More than 1 object on same Device Context (DC)

This is a discussion on More than 1 object on same Device Context (DC) within the Windows Programming forums, part of the Platform Specific Boards category; Is it possible to draw on a bitmap using a pen tool.. I would presume both BMP object and pen ...

  1. #1
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    More than 1 object on same Device Context (DC)

    Is it possible to draw on a bitmap using a pen tool.. I would presume both BMP object and pen object would need to be on the same DC if that make sense...

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    The bitmap needs to be on the same DC as the pen, yes.

    The DC has multiple types of objects that it uses for different purposes, such as Pen is used fro LineTo, DrawText for example, whilst a Brush is used for Fill functions, and the Bitmap is the "destination surface" that you draw onto.

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    Mats
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    Quote Originally Posted by matsp View Post
    The bitmap needs to be on the same DC as the pen, yes.

    The DC has multiple types of objects that it uses for different purposes, such as Pen is used fro LineTo, DrawText for example, whilst a Brush is used for Fill functions, and the Bitmap is the "destination surface" that you draw onto.

    --
    Mats
    Am thinking how do i select two objects on the same DC, does this mean i need to call SelectObject() twice?

    i.e...
    Code:
    oldPen = (HPEN)SelectObject(hMemDC, pen);	
    hOldBmp = SelectObject(hMemDC, hBmp);
    Is this code correct?

  4. #4
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    Yes, the SelectObject would "know" what type of object you are selecting and "do the right thing".

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    Quote Originally Posted by matsp View Post
    Yes, the SelectObject would "know" what type of object you are selecting and "do the right thing".

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    Mats
    here's my code... nothing works!

    Code:
    HPEN pen, oldPen;
    
    pen = CreatePen(PS_SOLID, 2, RGB(255, 0, 0));	
    hMemDC = CreateCompatibleDC(0);
    
    hOldBmp = SelectObject(hMemDC, hBmp);	
    oldPen = (HPEN)SelectObject(hMemDC, pen);				
    		
    MoveToEx(hMemDC, centre.x,centre.y, NULL);		
    LineTo(hMemDC, coord.x, coord.y.y);					
    
    SelectObject(hMemDC, oldPen); 
    SelectObject (hMemDC, hOldBmp);					
    
    //DeleteObject(pen);
    DeleteDC(hMemDC);									
    
    RadarBgrnd.Repaint ();
    anything wrong?

  6. #6
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    "nothing works" is a pretty poor description of a problem.

    Check that CreatePen and SelectObject are not returning NULL.

    Edit: Also check that LineTo() and MoveToEx returns non-zero.

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    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  7. #7
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    Quote Originally Posted by matsp View Post
    "nothing works" is a pretty poor description of a problem.

    Check that CreatePen and SelectObject are not returning NULL.

    Edit: Also check that LineTo() and MoveToEx returns non-zero.

    --
    Mats
    Was rather asking if the code is correct (logic & syntax) without even compiling it.. I still have issues with the tool i'm using (QUEST)... If the code is correct then i will know that QUEST is really not the tool for what am trying to do..

    Thanks

  8. #8
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    Looks OK to me, aside from what I perceive as a typo:
    Code:
    LineTo(hMemDC, coord.x, coord.y.y);
    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  9. #9
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    Quote Originally Posted by matsp View Post
    Looks OK to me, aside from what I perceive as a typo:
    Code:
    LineTo(hMemDC, coord.x, coord.y.y);
    --
    Mats
    Thanx Mat

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