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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(51.2, 37%, 14%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ECL%3C/text%3E%3C/svg%3E)
Hi to all,
I have a problem with redraw (or handle redraw message) with a win32 window in C++.
I open a normal (WS_OVERLAPPEDWINDOW) window and I handle the messages with a standard code.
My goal is to move a simple sketch (a rectangle painted with FillRect() ) with drag the mouse.
For this reason, I handle the WM_MOUSEMOVE message. When I obtain a WM_MOUSEMOVE, I get the X and Y coords, update the position of my rectangle and redraw it (I tried with two methosd: call redrawWindows() or redraw directly the rectangle in WM_MOUSEMOVE method, between GetDC() and ReleaseDC() ).
This works quite well only that after a few seconds of dragging the mouse, the drawing of the window no longer occurs. The client area remains white and I can no longer see my rectangle.
I cannot understand the reason for this behavior.
Do you have any suggestions on why and how to solve the problem?
Thank you all.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(92.8, 12%, 18%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EDL%3C/text%3E%3C/svg%3E)
Show the relevant section of your redrawing code. I'd suspect you're running out of GDI resources.
This is my simplified code:
//Global
MyRectangleClass* myRectangle = new MyRectangleClass(200,200,100,100);//this is my class. constructor with x,y,width,height in pixel
MyrectangleClass *choose_region; //chosen rectangle
//...
//Message handle in WndProc
case WM_PAINT:
HDC hdc = BeginPaint(hWnd, &ps);
EndPaint(hWnd, &ps);
break;
case WM_LBUTTONDOWN:
if (wParam == MK_LBUTTON)
{
choose_region = myRectangle;
}
break;
case WM_MOUSEMOVE:
if (wParam & MK_LBUTTON)
{
int xPos, yPos;
xPos = GET_X_LPARAM(lParam);
yPos = GET_Y_LPARAM(lParam);
//set new position
choose_region->setPosition(xPos, yPos);
//Redraw content
auto hdc = GetDC(hWnd);
if (hdc != NULL)
{
uint16_t x,y,bottom,right;
//Redraw my rectangle in new position
RECT rect;
rect.top = choose_region->getY();
rect.left = choose_region->getX();
rect.bottom = choose_region->getY() + choose_region->getHeight();;
rect.right = choose_region->getX() + choose_region->getLenght();
::FrameRect(hdc, &rect, CreateSolidBrush(RGB(10, 10, 0)));
ReleaseDC(hWnd, hdc);
}
}
break;
Looks like a GDI object leak is related to the use of CreateSolidBrush -- none of the created brushes are ever deleted.
An usual method for Drag & Drop is with ImageList APIs:
WM_LBUTTONDOWN : ImageList_BeginDrag, SetCapture, ImageList_DragEnter
WM_MOUSEMOVE : ImageList_DragMove
WM_LBUTTONUP : ImageList_EndDrag, ReleaseCapture
WM_PAINT : ImageList_Draw
Quick test :
Ok this is a possible best solution.
But I was hoping to do it in a simpler way; I don't understand why the way I use, despite the refresh problems, doesn't work ...
From your code, you must delete the brush handle, like :
HBRUSH hBrush = CreateSolidBrush(RGB(10, 10, 0));
// code
DeleteObject(hBrush);