Apr 06

Creating custom scrollbars with CSS; How CSS isn’t great for every task

Ajax, Bespin, JavaScript, Web Browsing with tags: , , 22 Comments »

Have you tried to create a nice rich experience and then been fighting the “defaults” to go the extra mile? This reared its head with me recently with Bespin. There are certain commands that pull up divs of content and we need to scroll through it. The problem is that the native scroll bar looks so out of place:

uglyscrollbar

WebKit recently released the ability to style scrollbars in HTML elements (but not the main window, which you have been able to do in IE for donkeys years much to many peoples chagrin).

I decided to take it for a spin and loaded up the examples that show you being able to do every type of scrollbar that you can imagine:

manyscrollbars

So, it shouldn’t be so hard should it. From the blog post I see a few magically ::-webkit-scrollbar CSS properties that I can plugin and be on my way. But looking at the example view source you see many pieces like this:

:not(.none):not(.double-start)::-webkit-scrollbar-track-piece:vertical:end:single-button,
:not(.none):not(.double-start)::-webkit-scrollbar-track-piece:vertical:end:double-button,
.single::-webkit-scrollbar-track-piece:vertical:end,
.double-end::-webkit-scrollbar-track-piece:vertical:end,
.double-both::-webkit-scrollbar-track-piece:vertical:end {
    margin-bottom: -6px;
}

Holy pseudo classes batman! To be fair, this is partly due to the example page having many types of scrollbars in one (hence the not this and not that but the other) but there are still nested classes that you need to grok to get this going.

I quickly built a debug scrollbar where I styled the various pieces with simple colors and borders so I can see which was which. I also went about making the scrollbar have one up arrow on top, and one down arrow on the bottom.

debugscrollbar

The parts and pieces of a scrollbar are quite simple:

  • Thumb: This is the piece that shows you where you are in the scrollbar. This is the chap that you can move around
  • Track: This is the area of the scrollbar that you can move the thumb up and down, or along (depending on the orientation). There is both the area between the top and the thumb, and between the bottom of the thumb and the bottom of the scrollbar
  • Buttons: There may be buttons that you can click to increment or decrement the selection (which moves the thumb). There are various styles (single button, double button, etc)
  • Resizer: This can change the are of the element (e.g. enlarge of shrink)
  • Corner: This area may show up with both horizontal and vertical scrollbars open

The debug scrollbar kinda shows these areas off in a simple visual way. Note how using display: block|none enabled me to setup the single button on top and bottom functionality:

/* Turn on a 13x13 scrollbar */
::-webkit-scrollbar {
    width: 13px;
    height: 13px;
}
 
::-webkit-scrollbar-button:vertical {
    background-color: red;
    border: 1px dashed blue;
}
 
/* Turn on single button up on top, and down on bottom */
::-webkit-scrollbar-button:start:decrement,
::-webkit-scrollbar-button:end:increment {
    display: block;
}
 
/* Turn off the down area up on top, and up area on bottom */
::-webkit-scrollbar-button:vertical:start:increment,
::-webkit-scrollbar-button:vertical:end:decrement {
    display: none;
}
 
/* Place The scroll down button at the bottom */
::-webkit-scrollbar-button:vertical:increment {
    background-color: black;
    border: 1px dashed blue;
}
 
/* Place The scroll up button at the up */
::-webkit-scrollbar-button:vertical:decrement {
    background-color: purple;
    border: 1px dashed blue;
}
 
::-webkit-scrollbar-track:vertical {
    background-color: blue;
    border: 1px dashed pink;
}
 
/* Top area above thumb and below up button */
::-webkit-scrollbar-track-piece:vertical:start {
    border: 1px solid #000;
}
 
/* Bottom area below thumb and down button */
::-webkit-scrollbar-track-piece:vertical:end {
    border: 1px dashed pink;
}
 
/* Track below and above */
::-webkit-scrollbar-track-piece {
    background-color: green;
}
 
/* The thumb itself */
::-webkit-scrollbar-thumb:vertical {
    height: 50px;
    background-color: yellow;
}
 
/* Corner */
::-webkit-scrollbar-corner:vertical {
    background-color: black;
}
 
/* Resizer */
::-webkit-scrollbar-resizer:vertical {
    background-color: gray;
}

By moving the scrollbar around I could quickly see how this all worked, and it got me to this point which enabled me to plugin the images to make this puppy work for Bespin:

bespinscrollbar

There were a couple of key tweaks needed to make this work:

Getting the buttons working

I used the same trick used in the debug example to turn on the up area above, and the down area below, and then it was just a matter of targeting the correct area for the arrow images:

/* Turn on single button up on top, and down on bottom */
::-webkit-scrollbar-button:start:decrement,
::-webkit-scrollbar-button:end:increment {
    display: block;
}
 
/* Turn off the down area up on top, and up area on bottom */
::-webkit-scrollbar-button:start:increment,
::-webkit-scrollbar-button:end:decrement {
    display: none;
}
 
/* Place The scroll down button at the bottom */
::-webkit-scrollbar-button:end:increment {
    background-image: url(images/scroll_cntrl_dwn.png);
}
 
/* Place The scroll up button at the up */
::-webkit-scrollbar-button:start:decrement {
    background-image: url(images/scroll_cntrl_up.png);
}

Get the track pieces to show

Next up was getting the gutter to show up. As mentioned early on, there is one track, but two areas that can show…. before the thumb and after. You can target these areas via -webkit-scrollbar-track-piece:start || :end and then it is a matter of using the multiple background ability available in new browsers. First we have the top of the gutter, and then a recurring background (and the same for the bottom). This way it just grows with the area that it gets:

/* Top area above thumb and below up button */
::-webkit-scrollbar-track-piece:vertical:start {
    background-image: url(images/scroll_gutter_top.png), url(images/scroll_gutter_mid.png);
    background-repeat: no-repeat, repeat-y;
}
 
/* Bottom area below thumb and down button */
::-webkit-scrollbar-track-piece:vertical:end {
    background-image: url(images/scroll_gutter_btm.png), url(images/scroll_gutter_mid.png);
    background-repeat: no-repeat, repeat-y;
    background-position: bottom left, 0 0;
}

The Thumb

To get the thumb working, I thought I would do the same background image trick with three images (top of thumb, bottom of thumb, and background for the middle). Unfortunately this didn’t seem to work for me as I couldn’t get the middle to not go through the top and bottom. So, instead, I went with another new CSS trick: border-image. Here I splice the top and bottom of a thumb (the top and bottom 8 pixels) and stretch the rest:

/* The thumb itself */
::-webkit-scrollbar-thumb:vertical {
    height: 56px;
    -webkit-border-image: url(images/scroll_thumb.png) 8 0 8 0 stretch stretch;
    border-width: 8 0 8 0;
}

John Resig has a nice readable post on border-image.

And, there you have it. Now we can have nice Bespin-y scrollbars throughout Bespin. This may not be complete though, as we have the ability to also tie in :active and :hover work if we wish (change the color when selecting etc).

Of course, many people had “custom scrollbars”. There are plenty of comments on the original Surfin’ Safari post, and various rants about Flash versions. I agree that we have all seen bizarre Flash versions of scrollbars that don’t look like them at all, and where the designer didn’t bother to put in support for the mousescroll ability etc, but this is a bit different. It let’s you merge in your look and feel, yet with native scrollbar functionality.

And, with Google recreating the button maybe we can feel a little bit better about tweaking the look of common UI elements as long as they are familiar enough to users to still make natural sense.

Now, the CSS declarative way to do scrollbars seems to get pretty ugly to me with all of he pseudo classes and various magic to get the functionality that you would like. I have to admit to liking Kevin’s demo of Flash Catalyst at Web 2.0 Expo and how it lets designers build out a scrollbar. We should be inspired to do tools like this. What if we had an API that wasn’t CSS, but let us say: “I want a Mac style double on the bottom button scrollbar. And, here is a thumb, here is a track, go for it”.

That being said, at least we do have the ability to do this kind of thing now. I hope that other browsers follow WebKit in this instance.

Apr 02

Bespin Concept Defrag Command; Exploring some fun visualizations

Tech 4 Comments »

One of the fun side effects of working with the community on a code editor that is built on Open Web technology is that we get to experiment. The number one priority is to move fast to create a performant highly usable editor, but how can an editor innovate?

A lot of editor innovation has happened behind the scenes, with code completion and the like. What can be done visually?

One idea is illustrated in the image below:

bespineditor_heatmap

As an individual developer, I often find myself working in the same few files while I complete a given task. Mylyn does an interesting job of keeping a notion of a context for tasks (such as fixing bug number 928394). As I jump between areas in a few files it could be nice to visualize that fact which is the item on the left of the editor. Areas can change colors based on usage and time spent, and I can click between them easily. When you mouse over an area it tells you what is there. (NOTE: Thanks to the work that Malte did, you can also use the command line and type goto MyFunctionName as a way to jump to a given function).

With this view in place, not only can we show your areas of jumpitude, but we can also show you what has changed in the file, say since your last commit so you can visualize your changes a little. Of course, this could be condensed down into the scrollbars themselves for simple cases, and only show a richer view when you ask for it.

Having this visualization in one file is nice, but what about watching the entire project? I don’t know about you, but I often find myself jumping between using another objects function, and seeing what it does (going to the declaration). This can show the cross linking. In fact, I also love the ability to jump through to a declaration from a method call. We have to get that into Bespin too, but have also looked at giving the option to call an action and popup the declaration inline so you don’t have to jump forward and back and can see the usage info while still seeing the code you are actually writing!

This also dove tails with the social collaborative aspects of Bespin. It is great to see where you have been editing, but what if we could also show where your team mates are editing. One key feature would be “tell me if someone stomped in an area that I am coding” … all so I can commit the code as fast as possible so the other poor bugger has to merge! ;) The data can be garnered via the obvious multiple people in collaboration mode, by cross checking edits coming in, and from commits themselves.

I am really jazzed to have a platform to play around with some experimental visualizations and I look forward to seeing your concepts. Worst case, we have the start of a Bespin defrag command!