//
// SvGridView.m
// SvSinglePixel
//
// Created by xiaoyong.cxy on 6/23/15.
// Copyright (c) 2015 smileEvday. All rights reserved.
//
#import "SvGridView.h"
#define SINGLE_LINE_WIDTH (1 / [UIScreen mainScreen].scale)
#define SINGLE_LINE_ADJUST_OFFSET ((1 / [UIScreen mainScreen].scale) / 2)
@implementation SvGridView
@synthesize gridColor = _gridColor;
@synthesize gridSpacing = _gridSpacing;
- (instancetype)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
self.backgroundColor = [UIColor clearColor];
_gridColor = [UIColor blueColor];
_gridLineWidth = SINGLE_LINE_WIDTH;
_gridSpacing = 30;
}
return self;
}
- (void)setGridColor:(UIColor *)gridColor
{
_gridColor = gridColor;
[self setNeedsDisplay];
}
- (void)setGridSpacing:(CGFloat)gridSpacing
{
_gridSpacing = gridSpacing;
[self setNeedsDisplay];
}
- (void)setGridLineWidth:(CGFloat)gridLineWidth
{
_gridLineWidth = gridLineWidth;
[self setNeedsDisplay];
}
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextBeginPath(context);
CGFloat lineMargin = self.gridSpacing;
/**
* https://developer.apple.com/library/ios/documentation/2DDrawing/Conceptual/DrawingPrintingiOS/GraphicsDrawingOverview/GraphicsDrawingOverview.html
* 僅當要繪製的線寬為奇數像素時，繪製位置需要調整
*/
CGFloat pixelAdjustOffset = 0;
if (((int)(self.gridLineWidth * [UIScreen mainScreen].scale) + 1) % 2 == 0) {
pixelAdjustOffset = SINGLE_LINE_ADJUST_OFFSET;
}
CGFloat xPos = lineMargin - pixelAdjustOffset;
CGFloat yPos = lineMargin - pixelAdjustOffset;
while (xPos < self.bounds.size.width) {
CGContextMoveToPoint(context, xPos, 0);
CGContextAddLineToPoint(context, xPos, self.bounds.size.height);
xPos += lineMargin;
}
while (yPos < self.bounds.size.height) {
CGContextMoveToPoint(context, 0, yPos);
CGContextAddLineToPoint(context, self.bounds.size.width, yPos);
yPos += lineMargin;
}
CGContextSetLineWidth(context, self.gridLineWidth);
CGContextSetStrokeColorWithColor(context, self.gridColor.CGColor);
CGContextStrokePath(context);
}
@end