Best way to move a panel ?

[Fred vS]

Hello Lazarus lovers.

I use the following code to move a panel with the mouse.
OK, the panel moves but not very fluently 

Witch code gonna do that better ?

Many thanks

Code: [Select]

var
xinit, yinit : integer;

 procedure panelMouseDown(Sender: TObject;
                         Button: TMouseButton; Shift: TShiftState; X, Y: Integer
                         );
                       begin
   xinit := X ;
    yinit := Y ;
                       end;

  procedure panelMouseMove(Sender: TObject;
                         Shift: TShiftState; X, Y: Integer);
                       begin
                         if ssLeft in Shift then

  begin

if  xinit > x then panel.left := panel.left - xinit - x)
else panel.left :=  panel.left + (x - xinit) ;
   
if  yinit > Y then panel.Top := panel.Top - (yinit - Y)
else panel.Top :=  panel.Top + (Y - lyinit) ;
 
              end;
                       end;

 

[KpjComp]

Could you see if this is any better.

[Fred vS]

@ KpjComp : Many thanks 
I gonna try it this night (but a first look, seems much better...).
Many thanks

[Fred vS]

@ KpjComp :

project1.lpr(16,30) Error: Identifier not found "RequireDerivedFormResource"

PS: I use  lazarus 0.9.30 and fpc 2.4.2 for Linux 64, Linux 32, Windows 64, Windows 32 and Mac OSX 32....

[KpjComp]

I think it's something that newer versions of Lazarus add.
You can just delete it..

[Fred vS]

OK KpjComp, your code is much better, thanks.

By the way, what is RequireDerivedFormResource ?
What do i miss if i do not use it ?

[KpjComp]

What do i miss if i do not use it ?

Not much really, it's all do with how Form's are created.

RequireDerivedFormResource makes sure that when the Forms Create method is called, a resource actually exists.   If you wanted to create a resourceless Form you should use CreateNew anyway, but if someone did TForm.Create and if the LFM file was missing would still succeed but have you wondering why your Form was blank

In the future, I'll try to remember to delete the line if I post an example.

[KpjComp]

For a bit of fun, if you wanted to move lots of TPanels, this technique works well.

I basically create an Imposter class for the TPanel ->

Code: [Select]

TPanel = class(ExtCtrls.TPanel)

This is a bit of a hack to allow you to keep your TPanel's at design time, but allow you to extend it's features.  You could add say a AllowMove properties etc, if you didn't want all TPanels to be moved etc.

[Fred vS]

Whaouw, KpjComp, many thanks, i gonna try it...

Do you think i can use the same method for moving images ( to create custom sliders...) ?

  by the way, i gonna post a other topic that maybe you could help me too 

[KpjComp]

Do you think i can use the same method for moving images ( to create custom sliders...) ?

Yes, I see no reason why not.

Basically this technique is similar to creating a custom component, but avoids you having to register with the IDE.  The only downside is that extra properties you add don't appear in the IDE, and you would need to fill these in via code.  eg. If you did add a property called moveable, you could only set this in code.

[Fred vS]

@ KpjComp : brilliant