[Pythoncard-users] fitToComponents method experiment

[Kevin A. <al...@se...>]

I have been getting sort of annoyed at the extra vertical whitespace 
that you have to stick into a static layout for GTK and the Mac in 
order for the layout to not have the components chopped off vertically 
on Windows. This is somewhere around 13-20 pixels of extra whitespace 
at the bottom. OTOH, on the Mac, you typically need extra whitespace 
around components so that the selection rectangle that is used on the 
currently selected component won't run into the edge of the frame. I 
haven't dug into the Apple HIG yet, but I think that is probably at 
least 7-10 pixels given how much whitespace most Mac apps seem to use 
for layout.

Anyway, I wrote up a prototype fitToComponents method that calculates 
the minimum size needed for the panel and then adds some padding. I 
stuck it in the Background class of model.py to see whether we might 
auto-compensate for the whitespace needs of each platform when a layout 
is loaded without having to resort to using a sizer for something so 
basic. Here's the method minus the comments and print statements.

     def fitToComponents(self, widthPadding=None, heightPadding=5):
         width = 0
         height = 0
         for c in self.components.itervalues():
             x, y = c.position
             w, h = c.size
             width = max(x + w, width)
             height = max(y + h, height)
         newWidth, newHeight = self.panel.size
         if widthPadding is not None:
             newWidth = width + widthPadding
         if heightPadding is not None:
             newHeight = height + heightPadding
         self.panel.SetSize((newWidth, newHeight))
         self.SetClientSize((newWidth, newHeight))

I tested on Windows and the Mac using the dialogs sample in cvs by 
adding the following method:

class Dialogs(model.Background):
     def on_initialize(self, event):
         self.fitToComponents(None, 5)

Then I ran the sample in various forms, adding a statusBar, removing 
the menubar and menus, etc. and it appears to behave as expected in all 
cases and looks better than the extra whitespace the sample would have 
by default on GTK and Mac. It works for changing the width of the 
window as well, but I'm not sure about how I feel on changing that 
automatically. One obvious issue is that human interface guidelines for 
each platform probably specify the amount of whitespace that should be 
used, the Mac is likely more than Windows, etc. so it might make more 
sense to have a default arg that will end up using what is appropriate 
for each platform, while still allowing the user code or resource to 
override that value.

My current thinking is that I would add an option to the Background 
resource format that takes a tuple and PythonCard would "fix" the 
layout when it adds the components. Since you might not want it to do 
this fix, it will be settable via the Background Info dialog and people 
generating layouts on the fly will always be able to call it manually 
as well.

There might be a bit of overlap with some of the experiments that Alex 
has been doing on auto-generating sizer wrappers on a layout. If you 
have any comments or suggestions related to this idea, I would like to 
hear them.

ka