How do I paint a child window with FillRect()? - c++

Question

I have a main window which is created with the following styles
WS_CAPTION | WS_MINIMIZEBOX | WS_SYSMENU | WS_TABSTOP | WS_GROUP | WS_VISIBLE
and with ex-stles
WS_EX_ACCEPTFILES | WS_EX_CONTROLPARENT | WS_EX_LEFT | WS_EX_LTRREADING.
This main window has a child window on it, which is an edit control created with styles
WS_VISIBLE | WS_CHILD | ES_READONLY
and ex-style
WS_EX_CLIENTEDGE.
I am going to use this edit control as a progress-bar control. I don't want to use standard Wind32 progress-bar control (PROGRESS_CLASS), because I want to do a some custom painting on it (e.g.; dynamically changing fill color, displaying text on it, etc).
I can paint any region of the main window by the following code:
// hWnd: Handle of the main window
case WM_PAINT:
hDc = BeginPaint(hWnd, &Ps);
Rect = AFunctionToGetCornerThePointsOfTheEditControl();
Rect.right = Rect.left + 3 * (Rect.right - Rect.left) / 4; // Fill 3/4 (75%) of it
Rect.left -= 10; // Enlarge the paint region a little
Rect.top -= 10; // so that we can see it if it stays
Rect.bottom += 10; // under the edit control.
hBrush = CreateSolidBrush(RGB(50,100,255));
ret = FillRect(hDc, &Rect, hBrush); // ret = 1 always
ler = GetLastError(); // ler = 0
EndPaint(hWnd, &Ps);
break;
It looks like this:
I changed this code a little to paint the child control instead:
// hWndEdit: Handle of the edit control
case WM_PAINT:
hDc = BeginPaint(hWndEdit, &Ps);
Rect = AFunctionToGetCornerThePointsOfTheEditControl();
Rect.right = Rect.left + 3 * (Rect.right - Rect.left) / 4; // Fill 3/4 (75%) of it
Rect.left -= 10;
Rect.top -= 10;
Rect.bottom += 10;
hBrush = CreateSolidBrush(RGB(50,100,255));
ret = FillRect(hDc, &Rect, hBrush); // ret = 0 always
ler = GetLastError(); // ler = 6 (ERROR_INVALID_HANDLE)
EndPaint(hWndEdit, &Ps);
break;
This time it doesn't work. The main windows completely disappears as soon as I drag some part it out of the screen area, and it becomes totally unresponsive. Desktop icons under it are visible, but are not clickable.
So, what do I have to do in order to paint the child window (the edit control)?

Answer 1

This article helped me a lot: Subclassing Controls
First, I create a separate message processing function for processing child messages.
LRESULT CALLBACK MyClass::ChildWindowProc( HWND hWnd,
UINT uMsg,
WPARAM wParam,
LPARAM lParam,
UINT_PTR uIdSubclass,
DWORD_PTR dwRefData)
{
static PAINTSTRUCT Ps;
static RECT Rect;
static HBRUSH hBrush1 = CreateSolidBrush(RGB(50,100,255));
static HBRUSH hBrush2 = CreateSolidBrush(RGB(255,100,50));
HDC hDc;
LRESULT lResult;
switch (uMsg)
{
case WM_PAINT:
switch (uIdSubclass)
{
case 1:
hDc = BeginPaint(hWnd, &Ps);
Rect.left = 0;
Rect.right = (LONG) (((double) ITEM2_WIDTH) * Status::GI()->Get_JobCurPercentage());
Rect.top = 0;
Rect.bottom = ITEM_HEIGHT - 3;
FillRect(hDc, &Rect, hBrush1);
EndPaint(hWnd, &Ps);
break;
case 2:
hDc = BeginPaint(hWnd, &Ps);
Rect.left = 0;
Rect.right = (LONG) (((double) ITEM2_WIDTH) * Status::GI()->Get_JobTotPercentage());
Rect.top = 0;
Rect.bottom = ITEM_HEIGHT - 3;
FillRect(hDc, &Rect, hBrush2);
EndPaint(hWnd, &Ps);
break;
default:
return DefSubclassProc(hWnd, uMsg, wParam, lParam);
}
break;
case WM_NCDESTROY:
//ReleaseDC(hWnd, hDc);
return DefSubclassProc(hWnd, uMsg, wParam, lParam);
break;
default:
return DefSubclassProc(hWnd, uMsg, wParam, lParam);
}
return 0;
}
Next, I bind this function to the controls:
SetWindowSubclass( /*_In_ HWND hWnd*/ ed_cur_Progress.hWnd,
/*_In_ SUBCLASSPROC pfnSubclass*/ ChildWindowProc,
/*_In_ UINT_PTR uIdSubclass*/ 1,
/*_In_ DWORD_PTR dwRefData*/ (DWORD_PTR) NULL);
SetWindowSubclass( /*_In_ HWND hWnd*/ ed_tot_Progress.hWnd,
/*_In_ SUBCLASSPROC pfnSubclass*/ ChildWindowProc,
/*_In_ UINT_PTR uIdSubclass*/ 2,
/*_In_ DWORD_PTR dwRefData*/ (DWORD_PTR) NULL);
And, that's all! The result is amazing.

Answer 2

WM_PAINT you are handling is main window's. you need to draw the editbox in its owner WM_PAINT message. I guess you get the error from "hDc = BeginPaint(hWndEdit, &Ps);", you may check it.