Lay out a short Article draft like a line of text in the composer (#187)

* Lay out a short Article draft like a line of text in the composer

A one-line draft made the input field about 8 pt taller than a line of text,
so the send button was no longer centered, and the expand button sat under
the send button until the draft reached four lines. The field now keeps the
one-line height while the draft fits it, and the expand button takes the
emoji button's slot next to the send button when there is no room above it.

* Keep plain text layout and grow a short draft's field smoothly

Move the expand button next to the send button only while an Article draft
is shown, so it can't cover the visible emoji button of a 4-line text input
at small font sizes, and shrink the draft's empty insets gradually instead
of jumping from the one-line height to the full measured height.

Author: null00x

packages/ChatUI/Sources/ChatUI/ChatInputView.swift

@@ -211,11 +211,17 @@ public final class ChatInputContainerView: FlippableView {
         accessory.isVisibility() ? 10 + accessory.size.height : 0
     }
 
+    fileprivate var richDraftSlotHeight: CGFloat {
+        let minHeight = CGFloat(textView.min_height)
+        let draftHeight = richDraftPreviewHeight - RichTextDraftPreviewView.vInset * 2
+        return max(minHeight, min(richDraftPreviewHeight, draftHeight * 2 - minHeight))
+    }
+
     public func contentHeight(for width: CGFloat) -> CGFloat {
         // A rich draft stands IN PLACE of the text (it looks like the entered content), so it replaces the
         // text's base height rather than stacking above an empty field.
         if richDraftPreviewHeight > 0 {
-            return max(richDraftPreviewHeight, CGFloat(textView.min_height)) + accessoryHeight
+            return richDraftSlotHeight + accessoryHeight
         }
         let base = (chatState == .normal || chatState == .editing) ? textViewSize(width).0.height : CGFloat(textView.min_height)
         return base + accessoryHeight
@@ -269,8 +275,7 @@ public final class ChatInputContainerView: FlippableView {
                 // doesn't flash at the origin before the next layout pass.
                 let sendAsInset: CGFloat = sendAsView != nil ? 34 + 3 : 0
                 let textLeftInset: CGFloat = 12 + sendAsInset
-                let slot = max(richDraftPreviewHeight, CGFloat(textView.min_height))
-                let previewY = accessoryHeight + (slot - richDraftPreviewHeight) / 2
+                let previewY = accessoryHeight + (richDraftSlotHeight - richDraftPreviewHeight) / 2
                 current.frame = NSMakeRect(textLeftInset, previewY, width, richDraftPreviewHeight)
             }
         } else if let view = richDraftPreview {
@@ -490,8 +495,7 @@ public final class ChatInputContainerView: FlippableView {
                 }
             }
             textView.isHidden = true
-            let slot = max(richDraftPreviewHeight, CGFloat(textView.min_height))
-            let previewY = textY + (slot - richDraftPreviewHeight) / 2
+            let previewY = textY + (richDraftSlotHeight - richDraftPreviewHeight) / 2
             transition.updateFrame(view: preview, frame: NSMakeRect(textLeftInset, previewY, textSize.width, richDraftPreviewHeight))
         } else {
             textView.isHidden = false
@@ -519,7 +523,14 @@ public final class ChatInputContainerView: FlippableView {
             }
             let bs = current.frame.size
             let sendColumnMidX = containerWidth - ChatInputSendButton.fieldInset - sendWidth / 2
-            let frame = NSMakeRect(sendColumnMidX - bs.width / 2, accessoryHeight + 8, bs.width, bs.height)
+            let stackedY = accessoryHeight + 8
+            let frame: NSRect
+            if richDraftPreview != nil, sendButton.isInField, stackedY + bs.height > contentHeight - sendSize.height {
+                let slot = actionsView.entertaiments.frame.size
+                frame = NSMakeRect(fieldContentWidth - (slot.width + bs.width) / 2, contentHeight - (slot.height + bs.height) / 2, bs.width, bs.height)
+            } else {
+                frame = NSMakeRect(sendColumnMidX - bs.width / 2, stackedY, bs.width, bs.height)
+            }
             if isNew {
                 current.frame = frame
             } else {