From 5e7a4290b22c5bba0e1578b16dc190835be34a87 Mon Sep 17 00:00:00 2001
From: Sebastian Leonhardt <sebastian.leonhardt@web.de>
Date: Thu, 20 Nov 2025 22:43:28 +0100
Subject: [PATCH] rockboy: fix wrong colors on some targets

This bug was found and located by a forum user, see
https://forums.rockbox.org/index.php/topic,54776.0.html

The old code used the FB_SCALARPACK macro which doesn't
respect swapped byte order.
Using FB_RGBPACK fixes it and furthermore makes the
fb.cc[] array superfluous.
I added a small optimization for 16 bit targets, since
the gameboy colors almost fit perfectly (5 bit per color).

Change-Id: If96b3943cb4ab902b880ff3d471add25e138fe8e
---
 apps/plugins/rockboy/fb.h          |  7 +------
 apps/plugins/rockboy/lcd.c         | 22 ++++++++++++----------
 apps/plugins/rockboy/sys_rockbox.c | 18 +-----------------
 3 files changed, 14 insertions(+), 33 deletions(-)

diff --git a/apps/plugins/rockboy/fb.h b/apps/plugins/rockboy/fb.h
index 96de665d14..bf5de413f3 100644
--- a/apps/plugins/rockboy/fb.h
+++ b/apps/plugins/rockboy/fb.h
@@ -10,12 +10,7 @@
 
 struct fb
 {
-#ifdef HAVE_LCD_COLOR
-    struct
-    {
-        int l, r;
-    } cc[3];
-#else
+#ifndef HAVE_LCD_COLOR
     int mode;
 #endif
     int enabled;
diff --git a/apps/plugins/rockboy/lcd.c b/apps/plugins/rockboy/lcd.c
index c53df5ce01..4976a4c036 100644
--- a/apps/plugins/rockboy/lcd.c
+++ b/apps/plugins/rockboy/lcd.c
@@ -1020,21 +1020,23 @@ static void updatepalette(int i)
     fb_data px;
 
     c = (lcd.pal[i<<1] | ((int)lcd.pal[(i<<1)|1] << 8)) & 0x7FFF;
+#if LCD_PIXELFORMAT == RGB565 || LCD_PIXELFORMAT == RGB565SWAPPED
+    /* extract color channels to 5 bit red and blue, and 6 bit green */
+    r = c & 0x001F;
+    g = (c & 0x03E0) >> 4;
+    b = c >> 10;
+    g |= (g >> 5);
+    px = FB_RGBPACK_LCD(r, g, b);
+#else
+    /* extract color channels and normalize to 8-bit */
     r = (c & 0x001F) << 3;
     g = (c & 0x03E0) >> 2;
-    b = (c & 0x7C00) >> 7;
+    b = c >> 7;
     r |= (r >> 5);
     g |= (g >> 5);
     b |= (b >> 5);
-
-    r = (r >> fb.cc[0].r) << fb.cc[0].l;
-    g = (g >> fb.cc[1].r) << fb.cc[1].l;
-    b = (b >> fb.cc[2].r) << fb.cc[2].l;
-
-    c = r|g|b;
-
-    px = FB_SCALARPACK_LCD(c);
-
+    px = FB_RGBPACK(r, g, b);
+#endif
     /* updatepalette might get called, but the pallete does not necessarily
      *  need to be updated.
      */
diff --git a/apps/plugins/rockboy/sys_rockbox.c b/apps/plugins/rockboy/sys_rockbox.c
index 64acd37563..b74370b815 100644
--- a/apps/plugins/rockboy/sys_rockbox.c
+++ b/apps/plugins/rockboy/sys_rockbox.c
@@ -255,23 +255,7 @@ void vid_init(void)
 {
     fb.enabled=1;
 
-#if defined(HAVE_LCD_COLOR)
-#if LCD_DEPTH >= 24
-    fb.cc[0].r = 0;  /* 8-8 (wasted bits on red) */
-    fb.cc[0].l = 16; /* this is the offset to the R bits (24-8) */
-    fb.cc[1].r = 0;  /* 8-6 (wasted bits on green) */
-    fb.cc[1].l = 8;  /* This is the offset to the G bits (24-8-8) */
-    fb.cc[2].r = 0;  /* 8-5 (wasted bits on red) */
-    fb.cc[2].l = 0;  /* This is the offset to the B bits (24-8-8-8) */
-#else
-    fb.cc[0].r = 3;  /* 8-5 (wasted bits on red) */
-    fb.cc[0].l = 11; /* this is the offset to the R bits (16-5) */
-    fb.cc[1].r = 2;  /* 8-6 (wasted bits on green) */
-    fb.cc[1].l = 5;  /* This is the offset to the G bits (16-5-6) */
-    fb.cc[2].r = 3;  /* 8-5 (wasted bits on red) */
-    fb.cc[2].l = 0;  /* This is the offset to the B bits (16-5-6-5) */
-#endif
-#else
+#if !defined(HAVE_LCD_COLOR)
     fb.mode=3;
 #endif
 }