[Lazarus] Drag (and show) images

[Donald Ziesig]

On 04/13/2018 04:45 AM, Giuliano Colla via Lazarus wrote:
>
> 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
>
>
>
Hi Giuliano!

It works perfectly. 8-) The best part is that it doesn't use any poorly 
documented library code and it doesn't hog the CPU either.

Many thanks,

Don

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