Return visible range as u32 range

src/rendering/mod.rs

@@ -111,20 +111,22 @@ where
                 .style
                 .height_mode
                 .calculate_displayed_row_range(&cursor);
-            let display_range_start = display_range.start;
-            let display_range_count = (display_range.end - display_range.start).saturating_as();
+            let display_range_start = display_range.start.saturating_as::<i32>();
+            let display_range_count = display_range.count() as u32;
             let display_size = Size::new(cursor.line_width(), display_range_count);
 
             let line_start = cursor.line_start();
 
             // FIXME: cropping isn't necessary for whole lines, but make sure not to blow up the
-            // binary size as well.
+            // binary size as well. We could also use a different way to consume invisible text.
             let mut display = display.clipped(&Rectangle::new(
                 line_start + Point::new(0, display_range_start),
                 display_size,
             ));
             if display_range_count == 0 {
+                // Display range can be empty if we are above, or below the visible text section
                 if anything_drawn {
+                    // We are below, so we won't be drawing anything else
                     let remaining_bytes = state.parser.as_str().len();
                     let consumed_bytes = self.text.len() - remaining_bytes;
 

src/style/height_mode.rs

@@ -202,7 +202,7 @@ impl HeightMode {
     /// If a line does not fully fit in the bounding box, some `HeightMode` options allow drawing
     /// partial lines. For a partial line, this function calculates, which rows of each character
     /// should be displayed.
-    pub(crate) fn calculate_displayed_row_range(self, cursor: &Cursor) -> Range<i32> {
+    pub(crate) fn calculate_displayed_row_range(self, cursor: &Cursor) -> Range<u32> {
         let overdraw = match self {
             HeightMode::Exact(overdraw) | HeightMode::ShrinkToText(overdraw) => overdraw,
             HeightMode::FitToText => VerticalOverdraw::Visible,

src/style/vertical_overdraw.rs

@@ -18,8 +18,8 @@ pub enum VerticalOverdraw {
 
 impl VerticalOverdraw {
     /// Calculate the range of rows of the current line that can be drawn.
-    pub(crate) fn calculate_displayed_row_range(self, cursor: &Cursor) -> Range<i32> {
-        let line_height = cursor.line_height().saturating_as::<i32>();
+    pub(crate) fn calculate_displayed_row_range(self, cursor: &Cursor) -> Range<u32> {
+        let line_height = cursor.line_height();
         match self {
             VerticalOverdraw::FullRowsOnly => {
                 if cursor.in_display_area() {
@@ -30,8 +30,9 @@ impl VerticalOverdraw {
             }
 
             VerticalOverdraw::Hidden => {
-                let offset_top = (cursor.top_left().y - cursor.y).max(0);
-                let offset_bottom = (cursor.bottom() - cursor.y).min(0) + line_height;
+                let offset_top = (cursor.top_left().y - cursor.y).saturating_as::<u32>();
+                let offset_bottom =
+                    line_height - (cursor.y - cursor.bottom()).saturating_as::<u32>();
 
                 offset_top..offset_bottom
             }