I have finally found the trigger, though not the cause, of the dreaded 'TWinControl.WMSize loop detected' exception that prevents the use of TCalendarDialog, TDateEdit, and TDateTimePicker with WinCE (http://bugs.freepascal.org/view.php?id=21282). These 3 controls consist of a TCalendar (with either Autosize=True or AlignalNone) embedded on a form. It is this particular autosizing/aligning which triggers the exception as setting Autosize to False and Align to AlNone works well.

TCalendar's width is 220 while the screen's width is 240 (my WinCE device). I tried to reproduce the error on a Linux desktop by enlarging TCalendar to be almost as wide as the screen with no success.

Any hints/ideas on what might be going on here?

Note: I have attached a patch (for testing) to the bug report, but this is a workaround and not THE solution.

Stephano

Maybe on WinCE the calendar is limited to some Width, but the WinCE interface does not report the correct constraints.

Calendar1.Constraints.Min/MaxInterfaceWidth

In this case the LCL sets a Width and the WinCE sets another creating a loop.

Mattias

I put a TCalendar with no autosizing/aligning and a TEdit with Align=AlBottom on the main form.
xxx.Constraints.Min/MaxInterfaceWidth for both components are 0/0 on WinCE and 1/0 on Linux (I used a button to trigger the output of the values).

Note that setting the calendar's autosize to true will cause the WMSize loop on program startup. This is not the case for the TEdit (setting Align to AlBottom works fine).

Stephano

This means the LCL assumes that TCalender can have any size on WinCE.

Set TForm OnResize:
  Calendar1.GetPreferredSize(w,h);
  Calendar1.SetBounds(0,0,w,h);

Mattias

The loop is still present (Calendar1.Align=AlBottom). However, note that the main's form autosize property is false (although WinCE might resize it anyway).

Any other things to try?

Stephano

Please set Calendar1.Align=alNone.
Does
TForm OnResize

   Calendar1.GetPreferredSize(w,h);
   Calendar1.SetBounds(0,0,w,h);

create a loop?

Mattias

It doesn't.

Stephano

[...] > create a loop? It doesn't.

Does this create a loop:

Calendar OnResize

Calendar1.SetBounds(0,0,ClientWidth,ClientHeight-50);

Mattias

I removed the TForm OnResize and put the above in Calendar OnResize. With AlNone there is no loop. WIth AlBottom there is.

Stephano