Shift the entire screen up by one scanline

twvd · Nov 29, 2023 · 6f2bde7 · 6f2bde7
1 parent b3ab5ee
commit 6f2bde7
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Showing 2 changed files with 16 additions and 6 deletions.
diff --git a/src/snes/ppu/mod.rs b/src/snes/ppu/mod.rs
@@ -22,6 +22,9 @@ use tile::{Tile, TILE_HEIGHT, TILE_WIDTH};
 pub const SCREEN_WIDTH: usize = 8 * 32;
 pub const SCREEN_HEIGHT: usize = 8 * 28;
 
+// The entire screen should be shifted up by 1 scanline
+const SCANLINE_OUTPUT_OFFSET: isize = -1;
+
 type VramWord = u16;
 const VRAM_WORDS: usize = 32 * 1024;
 const VRAM_WORDSIZE: usize = 2;
@@ -467,8 +470,11 @@ where
                 }
             } else {
                 self.vblank = false;
-                if self.last_scanline < SCREEN_HEIGHT {
-                    self.render_scanline(self.last_scanline);
+                if (self.last_scanline as isize)
+                    < ((SCREEN_HEIGHT as isize) - SCANLINE_OUTPUT_OFFSET)
+                    && (self.last_scanline as isize) + SCANLINE_OUTPUT_OFFSET >= 0
+                {
+                    self.render_scanline(self.last_scanline, SCANLINE_OUTPUT_OFFSET);
                 }
             }
         }

diff --git a/src/snes/ppu/render.rs b/src/snes/ppu/render.rs
@@ -275,7 +275,7 @@ where
         state
     }
 
-    pub fn render_scanline(&mut self, scanline: usize) {
+    pub fn render_scanline(&mut self, scanline: usize, output_offset: isize) {
         let windows = self.render_windows();
         let mainscreen = self.render_scanline_screen(
             scanline,
@@ -299,12 +299,13 @@ where
         );
 
         // Send line to screen buffer
+        let output_line = usize::try_from((scanline as isize) + output_offset).unwrap();
         let brightness = (self.inidisp & 0x0F) as usize;
         for x in 0..mainscreen.paletted.len() {
             if brightness == 0 || self.inidisp & 0x80 != 0 {
                 // Force blank or no brightness
                 self.renderer
-                    .set_pixel(x, scanline, SnesColor::BLACK.to_native());
+                    .set_pixel(x, output_line, SnesColor::BLACK.to_native());
                 continue;
             }
 
@@ -318,8 +319,11 @@ where
             );
 
             // Apply master brightness and output
-            self.renderer
-                .set_pixel(x, scanline, pixel.apply_brightness(brightness).to_native());
+            self.renderer.set_pixel(
+                x,
+                output_line,
+                pixel.apply_brightness(brightness).to_native(),
+            );
         }
     }