[lazarus] GTK team: please specify!

[Michael.VanCanneyt at Wisa.be]

On Sun, 2 Nov 2003, Mattias Gaertner wrote:

> On Sun, 2 Nov 2003 17:22:10 +0100 (CET)
> Michael.VanCanneyt at wisa.be wrote:
> 
> > 
> > 
> > On Sun, 2 Nov 2003, Mattias Gaertner wrote:
> > 
> > > On Sun, 2 Nov 2003 15:03:10 +0100
> > > Mattias Gaertner <nc-gaertnma at netcologne.de> wrote:
> > > 
> > > > > The WinAPI specifies that GetDC(GetDesktopWindow()) should return a 
> > > > > device context of the screen. We can use this DC to draw on.
> > > > 
> > > > Very funny. ;)
> > > > What has the winapi to do with the gtk?
> > > > We need the window DC without clipping and we need an event to know,
> > > > when the gtk has finished painting everything. And during moving we
> > > > have to paint as well.
> > > > When we got this, we can omit the paint on every message and we can
> > > > omit the designer widgets, because the rest is already implemented.
> > > > This solution would be very near to my initial wish in a former mail.
> > > > I will do some experiments... 
> > > 
> > > Ok. Maybe I found the solution.
> > > Now to the LCL.
> > > 
> > > GetDC will just return the "normal" device context for a window. Under
> > > gtk this is without the child windows (they are clipped away). 
> > > The designer needs a DC with childs. Something like GetRawDC or
> > > GetWholeDC or GetDCForWholeWindow or GetDesignerDC or ... . I guess
> > > under win32api this is already the default, so you have little to do. If
> > > not, how does win32api calls it?
> > 
> > Maybe a stupid suggestion, but why don't you draw all that on the form
> > window/canvas ?  All widgets/controls must always be somewhere on the 
> > form. Also, if you move widgets over parent boundaries (which can happen)
> > the designer handles can still be drawn, since their coordinates are
> > relative to the form window, not relative to the parent.
> 
> Because I didn't know the trick to get a device context for this, the gtk
> interface was young and unflexible and the message queue unordered. Now, I
> know the trick and the gtk interface has everything we need. Now I will do
> it. 
> Because this was always my goal, the designer needs only little changes for
> this. 

Sorry, I don't quite get the answer:  you will draw on the form canvas or not ? 

And why do you need the DC ? You could just as well use the canvas methods ? 
I don't know about Lazarus, but Form.Canvas is an existing property in Delphi.
It would make the code also 100% portable, without need for backend changes.
After all, Canvas is just a Delphi wrapper around a DC, so why not use it ?

Michael.