thank you in advance,
Alex

Re: enum in .c-file

Eugen Podsypalnikov7-Apr-10 1:19

Eugen Podsypalnikov

7-Apr-10 1:19

Try it

struct MV_Vector_{
    enum ref_type { ref = 1 } eref_member;
};

virtual void BeHappy() = 0;

Re: enum in .c-file

LionAM7-Apr-10 2:05

LionAM

7-Apr-10 2:05

Thank you,
it works.

Re: enum in .c-file

eusto7-Apr-10 1:22

eusto

7-Apr-10 1:22

that's not standard C.You have to also declare a variable

Re: enum in .c-file

CPallini7-Apr-10 1:33

CPallini

7-Apr-10 1:33

That's not C.
Smile | :)

Maximum limit of char array?

jannathali6-Apr-10 22:33

jannathali

6-Apr-10 22:33

hai,
Is there any maximum limit for the char array

Thanks in Advance

Re: Maximum limit of char array?

CPallini6-Apr-10 22:35

CPallini

6-Apr-10 22:35

jannathali wrote:
Is there any maximum limit for the char array

What do you mean, exactly?

Re: Maximum limit of char array?

jannathali6-Apr-10 22:38

jannathali

6-Apr-10 22:38

Is there any limit for the array size.
i.e char a[Max_Value];
Is there a limit for this value
Or i can give any big value like char a[40000]; etc

Re: Maximum limit of char array?

«_Superman_»6-Apr-10 22:42

«_Superman_»

6-Apr-10 22:42

If you're declaring it local to a function, the size is limited by the available stack space.
If you're declaring it globally, the size is limited by the data section size.

«_Superman_»
I love work. It gives me something to do between weekends.

Microsoft MVP (Visual C++)

Re: Maximum limit of char array?

CPallini6-Apr-10 22:48

CPallini

6-Apr-10 22:48

You may have such big values (why don't you try?).
Smile | :)

Re: Maximum limit of char array?

Cedric Moonen7-Apr-10 0:12

Cedric Moonen

7-Apr-10 0:12

In most of the cases (but there are some few exceptions), when you have to ask yourself such a question, it probably means that you have taken a bad design decision.

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

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