CODEWITHSUNDEEP
c++winapi
João Pereira
João Pereira

Reputation: 713

Trying to pass char index to DrawText

I'm using DrawText to draw some text to a bunch of rectangles I made in a plug-in.

Now i'm receiving a char pointer from embedded python:

char *a=PyString_AsString(value);

which, when I print to textfile gives: 1\n2\n3\n4\n5\n6\n7\n8\n9\n (this is just a sample character, the one I'm going to use is much more complex)

I want to use DrawText to print specific characters in a loop:

 for(int count=0;count<content.size();count++){
    dc->DrawText(a[count*2],&rect[count],DT_CENTER); //*2 to print only the numbers

but i can't because it says that argument is not of type char?? I can pass a, &a[count] but not a[count]. Why is this?

Also, when i print &a[2]to textfile it gives: 2\n3\n4\n5\n6\n7\n8\n9\n. Shouldn't it be only 2?

Note: DrawText function receives:

int DrawText(
   _In_     HDC hDC,
   _Inout_  LPCTSTR lpchText,
   _In_     int nCount,
   _Inout_  LPRECT lpRect,
   _In_     UINT uFormat
 );

Upvotes: 0

Views: 207

Answers (1)

David Heffernan
David Heffernan

Reputation: 612993

The first parameter of your DrawText method is a char* pointer. You are passing a single char instead, which is the type mismatch that the compiler is complaining about.

You can obtain a pointer to a specific character like this:

&a[count*2]

or like this:

a + count*2

The problem is that your three parameter OOP wrapper of DrawText has removed the nCount parameter of the Win32 DrawText function. Instead your wrapper is passing -1 which means that the character pointer is interpreted as a null-terminated string. The function will print all the characters until it reaches the null-terminator.

If you want to print a single character then you would need to pass 1 through the nCount parameter. There's no way for you to do that with your wrapper. You'd have to do this:

char temp[2];
temp[1] = 0;
temp[0] = a[count*2];
dc->DrawText(temp, ...);

In order to avoid this temporary buffer you would need to expose the nCount parameter of the raw Win32 API function.

Upvotes: 3

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