Merge pull request #767 from basecamp/flavorjones/active-storage-variants

Make sure the image variants we use are preprocessed

app/models/concerns/attachments.rb

@@ -1,6 +1,25 @@
 module Attachments
   extend ActiveSupport::Concern
 
+  # The variants we use must all declared here so that we can preprocess them.
+  #
+  # If they are not preprocessed, then Rails will attempt to transform the image on-the-fly when
+  # they are first viewed, which may be on the read replica where writing to the database is not
+  # allowed. Chaos will ensue if that happens.
+  #
+  # These variants are patched into ActionText::RichText in config/initializers/action_text.rb
+  VARIANTS = {
+    # vipsthumbnail used to create sized image variants has a intent setting to manage colors during
+    # resize. By setting an invalid intent value the gif-incompatible intent filtering is skipped and
+    # the gif can be rendered with all its frame intact.
+    #
+    # Only `n` is accepted as an override, using the full parameter name `intent` doesn’t work.
+    #
+    # This was cargo-culted from know-it-all and I imagine it may be fixed at some point.
+    small: { loader: { n: -1 }, resize_to_limit: [ 800, 600 ] },
+    large: { loader: { n: -1 }, resize_to_limit: [ 1024, 768 ] }
+  }
+
   def attachments
     rich_text_record&.embeds || []
   end

app/views/active_storage/blobs/web/_representation.html.erb

@@ -1,4 +1,4 @@
-<% size = local_assigns[:in_gallery] ? [800, 600] : [1024, 768] %>
+<% variant = Attachments::VARIANTS[local_assigns[:in_gallery] ? :small : :large] %>
 <% width = blob.metadata["width"] %>
 <% height = blob.metadata["height"] %>
 
@@ -14,10 +14,8 @@
   <audio controls="true" width="100%" preload="metadata">
     <source src="<%= rails_blob_url(blob) %>" type="<%= blob.content_type %>">
   </audio>
-<% elsif blob.variable? %>
-  <%= image_tag url_for(blob.variant(loader: { n: -1 }, resize_to_limit: size)), width: width, height: height %>
-<% elsif blob.previewable? %>
-  <%= image_tag url_for(blob.preview(resize_to_limit: size)), width: width, height: height %>
+<% elsif blob.variable? || blob.previewable? %>
+  <%= image_tag url_for(blob.variant(variant)), width: width, height: height %>
 <% else %>
   <span class="attachment__icon"><%= blob.filename.extension&.downcase.presence || "unknown" %></span>
 <% end %>

app/views/events/event/_attachments.html.erb

@@ -1,14 +1,14 @@
 <% if eventable&.has_attachments? %>
   <span class="event_attachments margin-block-half flex align-center gap-half">
     <% eventable.attachments.each do |attachment| %>
-      <% size = [800, 600] %>
+      <% variant = Attachments::VARIANTS[:small] %>
       <% width = attachment.metadata["width"] %>
       <% height = attachment.metadata["height"] %>
 
       <% if attachment.previewable? %>
-        <%= image_tag url_for(attachment.preview(resize_to_limit: size)), class: "attachment attachment--image", width: width, height: height %>
+        <%= image_tag url_for(attachment.preview(variant)), class: "attachment attachment--image", width: width, height: height %>
       <% elsif attachment.variable? %>
-        <%= image_tag url_for(attachment.variant(resize_to_limit: size)), class: "attachment attachment--image", width: width, height: height %>
+        <%= image_tag url_for(attachment.variant(variant)), class: "attachment attachment--image", width: width, height: height %>
       <% else %>
         <div class="attachment attachment--file attachment--<%= attachment.filename.extension -%>">
           <span class="attachment__icon"><%= attachment.filename.extension&.downcase.presence || "unknown" %></span>
@@ -16,4 +16,4 @@
       <% end %>
     <% end %>
   </span>
-<% end %> 
+<% end %>

config/initializers/action_text.rb

@@ -0,0 +1,20 @@
+module ActionText
+  module Extensions
+    module RichText
+      extend ActiveSupport::Concern
+
+      included do
+        # This overrides the default :embeds association!
+        has_many_attached :embeds do |attachable|
+          ::Attachments::VARIANTS.each do |variant_name, variant_options|
+            attachable.variant variant_name, variant_options.merge(preprocessed: true)
+          end
+        end
+      end
+    end
+  end
+end
+
+ActiveSupport.on_load(:action_text_rich_text) do
+  include ActionText::Extensions::RichText
+end