[lazarus] GTK team: please specify!

[Marc Weustink]

+ -----Original Message-----
+ From: Mattias Gaertner [mailto:nc-gaertnma at netcologne.de]
+ Sent: vrijdag 31 oktober 2003 14:43
+ To: lazarus at miraclec.com
+ Subject: Re: [lazarus] GTK team: please specify!
+
+
+ On Fri, 31 Oct 2003 12:51:10 +0100
+ Micha Nelissen <M.Nelissen at student.tue.nl> wrote:
+
+ > >>> About TControlSelection.DrawGrabbers:
+ > >>> FGrabbers[g].Left/Top are holding the position of a
+ > >>> grabber relative to the client origin of the form.
+ > >>> The line
+ > >>> Diff:=DC.FormOrigin;
+ > >>> gets the DC origin also relative to the form origin.
+ > >>> Therefore the grabber is painted at FGrabbers[g].Left-Diff.X.
+ >
+ > Indeed. I have fixed the code.
+
+ No.
+
+ You changed the Diff, which is absolutely correct. The bug lies
+ somewhere in the calculation of DC.FormOrigin.
+ Maybe my lines above were ambigious. An example:
+ A designer form is at 100,200, has a TGroupBox at 30,30, with a
+ border of 5,5.
+ And there is an non visual component icon at 50,50. These 50,50
+ is relative to the client origin of the form. This means the
+ icon should be drawn at 15,15 in the client area of the groupbox.

That depends. For a form the origin of a DC is the client origin. I
checked it a win32, and there it seems that either the groupbox has no
border (clientorigin is top left) or the DC origin is not at the client
origin. I guess the first. (the visual border is drawn on its own client
area)

So in the win32 case the icon is draw at 20, 20.


+ Paint messages:
+ Don't take this example too serious, it is the system that is important.
+ When the LCL gets a paint message for the groupbox, the
+ designer gets also the paint message. The paint message
+ DC origin (0,0) is the left,top of the client area of the groupbox.
+ So, relative to the client area of the form it is 35,35 = DC.FormOrigin.
+ So, the icon (at 50,50) is painted at 15,15.

[kept values unchanged]


+ The DC.FormOrigin is calculated in designerprocs.pp
+ function TDesignerDeviceContext.GetFormOrigin: TPoint;
+ This function is platform independent. It uses
+     FormClientOrig:=FormClientOrigin;
+     DCOrig:=DCOrigin;
+ So, maybe you should test, if these two functions return
+ correct values in win32. I guess it will be DCOrigin,
+ because it uses GetWindowOrgEx. Probably we have to replace
+ this call by another interface function, which does not
+ yet exists.

YM, we have to calculate the offset of a given DC relative to the form ?