core: Fix caret and selection rendering

This commit fixes issues with caret and selection rendering:
1. They had the wrong height and were rendered lower than expected
   for some fonts and sizes.
2. The caret was not being rendered at all when there was no text,
   but only when the text was set earlier and then deleted.
3. The selection was rendered with translate_x=-1,
   which caused overlap over some glyphs.

core/src/display_object/edit_text.rs

@@ -934,7 +934,7 @@ impl<'gc> EditText<'gc> {
                     && visible_selection.end() <= *end
                     && Utc::now().timestamp_subsec_millis() / 500 == 0
                 {
-                    Some((visible_selection.start() - start, end - start))
+                    Some(visible_selection.start() - start)
                 } else {
                     None
                 }
@@ -958,8 +958,11 @@ impl<'gc> EditText<'gc> {
         if let Some((text, _tf, font, params, color)) =
             lbox.as_renderable_text(edit_text.text_spans.displayed_text())
         {
-            let baseline_adjustment =
+            let baseline = font.get_baseline_for_height(params.height());
-                font.get_baseline_for_height(params.height()) - params.height();
+            let descent = font.get_descent_for_height(params.height());
+            let baseline_adjustment = baseline - params.height();
+            let caret_height = baseline + descent;
+            let mut caret_x = Twips::ZERO;
             font.evaluate(
                 text,
                 self.text_transform(color, baseline_adjustment),
@@ -967,29 +970,18 @@ impl<'gc> EditText<'gc> {
                 |pos, transform, glyph: &Glyph, advance, x| {
                     if let Some(glyph_shape_handle) = glyph.shape_handle(context.renderer) {
                         // If it's highlighted, override the color.
-                        match visible_selection {
+                        if matches!(visible_selection, Some(visible_selection) if visible_selection.contains(start + pos)) {
-                            Some(visible_selection) if visible_selection.contains(start + pos) => {
                             // Draw black selection rect
-                                let selection_box = context.transform_stack.transform().matrix
+                            self.render_selection(context, x, advance, caret_height);
-                                    * Matrix::create_box(
-                                        advance.to_pixels() as f32,
-                                        params.height().to_pixels() as f32,
-                                        0.0,
-                                        x + Twips::from_pixels(-1.0),
-                                        Twips::from_pixels(2.0),
-                                    );
-                                context.commands.draw_rect(Color::BLACK, selection_box);
 
                             // Set text color to white
                             context.transform_stack.push(&Transform {
                                 matrix: transform.matrix,
                                 color_transform: ColorTransform::IDENTITY,
                             });
-                            }
+                        } else {
-                            _ => {
                             context.transform_stack.push(transform);
                         }
-                        }
 
                         // Render glyph.
                         context
@@ -998,31 +990,21 @@ impl<'gc> EditText<'gc> {
                         context.transform_stack.pop();
                     }
 
-                    if let Some((caret_pos, length)) = caret {
+                    // Update caret position
-                        if caret_pos == pos {
+                    if let Some(caret) = caret {
-                            let caret = context.transform_stack.transform().matrix
+                        if pos == caret {
-                                * Matrix::create_box(
+                            caret_x = x;
-                                    1.0,
+                        } else if caret > 0 && pos == caret - 1 {
-                                    params.height().to_pixels() as f32,
+                            // The caret may be rendered at the end, after all glyphs.
-                                    0.0,
+                            caret_x = x + advance;
-                                    x + Twips::from_pixels(-1.0),
-                                    Twips::from_pixels(2.0),
-                                );
-                            context.commands.draw_rect(color, caret);
-                        } else if pos == length - 1 && caret_pos == length {
-                            let caret = context.transform_stack.transform().matrix
-                                * Matrix::create_box(
-                                    1.0,
-                                    params.height().to_pixels() as f32,
-                                    0.0,
-                                    x + advance,
-                                    Twips::from_pixels(2.0),
-                                );
-                            context.commands.draw_rect(color, caret);
                         }
                     }
                 },
             );
+
+            if caret.is_some() {
+                self.render_caret(context, caret_x, caret_height, color);
+            }
         }
 
         if let Some(drawing) = lbox.as_renderable_drawing() {
@@ -1032,6 +1014,43 @@ impl<'gc> EditText<'gc> {
         context.transform_stack.pop();
     }
 
+    fn render_selection(
+        self,
+        context: &mut RenderContext<'_, 'gc>,
+        x: Twips,
+        width: Twips,
+        height: Twips,
+    ) {
+        let selection_box = context.transform_stack.transform().matrix
+            * Matrix::create_box(
+                width.to_pixels() as f32,
+                height.to_pixels() as f32,
+                0.0,
+                x,
+                Twips::ZERO,
+            );
+        context.commands.draw_rect(Color::BLACK, selection_box);
+    }
+
+    fn render_caret(
+        self,
+        context: &mut RenderContext<'_, 'gc>,
+        x: Twips,
+        height: Twips,
+        color: Color,
+    ) {
+        let cursor_width = Twips::from_pixels(1.0);
+        let caret = context.transform_stack.transform().matrix
+            * Matrix::create_box(
+                cursor_width.to_pixels() as f32,
+                height.to_pixels() as f32,
+                0.0,
+                x - cursor_width,
+                Twips::ZERO,
+            );
+        context.commands.draw_rect(color, caret);
+    }
+
     /// Attempts to bind this text field to a property of a display object.
     /// If we find a parent display object matching the given path, we register oursevles and a property name with it.
     /// `set_text` will be called by the stage object whenever the property changes.
@@ -1977,19 +1996,9 @@ impl<'gc> TDisplayObject<'gc> for EditText<'gc> {
                     && visible_selection.start() == 0
                     && Utc::now().timestamp_subsec_millis() / 500 == 0
                 {
-                    let caret = context.transform_stack.transform().matrix
+                    let format = edit_text.text_spans.default_format();
-                        * Matrix::create_box(
+                    let caret_height = format.size.map(Twips::from_pixels).unwrap_or_default();
-                            1.0,
+                    self.render_caret(context, Twips::ZERO, caret_height, Color::BLACK);
-                            edit_text
-                                .text_spans
-                                .default_format()
-                                .size
-                                .unwrap_or_default() as f32,
-                            0.0,
-                            Twips::from_pixels(-1.0),
-                            Twips::from_pixels(2.0),
-                        );
-                    context.commands.draw_rect(Color::BLACK, caret);
                 }
             }
         } else {