fix the overflow bug on kerning / xmin on a new sprite (#725)

- [x] Changelog updated

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Affine background center position didn't work outside of the upper left quadrant of the gba's screen.
 - Fixed backtrace pointing to the wrong line of code (being out by one).
+- Fixes overflow caused by certain font characteristics on boundaries of sprites in the object text renderer.
 
 ## [0.20.2] - 2024/05/25
 

agb/src/display/object/font/preprocess.rs

@@ -86,8 +86,12 @@ impl Preprocessor {
                     );
                     self.width_in_sprite = 0;
                 }
-                if self.width_in_sprite != 0 {
-                    self.width_in_sprite += letter.xmin as i32;
+                self.width_in_sprite += letter.xmin as i32;
+                if self.width_in_sprite < 0 {
+                    if let Some(back) = widths.back_mut() {
+                        back.0 -= (-self.width_in_sprite).try_into().unwrap_or(0);
+                    }
+                    self.width_in_sprite = 0;
                 }
                 self.width_in_sprite += letter.advance_width as i32;
             }

agb/src/display/object/font/renderer.rs

@@ -99,9 +99,8 @@ impl WordRender {
             None
         };
 
-        if self.working.x_offset != 0 {
-            self.working.x_offset += font_letter.xmin as i32;
-        }
+        self.working.x_offset += font_letter.xmin as i32;
+        self.working.x_offset = self.working.x_offset.max(0);
 
         let y_position = font.ascent() - font_letter.height as i32 - font_letter.ymin as i32;