SoonDesign/frontend-web/vendor/js/guideLines.js

function initAligningGuidelines(canvas) {
 
	var ctx = canvas.getSelectionContext(),
		//aligningLineOffset = 0,
		//aligningLineMargin = 0,
		//aligningLineWidth = 1,
		//aligningLineColor = 'rgb(0,0,0)',
		aligningLineOffset = 4,
		aligningLineMargin = 5,//吸引
		aligningLineWidth = 6,
		aligningLineColor = '#6637FF',
		viewportTransform,
		zoom = 1;
 
	function drawVerticalLine(coords) {
		drawLine(
			coords.x + 0.5,
			coords.y1 > coords.y2 ? coords.y2 : coords.y1,
			coords.x + 0.5,
			coords.y2 > coords.y1 ? coords.y2 : coords.y1);
	}
 
	function drawHorizontalLine(coords) {
		drawLine(
			coords.x1 > coords.x2 ? coords.x2 : coords.x1,
			coords.y + 0.5,
			coords.x2 > coords.x1 ? coords.x2 : coords.x1,
			coords.y + 0.5);
	}
 
	function drawLine(x1, y1, x2, y2) {
		ctx.save();
		ctx.lineWidth = aligningLineWidth;
		ctx.strokeStyle = aligningLineColor;
		ctx.beginPath();
		let width = canvas.getWidth();
		let height = canvas.getHeight();
		ctx.moveTo(width / 2 - ( ( width / 2 - (x1) ) * zoom ) , height / 2 - ( ( height / 2 - (y1) ) * zoom ));//哪个点散射出来
		ctx.lineTo(width / 2 - ( ( width / 2 - (x2) ) * zoom ), height / 2 - ( ( height / 2 - (y2) ) * zoom ));//结束到哪个点
		//修复中心放大后的位置偏移 2021-10-24
		ctx.stroke();
		ctx.restore();
	}
 
	function isInRange(value1, value2) {
		value1 = Math.round(value1);
		value2 = Math.round(value2);
		for (var i = value1 - aligningLineMargin, len = value1 + aligningLineMargin; i <= len; i++) {
			if (i === value2) {
				return true;
			}
		}
		return false;
	}
 
	var verticalLines = [],
		horizontalLines = [];
 
	canvas.on('mouse:down', function () {
		viewportTransform = canvas.viewportTransform;
		zoom = canvas.getZoom();
	});
 
	canvas.on('object:moving', function(e) {
 
		var activeObject = e.target,
			canvasObjects = canvas.getObjects(),
			activeObjectCenter = activeObject.getCenterPoint(),
			activeObjectLeft = activeObjectCenter.x,
			activeObjectTop = activeObjectCenter.y,
			activeObjectBoundingRect = activeObject.getBoundingRect(),
			activeObjectHeight = activeObjectBoundingRect.height / viewportTransform[3],
			activeObjectWidth = activeObjectBoundingRect.width / viewportTransform[0],
			horizontalInTheRange = false,
			verticalInTheRange = false,
			transform = canvas._currentTransform;
 
		if (!transform) return;
 
		// It should be trivial to DRY this up by encapsulating (repeating) creation of x1, x2, y1, and y2 into functions,
		// but we're not doing it here for perf. reasons -- as this a function that's invoked on every mouse move
 
		for (var i = canvasObjects.length; i--; ) {
 
			if (canvasObjects[i] === activeObject) continue;
 
			var objectCenter = canvasObjects[i].getCenterPoint(),
				objectLeft = objectCenter.x,
				objectTop = objectCenter.y,
				objectBoundingRect = canvasObjects[i].getBoundingRect(),
				objectHeight = objectBoundingRect.height / viewportTransform[3],
				objectWidth = objectBoundingRect.width / viewportTransform[0];
 
			// snap by the horizontal center line
			if (isInRange(objectLeft, activeObjectLeft)) {
				verticalInTheRange = true;
				verticalLines.push({
					x: objectLeft,
					y1: (objectTop < activeObjectTop)
						? (objectTop - objectHeight / 2 - aligningLineOffset)
						: (objectTop + objectHeight / 2 + aligningLineOffset),
					y2: (activeObjectTop > objectTop)
						? (activeObjectTop + activeObjectHeight / 2 + aligningLineOffset)
						: (activeObjectTop - activeObjectHeight / 2 - aligningLineOffset)
				});
				activeObject.setPositionByOrigin(new fabric.Point(objectLeft, activeObjectTop), 'center', 'center');
			}
 
			// snap by the left edge
			if (isInRange(objectLeft - objectWidth / 2, activeObjectLeft - activeObjectWidth / 2)) {
				verticalInTheRange = true;
				verticalLines.push({
					x: objectLeft - objectWidth / 2,
					y1: (objectTop < activeObjectTop)
						? (objectTop - objectHeight / 2 - aligningLineOffset)
						: (objectTop + objectHeight / 2 + aligningLineOffset),
					y2: (activeObjectTop > objectTop)
						? (activeObjectTop + activeObjectHeight / 2 + aligningLineOffset)
						: (activeObjectTop - activeObjectHeight / 2 - aligningLineOffset)
				});
				activeObject.setPositionByOrigin(new fabric.Point(objectLeft - objectWidth / 2 + activeObjectWidth / 2, activeObjectTop), 'center', 'center');
			}
 
			// snap by the right edge
			if (isInRange(objectLeft + objectWidth / 2, activeObjectLeft + activeObjectWidth / 2)) {
				verticalInTheRange = true;
				verticalLines.push({
					x: objectLeft + objectWidth / 2,
					y1: (objectTop < activeObjectTop)
						? (objectTop - objectHeight / 2 - aligningLineOffset)
						: (objectTop + objectHeight / 2 + aligningLineOffset),
					y2: (activeObjectTop > objectTop)
						? (activeObjectTop + activeObjectHeight / 2 + aligningLineOffset)
						: (activeObjectTop - activeObjectHeight / 2 - aligningLineOffset)
				});
				activeObject.setPositionByOrigin(new fabric.Point(objectLeft + objectWidth / 2 - activeObjectWidth / 2, activeObjectTop), 'center', 'center');
			}
 
			// snap by the vertical center line
			if (isInRange(objectTop, activeObjectTop)) {
				horizontalInTheRange = true;
				horizontalLines.push({
					y: objectTop,
					x1: (objectLeft < activeObjectLeft)
						? (objectLeft - objectWidth / 2 - aligningLineOffset)
						: (objectLeft + objectWidth / 2 + aligningLineOffset),
					x2: (activeObjectLeft > objectLeft)
						? (activeObjectLeft + activeObjectWidth / 2 + aligningLineOffset)
						: (activeObjectLeft - activeObjectWidth / 2 - aligningLineOffset)
				});
				activeObject.setPositionByOrigin(new fabric.Point(activeObjectLeft, objectTop), 'center', 'center');
			}
 
			// snap by the top edge
			if (isInRange(objectTop - objectHeight / 2, activeObjectTop - activeObjectHeight / 2)) {
				horizontalInTheRange = true;
				horizontalLines.push({
					y: objectTop - objectHeight / 2,
					x1: (objectLeft < activeObjectLeft)
						? (objectLeft - objectWidth / 2 - aligningLineOffset)
						: (objectLeft + objectWidth / 2 + aligningLineOffset),
					x2: (activeObjectLeft > objectLeft)
						? (activeObjectLeft + activeObjectWidth / 2 + aligningLineOffset)
						: (activeObjectLeft - activeObjectWidth / 2 - aligningLineOffset)
				});
				activeObject.setPositionByOrigin(new fabric.Point(activeObjectLeft, objectTop - objectHeight / 2 + activeObjectHeight / 2), 'center', 'center');
			}
 
			// snap by the bottom edge
			if (isInRange(objectTop + objectHeight / 2, activeObjectTop + activeObjectHeight / 2)) {
				horizontalInTheRange = true;
				horizontalLines.push({
					y: objectTop + objectHeight / 2,
					x1: (objectLeft < activeObjectLeft)
						? (objectLeft - objectWidth / 2 - aligningLineOffset)
						: (objectLeft + objectWidth / 2 + aligningLineOffset),
					x2: (activeObjectLeft > objectLeft)
						? (activeObjectLeft + activeObjectWidth / 2 + aligningLineOffset)
						: (activeObjectLeft - activeObjectWidth / 2 - aligningLineOffset)
				});
				activeObject.setPositionByOrigin(new fabric.Point(activeObjectLeft, objectTop + objectHeight / 2 - activeObjectHeight / 2), 'center', 'center');
			}
		}
 
		if (!horizontalInTheRange) {
			horizontalLines.length = 0;
		}
 
		if (!verticalInTheRange) {
			verticalLines.length = 0;
		}
	});
 
	canvas.on('before:render', function() {

		if(canvas&&canvas.contextTop)
		{
			canvas.clearContext(canvas.contextTop);
		}


	});
 
	canvas.on('after:render', function() {
		for (var i = verticalLines.length; i--; ) {
			drawVerticalLine(verticalLines[i]);
		}
		for (var i = horizontalLines.length; i--; ) {
			drawHorizontalLine(horizontalLines[i]);
		}
		verticalLines.length = horizontalLines.length = 0;
	});
 
	canvas.on('mouse:up', function() {
		verticalLines.length = horizontalLines.length = 0;
		canvas.renderAll();
	});
}