ssb: Working toward a more sensible unread indication and user interface for setting read/unread.

apps/ssb/tf-message.js

@@ -323,13 +323,13 @@ ${JSON.stringify(mention, null, 2)}</pre
 		}
 	}
 
-	mark_read() {
+	mark_unread() {
 		this.dispatchEvent(new CustomEvent('channelsetunread', {
 			bubbles: true,
 			composed: true,
 			detail: {
 				channel: this.channel,
-				unread: this.message.rowid + 1,
+				unread: this.message.rowid,
 			},
 		}));
 	}
@@ -640,9 +640,9 @@ ${JSON.stringify(content, null, 2)}</pre
 							<button class="w3-button w3-theme-d1" @click=${this.react}>
 								React
 							</button>
-							${!content.root ?
+							${(!content.root && this.message.rowid <= this.channel_unread) ?
 								html`
-									<button class="w3-button w3-theme-d1" @click=${this.mark_read}>Set Read Here</button>
+									<button class="w3-button w3-theme-d1" @click=${this.mark_unread}>Mark Unread</button>
 								` :
 								undefined}
 						</p>