Add smoother line drawing algorithm, to fill in "skipped" pixels

canvas.js

@@ -18,6 +18,8 @@ FILL //Fill was done. A color is provided by "backcolor" and a pixel containing
 var pixelStates = []; //Last 20 pixel states stored here.
 var currentPixelState = -1; //Which pixel state we're on. Max out at 20.
 
+var lastDrawPoint = null;
+
 document.addEventListener("DOMContentLoaded",()=>{
 	var undoButton = document.createElement("button")
 	var redoButton = document.createElement("button")
@@ -35,6 +37,12 @@ document.addEventListener("DOMContentLoaded",()=>{
 			this.y = y;
 		}
 	}
+	class Point{
+		constructor(x,y) {
+			this.x = x;
+			this.y = y;
+		}
+	}
 	
 	//Returns a coordinate class.
 	var getCoordinates = (box)=>{
@@ -130,6 +138,8 @@ document.addEventListener("DOMContentLoaded",()=>{
 			if (e.target.tagName==="TH") {
 				if (mouseState>=0) {
 					var mycoords = getCoordinates(e.target)
+					if (lastDrawPoint===null) {
+						lastDrawPoint = new Point(mycoords.x,mycoords.y);
 						if (!(e.target.id in changedPixels)) {
 							if ("PIXELS" in changedPixels) {
 								changedPixels["PIXELS"]+=","+mycoords.x+","+mycoords.y
@@ -146,6 +156,89 @@ document.addEventListener("DOMContentLoaded",()=>{
 							}
 							changedPixels["STEPTYPE"]="ADD"
 						}
+					} else {
+						//SMOOTH DRAWING
+						//Draw pixels for each point in
+						//between both positions. That
+						//way there's no skipped points.
+						var slopeX = mycoords.x - lastDrawPoint.x
+						var slopeY = mycoords.y - lastDrawPoint.y
+						//Whichever is larger is the one
+						//we increment by 1 pixel each turn.
+						if (Math.abs(slopeY)>Math.abs(slopeX)) {
+							//Y increases by 1.
+							var Xincr = slopeX/Math.abs(slopeY);
+							var Yincr = Math.sign(slopeY)*1;
+							var currX = Number(lastDrawPoint.x)
+							var currY = Number(lastDrawPoint.y)
+							var iterations=0;
+							while (Math.floor(currY)!==Math.floor(mycoords.y)) {
+								currY+=Yincr;
+								currX+=Xincr;
+								if (iterations>=1) {
+									console.log("X:"+currX+","+currY+"/"+lastDrawPoint.x+","+lastDrawPoint.y+"/"+mycoords.x+","+mycoords.y)
+								}
+								var target = document.getElementById("pos_"+Math.ceil(currX)+"_"+currY);
+								if (!(target.id in changedPixels)) {
+									if ("PIXELS" in changedPixels) {
+										changedPixels["PIXELS"]+=","+Math.ceil(currX)+","+currY
+									} else {
+										changedPixels["PIXELS"]=Math.ceil(currX)+","+currY
+									}
+									changedPixels["old_"+target.id]=target.style.background;
+									if (mouseState<2) {
+										target.style.background=selectedColor;
+										changedPixels[target.id]=selectedColor;
+									} else {
+										target.style.background="white";
+										changedPixels[target.id]="white";
+									}
+									changedPixels["STEPTYPE"]="ADD"
+								}
+								if (currX>COLS || currY>ROWS || currX<0 || currY<0) {
+									new Error("Rip")
+									break;
+								}
+								iterations++;
+							}
+						} else {
+							var Xincr = Math.sign(slopeX)*1;
+							var Yincr = slopeY/Math.abs(slopeX);
+							var currX = Number(lastDrawPoint.x)
+							var currY = Number(lastDrawPoint.y)
+							var iterations=0;
+							while (Math.floor(currX)!==Math.floor(mycoords.x)) {
+								currY+=Yincr;
+								currX+=Xincr;
+								if (iterations>=1) {
+									console.log("Y:"+currX+","+currY+"/"+lastDrawPoint.x+","+lastDrawPoint.y+"/"+mycoords.x+","+mycoords.y)
+								}
+								var target = document.getElementById("pos_"+currX+"_"+Math.ceil(currY));
+								if (!(target.id in changedPixels)) {
+									if ("PIXELS" in changedPixels) {
+										changedPixels["PIXELS"]+=","+currX+","+Math.ceil(currY)
+									} else {
+										changedPixels["PIXELS"]=currX+","+Math.ceil(currY)
+									}
+									changedPixels["old_"+target.id]=target.style.background;
+									if (mouseState<2) {
+										target.style.background=selectedColor;
+										changedPixels[target.id]=selectedColor;
+									} else {
+										target.style.background="white";
+										changedPixels[target.id]="white";
+									}
+									changedPixels["STEPTYPE"]="ADD"
+								}
+								iterations++;
+								if (currX>COLS || currY>ROWS || currX<0 || currY<0) {
+									new Error("Rip")
+									break;
+								}
+							}
+						}
+						lastDrawPoint = new Point(mycoords.x,mycoords.y);
+					}
 				}
 			}
 		}
@@ -197,6 +290,7 @@ document.addEventListener("DOMContentLoaded",()=>{
 	var MouseStateDown = (e)=>{
 		e.preventDefault();
 		mouseState = e.button;
+		lastDrawPoint = null;
 		if (!fillTool) {
 			if (e.target.tagName==="TH") {
 				var mycoords = getCoordinates(e.target)