make text entry work when empty

docs/TODO_ux.md

@@ -68,6 +68,7 @@
 - speed
 	- make polygon store points and indices efficiently
 	- change ezgui API to allow uploading geometry once
+	- experiment with batching and not passing colors
 	- measure performance of huge maps
 - quality
 	- need padding around text

ezgui/src/text.rs

@@ -128,14 +128,15 @@ impl Text {
                     so_far.push_str(&span.text);
                     so_far
                 });
+                // Empty lines or whitespace-only lines effectively have 0 width.
                 glyphs
                     .pixel_bounds(Section {
                         text: &full_line,
                         scale: Scale::uniform(FONT_SIZE),
                         ..Section::default()
                     })
-                    .expect("can't get text dims of a whitespace-only span")
-                    .width()
+                    .map(|rect| rect.width())
+                    .unwrap_or(0)
             })
             .max()
             .unwrap() as f64;

ezgui/src/text_box.rs

@@ -28,12 +28,12 @@ impl TextBox {
 
         txt.add_line(self.line[0..self.cursor_x].to_string());
         if self.cursor_x < self.line.len() {
-            // TODO This bit was highlighted
+            // TODO This "cursor" looks awful!
+            txt.append("|".to_string(), Some(text::SELECTED_COLOR));
             txt.append(self.line[self.cursor_x..=self.cursor_x].to_string(), None);
             txt.append(self.line[self.cursor_x + 1..].to_string(), None);
         } else {
-            // TODO This bit was highlighted
-            txt.append(" ".to_string(), None);
+            txt.append("|".to_string(), Some(text::SELECTED_COLOR));
         }
 
         canvas.draw_blocking_text(g, txt, CENTERED);