Gradient and Boxed ProgressBars

• Download source files - 74.9 KB

Introduction

One basic limitation of the ProgressBar control provided by .NET is that it can't show the percentage on top of its rendered background. Given this limitation, I decided to create my own control as an exercise. But System.Windows.Forms.ProgressBar does not allow extra drawing to be done, so the new control must be created from scratch.

So I created a basic ProgressBar which has the basic properties Minimum, Maximum, Value, and Step, and an inner function PerformsStep which advances the Value appropriatly.

Appearance properties are provided for the aspects of color, border, and the percentage text. TextColorType specifies whether the text color used is the ForeColor, or it is automatically generated based on the background color that will be behind it.

Rolling functionality is supported, but it should not be used because it uses a Timer rather than a thread. It was created for testing purposes only.

Also, based on a tip I read, a custom Dictionary of Brush and Pen is used from the MyComponents.Objects namespace in order to maintain in memory every Brush and Pen used. These Dictionarys are optional and are automatically disposed.

This base control can be used in Forms, but its drawing is primitive and resembles progress bars of Win3.1.

Rendering is done by the following functions: DrawBackgroundRolling, DrawBackground, DrawText, and DrawBorder. DrawBackgroundRolling instead of DrawBackground is called when rolling is enabled. Any custom progressbar that wants to use the functionality must override the implementation of these functions which are called from the OnPaint event in the specific order, and only if they are needed, based on the relevant properties.

Custom controls

The first custom progressbar I built was one with a gradient between the color of the progress and the background. Two properties were introduced for this ProgressBarGradient. PercentageWidth specifies how much of the control's width will be used for the gradient transition. GradientType specifies whether PercentageWidth is 100% or specified.

Here is the code for DrawBackground:

protected override void DrawBackground(Graphics g)
{
    if (_iPercent == 0)
    {
        FillRectangle(g, ClientRectangle, xBrushes[BrushBackGround]);
        //return;
    }
    Rectangle[] xRecs = null;
    xRecs = Prepare3Parts();
    Rectangle xRectLeft = xRecs[0];
    Rectangle xRectMiddle = xRecs[1];
    Rectangle xRectRight = xRecs[2];
    xRectLeft.Width++;
    BrushAndFill(g, xRectMiddle, _ColorProgress, BackColor);
    FillRectangle(g, xRectLeft, xBrushes[BrushProgress]);
    FillRectangle(g, xRectRight, xBrushes[BrushBackGround]);

}

Prepare3Parts creates the left, middle, and right rectangles needed to draw the control.

The second custom progressbar is called ProgressBarBoxed and splits the control to boxes and fills them with the appropriate color relative to the current percent. The properties introduced are:

• NumberOfBlocks specifies the number of blocks to split the progressbar.
• ActiveBlockColor specifies the last color of the box if the percentage is between 1 and 99.
• InnerGridType specifies the type of grid used to separate the boxes.

Here is the implementation of DrawBackground:

protected override void DrawBackground(Graphics g)
{
    if (_iPercent == 0)
    {
        FillRectangle(g, ClientRectangle, xBrushes[BrushBackGround]);
    }
    for (int i = 0; i < _MaxBlockToDraw; i++)
    {
        FillRectangle(g, _BlockRects[i], xBrushes[BrushProgress]);
    }
    if(_MaxBlockToDraw<_NumberOfBlocks&&_MaxBlockToDraw>-1)
        FillRectangle(g, _BlockRects[_MaxBlockToDraw], xBrushes[BrushActiveBlock]);

    DrawInnerGrid(g);
}

Because the appearance of this control doesn't change at every change of Value, a trick is implemented to speed up the control. The base ProgressBar provides the functionality by implementing Invalide() of the control like this:

protected bool _TurnOffInvalidation;
protected new void Invalidate()
{
    if (!_TurnOffInvalidation)
        base.Invalidate();
    _TurnOffInvalidation = false;
}

FormProgressBarsTest was created to test the three variations of these progress bars and is derived form MyComponents.Windows.BaseForms.PropertyGridForm which is a form I have created to provide functionality for test forms of controls I create.

Finally, in the Solution, there is project named Functions where I store every function that may be reused in my projects.