Thread: MoveToEx() & LineTo() functions

Hi there..

Trying to draw a line on a frame using the MoveToEx and LineTo functions with no success.. Here's my code

Code:

void DrawOnFrame()
{
   hwnd = GetFrameWindow();
   hdc = GetDC(hwnd);								
   MoveToEx(hdc, 150, 150, NULL);
   LineTo(hdc, 150, 250);
   ReleaseDC (hwnd, hdc);							
}

// Call the function
DrawOnFrame();

Nothing shows on the frame...

Is the a way to change the color of the line? Maybe it defaults to the same color as the frame background

Originally Posted by matsp

You need to select a pen with a colour that shows up against your background (so not white!).

--
Mats

Mats, i ain't using a pen to draw in this case... Am just using two points (draw from point 1 to point 2)... No mouse involved...

Originally Posted by matsp

No, I don't mean a "MS paint" pen, but a GDI object type called PEN.

--
Mats

Could you explain a little further perhaps... Is PEN Object useful for just drawing a line using two points to change colors of the drawn line? So long i'll Google the use PEN..

Originally Posted by matsp

Have a look at CreatePen.

You will need to pass this object to SelectObject to select the pen.


--
Mats

Actually was busy going through it, but seems it's more for C++ than C, am coding C.. but will try that... Thanks

The GDI drawing functions, like lineto, use the default GDI objects ( pen and brush ) to draw. I believe the defaults are black pen and white brush. You can change this if needed. Look at GDI objects in the help. When you create a brush or pen you have to select them using SelectObject for the DC to use them.

Originally Posted by matsp

Not C++ at all in the link I gave.

--
Mats

Sorry, didn't notice the link

If you do a board search under 'mouse drawing (or perhaps draw with mouse) you'll find valid examples of this. Not suggesting copying someone else's code, but you could study it and find out why their code works and yours doesn't, along with taking in the advice given within said threads.

Originally Posted by matsp

You need to select a pen with a colour that shows up against your background (so not white!).

--
Mats

The code below is my first attempt of using the Pen tool, no success... Nothing shows on the frame... The brackground of my frame is (0,0,128) RGB...

Anything wrong with this code?

Code:

void DrawWithPen()
{
    PAINTSTRUCT pntS;
    HPEN pen, oldPen;

    hwnd = GetFrameWindow();							
    hdc = BeginPaint(hwnd, &pntS);						
    pen = CreatePen(PS_SOLID, 2, RGB(255, 255, 0));	
    oldPen = (HPEN)SelectObject(hdc, pen);				

    MoveToEx(hdc, 150, 150, NULL); 		
    LineTo(hdc, 150, 200); 		


    SelectObject(hdc, oldPen); 
    DeleteObject(pen);
    EndPaint(hwnd, &pntS);
}

calls the function...

DrawWithPen();

give this a try to see if ti works...

Code:

void DrawWithPen()
{
   // PAINTSTRUCT pntS;
    HPEN pen, oldPen;

    hwnd = GetFrameWindow();							
   // hdc = BeginPaint(hwnd, &pntS);
   hdc =  GetDC(hwnd);						
    pen = CreatePen(PS_SOLID, 2, RGB(255, 255, 0));	
    oldPen = (HPEN)SelectObject(hdc, pen);				

    MoveToEx(hdc, 150, 150, NULL); 		
    LineTo(hdc, 150, 200); 		
    SelectObject(hdc, oldPen); 
    DeleteObject(pen);
   // EndPaint(hwnd, &pntS);
}

Originally Posted by BobS0327

give this a try to see if ti works...

Code:

void DrawWithPen()
{
   // PAINTSTRUCT pntS;
    HPEN pen, oldPen;

    hwnd = GetFrameWindow();                            
   // hdc = BeginPaint(hwnd, &pntS);
   hdc =  GetDC(hwnd);                        
    pen = CreatePen(PS_SOLID, 2, RGB(255, 255, 0));    
    oldPen = (HPEN)SelectObject(hdc, pen);                

    MoveToEx(hdc, 150, 150, NULL);         
    LineTo(hdc, 150, 200);         
    SelectObject(hdc, oldPen); 
    DeleteObject(pen);
   // EndPaint(hwnd, &pntS);
}

No luck yet Bob, below is the entire code, tried the rectangle, doesn't work too

Code:

HDC hMemDC;
HBITMAP hBmp, hBmpOrig;
HBITMAP hOldBmp;
HWND hwnd;
HDC hdc;

// Function to draw the line
void DrawWithPen()
{
 // PAINTSTRUCT pntS;
HPEN pen, oldPen;

hwnd = GetFrameWindow();                            
// hdc = BeginPaint(hwnd, &pntS);
hdc =  GetDC(hwnd);                        
pen = CreatePen(PS_SOLID, 2, RGB(255, 255, 0));    
oldPen = (HPEN)SelectObject(hdc, pen);                

MoveToEx(hdc, 150, 150, NULL);         
LineTo(hdc, 150, 200);         
SelectObject(hdc, oldPen); 
DeleteObject(pen);
// EndPaint(hwnd, &pntS);
}

// DrawARectangle - draws a red rectangle with a green border
// No return value.
// hdc - handle to the device context

void DrawARectangle() 
{
HPEN hpen, hpenOld;
HBRUSH hbrush, hbrushOld;
PAINTSTRUCT pntS;

hwnd = GetFrameWindow();                            // Retrieve the frame handle
hdc = BeginPaint(hwnd, &pntS);                        // Prepare the specified window for painting
hpen = CreatePen(PS_SOLID, 10, RGB(0, 255, 0));

// Create a red brush.
hbrush = CreateSolidBrush(RGB(255, 0, 0));

// Select the new pen and brush, and then draw.
hpenOld = SelectObject(hdc, hpen);
hbrushOld = SelectObject(hdc, hbrush);
Rectangle(hdc, 100,100, 200,200);

// Do not forget to clean up.
SelectObject(hdc, hpenOld);
DeleteObject(hpen);
SelectObject(hdc, hbrushOld);
DeleteObject(hbrush);
EndPaint(hwnd, &pntS);
}

// CALL FUNCTION

DrawWithPen();
//DrawARectangle();

Where are you calling DrawWithPen()? Maybe your window needs to be invalidated so a Paint message is sent. Try running the program, then covering it with another window then bring your window back to the top. Does it draw now?