Fix form for donations thermometer

app/models/plugins/donations_thermometer.rb

@@ -37,7 +37,7 @@ def liquid_data(_supplemental_data = {})
   def currencies_hash(amount)
     # Get a hash with amount converted into all supported currencies.
     # Transform values from arrays of amounts to single amounts (e.g. GBP: [10] to GBP: 10)
-    Donations::Currencies.for([amount]).to_hash.with_indifferent_access.transform_values(&:pop)
+    Donations::Currencies.for([amount]).to_hash.with_indifferent_access.transform_values(&:pop).transform_values(&:to_d)
   end
 
   def fundraising_goal

app/views/plugins/actions_thermometers/_form.slim

@@ -1,4 +1,6 @@
 .col-md-7
+  // There's a single ThermometersController that handles both actions and donations thermometers, so use the
+  // generic plugins_thermometer_path for the toggle.
   = render partial: 'plugins/shared/toggle_form', locals: { plugin: plugin, path: plugins_thermometer_path(plugin) }
 
   - name = "plugins_actions_thermometer_#{plugin.id}"

app/views/plugins/donations_thermometers/_form.slim

@@ -1,4 +1,6 @@
 .col-md-7
+  // There's a single ThermometersController that handles both actions and donations thermometers, so use the
+  // generic plugins_thermometer_path for the toggle.
   = render partial: 'plugins/shared/toggle_form', locals: { plugin: plugin, path: plugins_thermometer_path(plugin) }
 
   - name = "plugins_donations_thermometer_#{plugin.id}"
@@ -8,5 +10,14 @@
     = render 'plugins/shared/plugin_metadata', f: f
 
     .form-group
-      = label_with_tooltip(f, :offset, t('plugins.thermometer.offset'), t('tooltips.thermometer.donations.offset'))
-      = f.text_field(:offset, class: 'form-control')
+      = label_with_tooltip(f, :offset_amount, t('plugins.thermometer.offset'), t('tooltips.thermometer.donations.offset'))
+      = number_field_tag :offset_amount, plugin.offset/100, class: 'form-control'
+      = f.hidden_field :offset, class: 'offset-in-cents'
+
+javascript:
+  $(function () {
+    $('#offset_amount').on('change', function(){
+      // change the value of the hidden offset-in-cents field to the manually entered offset amount * 100
+      $('.offset-in-cents').val($(this).val() * 100);
+    })
+  });

spec/liquid/liquid_renderer_spec.rb

@@ -220,6 +220,7 @@
       end
 
       before :each do
+        allow_any_instance_of(Plugins::DonationsThermometer).to receive(:liquid_data).and_return({})
         allow(PaymentProcessor::Currency).to receive(:convert)
       end