Scroll Settings in Blazor Diagram Component

20 Jun 202313 minutes to read

The diagram can be scrolled by using the vertical and horizontal scrollbars. In addition to the scrollbars, the mouse wheel can be used to scroll the diagram. The Diagram’s ScrollSettings allows you to read the current scroll status, current zoom and zoom factor values.

Get current scroll status

Scroll settings allow you to read the scroll status, CurrentZoom with a set of properties. To explore those properties, see Scroll Settings.

• CurrentZoom: Specifies the zooming level of the diagram page.
• MinZoom: Specifies the minimum zooming level of the diagram page.
• MaxZoom: Specifies the maximum zooming level of the diagram page.
• HorizontalOffset: Specifies the horizontal origin or left side origin of the view port of the diagram page.
• VerticalOffset: Specifies the vertical origin or top side of the view port of the diagram page.

Define scroll status

Diagram allows you to pan the diagram before loading, so that any desired region of a large diagram can be viewed. You can programmatically pan the diagram with the HorizontalOffset and VerticalOffset properties of scroll settings. The following code illustrates how to pan the diagram programmatically.

In the following example, the vertical scroll bar is scrolled down by 50px and the horizontal scroll bar is scrolled to right by 100px.

@using Syncfusion.Blazor.Diagram

<SfDiagramComponent Height="600px">
    @* Sets the ScrollSettings for the diagram *@
    <ScrollSettings HorizontalOffset="100" VerticalOffset="50">
    </ScrollSettings>
</SfDiagramComponent>

You can download a complete working sample from GitHub

Update scroll status

You can programmatically change the scroll offsets at runtime by using the external button click. The following code illustrates how to change the scroll offsets at runtime.

@using Syncfusion.Blazor.Diagram

<input type="button" @onclick="updateScrollValues"/>
<SfDiagramComponent Height="600px">
    @* Sets the ScrollSettings for the diagram *@
    <ScrollSettings HorizontalOffset="@horizontalOffset" VerticalOffset="@verticalOffset">
    </ScrollSettings>
</SfDiagramComponent>

@code{
    public double horizontalOffset { get; set; } = 100;
    public double verticalOffset { get; set; } = 100;

    public void updateScrollValues()
    {
        //Update scroll settings.
        verticalOffset = 400;
        horizontalOffset = 200;
    }
}

You can download a complete working sample from GitHub

ScrollChanged Event

The Diagram control provides the following event for the scroll settings.

Event Name	Event Type	Description
ScrollChanged	ScrollChangedEventArgs	Triggered when the scrollbar is updated

@using Syncfusion.Blazor.Diagram

<input type="button" @onclick="updateScrollValues"/>
<SfDiagramComponent Height="600px" ScrollChanged="ScrollChanged">
    @* Sets the ScrollSettings for the diagram *@
    <ScrollSettings HorizontalOffset="@horizontalOffset" VerticalOffset="@verticalOffset">
    </ScrollSettings>
</SfDiagramComponent>

@code{
    public double horizontalOffset { get; set; } = 100;
    public double verticalOffset { get; set; } = 100;

    public void updateScrollValues()
    {
        //Update the scroll settings.
        verticalOffset = 400;
        horizontalOffset = 200;
    }
    private void ScrollChanged(ScrollChangedEventArgs args)
    {

    }

}

AutoScroll

Autoscroll feature automatically scrolls the Diagram whenever the Node or Connector is moved beyond the boundary of the diagram. So that, it is always visible during dragging, resizing, and multiple selection operations. Autoscroll is automatically triggered when any one of the following is done towards the edges of the Diagram:

• Node dragging, resizing
• Connector dragging and end thumb dragging
• Rubber band selection

The auto-scroll behavior in diagram can be enabled or disabled by using the EnableAutoScroll property of the diagram. The following code example illustrates enabling or disabling the auto-scroll support for nodes.

@using Syncfusion.Blazor.Diagram
<SfDiagramComponent Height="400px" Width="400px" Nodes="@nodes" Connectors="@connectors">
    @* Sets the ScrollSettings for the diagram *@
    <ScrollSettings EnableAutoScroll=true @bind-ScrollLimit="@scrollLimit">
    </ScrollSettings>
</SfDiagramComponent>
@code
{
    ScrollLimitMode scrollLimit { get; set; } = ScrollLimitMode.Infinity;
    //Defines diagram's node collection.
    DiagramObjectCollection<Node> nodes;
    //Defines diagram's connector collection.
    DiagramObjectCollection<Connector> connectors = new DiagramObjectCollection<Connector>();
    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        // A node is created and stored in the nodes collection.
        Node node = new Node()
            {
                ID = "node1",
                // Position of the node.
                OffsetX = 250,
                OffsetY = 250,
                // Size of the node.
                Width = 100,
                Height = 100,
                Style = new ShapeStyle()
                {
                    Fill = "#6495ED",
                    StrokeColor = "white"
                }
            };
        // Add node.
        nodes.Add(node);
        Connector Connector = new Connector()
            {
                ID = "connector1",
                // Set the source and target point of the connector.
                SourcePoint = new DiagramPoint() { X = 100, Y = 100 },
                TargetPoint = new DiagramPoint() { X = 100, Y = 200 },
                // Type of the connector segments.
                Type = ConnectorSegmentType.Straight,
                Style = new ShapeStyle()
                {
                    StrokeColor = "#6495ED",
                    StrokeWidth = 1
                },
            };
        connectors.Add(Connector);
    }
}

The auto-scrolling region is limited by the ScrollLimit property of the ScrollSettings class.Please refer ScrollLimit page for more details about ScrollLimit.

OnAutoScrollChange gets triggered when the auto-scroll (scrollbars) is changed, and you can do your customization in this event. Please refer OnAutoScrollChange page for more details about OnAutoScrollChange.

You can download a complete working sample from GitHub

AutoScroll Padding

The AutoScrollPadding is used to specify the maximum distance between the object and the diagram’s edge that will trigger auto-scrolling. When auto-scrolling is enabled, the diagram viewport will automatically scroll in the direction of the mouse movement when the user drags a node or connector to the edge of the viewport. The padding to start the auto-scrolling at the edge can be controlled by setting the AutoScrollPadding property.

NOTE

The default value is 20 pixels.

The following code example illustrates how to set autoscroll padding.

@using Syncfusion.Blazor.Diagram
<SfDiagramComponent Height="600px" Width="600px" Nodes="@nodes">
    @* Sets the ScrollSettings for the diagram *@
    <ScrollSettings EnableAutoScroll=true AutoScrollPadding="@autoScrollBorder">
    </ScrollSettings>
</SfDiagramComponent>
@code
{
    DiagramObjectCollection<Node> nodes;
    DiagramMargin autoScrollBorder = new DiagramMargin() { Left = 30, Right = 30, Top = 30, Bottom = 30 };
    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        // A node is created and stored in the nodes collection.
        Node node = new Node()
            {
                ID = "node1",
                // Position of the node.
                OffsetX = 250,
                OffsetY = 250,
                // Size of the node.
                Width = 100,
                Height = 100,
                Style = new ShapeStyle()
                {
                    Fill = "#6495ED",
                    StrokeColor = "white"
                }
            };
        // Add node.
        nodes.Add(node);
    }
}

You can download a complete working sample from GitHub

Scroll limit

The scroll limit allows you to define the scrollable region of the Diagram while scrolling the page with the mouse. The ScrollLimit property of scroll settings helps to limit the scrolling area. It includes the following options:

• Infinity: Allows you to scroll in any directions without being restricted.
• Diagram: Allows you to scroll within the Diagram content.
• Limited: Allows you to scroll within the specified area.

The default operation is Diagram.

The following code example illustrates how to specify the scroll limit.

@using Syncfusion.Blazor.Diagram

<SfDiagramComponent Height="600px">
    @* Sets the ScrollLimit of scroll settings *@
     <ScrollSettings @bind-ScrollLimit="@scrollLimit" ></ScrollSettings>
</SfDiagramComponent>

@code{
    ScrollLimitMode scrollLimit { get; set; } = ScrollLimitMode.Infinity;
}

You can download a complete working sample from GitHub

To explore about the options , refer ScrollLimitMode.

ScrollLimit	Output
Diagram
Infinity

Scrollable Area

Scrolling beyond any particular rectangular area can be restricted by using the ScrollableArea property of scroll settings. To restrict scrolling beyond any custom region, set the ScrollLimit as “limited.” The following code example illustrates how to customize the scrollable area.

@using Syncfusion.Blazor.Diagram
<SfDiagramComponent Width="50%" Height="300px" Nodes="@nodes">
    <ScrollSettings  ScrollableArea="@scrollableArea" ScrollLimit="ScrollLimitMode.Limited">
    </ScrollSettings>
</SfDiagramComponent>
@code
{
    DiagramRect scrollableArea = new DiagramRect() { X = 0, Y = 0, Width = 500, Height = 500 };
    DiagramObjectCollection<Node> nodes;
    protected override void OnInitialized()
    {
        nodes = new DiagramObjectCollection<Node>();
        Node node = new Node()
            {
                ID = "node1",
                // Position of the node.
                OffsetX = 300,
                OffsetY = 50,
                // Size of the node.
                Width = 100,
                Height = 100,
                Style = new ShapeStyle()
                {
                    Fill = "#6495ED",
                    StrokeColor = "white"
                }
            };
        // Add node.
        nodes.Add(node);
    }
}

You can download a complete working sample from GitHub

CallBack Methods

• CurrentZoomChanged : Specifies the callback to be triggered when the current zoom value changes.
• HorizontalOffsetChanged : Specifies the callback to be triggered when the horizontal offset changes.
• VerticalOffsetChanged : Specifies the callback to be triggered when the vertical offset changes.
• MaxZoomChanged : Specifies the callback to trigger when the maximum zoom changes.
• MinZoomChanged : Specifies the callback to trigger when the minimum zoom changes.
• ScrollableAreaChanged : Specifies the callback to trigger when the scrollable area changes.
• ScrollLimitChanged : Specifies the callback to trigger when the scroll limit changes.

@using Syncfusion.Blazor.Diagram

<SfDiagramComponent Height="600px">
    @* Sets the ScrollLimit of scroll settings *@
     <ScrollSettings CurrentZoomChanged="OnCurrentZoomChanged"></ScrollSettings>
</SfDiagramComponent>

@code
{
    private void OnCurrentZoomChanged()
    {
        // Enter your code
    }
}