Moved OnDragStartDetected from TfpgWidget to TfpgWindowBase

* also introduced virtual DoDragStartDetected which executes
  the OnDragStartDetected event
* We also added a override of DoDragStartDetected in GDI for
  some extra tasks.

3 files changed, 23 insertions, 6 deletions

diff --git a/src/corelib/fpg_base.pas b/src/corelib/fpg_base.pas
index c81d9cd8..a5289474 100644
--- a/src/corelib/fpg_base.pas
+++ b/src/corelib/fpg_base.pas
@@ -435,6 +435,8 @@ type
     FSizeIsDirty: Boolean;
     FPosIsDirty: Boolean;
     FMouseCursorIsDirty: Boolean;
+    FOnDragStartDetected: TNotifyEvent;
+    FDragActive: boolean;
     function    HandleIsValid: boolean; virtual; abstract;
     procedure   DoUpdateWindowPosition; virtual; abstract;
     procedure   DoAllocateWindowHandle(AParent: TfpgWindowBase); virtual; abstract;
@@ -447,6 +449,7 @@ type
     procedure   DoSetMouseCursor; virtual; abstract;
     procedure   DoDNDEnabled(const AValue: boolean); virtual; abstract;
     procedure   DoAcceptDrops(const AValue: boolean); virtual; abstract;
+    procedure   DoDragStartDetected; virtual;
     procedure   SetParent(const AValue: TfpgWindowBase); virtual;
     function    GetParent: TfpgWindowBase; virtual;
     function    GetCanvas: TfpgCanvasBase; virtual;
@@ -459,6 +462,7 @@ type
     procedure   SetWidth(const AValue: TfpgCoord);
     procedure   HandleMove(x, y: TfpgCoord); virtual;
     procedure   HandleResize(AWidth, AHeight: TfpgCoord); virtual;
+    property    OnDragStartDetected: TNotifyEvent read FOnDragStartDetected write FOnDragStartDetected;
   public
     // The standard constructor.
     constructor Create(AOwner: TComponent); override;
@@ -1137,6 +1141,12 @@ begin
     Result := MinHeight;
 end;
 
+procedure TfpgWindowBase.DoDragStartDetected;
+begin
+  if Assigned(FOnDragStartDetected) then
+    FOnDragStartDetected(self);
+end;
+
 procedure TfpgWindowBase.SetParent(const AValue: TfpgWindowBase);
 begin
   FParent := AValue;
@@ -1257,6 +1267,7 @@ begin
   FSizeIsDirty := True;
   FMaxWidth := 0;
   FMaxHeight := 0;
+  FDragActive := False;
 end;
 
 procedure TfpgWindowBase.AfterConstruction;
diff --git a/src/corelib/fpg_widget.pas b/src/corelib/fpg_widget.pas
index 45a480dc..374a76ed 100644
--- a/src/corelib/fpg_widget.pas
+++ b/src/corelib/fpg_widget.pas
@@ -47,7 +47,6 @@ type
     FOnDragDrop: TfpgDragDropEvent;
     FOnDragEnter: TfpgDragEnterEvent;
     FOnDragLeave: TNotifyEvent;
-    FOnDragStartDetected: TNotifyEvent;
     FOnEnter: TNotifyEvent;
     FOnExit: TNotifyEvent;
     FOnMouseDown: TMouseButtonEvent;
@@ -61,7 +60,6 @@ type
     FOnScreen: boolean;
     FOnShowHint: THintEvent;
     FDragStartPos: TfpgPoint;
-    FDragActive: boolean;
     alist: TList;
     procedure   SetActiveWidget(const AValue: TfpgWidget);
     function    IsShowHintStored: boolean;
@@ -142,7 +140,6 @@ type
     { property events }
     property    OnClick: TNotifyEvent read FOnClick write FOnClick;
     property    OnDoubleClick: TMouseButtonEvent read FOnDoubleClick write FOnDoubleClick;
-    property    OnDragStartDetected: TNotifyEvent read FOnDragStartDetected write FOnDragStartDetected;
     property    OnEnter: TNotifyEvent read FOnEnter write FOnEnter;
     property    OnExit: TNotifyEvent read FOnExit write FOnExit;
     property    OnKeyPress: TKeyPressEvent read FOnKeyPress write FOnKeyPress;
@@ -471,7 +468,6 @@ begin
   FBackgroundColor := clWindowBackground;
   FTextColor      := clText1;
   FAcceptDrops    := False;
-  FDragActive     := False;
   FOnClickPending := False;
 
   inherited Create(AOwner);
@@ -728,8 +724,8 @@ begin
     if not FDragActive and (FDragStartPos.ManhattanLength(fpgPoint(msg.Params.mouse.x, msg.Params.mouse.y)) > fpgApplication.StartDragDistance) then
     begin
       FDragActive := True;
-      if Assigned(OnDragStartDetected) then
-        OnDragStartDetected(self);
+      // In Windows dragging is a blocking function, so FDragActive is false after this call
+      DoDragStartDetected;
     end;
   end;
 
diff --git a/src/corelib/gdi/fpg_gdi.pas b/src/corelib/gdi/fpg_gdi.pas
index a6a94c4d..c1560042 100644
--- a/src/corelib/gdi/fpg_gdi.pas
+++ b/src/corelib/gdi/fpg_gdi.pas
@@ -186,6 +186,7 @@ type
     procedure   DoSetMouseCursor; override;
     procedure   DoDNDEnabled(const AValue: boolean); override;
     procedure   DoAcceptDrops(const AValue: boolean); override;
+    procedure   DoDragStartDetected; override;
     property    WinHandle: TfpgWinHandle read FWinHandle;
   public
     constructor Create(AOwner: TComponent); override;
@@ -1906,6 +1907,15 @@ begin
   end;
 end;
 
+procedure TfpgGDIWindow.DoDragStartDetected;
+begin
+  inherited DoDragStartDetected;
+  { In windows OLE dragging is a blocking function, so it never returns until
+    OnStartDragDetected is complete. So we need to set FDragActive to False
+    here. }
+  FDragActive := False;
+end;
+
 constructor TfpgGDIWindow.Create(AOwner: TComponent);
 begin
   inherited Create(AOwner);