SWMM5 Delphi GUI Fovmap.pas Summary

 Below is a high-level summary of Fovmap.pas, the Delphi unit that defines SWMM’s Overview Map form (TOVMapForm). This form provides an outline view of the entire study area map, with a rectangular highlight showing the map region currently visible on the main MapForm.

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1. Purpose

Fovmap.pas implements TOVMapForm, a small, always-available form in EPA SWMM that displays:

• A miniature (bird’s-eye) view of the entire project map.
• A focus rectangle representing the bounds of the visible area on the main map (on TMapForm).
• Dragging this rectangle re-centers the main map’s view.

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2. TOVMapForm: Key Functionalities

1. OVmap (TMap):

   • A dedicated TMap object storing a scaled-down rendering of the main map’s geometry and any backdrop image.

2. FocusRect (TRect):

   • A rectangle drawn on the overview map indicating which portion is currently seen on TMapForm.

3. Form Life Cycle:

   • FormCreate: Instantiates OVmap, sets up defaults, and prepares for drawing the map outline.
   • FormDestroy: Frees the OVmap object.
   • FormClose: Hides (rather than frees) the overview map form.
   • FormResize & Rescale: Rescales and redraws the overview map to fit the form’s new dimensions.

4. Drawing & Refreshing:

   • Redraw: Renders an outline (or backdrop) of the entire project on an internal bitmap.
   • PaintFocusRect: Draws a bold red rectangle to highlight the main map’s current view.
   • ShowMapExtent: Computes and updates the focus rectangle coordinates based on the main map’s zoom and pan settings.

5. Dragging:

   • The user can click inside the focus rectangle and drag it around to shift the main map’s viewport.
   • FormMouseDown: Begins dragging if the mouse is within FocusRect.
   • FormMouseMove: Dynamically redraws a dashed rectangle as the user drags.
   • FormMouseUp: Repositions the focus rectangle, then re-centers the main map accordingly.

6. Miscellaneous:

   • NeedsUpdating: A boolean that indicates if changes are pending (e.g., waiting until the form becomes active before redrawing).
   • WMGetMinMaxInfo: Restricts how small the user can resize the overview form.

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3. Usage in SWMM

• Creation: Instantiated when SWMM starts. Stays hidden or visible based on a View menu toggle.
• Coordination with Main Map:
  • The main MapForm updates OVMapForm whenever project data or zoom changes, calling OVMapForm.Redraw or OVMapForm.ShowMapExtent.
  • If the user drags the focus rectangle in OVMapForm, it calls back to re-pan the main map’s window.
• Benefits:
  • Quickly locates and navigates large study areas.
  • Makes panning easier: user sees entire layout, and drags focus box to move main map’s window around.

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4. Summary

In Fovmap.pas, TOVMapForm provides a scaled-down “overview map” of the entire study area, with a highlighted rectangle to indicate the currently visible portion in the main map form. The user can drag this rectangle to reposition the main view. Internally, OVmap is a TMap object that draws an outline or backdrop image of the complete area, while FocusRect denotes the current zoom/pan region from TMapForm. This overview greatly aids navigation and spatial context in SWMM’s user interface.