Chapter 1

DeactivateGc();
}
This code has exact parallels to the code we saw in DrawTilesNow(): the activate and
begin-redraw brackets are needed to set everything up correctly. However, CONE doesn't
need to call Invalidate()here because the whole point of the redraw is that a region is
already known to be invalid. In fact, if CONE did call Invalidate() on the rectangle, it
would potentially extend the invalid region, which would waste processing time.
Inside the activate and begin-redraw brackets, CONE draws the control using Draw() and
passing the bounding rectangle. Then, CONE draws every component owned by this control
using DrawComponents(), which is coded as follows:
void CCoeControl::DrawComponents(const TRect& aRect) const
{
const TInt count = CountComponentControls();
for(TInt ii = 0; ii < count; ii++)
}
{
const CCoeControl* ctrl = ComponentControl(ii);
if(!(ctrl->OwnsWindow()) && ctrl->IsVisible())
}
{
TRect rect;
const TRect* pRect = (&aRect);
if(!((ctrl->Flags()) & ECanDrawOutsideRect))
{
rect = ctrl->Rect();
rect.Intersection(aRect);
if(rect.IsEmpty())
continue;
pRect = (&rect);
}
ResetGc();
ctrl->Draw(*pRect);
ctrl->DrawComponents(*pRect);
}
CONE simply redraws every visible lodger component whose rectangle intersects the invalid
rectangle and then its components in turn. CONE adjusts the bounding invalid rectangle
appropriately for each component control.
Note
CONE also makes an allowance for a rare special case: controls that can
potentially draw outside their own rectangle.