1. Define the sources and targets of Drag and Drop.
2. Declare the events to manage.
3. Act during the events.

• Drag and Drop in HTML 5 is supported by the Chrome and Firefox browsers (at the time this page is written).
• Please note: HTML 5 "Drag and Drop" cannot be used on sites displayed on cell phones. Indeed, the technology used cannot make the difference between an action of Drag and Drop and a gesture on mobile.
• This help page is based on the "WW_Drag_n_Drop_HTML5" example provided with WEBDEV.

• 3 "source" fields: these are the 3 fields displaying the extinguisher images. In the initialization code of these controls (server code), the DndSource property specifies that these controls are the source controls for a programmed Drag and Drop.
  

  // Indicates that the control is source for Drag and Drop 
  MySelf.DndSource = dndProgram

• 1 "destination" control: the image of the plan. The DndTarget property is used in the initialization code of this control (server code).
  

  // Indicates that the control is target for Drag and Drop 
  MySelf.DndTarget = dndProgram

• the name of the WLanguage procedure that will be run when the event is triggered.
• the control on which the event must be managed. You have the ability to specify a control or all the page controls.
• the event to manage. Several events are available: beginning and end of Drag and Drop, entry into and exit from the target control, rollover of the target control and drop on the target control. These events are identified by constants (dndXXX).

// Enables Drag and Drop on the image of the plane 
DnDEvent(Rollover, IMG_PLANE, dndDragOver) 
DnDEvent(Drop, IMG_PLANE, dndDrop)

Hovering the target

PROCEDURE HoverOver
// Modifies the cursor 
DnDCursor(dndMove)

Drop of Drag and Drop

1. The move action is accepted via DnDAccept.
   

   PROCEDURE Drop
   // Accept Drag and Drop 
   DnDAccept(dndMove)

2. The cursor position is retrieved via the _DND.MouseXPos and _DND.MouseYPos variables.
   These variables return the cursor position during the drop on the target.
   

   // Stores the cursor position
   nXImage = _DND.MouseXPos 
   nYImage = _DND.MouseYPos

3. The source control of "Drag and Drop" is also retrieved. According to the source control, the associated color will be stored for the drawing.
   

   // Retrieves the source control
   sExtinguisherID = _DND.SourceControl
   // The color differs according to the selected extinguisher 
   SWITCH sIDExtinguisher 
   	CASE IMG_EXTINGUISHER.Name 
   		nColor = 255 
   	CASE IMG_EXTINGUISHER1.Name 
   		nColor = 3243262 
   	CASE IMG_EXTINGUISHER2.Name 
   		nColor = 65535 
   	OTHER CASE
   		nColor = 16706050 
   END

4. The entire data (coordinates, color, size) is stored in an array so that it can be re-used when the drawing is performed by the DrawAll procedure.
   

   // Saves the coordinates 
   sCoordinates = sExtinguisherID + TAB + nXImage + TAB + nYImage + TAB + ...
   		EDT_SLIDER + TAB + nColor
   // Saves the information 
   gnCurrentIndex++ 
   garrListCoordinates[gnCurrentIndex] = sCoordinates
   // Draws the extinguishers on the plane 
   DrawAll()