images: improve logging when things are weird

refs: #3366

term/src/terminalstate/image.rs

@@ -110,7 +110,7 @@ impl TerminalState {
         let first_row = self.screen().visible_row_to_stable_row(self.cursor.y);
 
         let mut ypos = NotNan::new(params.source_origin_y as f32 / params.image_height as f32)
-            .context("computing ypos")?;
+            .with_context(|| format!("computing ypos {params:#?}"))?;
         let start_xpos = NotNan::new(params.source_origin_x as f32 / params.image_width as f32)
             .context("computing xpos")?;
 
@@ -256,9 +256,13 @@ pub(crate) fn check_image_dimensions(width: u32, height: u32) -> anyhow::Result<
             SizeFormatter::new(MAX_IMAGE_SIZE, DECIMAL),
         );
     }
+    if size == 0 {
+        anyhow::bail!("Ignoring image with 0x0 dimensions");
+    }
     Ok(())
 }
 
+#[derive(Debug)]
 pub(crate) struct ImageInfo {
     pub width: u32,
     pub height: u32,

term/src/terminalstate/iterm.rs

@@ -35,7 +35,15 @@ impl TerminalState {
         };
 
         if let Err(err) = check_image_dimensions(info.width, info.height) {
-            log::error!("{}", err);
+            log::error!("{err:#}, {info:#?}");
+            return;
+        }
+
+        if self.pixel_width == 0 || self.pixel_height == 0 {
+            error!(
+                "my pixel dimensions are wacky! {}x{}",
+                self.pixel_width, self.pixel_height
+            );
             return;
         }