Win8MarqueeProgressIndicator Control

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Introduction [^]

This short article presents a control, named Win8MarqueeProgressIndicator, that was requested by a reader of Win8ProgressRing Control. Basically, this control flattens the Win8ProgressRing control.

Only a brief discussion of its implementation will be provided. In the following discussions, properties that are specified by the developer are displayed in BoldMixedCase text. Variables, used internally by the software are displayed in italicized_lowercase text.

Table of Contents

• Introduction
• Table of Contents
• Visual Properties
• Control Properties
• Implementation
• Graphics Buffer
• Conclusion
• References
• Development Environment
• History

The symbol [^] returns the reader to the top of the Table of Contents.

Visual Properties [^]

The Win8MarqueeProgressIndicator control has two properties that form the user's visual image.

The developer specifies the control's top-left corner by dragging the control from the ToolBox to a position on the form. This position becomes ( 0, 0 ) in the control's graphic environment. The developer specifies the control_width by either dragging the control's resizing handles or by specifying the Control_Width property. After some computations, the control_height is set equal to the indicator_diameter.

The indicator color defaults to white. To change the indicator color, the developer specifies the new color through the Indicator_Color property.

The control's background color is transparent and cannot be changed.

Control Properties [^]

The Win8MarqueeProgressIndicator control has the following properties available to the developer:

// ********************** adjust_control_dimensions_from_width

void adjust_control_dimensions_from_width ( int new_width )
    {

    indicator_diameter = round ( 
                             ( double ) new_width / 
                             ( double ) MAXIMUM_POSITIONS );

    control_width = indicator_diameter * MAXIMUM_POSITIONS;
    control_height = indicator_diameter;

    this.Width=control_width;
    this.Height = control_height;
    }

The Pulse method is used to rotate the indicators once each time it is invoked. Its signature is:

public void Pulse ( )

Implementation [^]

The Win8MarqueeProgressIndicator control is a User-Drawn Control. Parts of the control are drawn when the control's OnPaint method is invoked.

The control's graphic is made up of two distinct graphic images: the background graphic and the indicator graphic.

Once drawn, the background graphic does not need to be redrawn unless Control_Width is changed. The indicator graphic must be redrawn when the background graphic is redrawn; when the animation changes the indicators' positions; or when the indicator color changes.

The control is made up of six circular indicators that travel rightward along the width of the control. At the far right, the indicators wrap around to the far left. Initially the indicators are centered within the control width.

The control uses Windows coordinates with the x-axis values increasing to the right; y-axis values increasing downward; and angles measured counterclockwise from the x-axis.

Starting with the most rightward indicator, it is moved to the next allowed indicator position (i.e., the indicator in position 18 is moved to position 20). To the right of control center are positions that will cause the indicators to appear to be accelerating. When an indicator is moved to position 32, its next position will be 0. Now as the indicator moves rightward it should appear to decelerate.

draw_indicator_graphic is invoked each time the interval timer raises the elapsed event.

// ************************************ draw_indicator_graphic

void draw_indicator_graphic ( Graphics graphics )
    {
    Brush       brush = new SolidBrush ( Indicator_Color );
    Rectangle   rectangle = new Rectangle ( );

    for ( int i = ( MAXIMUM_INDICATORS - 1 );
              ( i >= 0 );
              i-- )
        {
        int     index;
        double  position;
        int     x;
        int     y;

        index = position_indices [ i ];

        if ( index >= POSITIONS )
            {
            index = 0;
            }
        position = positions [ index ];

        x = round ( position *
                    ( double ) indicator_diameter );
        y = 0;

        rectangle.Location = new Point ( x, y );
        rectangle.Size = new Size ( indicator_diameter,
                                    indicator_diameter );
        graphics.FillEllipse ( brush, rectangle );

        index++;
        position_indices [ i ] = index;
        }

    brush.Dispose ( );
    }

Graphics Buffer [^]

The GraphicsBuffer class contains an off-screen bitmap used to draw graphic objects without flicker. Although .Net provides a Double Buffered Graphics capability, it is overkill for the Win8MarqueeProgressIndicator control.

GraphicsBuffer has been included within the control.

Conclusion [^]

This article has presented a control that provides a Windows 8 style marquee progress indicator.

References [^]

• Add Items to the Toolbox
• Double Buffered Graphics
• Graphics
• Implementing Events
• Raising an Event
• Rounding
• User-Drawn Controls

Development Environment [^]

Win8MarqueeProgressIndicator control was developed in the following environment:

History [^]