[Lazarus] Drag (and show) images

[Giuliano Colla]

Il 13/04/2018 02:40, Donald Ziesig via Lazarus ha scritto:

> You're right.  It gets *close* but not quite there.  I can move the 
> control so long as the mouse is *not* over the control while it is 
> moving :-(. I will look at this closer in the morning and see if I can 
> work around it (or if there is something I am missing).
>

You might find useful, as a guideline, the code I'm using in one of my 
application to drag a button so that it doesn't cover the useful part of 
an image. Just using the OnMouseDown, OnMouseMove and OnMouseUp of your 
TImage, and getting rid of the code you don't need, to perform an extra 
action on OnMouseUp, you should be able to do the trick.

>   TErrForm = class(TForm)
> ......
>   protected
>     ResetDragged: Boolean;
>     CursorPos: TPoint;
>     ObjectPos: TPoint;
> ....
>
> procedure TErrForm.ResetBtnMouseDown(Sender: TObject; Button: 
> TMouseButton;
>   Shift: TShiftState; X: LongInt; Y: LongInt);
> begin
>   ResetDragged := True;
>   CursorPos.X := Mouse.CursorPos.X;
>   CursorPos.Y := Mouse.CursorPos.Y;
>   with ResetBtn do begin;
>     ObjectPos.X := Left;
>     ObjectPos.Y := Top;
>     end;
> end;
>
> procedure TErrForm.ResetBtnMouseMove(Sender: TObject; Shift: TShiftState;
>   X: LongInt; Y: LongInt);
> begin
>   if ResetDragged then begin
>     with ResetBtn do begin
>       Left := ObjectPos.X + (Mouse.CursorPos.X - CursorPos.X);
>       Top := ObjectPos.Y +  (Mouse.CursorPos.Y - CursorPos.Y);
>       ResetPos.X := (Left * NormalGeometry.ClientWidth div 
> CurrImage.Width) + HorzScrollBar.Position;
>       ResetPos.Y := (Top * NormalGeometry.ClientHeight div 
> CurrImage.Height) + VertScrollBar.Position;
>       end;
>     end;
> end;
>
> procedure TErrForm.ResetBtnMouseUp(Sender: TObject; Button: TMouseButton;
>   Shift: TShiftState; X: LongInt; Y: LongInt);
> begin
>   if ResetDragged then begin
>     ResetDragged := False;
>     Paint;
>     end;
>   if (abs(Mouse.CursorPos.X - CursorPos.X) < 10) and 
> (abs(Mouse.CursorPos.Y - CursorPos.Y)< 10) then Close;
> end;

Hope that it helps.

Giuliano

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