scrollbox, scroll with mouse wheel

[Hansvb]

Scrolling with the mouse on a scroll box works only when the mouse hovers over the Scrollbars . If the mouse is over the rest of the scrolbox, scrolling does not work when using the mouse wheel.

How can you scroll a scroll box with the mouse wheel above the scrollbox and not just above the scrollbar off the scrollbox?

[molly]

How to decide which direction that would/should be when both horizontal and vertical scrollbars are present ? That's why it is not so logical to have it implemented by default, even though one could perhaps argue  that it should depend on which scrollbar is/are currently visible and in case both are visible scroll ........ (fill in the dots: randomly, both, horizontal, vertical, none) ?

[rvk]

How to decide which direction that would/should be when both horizontal and vertical scrollbars are present ?

Well, I can rock my mouse-wheel left and right so scrolling up and down should be for vertical scroll 

Also... The Explorer.exe (and I assume other programs too) gives preference over scrolling vertical with the mouse-wheel up/down, if there is both horizontal and vertical scrollbars. Rocking the wheel side to side scroll horizontal in that case. Only when there is no vertical scrollbar, up/down scrolling scrolls horizontal.

Not sure how it is on other OSes.
(I also can't check at the moment how it's done in Delphi)

[molly]

Well, I can rock my mouse-wheel left and right so scrolling up and down should be for vertical scroll 

Aah, yes indeed. But i am using a trackball for navigation (either that or touchscreen). I tried to 'rock' those, but that resulted in quit some unexpected behaviour

Point taken. Although i also have no clue on which events we should be looking at for those (let alone if every OS/widget supports it)

[rvk]

How can you scroll a scroll box with the mouse wheel above the scrollbox and not just above the scrollbar off the scrollbox?

@Hansvb, on what OS (and Laz-version) is this. If I create a TScrollBox with some buttons (outside the visible area) the mouse-wheel scroll works for the entire scrollbox (on Windows).

Could you otherwise create a small sample-project illustrating the problem?

[Hansvb]

My mistake. I filled the scollbox complete with buttons. When i make the buttons smaller than i use the mouse scrollwheel when hovering above the scrolbox. When the mouse is above the buttons in the scrollbox nothing happens.

Windows 7 64 bit. Lazarus 1.6 32 bit

[Hansvb]

Is it possible to scroll the scrollbox when the mouse is above a button which is on the scrollbox?

[rvk]

My mistake. I filled the scollbox complete with buttons. When i make the buttons smaller than i use the mouse scrollwheel when hovering above the scrolbox. When the mouse is above the buttons in the scrollbox nothing happens.

Windows 7 64 bit. Lazarus 1.6 32 bit

Simplest solution would be to hang this MouseWheel-event to all TButtons:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ButtonGeneralMouseWheel(Sender: TObject; Shift: TShiftState;
2.   WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
3. begin
4.   if WheelDelta > 0 then ScrollBox1.Perform(WM_VSCROLL,0,0);
5.   if WheelDelta < 0 then ScrollBox1.Perform(WM_VSCROLL,1,0);
6.   Handled := true;
7. end;

You could also create a override-class for TButton above your form-declaration which does this automatically so you don't have to assign it to each button yourself.

[rvk]

You could also create a override-class for TButton above your form-declaration which does this automatically so you don't have to assign it to each button yourself.

This is the method of overriding the TButton OnWheel event and sending the message to its parent. It will automatically do this for all your buttons on your form. Note the declaration/override above your form-declaration. It's an easy way to override components without having to modify and install them (although it might be considered by some as an hack )

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs,
9.   StdCtrls, Types;
10.  
11. type
12.   TButton = class(StdCtrls.TButton)
13.   protected
14.     function DoMouseWheel(Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint): Boolean; override;
15.   end;
16.  
17. type
18.  
19.   { TForm1 }
20.  
21.   TForm1 = class(TForm)
22.     Button1: TButton;
23.     Button2: TButton;
24.     Button3: TButton;
25.     Button4: TButton;
26.     Button5: TButton;
27.     Button6: TButton;
28.     Button7: TButton;
29.     ScrollBox1: TScrollBox;
30.   private
31.     { private declarations }
32.   public
33.     { public declarations }
34.   end;
35.  
36. var
37.   Form1: TForm1;
38.  
39. implementation
40. uses Windows;
41.  
42. {$R *.lfm}
43.  
44. function TButton.DoMouseWheel(Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint): Boolean;
45. begin
46.   if WheelDelta > 0 then Postmessage(Parent.Handle, WM_VSCROLL,0,0);
47.   if WheelDelta < 0 then Postmessage(Parent.Handle, WM_VSCROLL,1,0);
48. end;
49.  
50. { TForm1 }
51.  
52. end.

[Hansvb]

I do not understand how to  get one of both options working.

[rvk]

I do not understand how to  get one of both options working.

Which one?

In the first one you create one event (just declare the procedure manually in the form) and hang this event in all TButtons on your TScrollbox to the MouseWheel-event (either manually or through code).

In the second you declare a TButton override above the Form1 declaration which only has one procedure overridden (the DoMouseWheel).

Both methods work by sending the scrollcommand to the parent (which should be TScrollBox).

[Hansvb]

Option one works. Thanks. I was to quick yesterday i think

[micheus]

Simplest solution would be to hang this MouseWheel-event to all TButtons:

Code: Pascal  [Select][+][-]

1. procedure TForm1.ButtonGeneralMouseWheel(Sender: TObject; Shift: TShiftState;
2.   WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
3. begin
4.   if WheelDelta > 0 then ScrollBox1.Perform(WM_VSCROLL,0,0);
5.   if WheelDelta < 0 then ScrollBox1.Perform(WM_VSCROLL,1,0);
6.   Handled := true;
7. end;

I also thought it should work automatically, anyway your code help me. Thanks.

We can use a simplified version without the use of the if statement - I do prefer that always as possible:

begin
  sbxEntidade.Perform(WM_VSCROLL, ord(WheelDelta < 0), 0);
  Handled := true;
end;