I found this example here on Stack Overflow which is exactly what I was looking for:
https://stackoverflow.com/a/40013027/1955916
I tried several approaches to include this code in to Google Sites. I tried with an HTML gadget, directly as HTML and as JavaScript gadget. But so far nothing worked.
Based on the example of user Grant: document.getelementbyId in Google Script not working I think I am on a promising way, but it still does not work.
I have stored the following script in Google sites and published it as a web app. Then I included it as a Apps Script Gadget in my testpage. However, the only thing that is displayed is the Title. So I must have a fundamental error somewhere, but my current knowledge is really limited here.
Code.gs:
function doGet(e) {
return HtmlService.createHtmlOutputFromFile('Index');
}
Index.html:
<!DOCTYPE html>
<html>
<head>
<title>Demo of a canvas used to render seat plan in a Cinema</title>
<script>
var EMPTY = 0; // Still available for reservation and purchase.
var RESERVED = 1; // reserved but not yet paid for.
var BOUGHT = 2; // bought and paid for.
function Point(x,y) {
return { X: x, Y: y }
}
function Size(w,h) {
return {Width: w, Height: h}
}
function Rectangle(left,top,width,height) {
return {TopLeft: Point(left,top), Size: Size(width,height)}
}
function seatColorFromSeatStatus(seatStatus) {
switch(seatStatus) {
case EMPTY: return "white";
case RESERVED: return "green";
case BOUGHT: return "red";
default: return "black"; // Invalid value...
}
}
function mapSeatStatusToSeatColor(seats)
{
var result = {};
for(seat in seats) {
result[seat] = seatColorFromSeatStatus(seats[seat])
}
return result;
}
function seatKeyFromPosition(row,col) {
return JSON.stringify([row,col]);
}
function seatRowFromKey(key) {
return (JSON.parse(key))[0];
}
function seatColFromKey(key) {
return (JSON.parse(key)[1]);
}
function getSeatInfo(nrows,ncolumns) {
var result = { NRows: nrows, NColumns: ncolumns, Seats : {} };
for(row = 0; row < nrows; row++) {
for( col = 0; col < ncolumns; col++ ) {
result.Seats[seatKeyFromPosition(row,col)] = EMPTY;
}
}
result.Seats[seatKeyFromPosition(0,0)] = RESERVED;
result.Seats[seatKeyFromPosition(1,3)] = BOUGHT;
return result;
}
function renderSeat(ctx,r,fillColor) {
var backup = ctx.fillStyle;
ctx.strokeStyle = "blue";
ctx.rect(r.TopLeft.X+2,r.TopLeft.Y+2,r.Size.Width-4,r.Size.Height-4);
ctx.stroke();
ctx.fillStyle = fillColor;
ctx.fillRect(r.TopLeft.X+3,r.TopLeft.Y+3,r.Size.Width-5,r.Size.Height-5);
ctx.fillStyle = backup;
}
function renderSeatplan(seatInfo) {
var nrows = seatInfo.NRows;
var ncolumns = seatInfo.NColumns;
var seatColors = mapSeatStatusToSeatColor(seatInfo.Seats)
var canvas = document.getElementById("seatplan");
var ctx = canvas.getContext("2d");
var borderWidth = 10;
var rcContent = Rectangle(
borderWidth
, borderWidth
, canvas.width - 2 * borderWidth
, canvas.height - 2 * borderWidth
);
var szCell = Size(
Math.floor(rcContent.Size.Width / (ncolumns + 1))
, Math.floor(rcContent.Size.Height / (nrows + 1))
);
ctx.font = "30px Arial";
for(row = -1; row < nrows; row++) {
for(col = -1; col < ncolumns; col++ ) {
var r = Rectangle(
rcContent.TopLeft.X + szCell.Width * (col+1)
,rcContent.TopLeft.Y + szCell.Height * (row+1)
,szCell.Width
,szCell.Height
);
var center = Point(szCell.Width / 2, szCell.Height / 2);
if (row == -1 && col == -1) {
// nothing to render.
}
else if(row == -1){
// render column headers as numbers...
ctx.fillStyle = "black";
ctx.textAlign = "center";
ctx.fillText(col.toString(),r.TopLeft.X+center.X,r.TopLeft.Y+center.Y+6);
}
else if(col == -1){
// render row header
ctx.fillStyle = "black";
ctx.textAlign = "center";
ctx.fillText(String.fromCharCode(65 + row),r.TopLeft.X+center.X+4,r.TopLeft.Y+center.Y+6);
}
else
{
// render seat
renderSeat(ctx,r,seatColors[seatKeyFromPosition(row,col)]);
}
}
}
}
</script>
</head>
<body>
<form id="myForm" onsubmit="renderSeatplan(getSeatInfo(10,16));">
</form>
<div id="output"></div>
<h1>Seatplan</h1>
<canvas id="seatplan" width="640" height="480"></canvas>
</body>
</html>
The code of the Index.html on its own is proven, as it works in the example from user BitTrickler (see link above) I have seen.
