[Lazarus] Qt Ws doesn't support properly GetWindowSize() and GetWindowRect()

[zeljko]

On 15.12.2017 17:08, Giuliano Colla via Lazarus wrote:
> This snippet of code, which executes as expected with GTK2 WS, fails 
> with QT WS:
> 
>> procedure TForm1.btnWsizeClick(Sender: TObject);
>> var  aHandle: THandle;
>>    aWidth,aHeight: Integer;
>>    aRect: TRect;
>> begin
>>    aHandle:= Form1.Handle;
>>    if GetWindowSize(aHandle,aWidth,aHeight) then begin
>>      Label3.Caption:= Format('Width: %d Height: %d',[aWidth,aHeight]);
>>    end
>>    else Label3.Caption:= 'Failed to get Window Size';
>>    GetWindowRect(aHandle,aRect);
>>    Label3.Caption:= Label3.Caption + Format(' Rect: %d,%d',[
>>    aRect.Right-aRect.Left,
>>    aRect.Bottom-aRect.Top]);
>>    Label3.Visible:= True;
>> end;
> 
> As it is, it crashes with an AV in the GetWindowSize call. The failing 
> call is in TQtWidget.GetWidget: it executes Result := 
> QWidgetH(TheObject) where TheObject appears to have taken a bogus value.
> 
> If I remove the offending call, then the subsequent GetWindowRect() 
> returns bogus values, sort of -32704 and -85984614 instead of 689 and 522.
> 
> Under GTK2 both calls work as expected.
> 
> Tested under Linux x86_64 (CentOs 6) with Lazarus 1.8 - QT45 - fpc 3.0.4
> 
> It doesn't appear to be a regression, because it does the same even with 
> a very old Lazarus 1.2.6 , qt45 and fpc 2.6.4
> 
> Should I report a bug or is it a known issue?

It's bug in your code (range error). You're using aHandle: 
System.THandle (longint) instead of LCLIntf.THandle which is of ptruint 
type.
Best and correct usage would be to use HWND type which is what it needs 
to be on all platforms and widgetsets.
When aHandle type is corrected, or LCLType is included with it's THandle 
then everything works as expected.
Don't ask me my gtk2 works, in any case it's wrong on 64bit platform.

zeljko