Fix bug where coloring in same pixel and dragging over it with color prevents undo from working properly

canvas.js

@@ -130,6 +130,7 @@ document.addEventListener("DOMContentLoaded",()=>{
 			if (e.target.tagName==="TH") {
 				if (mouseState>=0) {
 					var mycoords = getCoordinates(e.target)
+					if (!(e.target.id in changedPixels)) {
 						if ("PIXELS" in changedPixels) {
 							changedPixels["PIXELS"]+=","+mycoords.x+","+mycoords.y
 						} else {
@@ -148,6 +149,7 @@ document.addEventListener("DOMContentLoaded",()=>{
 				}
 			}
 		}
+	}
 	var MouseClickListener = (e)=>{
 		e.preventDefault();
 	}
@@ -198,6 +200,7 @@ document.addEventListener("DOMContentLoaded",()=>{
 		if (!fillTool) {
 			if (e.target.tagName==="TH") {
 				var mycoords = getCoordinates(e.target)
+				if (!(e.target.id in changedPixels)) {
 					if ("PIXELS" in changedPixels) {
 						changedPixels["PIXELS"]+=","+mycoords.x+","+mycoords.y
 					} else {
@@ -214,6 +217,7 @@ document.addEventListener("DOMContentLoaded",()=>{
 					changedPixels["STEPTYPE"]="ADD"
 				}
 			}
+		}
 		toolbar.style.visibility = "hidden";
 	}