canvas如何实现按比例沾满全屏
- document.documentElement.clientWidth: 可见区域宽度;
- document.documentElement.clientHeight: 可见区域高度。
- canvas.width = document.documentElement.clientWidth
- canvas.height = document.documentElement.clientHeight
- screen.availWidth：屏幕可用宽度；
- screen.availHeight：屏幕可见高度。
- canvas.width = screen.availWidth;
- canvas.height = screen.availHeight;
- screen.width：屏幕显示宽度
- screen.height：屏幕显示高度
- canvas.width = screen.width
- canvas.height = screen.height
- window.innerWidth：窗口的宽度
- window.innerHeight：窗口的高度
- canvas.width = window.innerWidth
- canvas.height = window.innerHeight
