Problem with big canvas on ScrollBox
lazarus / 39-Graphics

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Tomi · 2024-03-01 14:08

Hello!

I put images onto a ScrollBox and I would like copy pieces from those
onto an other image with CopyRect() function. But when I click on the
edge of these images on the ScrollBox, then the small image contains
the pieces of scrollbar instead the other parts of the image, which
sticking out from ScrollBox.
Then, when I scroll away the image, CopyRect() produces white
rectangles instead of right image. So, how big is the canvas of an
image? Is it equal only with its visible area? Or how can I access to
its whole parts when I scroll it back and forth?
I create images with this procedure:
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 procedure
TForm1.buttonImageAdClick(Sender: TObject);begin   if
(imageOpener.Execute) and (sourcetiles<255) then   begin   
 tileimage[sourcetiles+1]:=TImage.Create(Self);   
 tileimage[sourcetiles+1].Parent:=placeofTiles;   
 tileimage[sourcetiles+1].Autosize:=true;   
 tileimage[sourcetiles+1].Transparent:=true;   
 tileimage[sourcetiles+1].Picture.LoadFromFile(imageOpener.FileName); 
   tileimage[sourcetiles+1].OnMouseUp:=@clickontile;   
 tileimage[sourcetiles+1].Left:=0;     if sourcetiles=0 then   
 begin        tileimage[sourcetiles+1].Top:=0;        actualtile:=1; 
  end     else        tileimage[sourcetiles+1].Top:=tileimage[sourceti
les].Top+tileimage[sourcetiles].height+2;     inc(sourcetiles); 
 end;end;and this is where I copy small images from the tiles:
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 procedure
TForm1.clickontile(Sender: TObject; Button: TMouseButton;  Shift:
TShiftState; X, Y: Integer);var i: byte;begin     for i:=0 to
sourcetiles-1 do     begin       if (X>=tileimage[i+1].Left) and
(X<=tileimage[i+1].Left+tileimage[i+1].width) and
(Y>=tileimage[i+1].Top) and
(Y<=tileimage[i+1].Top+tileimage[i+1].height) then       begin       
   if copytileexists=false then            begin             
copytile:=TImage.Create(Self);              copytile.Parent:=self;   
         copytile.Left:=X;//+tilePlace.HorzScrollbar.position;       
     copytile.Top:=Y;//+tilePlace.VertScrollbar.position;            
copytile.width:=tilewidth;              copytile.height:=tileheight; 
         end;            copytile.canvas.copyrect(Rect(0,0,tilewidth,t
ileheight),tileimage[i+1].canvas,Rect(X,Y,X+tilewidth,Y+tileheight)); 
          copytileexists:=true;            Break;       end;   
 end;end;

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Tomi · 2024-03-02 14:34

Well, carefully read about these problem it seems that it is not easy
to access to offscreen part of the images.
But then how store the OS or Lazarus itself the content of whole
image? Since I can see that when I scroll away the image in the
ScrollBox.