[Solved]  Drag and drop an image file onto a page with more than one
TPanel
lazarus / 31-LCL

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Paul1986 · 2021-02-02 03:14

I have a multi page application that can have several TPanels on a
page.  The panels display images that can be merged in a variety of
ways.
I'd like to add a drag and drop option  so a user can drop an image
file onto one of the TPanels.  AllowDropFiles is enabled for the form
and I figured out a way of identifying the page the file was dropped
onto but I can't figure how to identify the intended TPanel.

To identify the page concerned I used the TPageControl.ActivePage
property that seems to be reliable.  What I want to know is the
name/id of the panel on which the image was dropped.  I've tried the
focus events but that didn't work.  Do I have to start tracking the
mouse?

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jamie · 2021-02-02 22:07

TheControl := MyPageorTabSheet.ControlAtPos(Point(X,Y), Flase {Don't
allow disabled});


If TheControl is TPanel then.....

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lucamar · 2021-02-02 23:17

I was thinking about something on that line; the problem is that
OnDropFiles doesn't tell you where the files where dropped so you'd
have to keep track of the mouse position with OnMouseMove (or the
current control with OnMouseEnter/ONMouseLeave) handlers. But then
you'll have to track for all controls (or at lest all interested
control) and the coordinates (if using OnMouseMove) are then control-
relative.

Sure, no big deal, but a litttle tedious and a bit error prone ...

So to answer the OP's question: yes, I think you'll have to track the
mouse ...

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Paul1986 · 2021-02-03 06:05

Thanks for the help.  Based on the above, and another post about
ControlAtPos I found in a 2019 thread, I have this piece of code that
seems to work:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i        mPos
:= ScreenToClient(Mouse.CursorPos);        aControl :=
ImagePages.ActivePage.ControlAtPos(mPos,
[capfRecursive,capfAllowWinControls]);        if (aControl = nil)
then        begin          Form1.MemoRecord.Lines.Add('Hmm - nil/null
control');        end else        begin          if (aControl is
TPanel) then          begin           
Form1.MemoRecord.Lines.Add('Control is ' + aControl.GetNamePath);    
      Form1.MemoRecord.Lines.Add('Mouse X: ' + IntToStr(mPos.x) + ',
Y: ' + IntToStr(mPos.y));          end else          begin           
Form1.MemoRecord.Lines.Add('Not a TPanel control');          end;    
  end;               

When debugging and stopping at a breakpoint, I was getting some
negative positions for the mouse location so I wonder it that is a
side effect of the debugger.  So I added some debug lines to record
the mouse position and the numbers look about right.

Thanks again for your help.    This thread can be closed/solved
thanks.

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lucamar · 2021-02-03 09:38

Quote from: Paul1986 on February 03, 2021, 07:05:17 amThanks again for
your help.    This thread can be closed/solved thanks.
It's a nice solution that you found
To mark as solved, edit your first post and add [SOLVED] at the front
of the "Subject" line.

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Paul1986 · 2021-02-03 11:52

Quote from: lucamar on February 03, 2021, 10:38:25 am...
To mark as solved, edit your first post and add [SOLVED] at the front
of the "Subject" line.

Thanks,  I should have known that but its been a while since I was
last here.