CODEWITHSUNDEEP
windowswinapi
Muzib
Muzib

Reputation: 2581

My code isn't enough to show a triangle

The codes below is in winmain function after registering a class for the parent window:

RECT disrect;
HWND stat = CreateWindow("BUTTON","abcdef",
    WS_CHILD|WS_VISIBLE|BS_OWNERDRAW,10,150,500,100,dis,0,0,0); 
HDC hdc=GetDC (stat);
FillRect(hdc,&disrect,CreateSolidBrush(RGB(3,5,54)));   
SetTextColor(hdc,RGB(25,250,250));
POINT p[3];   
p[1].x=280;
p[1].y=280;
p[2].x=280;
p[2].y=290;
p[3].x=285;
p[3].y=285;
Polygon(hdc,p,3);
TextOut(hdc,10,10,"hhhhh",5);

But when I run it, only shows a white rectangle into the parent window, neither the rect is filled with black brush, nor there is any text in it.

Could you guys tell me where I am wrong?

Upvotes: 1

Views: 67

Answers (2)

andlabs
andlabs

Reputation: 11578

A few issues, in addition to not using WM_PAINT.

First, merely calling CreateSolidBrush() is not enough to mark that brush as the one for your drawing operations to use. You have to select the brush into a DC (device context) before you can use it. This is done with the SelectObject() function. General usage looks like

HBRUSH prevBrush;

prevBrush = SelectObject(hdc, newBrush);
// drawing functions
SelectObject(hdc, prevBrush);

Yes, it is important to restore the previous brush when finished, even on a fresh DC; the initial state must be restored. The initial state uses a brush that draws nothing; this is why your Polygon() doesn't draw anything. SelectObject() is used for all the various things you use to draw with (pens, fonts, etc.), not just brushes.

Second, in C array indices start at 0 and go to size - 1, not start at 1 and go to size. So instead of saying pt[1], pt[2], and pt[3], you say pt[0], pt[1], and pt[2]. Your compiler should have warned you about this.

Third, as the documentation for CreateSolidBrush() will have said, once you are finished with the brush you must destroy it with DeleteObject(). You must do this after selecting the previous brush back in. You must also do this with the brush you used in the FillRect() call.

Upvotes: 1

Serge Ballesta
Serge Ballesta

Reputation: 148860

Unless you want to display animations, you should never try to directly write to a window that way, because many events could cause the window to redraw itself erasing what you have just written.

The correct way is to put it in the WM_PAINT handler.

Upvotes: 1

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