win32_step_18 - 8BitsCoding/RobotMentor GitHub Wiki

#include <stdlib.h>
#include <time.h>

#define MAX_COUNT 100

struct Circle {
	int x;
	int y;
	int r;
	COLORREF color;
};

Circle g_pos[MAX_COUNT];

void MakeCircleData(Circle * ap_data, RECT * ap_rect)
{
	ap_data->x = rand() % ap_rect->right;
	ap_data->y = rand() % ap_rect->bottom;
	ap_data->r = rand() % 50 + 10;
	ap_data->color = RGB(rand() % 256, rand() % 256, rand() % 256);
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	if (uMsg == WM_PAINT) {
		PAINTSTRUCT ps;
		HDC h_dc = BeginPaint(hWnd, &ps);

		Circle *p = g_pos;
		HBRUSH h_brush;
		HGDIOBJ h_old_brush = GetCurrentObject(h_dc, OBJ_BRUSH);

		for (int i = 0; i < MAX_COUNT; i++) {
			h_brush = CreateSolidBrush(p->color);
			h_old_brush = SelectObject(h_dc, h_brush);
			Ellipse(h_dc, p->x - p->r, p->y - p->r, p->x + p->r, p->y + p->r);
			p++;
			
			DeleteObject(h_brush);
		}

		SelectObject(h_dc, h_old_brush);
		EndPaint(hWnd, &ps);
		return 0;
	}
	else if (uMsg == WM_CREATE) {
		srand((unsigned int)time(NULL));
		RECT r;
		GetClientRect(hWnd, &r);

		for (int i = 0; i < MAX_COUNT; i++) {
			MakeCircleData(g_pos + i, &r);
			/*
			g_pos[i].x = rand() % r.right;
			g_pos[i].y = rand() % r.bottom;
			g_pos[i].r = rand() % 50 + 10;
			g_pos[i].color = RGB(rand() % 256, rand() % 256, rand() % 256);
			*/
		}

		SetTimer(hWnd, 1, 50, NULL);
		return 0;
	}
	else if (uMsg == WM_TIMER) {
		if (wParam == 1) {
			RECT r;
			GetClientRect(hWnd, &r);

			Circle *p = g_pos;
			for (int i = 0; i < MAX_COUNT; i++) {
				p->r--;
				if (p->r <= 1) {
					MakeCircleData(p, &r);
				}
				p++;
			}
			InvalidateRect(hWnd, NULL, TRUE);
		}
	}
	else if (uMsg == WM_DESTROY) {
		KillTimer(hWnd, 1);
		PostQuitMessage(0);
	}
		

	return DefWindowProc(hWnd, uMsg, wParam, lParam);
}