fix(block): make inner aware of title positions (#657)

Previously, when computing the inner rendering area of a block, all
titles were assumed to be positioned at the top, which caused the
height of the inner area to be miscalculated.

src/widgets/block.rs

@@ -508,14 +508,15 @@ impl<'a> Block<'a> {
             inner.x = inner.x.saturating_add(1).min(inner.right());
             inner.width = inner.width.saturating_sub(1);
         }
-        if self.borders.intersects(Borders::TOP) || !self.titles.is_empty() {
+        if self.borders.intersects(Borders::TOP) || self.have_title_at_position(Position::Top) {
             inner.y = inner.y.saturating_add(1).min(inner.bottom());
             inner.height = inner.height.saturating_sub(1);
         }
         if self.borders.intersects(Borders::RIGHT) {
             inner.width = inner.width.saturating_sub(1);
         }
-        if self.borders.intersects(Borders::BOTTOM) {
+        if self.borders.intersects(Borders::BOTTOM) || self.have_title_at_position(Position::Bottom)
+        {
             inner.height = inner.height.saturating_sub(1);
         }
 
@@ -532,6 +533,12 @@ impl<'a> Block<'a> {
         inner
     }
 
+    fn have_title_at_position(&self, position: Position) -> bool {
+        self.titles
+            .iter()
+            .any(|title| title.position.unwrap_or(self.titles_position) == position)
+    }
+
     /// Defines the padding inside a `Block`.
     ///
     /// See [`Padding`] for more information.
@@ -939,6 +946,78 @@ mod tests {
         );
     }
 
+    #[test]
+    fn inner_takes_into_account_border_and_title() {
+        let test_rect = Rect::new(0, 0, 0, 2);
+
+        let top_top = Block::default()
+            .title(Title::from("Test").position(Position::Top))
+            .borders(Borders::TOP);
+        assert_eq!(top_top.inner(test_rect), Rect::new(0, 1, 0, 1));
+
+        let top_bot = Block::default()
+            .title(Title::from("Test").position(Position::Top))
+            .borders(Borders::BOTTOM);
+        assert_eq!(top_bot.inner(test_rect), Rect::new(0, 1, 0, 0));
+
+        let bot_top = Block::default()
+            .title(Title::from("Test").position(Position::Bottom))
+            .borders(Borders::TOP);
+        assert_eq!(bot_top.inner(test_rect), Rect::new(0, 1, 0, 0));
+
+        let bot_bot = Block::default()
+            .title(Title::from("Test").position(Position::Bottom))
+            .borders(Borders::BOTTOM);
+        assert_eq!(bot_bot.inner(test_rect), Rect::new(0, 0, 0, 1));
+    }
+
+    #[test]
+    fn have_title_at_position_takes_into_account_all_positioning_declarations() {
+        let block = Block::default();
+        assert!(!block.have_title_at_position(Position::Top));
+        assert!(!block.have_title_at_position(Position::Bottom));
+
+        let block = Block::default().title(Title::from("Test").position(Position::Top));
+        assert!(block.have_title_at_position(Position::Top));
+        assert!(!block.have_title_at_position(Position::Bottom));
+
+        let block = Block::default().title(Title::from("Test").position(Position::Bottom));
+        assert!(!block.have_title_at_position(Position::Top));
+        assert!(block.have_title_at_position(Position::Bottom));
+
+        let block = Block::default()
+            .title(Title::from("Test").position(Position::Top))
+            .title_position(Position::Bottom);
+        assert!(block.have_title_at_position(Position::Top));
+        assert!(!block.have_title_at_position(Position::Bottom));
+
+        let block = Block::default()
+            .title(Title::from("Test").position(Position::Bottom))
+            .title_position(Position::Top);
+        assert!(!block.have_title_at_position(Position::Top));
+        assert!(block.have_title_at_position(Position::Bottom));
+
+        let block = Block::default()
+            .title(Title::from("Test").position(Position::Top))
+            .title(Title::from("Test").position(Position::Bottom));
+        assert!(block.have_title_at_position(Position::Top));
+        assert!(block.have_title_at_position(Position::Bottom));
+
+        let block = Block::default()
+            .title(Title::from("Test").position(Position::Top))
+            .title(Title::from("Test"))
+            .title_position(Position::Bottom);
+        assert!(block.have_title_at_position(Position::Top));
+        assert!(block.have_title_at_position(Position::Bottom));
+
+        let block = Block::default()
+            .title(Title::from("Test"))
+            .title(Title::from("Test").position(Position::Bottom))
+            .title_position(Position::Top);
+        assert!(block.have_title_at_position(Position::Top));
+        assert!(block.have_title_at_position(Position::Bottom));
+    }
+
     #[test]
     fn border_type_can_be_const() {
         const _PLAIN: border::Set = BorderType::border_symbols(BorderType::Plain);

src/widgets/paragraph.rs

@@ -295,7 +295,7 @@ mod test {
         backend::TestBackend,
         style::{Color, Modifier, Stylize},
         text::{Line, Span},
-        widgets::Borders,
+        widgets::{block::Position, Borders},
         Terminal,
     };
 
@@ -478,6 +478,20 @@ mod test {
         );
     }
 
+    #[test]
+    fn test_render_paragraph_with_block_with_bottom_title_and_border() {
+        let block = Block::default()
+            .title("Title")
+            .title_position(Position::Bottom)
+            .borders(Borders::BOTTOM);
+        let paragraph = Paragraph::new("Hello, world!").block(block);
+
+        test_case(
+            &paragraph,
+            Buffer::with_lines(vec!["Hello, world!  ", "Title──────────"]),
+        );
+    }
+
     #[test]
     fn test_render_paragraph_with_word_wrap() {
         let text = "This is a long line of text that should wrap      and contains a superultramegagigalong word.";