Static LED control - CDigiStatic 1.3

Overview

This article presents a CStatic derived class for displaying numbers or text like a LED Display. This control does not use bitmaps. Everything is drawn with lines and Bezier curves. First I made some classes to draw a character, which consists of segments that can be any closed shape, by only giving some points. The points can be connected by lines or by Bezier curves to make nice smoothened characters. The theory of fitting Bezier curves can be found in bezdist.pdf, created by Jim Fitzsimmons, in my demo project cabinet. The CDigiStatic resizes itself automatically, which can be experienced with the demo app, wherefore I used the resizing dialog code from Hans Bühler.

To design the characters I looked around for different styles. The best inspiration came out of my car. I used characters from the date/time/temperature display and from my RDS-radio. 14- and 7-segment displays in straight and smooth style are supported and one common character for displaying a decimal point or a colon. I changed the designs a lot to get aesthetically best results, but I didn't go crazy by changing all the points every time because I do some nifty mirroring for most of the segments. For example I only specified 5 segments for the 14 segment display.

The demo application shows all possibilities of this control.

Overview of possible Characters

These are normalized characters with all segments turned on in all styles. The coordinates of these pictures were used to find the corners and Bezier points. You can adjust the coordinates or dimensions if you like. Then you can take them over to the source the same way as I did. The height of every design is the same only the width may be different, necessary for easy scaling.

Public Functions

SetText

void SetText(LPCTSTR lpszText);

Call this function to set the text of the control. For more info see SetDrawImmediately()

Format

void Format(LPCTSTR lpszFormat, ...);
void Format( UINT nFormatID, ... );

Call this member function to write formatted data to a CDigiStatic in the same way that sprintf formats data into a C-style character array. This function formats and stores a series of characters and values in the CDigiStatic. Each optional argument (if any) is converted and output according to the corresponding format specification in lpszFormat or from the string resource identified by nFormatID.

SetColor

void SetColor(COLORREF OffColor, COLORREF OnColor);

Sets the on and off color of the segments of the CDigiStatic control. Segments that are off will not be painted when the DS_NO_OFF style is used.

GetOnColor

COLORREF GetOnColor() const

Call this member function to retrieve the color that is used to indicate the segment is on

GetOffColor

COLORREF GetOffColor() const

Call this member function to retrieve the color that is used to indicate the segment is off

SetDrawImmediately

void SetDrawImmediately(BOOL Enable = TRUE);

If Enable set to TRUE a call to SetText() or Format() will redraw the window before the function returns. If Enable set to FALSE (the default of CDigiStatic) the client area is marked for painting when the next WM_PAINT message occurs.

SetBkColor

COLORREF SetBkColor(COLORREF BackColor = BLACK);

Sets the current background color to the specified color and returns the previous background color. The value of the background color will be ignored when Transparency mode is enabled.

SetTransparent

void SetTransparent(BOOL bSet = TRUE);

Set to TRUE only the segments will be drawn and the background will be transparent and show the window underneath it. Nice if you use a skinned window. Set to FALSE will fill the background with the current background color.

ModifyDigiStyle

BOOL ModifyDigiStyle(DWORD dwRemove, DWORD dwAdd);

With the ModifyDigiStyle function you can add or remove specific CDigiStatic styles. The styles, which can be combined by using the bitwise OR ( | ) operator, are:

• CDigiStatic::DS_SMOOTH // Smooth kind of characters
• CDigiStatic::DS_STYLE14 // use always 14 segment display.
• CDigiStatic::DS_SZ_PROP // size proportional(default)
• CDigiStatic::DS_NO_OFF // Don't draw the off segments
• CDigiStatic::DS_SOFT // ambient bleeding to background

How to use (in a dialog):

1. Add digistatic.h, digistatic.cpp, memdc.h, curvefit.h, curvefit.cpp and rgbcolor.h to your project environment.
2. Add a static control to your dialog resource.
3. Change its ID to something like IDC_LEDTEXT, open class-wizard and assign a member variable, type control (CStatic) to it (m_LedText for example).
4. Open your dialog class's header file. Add #include "digistatic.h". Find the line CStatic m_LedText and replace the CStatic by CDigiStatic.
5. In OnInitDialog() you can give it some text with SetText(), change the colors with SetColor() or for the background SetBkColor(). Or, you can set the right style with ModifyDigistyle().
6. Compile and run.

Acknowledgements

• Hans Bühler - For using his resizing software for the demo application.
• Keith Rule - For creating the memdc class for flickerfree drawing. Modified for support of transparent background
• Massimo Colurcio - HMX controls for making a skinned demo application easy.
• Daniel DeGeest - For helping me with transparency, testing and suggestions.

History