WMSetCursor
lazarus / 7-LCL

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tk · 2009-08-05 08:49

Hi,
I am porting a control to Lazarus that uses several own mouse cursors.
Here I found another major incompatibility with VCL. I don't want to
put these to Screen.Cursors because there is no unique way to
dynamically determine the first empty index for new cursors both in
Delphi and Lazarus. Not only because of that I believe WMSetCursor
should give the possibility to set cursor directly via
WidgetSet.SetCursor as it was always meant in Delphi and should not be
beaten by some non-overridable Upda]"]>BlockeduseCursor method in
TControl class that is called from WMMouseMove. For custom cursors
used only by components this is IMHO required.

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Marc · 2009-08-05 09:26

the problem is that cursor handing of windows is very different than
other widgetsets. Using WMSetCursor is something you really don't want
to simulate on those widgetsets.
Therefore using WidgetSet.Setcursor should be avoided.
You still can use screen.cursors, since the first empty index is 1
(all default cursors have a index <= 0)

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tk · 2009-08-05 10:23

This is the problem as there is no unique way how to determine if
Screen.Cursors[1] is empty or not.

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tk · 2009-08-05 17:49

I solved this issue first with a tiny LCL modification (introduced
TControl.WMSetcursor+some adds) and then better with
win32callback.WindowProc subclassing. The control stays Windows only
anyway. I think WMSetcursor effect (ability to use Windows.Setcursor)
should not be beaten at least on the Windows target. If anybody is
interested in this modification I can send the LCL sources (L.
0.9.26.2beta).

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Martin_fr · 2009-08-05 21:13

You may want to upgrade to the latest SVN or Snapshot, if you haven't.

There is a modification, in that SetCursor on windows now acts
immediately and not only on the next mouse move.

The other thing is (but I do not know how guaranteed this is to be
kept like this): At current the cursor is set from within
TCONTROL__WMMOUSEMOVE
calling TCONTROL__UPDA]"]>BlockedUSECURSOR
calling TWINCONTROL__SETTEMPCURSOR

SetTempcursor is virtual, so you can overwrite it.

as for the WMsetMouse message, if your are on windows. If your control
returns crDefault you may get an LM_SETMOUSE message, which you can
capture

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tk · 2009-08-06 07:40

Thx. There is a stuff (HandleSetCursor) in win32callback.inc that is
making problems here - with subclassing it can be solved now
generally.