This article describes an approach to constructing a cool segmented LED displayer that is similar to the LEDs used in alarm clocks and industry monitors. This control can be used to display time, numerical values and even some English characters. I hope it will be helpful in programs such as hardware simulators.
In this section, I would like to give a brief introduction to the ideas behind this control. In a 7-segment LED displayer, one character is composed of at most 7 segments, as in the picture shown below.
Each segment has the following properties: the width of the segment, the bevel rate of the corners in the segment and the interval between segments.
If we mark those 7 segments with numbers, as the picture shows in Figure 1, then we can use indices to represent different characters. For example, the character "1" can be represented as (2, 3) and the character "5" can be represented as (1, 6, 7, 3, 4). To draw the whole scene, we should first calculate the bound rectangles where a certain character is drawn. Then the segments in each specified bound rectangle should be drawn. The algorithm for drawing a 7-segmented LED character in a specified bound rectangle is shown in Figure 3.
This control is quite easy to use. Just drag it from the toolbox to your form in design mode. Then adjust its provided properties in the designer or at runtime to modify its appearance. The properties are listed in the table below:
BorderWidth |
int |
Get or set the width of the border around the control. |
BorderColor |
System.Color |
Get or set the color of the border around the control. |
HighlightOpaque |
byte |
Get or set the opaque value of the highlight. 0 implies that the highlight will end transparent, while 100 implies that the highlight will keep its transparency from the beginning. |
ShowHighlight |
bool |
Get or set a value indicating whether to show the highlight area on the control. If it is set to false, the value of the HighlightOpaque property is ignored. |
CornerRadius |
int |
Get or set the corner radius for the control. If RoundCorner equals false, the value of this property is ignored. The valid value is from 1 to 10. |
GradientBackground |
bool |
Get or set a value indicating whether the background was filled in gradient colors. |
BackColor_1 |
System.Color |
Get or set the first background color. If GradientBackground equals true, this color will be the color at the top of the background rectangle. Otherwise, this color will be the solid background color. |
BackColor_2 |
System.Color |
Get or set the second background color. If GradientBackground equals true, this color will be the color at the bottom of the background rectangle. Otherwise, this color will be ignored. |
RoundCorner |
bool |
Get or set the border style. If it is true, the border of the control will be a round rectangle. Otherwise, the border is a normal rectangle. |
SegmentIntervalRatio |
int |
Get or set the segment-interval ratio. The larger this value is, the wider the gaps between segments are. |
TextAlignment |
Alignment |
Get or sthe alignment style of the text. |
SegmentWidthRatio |
int |
Get or set the segment-width ratio. The larger this value is, the wider the segments are. |
TotalCharCount |
int |
Get or set the total number of characters to display. If the number of characters contained in the displaying text is larger than this value, the displaying character will be truncated. |
BevelRate |
float |
Get or set the bevel rate of each segment. Please refer to Figure 2 for further information. |
FadedColor |
System.Color |
Get or set the color of faded background characters. |
Text |
string |
Get or set the text of the control. |
A control at presentation level may do lots of painting. Most of the time, the control has to be repainted when one of its properties is changed. This may cause multiple invalidating if several properties of the control are changed in quick succession. In order to avoid multiple painting, we can implement the ISupportInitialize interface in our control. First, we set a member variable in the BeginInit() method.
private bool m_bIsInitializing = false;
void ISupportInitialize.BeginInit()
{
m_bIsInitializing = true;
}
Then we rewrite our properties in the following manner:
public Color FadedColor
{
get
{
return m_colFadedColor;
}
set
{
if (m_colFadedColor == value)
return;
m_colFadedColor = value;
// check if the control is in initializing mode
if (!m_bIsInitializing)
{
Invalidate();
}
}
}
At last, in the EndInit() method, we turn off the initialization mode and repaint the control.
void ISupportInitialize.EndInit()
{
m_bIsInitializing = false;
Invalidate();
}
Now we can use batch initialization to prevent successive painting of the control.
((System.ComponentModel.ISupportInitialize)mycontrol).BeginInit();
mycontrol.BackColor = System.Drawing.Color.Transparent;
mycontrol.BackColor_1 = System.Drawing.Color.Black;
mycontrol.BackColor_2 = System.Drawing.Color.Transparent;
mycontrol.BevelRate = 0.5F;
mycontrol.BorderColor = System.Drawing.Color.White;
mycontrol.FadedColor = System.Drawing.Color.Black;
((System.ComponentModel.ISupportInitialize)mycontrol).EndInit();
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~ do you mean that you want to copy the text on the control?
