Re: [Lazarus] TLabel inside a TScrollBox (under Win32) MouseWheel issue

[Sandro Cumerlato]

To whom who may concern...

I've created a sample package with an example to demonstrate how to
solve this issue without altering the LCL, but providing a derived
component instead:

https://code.google.com/p/mousewheelcontrols/

Comments are welcome.

Sandro Cumerlato


On 15 July 2014 19:43, Sandro Cumerlato  wrote:
> Reference: "[Lazarus] Scrollbox and mousewheel"
> http://lists.lazarus.freepascal.org/pipermail/lazarus/2012-July/074650.html
>
>
> Hello everybody,
> I'm writing to you about an issue discovered while using a TLabel
> inside a TScrollBox (under Win32).
>
> The problem is that the TLabel hides the MouseWheel action of the
> TScrollBox if the mouse is over the TLabel.
>
> To solve this problem I've exposed the Label1.OnMouseWheel property to
> call the following ScrollBox1.OnMouseWheel event:
>
> procedure TFormMain.SrollBox1MouseWheel(Sender: TObject; Shift: TShiftState;
>   WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
> begin
>   with SrollBoxRight.VertScrollBar do
> Position := Position - Sign(WheelDelta) * Increment;
>   Handled := true;
> end;
>
>
> The attached patch exposes the TLabel.OnMouseWheel event to solve the
> TLabel/TScrollBox MouseWheel issue.
>
> For the same reason, IMHO, other GUI controls that can be inserted
> into a TScrollBox should expose OnMouseWheel event.
>
>
> Thank you for reading!
>
> Sandro Cumerlato

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[Lazarus] TLabel inside a TScrollBox (under Win32) MouseWheel issue

[Sandro Cumerlato]

Reference: "[Lazarus] Scrollbox and mousewheel"
http://lists.lazarus.freepascal.org/pipermail/lazarus/2012-July/074650.html


Hello everybody,
I'm writing to you about an issue discovered while using a TLabel
inside a TScrollBox (under Win32).

The problem is that the TLabel hides the MouseWheel action of the
TScrollBox if the mouse is over the TLabel.

To solve this problem I've exposed the Label1.OnMouseWheel property to
call the following ScrollBox1.OnMouseWheel event:

procedure TFormMain.SrollBox1MouseWheel(Sender: TObject; Shift: TShiftState;
  WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
begin
  with SrollBoxRight.VertScrollBar do
Position := Position - Sign(WheelDelta) * Increment;
  Handled := true;
end;


The attached patch exposes the TLabel.OnMouseWheel event to solve the
TLabel/TScrollBox MouseWheel issue.

For the same reason, IMHO, other GUI controls that can be inserted
into a TScrollBox should expose OnMouseWheel event.


Thank you for reading!

Sandro Cumerlato
Index: /freepascal/laz/1.3/lcl/stdctrls.pp
===
--- /freepascal/laz/1.3/lcl/stdctrls.pp (revisione 45865)
+++ /freepascal/laz/1.3/lcl/stdctrls.pp (copia locale)
@@ -1502,6 +1502,7 @@
 property OnMouseUp;
 property OnMouseEnter;
 property OnMouseLeave;
+property OnMouseWheel;
 property OnChangeBounds;
 property OnContextPopup;
 property OnResize;
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