efg's Till Lab Report

Purpose
The purpose of this project is to create a count-down timer to count down in days, hours, minutes, and seconds to any specified target date and time.

Discussion
Several actions are taken in the FormCreate method for TCountDownForm. One of these actions is to establish OnMinimize and OnRestore methods for when the form is minimized:

The TILL.INI file contains several important data times, including the Title, Target Time, Font Size, and the Form's Top and Left position properties.

// Default if no .INI file is present
TopMessage.Caption := 'Till Next Year';
TargetTime := EncodeDate(StrToInt(FormatDateTime('yyyy',Now))+1,1,1);

// Read .INI file with defaults
Filename := ChangeFileExt(ParamStr(0), '.INI');
IF   FileExists(Filename)
THEN BEGIN
IniFile := TIniFile.Create(Filename);
TRY
    Top := IniFile.ReadInteger(FORMSection, FORMTop, Top);
    Left := IniFile.ReadInteger(FORMSection, FORMLeft, Left);

    FontSize := IniFile.ReadInteger(OPTIONSSection, OPTIONSFontSize,
                      Days.Font.Size);
    UpdateFontSize(FontSize);

    TopMessage.Caption := IniFile.ReadString(OPTIONSSection,OPTIONSTitle,
                                           'Till Next Year');
    DateTimeString := Inifile.ReadString(OPTIONSSection,OPTIONSTargetDateTime,'');

    IF   LENGTH(DateTimeString) > 0
    THEN TargetTime := StrToFloat(DateTimeString)
FINALLY
    IniFile.Free
END
END;

The FormClose updates the Top and Left properties in the TILL.INI in case the screen was moved.

The main work of the program is performed in the TimerTickTimer method of the TimerTick object:

procedure TCountDownForm.TimerTickTimer(Sender: TObject);
  VAR
    dd          :  Cardinal;
    Fraction    :  TDateTime;
    hh          :  WORD;
    Milliseconds:  WORD;
    mm          :  WORD;
    ss          :  WORD;
    TimeDiff    :  TDateTime;
begin
  TimeDiff := TargetTime - Now;
  IF   TimeDiff < 0
  THEN BEGIN
    UpdateNumericDisplay (0, 0, 0, 0);
    TimerTick.Enabled := FALSE;             // Turn off timer messages
    TimerDone.Enabled := TRUE;              // Separate processing when done
    DoneState := 0;

    // Use clRed to indicate time has elapsed
    Days.Font.Color    := clRed;
    Hours.Font.Color   := Days.Font.Color;
    Colon1.Font.Color  := Days.Font.Color;
    Minutes.Font.Color := Days.Font.Color;
    Colon2.Font.Color  := Days.Font.Color;
    Seconds.Font.Color := Days.Font.Color
  END
  ELSE BEGIN
    dd       := Trunc(TargetTime - Now);    // Full days remaining
    Fraction := Frac(TargetTime - Now);     // Fractional days remaining
    DecodeTime (Fraction , hh, mm, ss, Milliseconds);
    UpdateNumericDisplay (dd, hh, mm, ss);
  END

end;

The UpdateNumericDisplay method updates the main form, or changes the caption shown on the Task Bar icon when the form is minimized. A lot of extra logic is present to dynamically change the main form for different sizes of numeric values.

PROCEDURE TCountDownForm.UpdateNumericDisplay (CONST dddd:  Cardinal;
                                               CONST hh, mm, ss:  WORD);
  VAR
    j           :  INTEGER;
    WidthTitle   :  INTEGER;
    WidthNumerics:  INTEGER;
BEGIN
  IF   DisplayState = wsMinimized
  THEN BEGIN
    Application.Title := Format('%2d %2d:%2.2d:%2.2d', [dddd,hh,mm,ss]);
  END
  ELSE BEGIN
    // Use separate fields to avoid flicker when values don't change
    CountDownForm.Days.Caption    := Format('%d', [dddd]);
    CountDownForm.Hours.Caption   := Format('%d', [hh]);
    CountDownForm.Minutes.Caption := Format('%2.2d', [mm]);
    CountDownForm.Seconds.Caption := Format('%2.2d', [ss]);

    // Adjust geometry of labels -- vertical first
    // Top position of Days/Hours/Minutes/Seconds labels
    // Size of TopMessage is fixed.  Top of numeric labels is fixed.
    j := TopMessage.Height + Days.Height;
    DaysLabel.Top := j;
    HoursLabel.Top := j;
    MinutesLabel.Top := j;
    SecondsLabel.Top := j;
    CountDownForm.ClientHeight := j + DaysLabel.Height;

    // Adjust geometry of labels -- horizontally
    WidthTitle := SpeedButtonSetup.Width +
                  TopMessage.Width       +
                  SpeedButtonSetup.Width;
    WidthNumerics := Colon1.Width DIV 2 +
                     Days.Width         +
                     Colon1.Width       +
                     Hours.Width        +
                     Colon1.Width       +
                     Minutes.Width      +
                     Colon2.Width       +
                     Seconds.Width      +
                     Colon1.Width DIV 2;
    IF   WidthTitle > WidthNumerics
    THEN ClientWidth := WidthTitle
    ELSE ClientWidth := WidthNumerics;

    TopMessage.Left := (ClientWidth - TopMessage.Width) DIV 2;

    Days.Left    := Colon1.Width DIV 2;
    Hours.Left   := Days.Left + Days.Width + Colon1.Width;
    Colon1.Left  := Hours.left + Hours.Width;
    Minutes.Left := Colon1.Left + Colon1.Width;
    Colon2.Left  := Minutes.Left + Minutes.Width;
    Seconds.Left := Colon2.Left + Colon2.Width;

    DaysLabel.Left    := Days.Left    + (Days.Width    - DaysLabel.Width) DIV 2;
    HoursLabel.Left   := Hours.Left   + (Hours.Width   - HoursLabel.Width) DIV 2;
    MinutesLabel.Left := Minutes.Left + (Minutes.Width - MinutesLabel.Width) DIV 2;
    SecondsLabel.Left := Seconds.Left + (Seconds.Width - SecondsLabel.Width) DIV 2
  END
END {UpdateDisplay};

Before using the approach shown above, I considered using a Form.OnResize and adjusting the font so the text would fit. I concluded setting the font and adjusting the size of all the TLabels was an easier approach.

The FormCreate of the FormSetup definition included special DateTime_SetFormat calls to establish a 4-digit year and a 24-hour clock with the two TDateTimePickers used on this form:

USES
  CommCtrl;  // DateTime_SetFormat

procedure TFormSetup.FormCreate(Sender: TObject);
begin
  // 4-digit year
  DateTime_SetFormat(DateTimePickerDate.Handle, pChar('M-dd-yyy'));

  // 24-hour clock
  DateTime_SetFormat(DateTimePickerTime.Handle, pChar('H:mm:ss'));
end;

A ShellExecute call is used to place a hyperlink to the Computer Lab on the Setup screen:

Keywords
TTimer, Now, TDateTime, TDateTimePicker, DateTime_SetFormat, Application.OnRestore, Application.OnMinimize, Application.Title, Format, ClientWidth, ClientHeight, Trunc, Frac, DecodeTime, EncodeDate, TIniFile, WritePrivateProfileString, ShellExecute

Count-Down Timer