C++

Forum

 
DrawText() called but doesn't display its text

MsPhelix (20)
Hi,

I have a case WM_PAINT in my WndProc() function that correctly displays some text.

first in my .h file
1
2
3
4
5
6
7
 
LPCTSTR g_DisplayText = _T("when in the course of human events");
LPCTSTR g_DisplayGreenText = _T("You selected Green.");
Rect g_Rect;
BOOL g_bDisplayGreenText;
int g_LineX = 15;
int g_LineY = 5;
int g_LineHeight = 21;


now in my WndProc() case WM_PAINT:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
 
// initialize the RECT that positions each line of text
g_Rect.left = g_LineX;
g_Rect.top = g_LineY;

// draw the first line of text
DrawText(hdc, g_DisplayText, -1, &g_Rect, DT_SINGLELINE | DT_NOCLIP);
g_Rect.top += g_LineHeight;

// conditionally draw the green text
if(g_bDisplayGreenText)
{
    DrawText(hdc, g_DisplayGreenText, -1, &g_Rect, DT_SINGLELINE | DT_NOCLIP);
				g_Rect.top += g_LineHeight;
    g_Rect.top += g_LineHeight;
}


This correctly displays the first line of text but not the green text.
if(I set g_bDisplayGreenText = true; either in the .h or before the if(g_bDisplayGreenText) block, it also correctly displays the green text.

I have a dialog called as follows:
1
2
3
4
5
6
7
8
9
10
11
 
case ID_MODAL:
{
    int ret = DialogBox(GetModuleHandle(NULL), MAKEINTRESOURCE(IDD_MODALDLG), hWnd, ModalDlgProc);
    if(ret == IDOK)
    {
	if(g_bDisplayGreenText)
	{
	    PostMessage(hWnd, WM_PAINT, 0, 0);
	}
    }
}


ModalDlgProc() correctly sets g_bDisplayGreenText = true if the user selects green.

The code correctly gets to the PostMessage(hWnd, WM_PAINT, 0, 0); call in case ID_MODAL.

WM_PAINT correctly gets to the DrawText(hdc, g_DisplayGreenText, -1, &g_Rect, DT_SINGLELINE | DT_NOCLIP); call.

But the green text does not display! boo hoo :(

What's going on? Any ideas on how to fix this?
Last edited on
knn9 (170)
Instead of using PostMessage(), try this:

1
2
 
InvalidateRect(hWnd, NULL);
UpdateWindow(hWnd);

I don't know if it will help but it should be the correct way to do it(UpdateWindow() generates a WM_PAINT).

Last edited on
MsPhelix (20)
Thank you!

That did it. However the InvalidateRect() call needs a third parameter:

1
2
 
InvalidateRect(hWnd, NULL, true);
UpdateWindow(hWnd);

The true erases the background. I also tried it with false and saw no visible difference but I assume it would matter in some cases.
Topic archived. No new replies allowed.