Smallscreen mod for GtkFileChooser

OpenEmbedded have had smallscreen patch for GtkFileSelection widget for quite some time now, but unfortunately it doesn't affect usability of the most software, simply because many programs now use GtkFileChooser widget instead. GTK+ 2.12 manual also following about the matter: "GtkFileSelection has been superseded by the newer GtkFileChooser family of widgets."

Let's look how standard GtkFileChooserDialog looks on QVGA portrait device (240x320):



Note that "Places" pane on left cannot be shrinked beyond the size shown, which doesn't leave room for any useful display of filenames, so the dialog is clearly unusable.

So, I've took time to patch GTK+ 2.10.14 (this is the version used by Angstrom 2007.12, and my primary focus is to improve its usability on the supported devices) to make the widget be more PDA-friendly. I started with "data-driven" changes (meaning changing numbers and strings, but note code constructs):

• Reduced Gnome Human Interface Guidelines mandated spacing and borders of 6 and 12 pixels to 2. It's nice to have standards (even though Gnome doesn't offer us opportunity to choose from ;-) ), but on small screens, there's simply not enough space to spend pixel-wealth on gaps.
• Removed labels from Places pane's buttons, leaving only icons.
• Made Places pane shrinkable.
  

Even these changes made big difference, but stopping there would be to leave the dialog in barely usable state, and I'm really hope for a Linux GUI environment which is comfortable to use.

So, adaptive relayout was required, based on "PDA" mode being active. I first started with defining PDA mode as being portrait screen orientation, but thinking further, the problem, at least for GtkFileChooser, can be defined as follows: there's just too little of horizontal space available, and there should be efforts applied to use it to show as much of user's filenames' length as possible. Based on this note, PDA mode was defined as having a screen width below some threshold. This threshold was set as absolute value, but is not really arbitrary, and tied to real-world available screen sizes. I found that standard dialog looks pretty well in VGA landscape orientation, but still leaves too little space for filenames
in portrait orientation. So, threshold was set to 490 (to account for fudge factor ;-) ).

Now, with the above note on horizontal space scarcity, and keeping in mind that screen area at all is scarce, for vertical space should be saved too, following dynamic layout changes are done to dialog when being in PDA mode (i.e. run on the screen <490 pixels width):

• Vertical split pane is used for Places vs Filelist
• Buttons are packed to the left instead of bottom of Places
• Actually, only "Add" button was left, as "Remove" action can be easily accessed from Places list context menu, and most importantly, intuitively can be expected there. ("Add to shortcuts" choice is available for context menu on Filelist items, but who'd look for it there, without knowing it is?). This allows for more visually pleasing layout when Places pane is minimized.
• Dialog itself is sized to take all available width (originally, GTK+ sizes it to take no more than 3/4 of screen width, if possible, or packed requested size otherwise).
  

All in all, that's how the dialog looks now:


A refreshing change, with pretty long filenames being easily visible.

I've tested the patch pretty well, plus code changes are pretty small, so I intend to commit it to OE soon, and RFC its addition to Angstrom stable branch after it gets more review and testing.

There're still few things to consider and do to make it even more usable on small, PDA-like screens:

• Catch and process screen geometry change events - I'm pretty sure this is not done by GTK+ currently, and on dynamic screen device like PDA could make parts of dialog go offscreen when switching from landscape to portrait and vice-versa.
• Possibly, adjust screen width threshold based on more testing (original value was based on review of big-gaps dialogs, maybe smaller gaps affect that).
• Alternatively, gaps can be calculated on the fly, so original Gnome HIG-mandated values would be used on big screens, and small values only in PDA mode.
• Default "File system" choice in Places is superflous, it can be accessed with the icon from the path buttons at the top of dialogs. Unfortunately, screenshots above have it scrolled away. And having "File system" is Places causes exactly same problem: it takes space and calls for scrolling, so we'd better skip it there altogether, letting user to access own choices easier.
• Think about dialog height. Currently, as seen from above screenshot, it leaves bunch of screen area unused, and (apparently) due to Matchbox window management constraints, it cannot be resized by user. We could fit 1-2 more filenames if sized the dialog near-fullscreen. But that would look OK for QVGA, but already artificial for VGA.
  

Finally, it would be fun to have a look at GTK+ 2.12. As they say, it has stuff contributed by Nokia based on N770/N800 work, so I keep my fingers crossed that I didn't do monkey's job! ;-) Nonetheless, the focus is current Angstrom release, as I wrote above.