Month: October 2017

GTK+ 3.92

Yesterday, we released GTK+ 3.92.1, 重庆市. Since it has been a while since the last 3.91 release, here is a brief look at the major changes.

This release is another milestone on our way towards GTK+ 4. And while a lot still needs to be done, this release allows a first glimpse at some of the things we hope to achieve in GTK+ 4.

GSK

Much of the work since the last release has gone into GSK. The Vulkan renderer is now close to complete, as far as avoiding cairo fallbacks goes. The only missing piece are blurred shadows (admittedly, an important piece).

One major step forward since the 3.91.2 release is that we no longer use cairo fallbacks for all text. Instead, text (in labels and entries, sadly not in text views yet) gets translated into text nodes. Each text node contains a PangoGlyphString and a PangoFont. The Vulkan renderer uses a glyph cache to avoid re-rendering the glyphs for each frame.

The internal logic of the Vulkan renderer has been reworked to use textures instead of cairo surfaces for intermediate results and thus avoid more cairo fallbacks.

Other node types that have gained support in the Vulkan renderer include blurs, repeat nodes, blend modes and cross-fades. In some cases, the shaders we use are very naive implementations. Help with improving them would be more than welcome!

As a first example of what we can do with render nodes, we have implemented a blur-under feature for GtkOverlay. This works by capturing the ‘main child’ of the overlay as a render node, and then reusing it several times, with the right clipping, and sometimes with a blur node.

Inspector

To help you explore GSK, the inspector now shows Vulkan information and the recorder shows a lot more information about render nodes.

Input

On the input side, events have gained accessors, and we are no longer accessing their fields directly. This is an intermediate step, cleaning up events is still a work in progress. We have moved the traditional widget signals for events (such as ::key-press-event) to an event controller, and most widgets inside GTK+ have stopped using them altogether.

Build System

We have switched over to using Meson exclusively for GTK+, and the 3.92.1 release is the first one done using Meson’s dist support. To get the release out the door, we also had to port the documentation, the test suite and the installed tests to using Meson.

There are still some rough edges (we don’t get all dependencies 100% right), but overall, Meson worked out well for us.

The rest

Of course, everybody loves Emoji, and the same color Emoji support that has landed in GTK+ 3.22 is also available in this release. Beyond that, font support in CSS has improved a bit with support for the CSS3 font-variant property.

Of course, this relies on fonts that have the corresponding features.

Try it out

With GTK+ 3.92.1, it should be easy to try some of these things out for yourself.

And if you’ve always wanted to get into GTK+ development but never found the right opportunity, now is a great time to get involved!

A scrolling primer

A few years ago, I wrote a post about scrolling in GTK+ 3. Time for another look!

The common case

The basic idea of the changes described back then is still the same. We expect touchpad (or track point) scrolling to be one of the most common forms of scrolling, and the scrollbar operates as a narrow indicator for this.

As you can see, we change the cursor to indicate scrolling, and it you can freely scroll in all directions. It is kinetic, too.

Classical scrolling

Of course, it is still possible to just click and drag the slider, for classical scrolling.

Another aspect of ‘classical’ scrolling is that you can click on the trough outside the slider, and either warp the position to where you clicked, or jump in page-size increments.

By default, a primary click warps, and Shift-primary click goes by pages. We just added back middle click as an alternative to Shift-primary click, since this is a common alternative that many people are used to. For mainly historical reasons, GTK+ has a setting, gtk-primary-button-warps-slider, which switches the roles of primary click and Shift-primary click for this.

The typical keyboard shortcuts (Page Up, Page Down, Home, End) let you control scrolling with the keyboard.

Smooth scrolling

There’s more to scrolling in GTK+ that you may not know about. One feature that we introduced long ago is a ‘zoom’ or ‘fine adjustment’ mode, which slows the scrolling down to allow pixel-precise positioning.

To trigger this mode you can either use a long press or shift-click in the slider. As you can see in the video, once you move the pointer below or above the scrollbar, it will keep scrolling at the same relaxed speed until you let go.

As a variation on this theme, more recently we added a variable speed variant of smooth scrolling.

To trigger it, you secondary click in the trough outside the slider. Once the scrolling starts, you can control the speed by moving the pointer closer or farther away from the scrollbar. This is pretty addictive, once you’ve discovered it!

Custom locations

As the last feature, applications can add a context menu that gets triggered by secondary click on the slider, and make it scroll to important positions.

Thats it, scroll on!