WM_PAINT after some redraws it freaks out - winapi

Question

I am trying out the win32 api so I decided to try to draw a checkers board on a windows, just for testing
it happens that I can draw the checkers board and I tried to implement some interactivity on it. To do it so, I am storing the mouse click on a static and using it on the WM_PAINT to draw a red border around the clicked house.
the problem is that after a few clicks the windows freaks out, screen gets all white without the brushes fill and I can find the window title, it a complete mess.
This is the code I have
#include <windows.h>
#include "WindowsX.h"
#include "stdafx.h"
#include <vector>
#include <stdlib.h>
//const char g_szClassName[] = "myWindowClass";
POINT p;
void TabuleiroCasas(std::vector<RECT>* rc, RECT rcClient)
{
for(int i = 0; i < 8; i++)
{
for(int j = 0; j < 8; j++)
{
int width = (rcClient.right-200 - rcClient.left) / 8;
int height = (rcClient.bottom - rcClient.top) / 8;
RECT r;
r.left = width*j;
r.top = rcClient.bottom - (height * i);
r.right = width*(j+1);
r.bottom = rcClient.bottom - height * (i+1);
rc->push_back(r);
}
}
}
// Step 4: the Window Procedure
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
HPEN hPen = CreatePen(PS_SOLID, 1, RGB(255,255,255));
HPEN hPenSel = CreatePen(PS_SOLID, 3, RGB(255,0,0));
HBRUSH hBrushgrey =CreateSolidBrush(RGB(200,200,200));
HBRUSH hBrushblack =CreateSolidBrush(RGB(255,255,255));
HBRUSH hBrushwhite = CreateSolidBrush(RGB(0,0,0));
PAINTSTRUCT Ps;
std::vector<RECT> casas;
int xPos;
int yPos;
switch(msg)
{
case WM_LBUTTONDOWN:
GetCursorPos(&p);
InvalidateRect(hwnd, NULL, true);
break;
case WM_PAINT:
try
{
RECT rcClient;
GetClientRect(hwnd, &rcClient);
HDC hdc;
//DESENHA TABULEIRO
hdc = BeginPaint(hwnd, &Ps);
SelectObject(hdc, hBrushgrey);
Rectangle(hdc, rcClient.left, rcClient.top, rcClient.right, rcClient.bottom);
Rectangle(hdc, rcClient.left, rcClient.top, rcClient.right-200, rcClient.bottom);
TabuleiroCasas(&casas, rcClient);
for(int i = 0; i < casas.size(); i++)
{
if ( ((i + (i / 8)) % 2) == 1)
{
SelectObject(hdc, hBrushwhite);
Rectangle(hdc, casas[i].left ,casas[i].bottom, casas[i].right, casas[i].top);
}
else
{
SelectObject(hdc, hBrushblack);
Rectangle(hdc, casas[i].left ,casas[i].bottom, casas[i].right, casas[i].top);
}
}
for(int i = 0; i < casas.size(); i++)
{
if((p.x > casas[i].left) && (p.x < casas[i].right) && (p.y < casas[i].top) && (p.y > casas[i].bottom))
{
SelectObject(hdc, hPenSel);
Rectangle(hdc, casas[i].left ,casas[i].bottom, casas[i].right, casas[i].top);
}
}
EndPaint(hwnd, &Ps);
}
catch(int e)
{
}
break;
case WM_SIZE:
//InvalidateRect(hwnd, NULL, false);
break;
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow)
{
WNDCLASSEX wc;
HWND hwnd;
MSG Msg;
//Step 1: Registering the Window Class
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wc.lpszMenuName = NULL;
wc.lpszClassName = L"Damas";
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
if(!RegisterClassEx(&wc))
{
MessageBox(NULL, L"Window Registration Failed!", L"Error!",
MB_ICONEXCLAMATION | MB_OK);
return 0;
}
// Step 2: Creating the Window
hwnd = CreateWindowEx(
3,
L"Damas",
L"The title of my window",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT, 800, 600,
NULL, NULL, hInstance, NULL);
if(hwnd == NULL)
{
MessageBox(NULL, L"Window Creation Failed!", L"Error!",
MB_ICONEXCLAMATION | MB_OK);
return 0;
}
ShowWindow(hwnd, nCmdShow);
UpdateWindow(hwnd);
// Step 3: The Message Loop
while(GetMessage(&Msg, NULL, 0, 0) > 0)
{
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}
return Msg.wParam;
}

Answer 1

The problem can be found right at the top of your window procedure. You are creating a bunch of GDI objects every time your WndProc is called:
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
HPEN hPen = CreatePen(PS_SOLID, 1, RGB(255,255,255));
HPEN hPenSel = CreatePen(PS_SOLID, 3, RGB(255,0,0));
HBRUSH hBrushgrey =CreateSolidBrush(RGB(200,200,200));
HBRUSH hBrushblack =CreateSolidBrush(RGB(255,255,255));
HBRUSH hBrushwhite = CreateSolidBrush(RGB(0,0,0));
.....
}
You don't ever return these to the system and so eventually you exhaust available GDI resources. Create those objects once only at application initialization time.
That call to DeleteDC looks very suspicious to me. You certainly do not need it. Remove it.
Another problem that you have is the code to retrieve the mouse position. You never use GetCursorPos for that since the mouse may have moved since the message was posted. You can get it from lParam. Like this:
p.x = GET_X_LPARAM(lParam);
p.y = GET_Y_LPARAM(lParam);
You'll need to include the Windowsx header properly. It's done like this:
#include <WindowsX.h>
Note the difference from your code in the question.