From d15d5599ab01ac1774f879d92dbec71e2654741e Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Thu, 20 Apr 2023 09:20:44 +0200
Subject: Add dirty tiles to screen fill functions

---
 src/ppu.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/ppu.c b/src/ppu.c
index 8e1710c..1d29725 100644
--- a/src/ppu.c
+++ b/src/ppu.c
@@ -247,11 +247,20 @@ ppu_pixel(u32 *layer, u16 x, u16 y, u8 clr) {
     dirty_tiles[tile_y] |= 1 << tile_x;
 }
 
+static inline
+void
+redraw(void) {
+    for (size_t i = 0; i < 21; i++) {
+        dirty_tiles[i] = 0xFFFFFFFF;
+    }
+}
+
 IWRAM_CODE
 void clear_screen(u32 *layer, u8 clr)  {
     // We have to make sure we leave the last tile blank to use as alpha channel
     // when moving the BG during double buffering in case we are using that.
     dma_fill(layer, 0x11111111 * clr, KB(20) - 32, 3);
+    redraw();
 }
 
 IWRAM_CODE
@@ -267,6 +276,7 @@ draw_hline(u32 *layer, size_t x0, size_t x1, size_t y0, u8 clr) {
     size_t start_col = x0 % 8;
     size_t end_col = x1 % 8;
     size_t start_row = y0 % 8;
+    u32 dirtyflag = (1 << tile_x0) | (1 << tile_x1);
 
     // Horizontal line. There are 3 cases:
     //     1. Lines fit on a single tile.
@@ -290,11 +300,14 @@ draw_hline(u32 *layer, size_t x0, size_t x1, size_t y0, u8 clr) {
         *dst = (*dst & ~(mask << shift_left)) | (row << shift_left);
         dst += 8;
         for (size_t i = 1; i < dtx; i++) {
+            dirtyflag |= (1 << (tile_x0 + i));
             *dst = row;
             dst += 8;
         }
         *dst = (*dst & ~(mask >> shift_right)) | (row >> shift_right);
     }
+
+    dirty_tiles[tile_y] |= dirtyflag;
 }
 
 IWRAM_CODE
@@ -314,7 +327,6 @@ screen_fill(u32 *layer, u16 x0, u16 y0, u16 x1, u16 y1, u8 clr) {
     for (size_t y = y0; y <= y1; y++) {
         draw_hline(layer, x0, x1, y, clr);
     }
-    // TODO: dirty?
 }
 
 #if NEW_PPU == 0
@@ -731,13 +743,6 @@ flipbuf(Ppu *p) {
     }
 }
 
-void
-redraw(void) {
-    for (size_t i = 0; i < 21; i++) {
-        dirty_tiles[i] = 0xFFFFFFFF;
-    }
-}
-
 typedef struct KeyboardChar {
     int x;
     int y;
-- 
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