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Using Offset with Templates

edited January 2006 in General
The help file states that you can use the property Offset to reserve space
at the beginning to the template definition.

It states that the information can be read in the OnLoadStart event and
written in the OnSaveEnd event of the Template.

How do you get access to the template date? Could you supply an example of
how to do this??

Thank you . . . .



--- posted by geoForum on http://delphi.newswhat.com

Comments

  • edited January 2006

    -----------------------------------------------------
    Tech Tip: Storing Custom Information with Templates
    -----------------------------------------------------

    Question:
    ---------

    How can I store descriptive information with my report template?


    Solution:
    ---------

    1. If you are storing the templates to a database, then you can use the
    Report.Template.OnSaveEnd and OnLoadEnd events to store and load the custom
    information to appropriate data fields for the record. (This is the
    technique used by the ReportExplorer.)

    2. If you are storing templates to .rtm files, then you will need to store
    the custom information in an Offset area of the template file. The
    Report.Template object enables you do this by utilizing the Template.Offset
    property and the Template.OnLoadStart and OnLoadEnd events. Below is a
    detailed example.



    Example:
    --------
    - Create a new application.
    - Add to the main form one TButton, one TppReport and one TppDesigner.
    - Set the Designer's Report property to ppReport1.
    - Add ppTypes to the uses clause.


    type
    TForm1 = class(TForm)
    Button1: TButton;
    ppReport1: TppReport;
    ppDesigner1: TppDesigner;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    private
    procedure LoadReportStreamEvent(Sender: TObject; Stream: TStream);
    procedure SaveReportStreamEvent(Sender: TObject; Stream: TStream);

    public

    end; { class TForm1 }


    {note: use compiler directive to declare strings as 'ShortStrings'
    this is required for record structures}

    {$H-}

    {record structure used to store information inside report template }
    TmyTemplateInfo = record
    HeaderID: Integer;
    Comments: String;
    DateTime: TDateTime;

    end; {record, TppTemplateRec}

    {$H+}


    const
    cHeaderID = 12345;

    implementation


    {-------------------------------------------------}
    { TForm1.FormCreate }

    procedure TForm1.FormCreate(Sender: TObject);
    begin

    {setup Template events }
    ppReport1.Template.Format := ftASCII;
    ppReport1.Template.Offset := SizeOf(TmyTemplateInfo);
    ppReport1.Template.OnLoadStart := LoadReportStreamEvent;
    ppReport1.Template.OnSaveEnd := SaveReportStreamEvent;

    end; {procedure, FormCreate}

    {-------------------------------------------------}
    { TForm1.Button1Click }

    procedure TForm1.Button1Click(Sender: TObject);
    begin

    ppDesigner1.Show;

    end; {procedure, Button1Click}

    {--------------------------------------------------}
    { TForm1.LoadReportStreamEvent }

    procedure TForm1.LoadReportStreamEvent(Sender: TObject; Stream: TStream);
    var
    lTemplateInfo: TmyTemplateInfo;
    lsMessage: String;

    begin

    {read string stored in template header }
    Stream.Seek(0, soFromBeginning);
    Stream.Read(lTemplateInfo, SizeOf(TmyTemplateInfo));

    {note: if not one of the templates with our header info, then set Offset
    to 0 }
    if lTemplateInfo.HeaderID = cHeaderID then
    begin
    lsMessage := 'Reading data from template file: ' + #13#10 + #13#10 +
    lTemplateInfo.Comments + ' (' +
    DateTimeToStr(lTemplateInfo.DateTime) + ')';

    MessageDlg(lsMessage, mtInformation, [mbOK],0);
    ppReport1.Template.Offset := SizeOf(TmyTemplateInfo);
    end
    else
    ppReport1.Template.Offset := 0;

    end; {procedure, LoadReportStreamEvent}


    {------------------------------------------------------------------------------}
    { TForm1.SaveReportStreamEvent }

    procedure TForm1.SaveReportStreamEvent(Sender: TObject; Stream: TStream);
    var
    lTemplateInfo: TmyTemplateInfo;
    lsMessage: String;

    begin

    lTemplateInfo.HeaderID := cHeaderID;
    lTemplateInfo.Comments := 'This comment is being stored inside the report
    template, ' + #13#10 +
    'along with the date and time written. ';
    lTemplateInfo.DateTime := Now;

    {write info to template header}
    Stream.Seek(0, soFromBeginning);
    Stream.Write(lTemplateInfo, SizeOf(TmyTemplateInfo));

    lsMessage := 'Writing data to template file: ' + #13#10 + #13#10 +
    lTemplateInfo.Comments + ' (' +
    DateTimeToStr(lTemplateInfo.DateTime) + ')';
    MessageDlg(lsMessage, mtInformation, [mbOK],0);

    end; {procedure, SaveReportStreamEvent}








    Best regards,

    Nard Moseley
    Digital Metaphors
    www.digital-metaphors.com
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