Add support for previewing images in room scrollback (#108)

src/message/mod.rs

@@ -51,7 +51,9 @@ use modalkit::tui::{
 };
 
 use modalkit::editing::{base::ViewportContext, cursor::Cursor};
+use ratatui_image::protocol::Protocol;
 
+use crate::config::ImagePreviewSize;
 use crate::{
     base::{IambResult, RoomInfo},
     config::ApplicationSettings,
@@ -585,12 +587,20 @@ impl<'a> MessageFormatter<'a> {
     }
 }
 
+pub enum ImageStatus {
+    None,
+    Downloading(ImagePreviewSize),
+    Loaded(Box<dyn Protocol>),
+    Error(String),
+}
+
 pub struct Message {
     pub event: MessageEvent,
     pub sender: OwnedUserId,
     pub timestamp: MessageTimeStamp,
     pub downloaded: bool,
     pub html: Option<StyleTree>,
+    pub image_preview: ImageStatus,
 }
 
 impl Message {
@@ -598,7 +608,14 @@ impl Message {
         let html = event.html();
         let downloaded = false;
 
-        Message { event, sender, timestamp, downloaded, html }
+        Message {
+            event,
+            sender,
+            timestamp,
+            downloaded,
+            html,
+            image_preview: ImageStatus::None,
+        }
     }
 
     pub fn reply_to(&self) -> Option<OwnedEventId> {
@@ -681,6 +698,36 @@ impl Message {
         }
     }
 
+    /// Get the image preview Protocol and x,y offset, based on get_render_format.
+    pub fn line_preview<'a>(
+        &'a self,
+        prev: Option<&Message>,
+        vwctx: &ViewportContext<MessageCursor>,
+        info: &'a RoomInfo,
+    ) -> Option<(&dyn Protocol, u16, u16)> {
+        let width = vwctx.get_width();
+        // The x position where get_render_format would render the text.
+        let x = (if USER_GUTTER + MIN_MSG_LEN <= width {
+            USER_GUTTER
+        } else {
+            0
+        } + 1) as u16;
+        // See get_render_format; account for possible "date" line.
+        let date_y = match &prev {
+            Some(prev) if !prev.timestamp.same_day(&self.timestamp) => 1,
+            _ => 0,
+        };
+        if let ImageStatus::Loaded(backend) = &self.image_preview {
+            return Some((backend.as_ref(), x, date_y));
+        } else if let Some(reply) = self.reply_to().and_then(|e| info.get_event(&e)) {
+            if let ImageStatus::Loaded(backend) = &reply.image_preview {
+                // The reply should be offset a bit:
+                return Some((backend.as_ref(), x + 2, date_y + 1));
+            }
+        }
+        None
+    }
+
     pub fn show<'a>(
         &'a self,
         prev: Option<&Message>,
@@ -791,6 +838,19 @@ impl Message {
                 msg.to_mut().push_str(" \u{2705}");
             }
 
+            if let Some(placeholder) = match &self.image_preview {
+                ImageStatus::None => None,
+                ImageStatus::Downloading(image_preview_size) => {
+                    Some(Message::placeholder_frame(Some("Downloading..."), image_preview_size))
+                },
+                ImageStatus::Loaded(backend) => {
+                    Some(Message::placeholder_frame(None, &backend.rect().into()))
+                },
+                ImageStatus::Error(err) => Some(format!("[Image error: {err}]\n")),
+            } {
+                msg.to_mut().insert_str(0, &placeholder);
+            }
+
             wrapped_text(msg, width, style)
         }
     }
@@ -803,6 +863,24 @@ impl Message {
         settings.get_user_span(self.sender.as_ref(), info)
     }
 
+    /// Before the image is loaded, already display a placeholder frame of the image size.
+    fn placeholder_frame(text: Option<&str>, image_preview_size: &ImagePreviewSize) -> String {
+        let ImagePreviewSize { width, height } = image_preview_size;
+        let mut placeholder = "\u{230c}".to_string();
+        placeholder.push_str(&" ".repeat(width - 2));
+        placeholder.push_str("\u{230d}\n");
+        placeholder.push(' ');
+        if let Some(text) = text {
+            placeholder.push_str(text);
+        }
+
+        placeholder.push_str(&"\n".repeat(height - 2));
+        placeholder.push('\u{230e}');
+        placeholder.push_str(&" ".repeat(width - 2));
+        placeholder.push_str("\u{230f}\n");
+        placeholder
+    }
+
     fn show_sender<'a>(
         &'a self,
         prev: Option<&Message>,