by carlos garcia campos

GTK+/MeeGo Handset integration: Week 2

First of all, thank you very much to all the people who gave me so useful feedback after my previous post.

The idea for this week was to start integrating the HildonPanneableArea code into GtkScrolledWindow, however both Chris and Karl emailed me suggesting to use a time based approach rather than the one used by hildon. Chris pointed me to MxKineticScrollView, which is the evolution of HildonPanneableArea. The code is much easier and cleaner than the hildon one, so I decided to use it instead.

One of the things that caught my attention was that MxKineticScrollView doesn’t need to synthesize events. This is because clutter implements capture and bubble event handling. GTK+ does always bubble so that events are propagated from child to parent. Having support for capture event handling makes the kinetic scrolling implementation easier and simpler, so following the same approach than clutter, I wrote an initial patch to add GtkWidget::captured-event signal.

Using the new captured-event signal, integrate the MxKineticScrollView code into GtkScrolledWindow was a bit easier. I still had to use an input-only event window, and grab the device on button press to make sure that motion and button release events were received on the scrolled window. It’s still far from finished but I have already published a work in progress patch and a new test to try it out.

During the next week I plan to continue working on kinetic scrolling, fixing issues and completing the implementation with the missing features.

by carlos garcia campos

GTK+/MeeGo Handset integration: Week 1

One of the main goals of the project is to improve the mobile experience in GTK+ by contribution upstream rather than creating another library. The Hildon library contains several widgets and features that could be ported or integrated into GTK+: HildonLiveSearch, HildonPannableArea, GtkEntry:hint-text property, GtkWidget::tap-and-hold signal.

HildonPannableArea

This is a scrollable widget, similar to GtkScrolledWindow, that allows the user to tap on any part of the widget and drag it. It also implements kinetic scrolling which is a feature currently present in most of the mobile platforms.

During this week I have focused on HildonPannableArea, trying to understand the code (there are several tricky parts) and thinking about how it could be integrated into GtkScrolledWindow. My initial idea was to port HildonPannableArea as a standalone widget deriving from GtkScrolledWindow, but there are use cases where switching between normal and touch mode makes sense, like with laptops that can work as tablets as Bastien pointed out. So, the idea is to integrate HildonPannableArea code into GtkScrolledWindow to add a kinetic mode. I started porting HildonPannableArea to GTK+3 and cleaning up the code a bit to make the integration easier. Next week I’ll focus on the real integration.

by carlos garcia campos

Cairo 1.10

Yes, it’s true, Cairo 1.10 has been finally released. Chris already summarized two years of development in 60 lines, so I’m going to talk about how this release affects to Evince/Poppler.

Blend Modes

Cairo 1.10 has some new operators inspired by PDF blend modes, that allowed us to easily implement PDF blend modes in the poppler cairo backend

PDF Blend Modes
PDF Blend Modes

Here is an example of a PDF document combining the use of Multiply blend mode with gradients

Scooby gradient rendered with Cairo 1.8
Scooby gradient rendered by poppler with Cairo 1.8
Scooby gradient rendered by poppler with Cairo 1.10
Scooby gradient rendered by poppler with Cairo 1.10
Scooby gradient rendered by xpdf
Scooby gradient rendered by xpdf

Blend modes are also important for annotations, since highlight annotations are usually implemented by using the Multiply blend mode

Performance

There were some PDF documents where the performance of the poppler cairo backend was really bad. It seems that, with such particular documents, poppler was clipping too much. Of course, Chris fixed it, see the screenshot:

Poppler with cairo 1.8 and 1.10
Poppler with cairo 1.8 and 1.10

Output file size when printing

Thanks to cairo_surface_set_mime_data now we can attach the original uncompressed image to the ps/pdf surface that will be used when creating the resulting ps/pdf file. It drastically reduces the size of the ps/pdf output files created when printing documents that contain images

Fit to contents/Trim margins

This hasn’t been implemented in Evince yet, but using the new recording surface we can get the page bounding box and use it to implement a new fit to contents zoom mode.

Thanks!

Thank you very much to everybody involved in this release

by carlos garcia campos

XPS Documents

I’d never heard about XPS format until someone filed a bug report asking to support it in Evince. It doesn’t seem to be commonly used, at least in the free software community, since there are just a few requests in bugzilla. However, I downloaded and read the XPS specification (thanks to Okular) just out of curiosity, and it sounded like something fun to implement. Taking advantage of the quiet summer days I started to write a library based on GLib/GObject and Cairo to render XPS documents.

Today, the library implements the minimum stuff to be able to read the XPS spec (rendering, outline and links) and I’ve added a new backend to Evince that uses it. There are still some known bugs and many things to do, but it’s possible to read quite a lot of XPS documents with Evince already.

XPS Specification in Evince
XPS Specification in Evince
by carlos garcia campos

Adding new annotations with Evince

I’ve finally added support for adding new annotations to Evince. At the moment only text annotations are supported and it requires poppler from current git master. There are still things to do, but the main functionality is working now. The idea is to add support for more annotation types (geometry, highlight, file attachments, …) during the next release cycle, since we are close to feature freeze. Click on the image to see a screencast showing how it currently works, you can add annotations from the side panel, change the default properties (author, color, transparency, icon, …), and save a copy that can be opened with any other document viewer that supports annotations like, of course, Acrobat Reader.

Evince annotations
(click to play back, ogg/theora, ~8,7M MBytes)

By the way

I'm attending GUADEC

by carlos garcia campos

libpanel-applet3

I’ve finally found some time to blog about this. The bonobo-less gnome-panel branch was merged into master, so since version 2.31.2 gnome-panel doesn’t depend on bonobo anymore. The API is mostly the same, but there are some minor changes since the old API exposed bonobo stuff. This of course means that applets need to be ported to the new API. There’s already a GNOME Goal with a porting guide, and I already ported most of the gnome-applets so there are a few examples too.

by carlos garcia campos

Why I can’t use GNOME Shell


GNOME Shell
GNOME Shell

This is GNOME Shell running without any other application running except GNOME System Monitor. The CPU usage is always around 60%, which makes the system unusable after a few minutes. I guess it’s actually an issue of the nvidia drivers, but the fact is that I can’t use GNOME Shell.

GNOME Panel
GNOME Panel

And this is GNOME Panel. Maybe I’m too used to it, but I really like the old panel approach, and my applets, specially the workspace switcher. I have never seen a better way to change between workspaces than the current workspace switcher applet, it’s fast and intuitive.

By the way, the screenshot shows a special GNOME Panel, it’s bonobo-free! A few years ago I already tried to port libpanel-panel from bonobo to D-Bus, but at that time breaking compatibility with bonobo applets was not accetable. Now we really want to get rid of bonobo in GNOME 3, and I’m not the only one who can’t use GNOME Shell, so GNOME Panel is not going to die in a near future. I’ve already proposed an updated patch for gnome-panel, the challenge now is porting all the applets which might be a new GNOME Goal.