How to redirect mouse wheel message to a cxGrid

Fabrizio ExDev

created 11 years ago

Hello,I'm trying to redirect mouse wheel message to controls in order to allow scroll without clicking on them (You just need to move mouse on control that you want to scroll).It works good with TcxRichEdit but I'm encountering some problems with TcxGrid.
I've attached a complete sample that you can test. There's also an image inside zip archive with all you need to do in order to recreate the issue (step by step).Furthermore, sample project contains a "debug TcxRichEdit" where you can send messages by using "DebugMessage" method.Please ask if you need other informations.Thanks to everyone.

MouseWheelTest.zip

Answers approved by DevExpress Support

DevExpress Support Team

created 11 years ago (modified 11 years ago)

Hello,
I believe a similar question has been already discussed in our Support Center. Please refer to the Q276698: How to scroll unbound cxGrid with mousewheel when grid is unfocused ticket for the information.

Show previous comments (5)

Fabrizio ExDev 11 years ago

Thanks for your answer, unfortunately that approach seems to have some problems.
I did what Ingvar suggests in the ticket but there's a case where it doesn't work good.
Case 1 (it works).
Focused control = FocusedButton (TcxButton)
Mouse cursor on control = MainEdt (TcxRichEdit)
Conclusion: MainEdt's scrollbar scrolls as expected.
Case 2 (it works)
Focused control = MainEdt (TcxRichEdit)
Mouse cursor on control = MainGrid (TcxGrid)
Conclusion: MainGrid's scrollbar scrolls as expected.
Case 3 (it doesn't works!)
Focused control = MainGrid (TcxGrid)
Mouse cursor on control = MainEdt(TcxRichEdit)
Conclusion: MainEdt's scrollbar doesn't scroll and MainGrid's scrollbar scrolls!
So, why it doesn't works if TcxGrid is focused?
Here's my function's code (without debug lines):
function TMouseWheelTest.RedirectMouseWheel(var Msg: tagMSG) : boolean;
var
  Point: TPoint;
  Control: TWinControl;
  AScrollPos: Integer;
begin
  Result := (Msg.message = WM_MOUSEWHEEL);
  if(Result) then
  begin
    Point.X := Word(Msg.lParam);
    Point.Y := HiWord(Msg.lParam);
    Control := FindVCLWindow(Point);
    Result := (Assigned(Control) AND (not Control.Focused));
    if(Result) then
    begin
      if(Control is TcxGridSite) then
      begin
        AScrollPos := TcxGridSite(Control).VScrollBar.Position;
        if(Msg.wParam > 0)
        then TcxControlAccess(Control).Scroll(sbVertical, scLineUp, AScrollPos)
        else TcxControlAccess(Control).Scroll(sbVertical, scLineDown, AScrollPos);
      end else
        SendMessage(Control.Handle, WM_MOUSEWHEEL, Msg.wParam, Msg.lParam);
    end;
  end;
end;
I've attached my example project.
Thanks for your willingness.

MouseWheelTest.zip

DevExpress Support Team 11 years ago

We are working on your request, but it can take us some time to examine it. We will get back to you once we have any results or need additional information. Thank you for your patience.

DevExpress Support Team 11 years ago

Hello,
I've modified your sample to work with our controls. Please take a look at the attachment.
Also, I need to note that the behavior you desire is contrary to the standard VCL behavior.

dxSample.zip

Fabrizio ExDev 11 years ago

Hello, I know but I need that mouse wheel messages are sent to the control under mouse cursor. (In all my application).
The approach in your modified sample seems to work good also with devexpress controls, thanks a lot for your support.

Poul Halgaard 10 years ago

I'm working on upgrading fra v12 to newest v14,
The example does not work in v14. And I cannot get it to work. (I suspect a problem in v14)
It is only after selecting one of the controls it works a bit and the Richedit does not work at all.
Also you have these minor problems in the example:
This code:
Result := (Assigned(Control) AND (not Control.Focused));
if(Control is TcxControl) or (Control.Parent is TcxControl) then

Access viol. if Result = nil.
FindVCLWindow is STILL broken in XE6 as it has been since 2010 at least.
You have to make your own if your layout is more complex.
(this is just a note to other developers)
you also need ScreenToClient(MousePos);
Can you make your sample function with v14 please?
I have a lot of trouble getting wheel to function in my app. as it did before. But I guess if your sample works I can also find how to make my app do it.

DevExpress Support Team 10 years ago

Hello Poul,

To process your recent post more efficiently, I created a separate ticket on your behalf: T195976: How to redirect mouse wheel message to a cxGrid with VCL 14.2. This ticket is currently in our processing queue. Our team will address it as soon as we have any updates.

John Friel 10 years ago

Here's how I solved this problem. I dropped an ApplicationEvents control on my main form and then hooked the OnMessage event as follows:

Delphi
procedure TMainForm.ApplicationEvents1Message(var Msg: tagMSG; var Handled: Boolean);  
var  
 mousePos  : TPoint;  
 wc        : TWinControl;  
 AGridSite : TCxGridSite;  
begin  
  //mouse wheel scrolling for the control under the mouse  
  if Msg.Message = WM_MOUSEWHEEL then  
  begin  
    mousePos.x := Word(Msg.LParam);  
    mousePos.y := HiWord(Msg.LParam);  
    wc         := FindVCLWindow(mousePos);  
    if wc = nil then  
    begin  
      Handled := False;  
    end  
    else  
      if wc is TCxGridSite then  
      begin  
        AGridSite := wc as TCxGridSite;  
        if (AGridSite.GridView.ClassType = TcxGridDBTableView) or  
           (AGridSite.GridView.ClassType = TcxGridTableView) then  
        begin  
          if Msg.WParam > 0 then  
            AGridSite.GridView.Site.ScrollContent(dirUp)  
          else  
            AGridSite.GridView.Site.ScrollContent(dirDown);  
          Handled := true;  
        end  
      end  
      else  
      begin  
        if wc.handle <> Msg.hwnd then  
        begin  
          SendMessage(wc.handle, WM_MOUSEWHEEL, Msg.WParam, Msg.LParam);  
          Handled := true;  
        end;  
      end;  
  end;  
end;

This allows my unfocused cxGrid and cxDBGrids to scroll when the mouse is over them.
YMMV.

John Friel 10 years ago

I should have noted that I'm using Delphi XE and 14.2.2 and this has worked with all releases of DevExpress.

Created: November 14, 2013 11:21 AM

Modified: January 13, 2015 1:45 PM

Platform: VCL

Product: ExpressQuantumGrid Suite

Build: 12.2.4

IDE: CodeGear Delphi 2007

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How to redirect mouse wheel message to a cxGrid

Answers approved by DevExpress Support

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