UX: AI composer helper refinements (#1387)

This update includes a variety of small refinements to the AI composer helper:

- prevent height jump when going from loading text placeholder → proofreading text streaming
- update padding on AI helper options list to be more suitable with typical Discourse menu design
- for composer helper results that are not `showResultAsDiff` (i.e. translation):
   - update before/after diff design to be more subtle
   - results should be in normal font (as the text is cooked and not raw markdown)
- fix: smooth streaming animation stuck showing dot icon even after smooth streaming is done

assets/javascripts/discourse/components/modal/diff-modal.gjs

@@ -5,6 +5,7 @@ import didInsert from "@ember/render-modifiers/modifiers/did-insert";
 import willDestroy from "@ember/render-modifiers/modifiers/will-destroy";
 import { service } from "@ember/service";
 import { htmlSafe } from "@ember/template";
+import { or } from "truth-helpers";
 import CookText from "discourse/components/cook-text";
 import DButton from "discourse/components/d-button";
 import DModal from "discourse/components/d-modal";
@@ -41,6 +42,10 @@ export default class ModalDiffModal extends Component {
   }
 
   get diffResult() {
+    if (this.loading) {
+      return this.escapedSelectedText;
+    }
+
     if (this.diffStreamer.diff?.length > 0) {
       return this.diffStreamer.diff;
     }
@@ -50,10 +55,22 @@ export default class ModalDiffModal extends Component {
     return this.escapedSelectedText;
   }
 
+  get smoothStreamerResult() {
+    if (this.loading) {
+      return this.escapedSelectedText;
+    }
+
+    return this.smoothStreamer.renderedText;
+  }
+
   get isStreaming() {
     // diffStreamer stops Streaming when it is finished with a chunk, looking at isDone is safe
     // it starts off not done
-    return !this.diffStreamer.isDone || this.smoothStreamer.isStreaming;
+    if (this.args.model.showResultAsDiff) {
+      return !this.diffStreamer.isDone;
+    }
+
+    return this.smoothStreamer.isStreaming;
   }
 
   get primaryBtnLabel() {
@@ -154,42 +171,37 @@ export default class ModalDiffModal extends Component {
           {{willDestroy this.cleanup}}
           class="text-preview"
         >
-          {{#if this.loading}}
-            <div class="composer-ai-helper-modal__loading">
-              {{~@model.selectedText~}}
-            </div>
-          {{else}}
-            <div
-              class={{concatClass
-                "composer-ai-helper-modal__suggestion"
-                "streamable-content"
-                (if this.isStreaming "streaming")
-                (if @model.showResultAsDiff "inline-diff")
-                (if this.diffStreamer.isThinking "thinking")
-              }}
-            >
-              {{~#if @model.showResultAsDiff~}}
-                <span class="diff-inner">{{htmlSafe this.diffResult}}</span>
+          <div
+            class={{concatClass
+              "composer-ai-helper-modal__suggestion"
+              "streamable-content"
+              (if this.isStreaming "streaming")
+              (if @model.showResultAsDiff "inline-diff")
+              (if this.diffStreamer.isThinking "thinking")
+              (if this.loading "composer-ai-helper-modal__loading")
+            }}
+          >
+            {{~#if @model.showResultAsDiff~}}
+              <span class="diff-inner">{{htmlSafe this.diffResult}}</span>
+            {{else}}
+              {{#if (or this.loading this.smoothStreamer.isStreaming)}}
+                <CookText
+                  @rawText={{this.smoothStreamerResult}}
+                  class="cooked"
+                />
               {{else}}
-                {{#if this.smoothStreamer.isStreaming}}
+                <div class="composer-ai-helper-modal__old-value">
+                  {{~this.escapedSelectedText~}}
+                </div>
+                <div class="composer-ai-helper-modal__new-value">
                   <CookText
-                    @rawText={{this.smoothStreamer.renderedText}}
+                    @rawText={{this.smoothStreamerResult}}
                     class="cooked"
                   />
-                {{else}}
-                  <div class="composer-ai-helper-modal__old-value">
-                    {{@model.selectedText}}
-                  </div>
-                  <div class="composer-ai-helper-modal__new-value">
-                    <CookText
-                      @rawText={{this.smoothStreamer.renderedText}}
-                      class="cooked"
-                    />
-                  </div>
-                {{/if}}
+                </div>
               {{/if}}
-            </div>
-          {{/if}}
+            {{/if}}
+          </div>
         </div>
       </:body>
 

assets/stylesheets/common/streaming.scss

@@ -111,7 +111,7 @@ mark.highlight {
   animation-name: mark-blink;
 }
 
-.composer-ai-helper-modal__loading {
+.composer-ai-helper-modal__loading.inline-diff {
   white-space: pre-wrap;
 }
 

assets/stylesheets/modules/ai-helper/common/ai-helper.scss

@@ -1,11 +1,13 @@
 @use "lib/viewport";
 
 .composer-ai-helper-modal {
-  .text-preview,
   .inline-diff {
     font-family: var(--d-font-family--monospace);
     font-variant-ligatures: none;
+  }
 
+  .text-preview,
+  .inline-diff {
     ins {
       background-color: var(--success-low);
       text-decoration: none;
@@ -55,13 +57,16 @@
   }
 
   &__old-value {
-    background-color: var(--danger-low);
+    white-space: pre-wrap;
+    border-left: 2px solid var(--danger);
+    padding-left: 1rem;
     color: var(--danger);
     margin-bottom: 1rem;
   }
 
   &__new-value {
-    background-color: var(--success-low);
+    border-left: 2px solid var(--success);
+    padding-left: 1rem;
     color: var(--success);
   }
 
@@ -77,7 +82,6 @@
 }
 
 .ai-composer-helper-menu {
-  padding: 0.25rem;
   max-width: 25rem;
   list-style: none;
 
@@ -701,7 +705,7 @@
     width: 100%;
     border-radius: 0;
     margin: 0;
-    padding: 0.5em 1rem;
+    padding: 0.7rem 1rem;
 
     &:focus,
     &:hover {