Pan and Zoom Programmatically in a JavaScript Diagram

We will build a diagram with 50 random nodes and we will zoom and pan this diagram programmatically. Here is a screenshot of the final diagram, which is a link to the sample:

We will use the MindFusion Diagramming library for JavaScript.

I. Project Setup

We add a reference to the MindFusion.Diagramming.js and MindFusion.Common.js files. We also add a reference to another file called MouseEvents.js. This is our code-behind file.

<script src="MindFusion.Common.js" type="text/javascript"></script>
<script src="MindFusion.Diagramming.js" type="text/javascript"></script>
<script src="MouseEvents.js" type="text/javascript"></script>

In the BODY of the web page we create a Canvas element, to which we assign an id. This is important, because we will refer to the Canvas in code:

<div style="width: 100%; height: 100%; overflow: auto;">
    <canvas id="diagram_canvas" width="2100" height="2100">
        This page requires a browser that supports HTML 5 Canvas element.
    </canvas>
</div>

II. Diagram Settings

In the code-behind file that we called MouseEvents.js we use the DOMContentLoaded event to initialize the diagram.

document.addEventListener("DOMContentLoaded", function ()
{
    // create a Diagram component that wraps the "diagram_canvas" canvas
    diagram = MindFusion.AbstractionLayer.createControl(Diagram, null, null, null, document.getElementById("diagram_canvas"));
    diagram.setBounds(new Rect(5, 5, 2000, 1000));

We use the createControl method of the AbstractionLayer class to create an instance of the Diagram class. The setBounds method determines the size of the diagram’s drawing area. If this size is bigger than the size of the Canvas, the diagram automatically shows scrollbars. Note that only if the diagram’s area is larger than the canvas we can use panning.

We use some settings of the Diagram class to customize the application:

diagram.setDefaultShape("Rectangle");
diagram.setRouteLinks(true);
diagram.setRoundedLinks(true);
diagram.setShowGrid(false);

The links will be routed and rounded and no grid will be rendered.

III. Diagram Items

We create the diagram nodes with the createShapeNode method of the Factory class. The Factory class as an instance is available through the getFactory() method:
for(var i = 0; i < 50; i++)

    {
        var colorIndex = Math.floor(Math.random() * 3);  
        var shape = diagram.getFactory().createShapeNode(new Rect(136, 36, 20, 10));
        shape.setBrush({ type: 'SolidBrush', color: colors[colorIndex] });
        if(i % 3   == 0)
            shape.setShape('Ellipse');
        else 
            shape.setShape('Rectangle');
        if( i % 7 == 0)
        {
            shape.setBounds(new Rect(136, 36, 16, 8));	
        }
		
        shape.setText("Node " + (i + 1).toString());
        shape.setTextColor("white");
    }

We make each third shape Ellipse and we choose the brush on a random principle out of three brushes, that we initialized in an array. Each seventh shape is slightly smaller – that is set with the setBounds method, which takes as an argument a Rect, that is slightly smaller than the Rect instance that we use when we create the shape nodes.

The connectors among the nodes are created with the createDiagramLink method of Factory . We cycle through all 50 nodes and connect each one of them with a randomly taken node from the diagram nodes collection. This collection is available through the nodes proeprty of the Diagram class:

diagram.nodes.forEach(function(node)
{
    var nodeIndex = Math.floor(Math.random() * 50);  

    var node2 = diagram.nodes[nodeIndex];
    var link = diagram.getFactory().createDiagramLink(node, node2);
    link.setHeadShape("Circle");
})

We customize the appearance of the link through the setHeadShape method. We choose the ‘Circle’ shape as a head to each link.

We have created the diagram items with the same bounds, which means they are on top of each other. The best way to arrange them is with one of the automatic layout algorithms, available with the JsDiagram. They are members of the MindFusion.Graphs namespace – you can check the rest. In our sample we’ve chosen the LayeredLayout ,which provides quite nice result. We set its direction to LayoutDirection .There a few other properties that we’ve set that regulate the node distance, the layer distance and more:

var layout = new MindFusion.Graphs.LayeredLayout();
layout.direction = MindFusion.Graphs.LayoutDirection.LeftToRight;
layout.siftingRounds = 0;
layout.nodeDistance = 8;
layout.layerDistance = 8;
diagram.arrange(layout);

All layouts are applies through the arrange method of the Diagram that takes an instance of the layout as an argument.

IV. Pan and Zoom

We will implement pan and zoom by handling standard DOM events. The first one is the “wheel” event, which we attach to the diagram canvas element:

var dgrm = document.getElementById('diagram_canvas');

dgrm.addEventListener('wheel', function(e)
{
    var zoom = diagram.getZoomFactor();
    zoom -= e.deltaY / 10;
    if (zoom > 10)
        diagram.setZoomFactor(zoom);

    e.preventDefault(); // do not scroll
});

We use the getZoomFactor and setZoomFactor methods of the Diagram , to manipulate the zoom ratio. The zoom step is calculated based on the deltaY value of the event args. You can command the amount of zoom by dividing by a smaller or a larger number. It is important that we call preventDefault() on the event arguments, to surpass the default response of the canvas to the wheel event.

The panning is implemented by handling the mousedown and mouseup DOM events of the Canvas.

/* events fired on the draggable target */
dgrm.addEventListener('mousedown', function(e)
{
 if( e.ctrlKey)
	diagram.setBehavior(MindFusion.Diagramming.Behavior.Pan);
 
}, false);

dgrm.addEventListener('mouseup', function(e)
{
 if( e.ctrlKey)
	diagram.setBehavior(MindFusion.Diagramming.Behavior.LinkShapes);
 
}, false);

If we want to make the Diagram pan we need simply to change the diagram’s behavior with the setBehavior method. The options are members of the Behavior enumeration. When the user clicks on the Diagram and the Ctrl key is pressed, we change the diagram’s behavior to “Pan”. When the mouse is up, but the Ctrl key is pressed, we rest the behavior back to LinkShapes. This is the default behavior, where dragging with the mouse creates new shapes, while dragging between existing DiagramShape -s, creates DiagramLink -s.

With that our sample is ready. You can download the source code from this link:

Download the Mouse Events Sample with JavaScript Diagram

Technical support is available through MindFusion forum here.

About Diagramming for JavaScript: This native JavaScript library provides developers with the ability to create and customize any type of diagram, decision tree, flowchart, class hierarchy, graph, genealogy tree, BPMN diagrams and much more. The control offers rich event set, numerous customization options, animations, graph operations, styling and themes. You have more than 100 predefined nodes, table nodes and more than 15 automatic layout algorithms. Learn more about Diagramming for JavaScript at https://mindfusion.eu/javascript-diagram.html.

JavaScript Database Designer with SQL Generator

We are going to use the JS flowchart library as a database design tool. We will create DB tables, add rows, connect the tables and generate SQL statements that would create the tables.

Here is a screenshot of the application:

Database Designer Application with SQL Generator

Database Designer Application with SQL Generator

I. Project Setup

We need two JavaScript libraries for the flowchart:

  • MindFusion.Common.js
  • MindFusion.Diagramming.js

We copy them in the work folder of the project, where we will put the HTML and the JavaScript code behind. Then we create an HTML file and name it DBDesign.html. There we will reference the two JavaScript libraries:

http://MindFusion.Common.js
http://MindFusion.Diagramming.js

We reference those two libraries at the end of the HTML file, just before the closing tag. This way we are sure that the majority of the browsers will load the scripts correct.

We need an HTML 5 Canvas element for the diagram to draw itself onto and we create one inside a <div> tag:

This page requires a browser that supports HTML 5 Canvas element.

It’s important to set and id for the Canvas element, that’s how we will get it in the JavaScript code behind file.

We create the JS file to be used by this project as DBDesign.js and we place it in the same directory as the two other JS files. We add a reference to it in the HTML page:

http://DBDesign.js

II. UI Controls

The DBDesigner has a line of controls at the bottoms that provide menus – add/edit/delete row, create/delete/rename table and a button for connection info. We create them as buttons:

…..

We add a textarea for the generated SQL and we close the div:

 

When the user presses one of those buttons we show a dialog. The dialogs are forms. Here is the form that renames a table:

III. General Diagram Settings

Let’s start coding the JavaScript methods for the DBDesign application. We use the document.ready method to initialize the Diagram:

var Diagram = MindFusion.Diagramming.Diagram;

var diagram;

$(document).ready(function () {
   // create a Diagram component that wraps the "diagram" canvas
   diagram = MindFusion.AbstractionLayer.createControl(Diagram, null, null, null, $("#diagram")[0]);
……….

});

We use the id of the diagram Canvas that we set in the web page and now create the diagram control. Once we have it we set some properties to it:

// set some Diagram properties.
diagram.setBehavior(Behavior.LinkTables);
diagram.setAllowSelfLoops(false);
diagram.setBackBrush('#F0F0F0');
diagram.setLinkHeadShape('Triangle');
diagram.setLinkHeadShapeSize(4);
diagram.getSelection().allowMultipleSelection = false;

We change the default Behavior of the diagram control to “LinkTables”, which means users would be able to connect table rows. We stop users from creating self loops on tables and add some styling: the back brush is set to light gray, the head shape of links is ‘Triangle’ and we forbid the users to select multiple objects.

The styling of the diagram is done through themes. We create a theme and add to it a style for the table nodes:

// set the Diagram style.
var theme = new Theme();

var tableNodeStyle = new Style();
tableNodeStyle.setBrush({ type: 'LinearGradientBrush', color1: 'rgb(224, 233, 233)', color2: 'rgb(102, 154, 204)', angle: 30 });
tableNodeStyle.setTextColor({ type: 'SolidBrush', color: 'rgb(45, 57, 86)' });
tableNodeStyle.setStroke('rgb(192, 192, 192)');

The tableNodeStyle sets the brush, text color and stroke for the tables. Let’s tell the theme object that this is the style for table nodes:

theme.styles['std:TableNode'] = tableNodeStyle;

And let’s tell the diagram control that it has a theme:

diagram.setTheme(theme);

Link styling is done in the same way and you can find the code in the *.zip file that is available for download.

IV. Events

Handling events is the most important part of this application. We have events raised by the diagram elements and we have events that are raised by the JavaScript buttons. Let’s start with the js buttons. When the web page is loaded there is a single button active from the row of buttons available at the bottom of the page – “Create table”. In the document.ready() method we wire the button with an event:

$('#btnCreateTable').button().click(function (event) { createTable(); });

This event calls the createTable method that generates a TableNode instance:

function createTable() {
	// create a new table with the specified extent
	var table = diagram.getFactory().createTableNode(
				15 + tableCount * 3, 15 + tableCount * 4, 50, 60);
	table.setText("Table" + tableCount++);
	table.redimTable(2, 0);
	table.setScrollable(true);
	table.setConnectionStyle(ConnectionStyle.Rows);

	// set the first column to resize with the table
	table.getColumn(0).columnStyle = ColumnStyle.AutoWidth;

	generateSQL();
}

The createTableNode method accepts as arguments the x and y coordinates of the new TableNode and its width and height. We create initially the table with two columns and no rows. By default the tables can be scrolled and the links connect table rows.

The generateSQL method is a simple one – it just creates an SQL table. You can expand the sample with more complicated SQL statements but in our case we just create a table with the columns that were set to the TableNode:

function generateSQL() {
   var text = '';

   // enumerate all tables in the current diagram
   ArrayList.forEach(diagram.nodes, function (table) {
   text += "CREATE TABLE " + table.getText() + "\r\n(";

   // enumerate all rows of a table
   for (var r = 0; r < table.cells.rows; ++r) {
   // get text of cells in current row
   text += "\t" + table.getCell(0, r).getText() + " " + table.getCell(1, r).getText();
   if (r < table.cells.rows - 1)
	 text += ",\r\n";
   }
	text += "\r\n);\r\n\r\n";
   });

  $('#generatedSql')[0].innerHTML = text;
}

When the SQL text is generated we assign it to the textarea instance that we created.

V. Diagram Events

Here we will talk about the events fired by the diagram control. Once a table is created the users can double click on it to create new rows, edit or delete existing rows. This happens when we handle the nodeDoubleClicked event:

diagram.addEventListener(Events.nodeDoubleClicked, function (sender, args) {
	if (tblClicked != args.getNode()) {
		tblClicked = args.getNode();
	}
….

});

Here we identify the table that is clicked and then we have to decide which dialogue to show:

if (tblClicked) {
		var cellClicked = tblClicked.cellFromPoint(args.getMousePosition());
		if (cellClicked) {
			rowClicked = cellClicked.row;
			editRowOpen();
		}
		else if (tblClicked.hitTestManipulators(args.getMousePosition()) == null) {
		if (args.getMousePosition().y <= tblClicked.getBounds().y + tblClicked.getCaptionHeight())
			renameTableOpen();
			else
			addRowOpen();
		    }
		}

If an existing cell is clicked we open the editRow form. If the caption of the table was clicked we open the form for rename of a table. If none of those, we open the form that adds a new row.

Let’s look how the addRow dialogue opens:

function addRowOpen() {
  var table = tblClicked || diagram.getActiveItem();

  if (!table || !AbstractionLayer.isInstanceOfType(TableNode, table))
	return;

   addRowDialog.dialog("open");
}

the method calls the dialog method of addRowDialog. At the beginning of the js file we have declared a variable:

var addRowDialog = null

Then we create the addRowDialog object:

addRowDialog = $("#addRow-dialog").dialog({
		autoOpen: false,
		resizable: false,
		height: 'auto',
		width: 250,
		modal: false,
		buttons: {
			"OK": addRow,
			Cancel: function () {
				addRowDialog.dialog("close");
			}
		},
		close: function () {
			addRowType.val("NUMBER");
			addRowType.selectmenu("refresh");
			addRowForm[0].reset();
		}
	});
	addRowForm = addRowDialog.find("form").on("submit", function (event) {
		event.preventDefault();
		addRow();
	});

Here we create the dialog that has auto height, width of 250 and two buttons: OK and Cancel. The Cancel button closes the dialog. When the user has pressed OK the form is submitted and the addRow method is called.

The form that shows is defined in the HTML page and looks like that:

NUMBER CHAR(32) DATE VARCHAR BLOB

The addRow method gets the clicked table and gets the two cells at the last row. It gets the text that was chosen in the dialog and assigns it to the cells. Then the dialog is closed and the SQL is generated once again.

function addRow() {
	var table = tblClicked || diagram.getActiveItem();

	if (!table || !AbstractionLayer.isInstanceOfType(TableNode, table))
		return;

	table.addRow();

	var lastRow = table.cells.rows - 1;

	// use the cell indexer to access cells by their column and row
	table.getCell(0, lastRow).setText(addRowName[0].value);
	table.getCell(1, lastRow).setText(addRowType[0].value);

	// close the dialog
	addRowDialog.dialog("close");

	// refresh SQL definition
	generateSQL();
}

And that’s the end for this tutorial. You can download the sample together with the necessary JavaScript libraries from this link:

Download the JavaScript Database Designer Application

Find out more about MindFusion JavaScript Diagram Library at https://mindfusion.eu/javascript-diagram.html