SWMM5 Delphi GUI Dlabel.pas Summary

 Below is an overview of Dlabel.pas, a Delphi unit from SWMM 5.2 that provides a simple form (TLabelForm) for adding text labels to the study area map.

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1. Purpose and Context

In SWMM, the user can place custom text labels onto the map to annotate features or provide additional information. The TLabelForm in this unit is a frameless modal dialog that allows the user to type a label, which is then placed at a specified map location.

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2. The Form: TLabelForm

Key points:

1. TEdit (Edit1): A single-line edit box where the user can type the text of the label.
2. Dialog Behavior:
   • The form is frameless, so it does not have a typical caption bar or system menu.
   • It behaves like a modal dialog (the user must dismiss it before returning to the main application).

2.1 Form Layout

• In FormCreate, the code sets the Edit1 control’s left and top to 0, and then resizes the form’s ClientWidth and ClientHeight to match the edit control’s dimensions.
• As a result, the dialog basically appears just as a text box without surrounding borders.

2.2 Closing the Form

• FormClose: sets Action := caFree so that when the user closes the dialog, it is destroyed and removed from memory.

2.3 Key Handlers

• Edit1KeyPress:
  • Enter (#13): causes ModalResult := mrOK, effectively closing the dialog and returning an “OK” result.
  • Escape (#27): causes ModalResult := mrCancel, canceling the label creation.

This means the user can press Enter to confirm the typed label or Escape to cancel.

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3. Summary of Operation

1. Initialization:

   • The form and its single TEdit control are created, sized to match the TEdit’s width and height.
   • The form has no border or caption to give a minimalist text-entry appearance.

2. User Interaction:

   • The user enters text in the TEdit box.
   • Pressing Enter closes the form with OK; pressing Escape closes it with Cancel.

3. Result:

   • When returning with OK, the calling code can retrieve the text from Edit1.Text to place a new label on the map.
   • If Cancel, no label is created.

Thus, Dlabel.pas provides a lightweight, no-frills interface for placing user-defined text labels on the SWMM map.