Leon Mika

Spent a bit more time working on Photo Bucket this last week¹, particularly around galleries. They’re progressing quite well. I’m made some strides in getting two big parts of the UI working now: adding and removing images to galleries, and re-ordering gallery items via drag and drop.

I’ll talk about re-ordering first. This was when I had to bite the bullet and start coding up some JavaScript. Usually I’d turn to Stimulus for this but I wanted to give HTML web components a try. And so far, they’ve been working quite well.

The gallery page is generated server-side into the following HTML:

<main>
  <pb-draggable-imageset href="/_admin/galleries/1/items" class="image-grid">
    <pb-draggable-image position="0" item-id="7">
      <a href="/_admin/photos/3">
        <img src="/_admin/img/web/3">
      </a>
    </pb-draggable-image>
        
    <pb-draggable-image position="1" item-id="4">
      <a href="/_admin/photos/4">
        <img src="/_admin/img/web/4">
      </a>
    </pb-draggable-image>
        
    <pb-draggable-image position="2" item-id="8">
      <a href="/_admin/photos/1">
        <img src="/_admin/img/web/1">
      </a>
    </pb-draggable-image>        
  </pb-draggable-imageset>
</main>

Each <pb-draggable-image> node is a direct child of an <pb-draggable-imageset>. The idea is that the user can rearrange any of the <pb-draggable-image> elements within a single <pb-draggable-imageset> amongst themselves. Once the user has moved an image onto to another one, the image will signal its new position by firing a custom event. The containing <pb-draggable-imageset> element is listening to this event and will respond by actually repositioning the child element and sending a JSON message to the backend to perform the move in the database.

A lot of this was based on the MDN documentation for drag and drop and it follows the examples quite closely. I did find a few interesting things though. My first attempt at this was to put it onto the <pb-draggable-image> element, but I wasn’t able to get any drop events when I did. Moving the draggable attribute onto the <a> element seemed to work. I not quite sure why this is. Surely I can’t think of any reason as to why it wouldn’t work. It may had something else, such as how I was initialising the HTTP components.

Speaking of HTML components, there was a time where the custom component’s connectedCallback method was being called before the child <a> elements were present in the DOM. This was because I had the <script> tag in the the HTML head and configured to be evaluated during parsing. Moving it to the end of the body and loading it as a module fixed that issue. Also I found that moving elements around using element.before and element.after would actually call connectedCallback and disconnectedCallback each time, meaning that any event listeners registered within connectedCallback would need to be de-registered, otherwise events would be handled multiple times. This book-keeping was slightly annoying, but it worked.

Finally, there was moving the items with the database. I’m not sure how best to handle this, but I have that method that seems to work. What I’m doing is tracking the position of each “gallery item” using a position field. This field would be 1 for the first item, 2 for the next, and so on for each item in the gallery. The result of fetching items would just order using this field, so as long as they’re distinct, they don’t need to be a sequence incrementing by 1, but I wanted to keep this as much as possible.

The actual move involves two update queries. The first one will update the positions of all the items that are to shift left or right by one to “fill the gap”. The way it does this is that when an item is moved from position X to position Y, the value of position between X and Y would be changed by +1 if X > Y, or by –1 if Y > X. This is effectively the same as setting position X to X + 1, and so on, but done using one UPDATE statement. The second query just sets the position of item X to Y.

So that’s moving gallery items. I’m not sure how confident I am with this approach, but I’ve been testing this, both manually and by writing unit tests. It’s not quite perfect yet: I’m still finding bugs (I found some while coming up with these screencasts). Hopefully, I’ll be able to get to the bottom of them soon.

The second bit of work was to actually add and remove images in the gallery themselves. This, for the moment, is done using a “gallery picker” which is available in the image details. Clicking “Gallery” while viewing an image will show the list of galleries in the system, with toggles on the left. The galleries an image already belongs to is enabled, and the user can choose the galleries they want the image to be in by switching the toggles on and off. These translate to inserts and remove statements behind the scenes.

The toggles are essentially just HTML and CSS, and a bulk of the code was taken from this example, with some tweaks. They look good, but I think I may need to make them slightly smaller for mouse and keyboard.

I do see some downside with this interaction. First, it reverses the traditional idea of adding images to a gallery: instead of doing that, your selecting galleries for an image. I’m not sure if this would be confusing for others (it is modelled on how Google Photos works). Plus, there’s no real way to add images in bulk. Might be that I’ll need to add a way to select images from the “Photos” section and have a dialog like this to add or remove them all from a gallery. I think this would go far in solving both of these issues.

So that’s where things are. Not sure what I’ll work on next, but it may actually be import and export, and the only reason for this is that I screwed up the base model and will need to make some breaking changes to the DB schema. And I want to have a version of export that’s compatible with the original schema that I can deploy to the one and only production instance of Photo Bucket so that I can port the images and captions over to the new schema. More on this in the future, I’m sure.