Change WM_MOUSEACTIVATE handling

The current handling of the WM_MOUSEACTIVATE message in the dxBars unit does not take the MouseActivate event into account. As a consequence of this it is impossible to control what happens when the user activates the application with a mouse click.

For example, we have an application with a ribbon and a number of forms docked to the main form. The docked forms are called "views".
The buttons on the ribbon are enabled and disabled depending of which view is active. We also have contextual tabs on the ribbon which depends on the active view.

This works fine as long as all views remain docked to the main form but if the user undocks a view, e.g. to move it to another monitor, the current behavior in dxBars breaks our enable/disable logic: As soon as the user clicks a button on the ribbon, the button activates the main form.
This becomes a problem if we for example have two views: One docked and one undocked. With the undocked view active, the user clicks a button. This causes the button to activate the main form which in turn deactivates the undocked view and activate the docked view thus changing the context. In effect it becomes impossible to click any button that depends on the undocked view being active.

Luckily Windows provides a mechanism to solve this problem: The WM_MOUSEACTIVATE message. WM_MOUSEACTIVATE is surfaced neatly by the VCL as the MouseActivate event handler. By handling the MouseActivate event on the main form we should be able to specify that a mouse click should not activate the window by setting the MouseActivate to maNoActivate. In this example we block activation if the form is already active:

Delphi
procedure TMyForm.FormMouseActivate(Sender: TObject;
  Button: TMouseButton; Shift: TShiftState; X, Y, HitTest: Integer;
  var MouseActivate: TMouseActivate);
begin
  if (not IsFormActive(Self)) then
    MouseActivate := maNoActivate;
end;

Unfortunately this is where dxBars gets in the way. The way WM_MOUSEACTIVATE is handled in dxBars it is not possible to override the handling with the MouseActivate event handler because dxBars unconditionally activate the window regardless of any prior handling of WM_MOUSEACTIVATE.

I request that this behavior be changed so dxBars take WM_MOUSEACTIVATE into account.

The following changes implement the change in the dxBars unit:

Delphi
// Do not explicitly activate window in `WM_MOUSEACTIVATE` handler.
// Optional: Take prior handling of `WM_MOUSEACTIVATE` into account.
procedure TdxDockControl.WMMouseActivate(var Message: TWMMouseActivate);
begin
  inherited;
  if (FBarManager <> nil) and not IsDesigning and (dxBarGetParentPopupWindow(Self, True) = nil) then
  begin
    {$ifdef PATCHED}
    // Only modify result if no one else did (e.g. parent MouseActivate event)
    if (Message.Result = 0) then
    {$endif PATCHED}
      Message.Result := MA_NOACTIVATE;
    dxSetZOrder(MainForm.Handle, HWND_TOP {$ifndef PATCHED}, True{$endif PATCHED});
  end;
end;

Delphi
// Optional: Take prior handling of `WM_MOUSEACTIVATE` into account.
procedure TCustomdxBarControl.WMMouseActivate(var Message: TWMMouseActivate);
begin
  inherited;
  {$ifdef PATCHED}
  // Only modify result if no one else (e.g. parent MouseActivate event) did
  if (Message.Result = 0) then
  {$endif PATCHED}
    Message.Result := MA_NOACTIVATE;
end;

Delphi
// Do not activate the window if application is already active.
procedure TdxBarControl.DoBarGetFocus(ASelectedItem: TdxBarItemControl);
...
begin
...
  if not IsCustomizing and not (IsPopup and ParentBar.Focused) and (dxBarGetParentPopupWindow(Self, True) = nil) then
    // Only activate if application isn't already active. Required in order for custom WM_MOUSEACTIVATE handling to work.
    dxSetZOrder(MasterForm.Handle, HWND_TOP, {$ifdef PATCHED}not Application.Active{$else PATCHED}True{$endif PATCHED});
...
end;

Only the modified calls to dxSetZOrder are required. The rest are just to make custom WM_MOUSEACTIVATE handling (e.g. MouseActivate event) work as it should.