2 files changed, 44 insertions, 33 deletions

diff --git a/gflib/bg.c b/gflib/bg.c
index c3a4be1d4..c96bcbc23 100644
--- a/gflib/bg.c
+++ b/gflib/bg.c
@@ -776,75 +776,75 @@ void SetBgAffine(u8 bg, s32 srcCenterX, s32 srcCenterY, s16 dispCenterX, s16 dis
     SetBgAffineInternal(bg, srcCenterX, srcCenterY, dispCenterX, dispCenterY, scaleX, scaleY, rotationAngle);
 }
 
-u8 Unused_AdjustBgMosaic(u8 a1, u8 a2)
+u8 Unused_AdjustBgMosaic(u8 val, u8 mode)
 {
-    u16 result = GetGpuReg(REG_OFFSET_MOSAIC);
-    s16 test1 = result & 0xF;
-    s16 test2 = (result >> 4) & 0xF;
+    u16 mosaic = GetGpuReg(REG_OFFSET_MOSAIC);
+    s16 bgH = mosaic & 0xF;
+    s16 bgV = (mosaic >> 4) & 0xF;
 
-    result &= 0xFF00;
+    mosaic &= 0xFF00; // clear background mosaic sizes
 
-    switch (a2)
+    switch (mode)
     {
-    case 0:
+    case BG_MOSAIC_SET_HV:
     default:
-        test1 = a1 & 0xF;
-        test2 = a1 >> 0x4;
+        bgH = val & 0xF;
+        bgV = val >> 0x4;
         break;
-    case 1:
-        test1 = a1 & 0xF;
+    case BG_MOSAIC_SET_H:
+        bgH = val & 0xF;
         break;
-    case 2:
-        if ((test1 + a1) > 0xF)
+    case BG_MOSAIC_ADD_H:
+        if ((bgH + val) > 0xF)
         {
-            test1 = 0xF;
+            bgH = 0xF;
         }
         else
         {
-            test1 += a1;
+            bgH += val;
         }
         break;
-    case 3:
-        if ((test1 - a1) < 0)
+    case BG_MOSAIC_SUB_H:
+        if ((bgH - val) < 0)
         {
-            test1 = 0x0;
+            bgH = 0x0;
         }
         else
         {
-            test1 -= a1;
+            bgH -= val;
         }
         break;
-    case 4:
-        test2 = a1 & 0xF;
+    case BG_MOSAIC_SET_V:
+        bgV = val & 0xF;
         break;
-    case 5:
-        if ((test2 + a1) > 0xF)
+    case BG_MOSAIC_ADD_V:
+        if ((bgV + val) > 0xF)
         {
-            test2 = 0xF;
+            bgV = 0xF;
         }
         else
         {
-            test2 += a1;
+            bgV += val;
         }
         break;
-    case 6:
-        if ((test2 - a1) < 0)
+    case BG_MOSAIC_SUB_V:
+        if ((bgV - val) < 0)
         {
-            test2 = 0x0;
+            bgV = 0x0;
         }
         else
         {
-            test2 -= a1;
+            bgV -= val;
         }
         break;
     }
 
-    result |= ((test2 << 0x4) & 0xF0);
-    result |= (test1 & 0xF);
+    mosaic |= ((bgV << 0x4) & 0xF0);
+    mosaic |= (bgH & 0xF);
 
-    SetGpuReg(REG_OFFSET_MOSAIC, result);
+    SetGpuReg(REG_OFFSET_MOSAIC, mosaic);
 
-    return result;
+    return mosaic;
 }
 
 void SetBgTilemapBuffer(u8 bg, void *tilemap)
diff --git a/gflib/bg.h b/gflib/bg.h
index 3a0bf3bf9..d8b5a5404 100644
--- a/gflib/bg.h
+++ b/gflib/bg.h
@@ -28,6 +28,17 @@ enum {
 	BG_COORD_SUB,
 };
 
+// Modes for Unused_AdjustBgMosaic
+enum {
+    BG_MOSAIC_SET_HV,
+    BG_MOSAIC_SET_H,
+    BG_MOSAIC_ADD_H,
+    BG_MOSAIC_SUB_H,
+    BG_MOSAIC_SET_V,
+    BG_MOSAIC_ADD_V,
+    BG_MOSAIC_SUB_V,
+};
+
 struct BgTemplate
 {
     u16 bg:2;                   // 0x1, 0x2 -> 0x3