- Added some asserts to drawgfx and drawgfxzoom

- Moved some variable declerations so that they are only visible where they are actually used

Note that the diff is large only because I removed a level of indentation from a huge chunk of code.
I could do that because the case it was checking for was already caught by one of the asserts added.

src/emu/drawgfx.c

@@ -1340,13 +1340,11 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 		const rectangle *clip,int transparency,int transparent_color,
 		int scalex, int scaley,mame_bitmap *pri_buffer,UINT32 pri_mask)
 {
-	rectangle myclip;
+	/* verify arguments */
+	assert(dest_bmp != NULL);
+	assert(gfx != NULL);
 
-	UINT8 ah, al;
+	if ((scalex == 0) || (scaley == 0)) return;
-
-	al = (pdrawgfx_shadow_lowpri) ? 0 : 0x80;
-
-	if (!scalex || !scaley) return;
 
 	if (scalex == 0x10000 && scaley == 0x10000)
 	{
@@ -1372,6 +1370,8 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 	/* force clip to bitmap boundary */
 	if (clip)
 	{
+		rectangle myclip;
+
 		myclip.min_x = clip->min_x;
 		myclip.max_x = clip->max_x;
 		myclip.min_y = clip->min_y;
@@ -1388,8 +1388,6 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 
 	/* 8-bit destination bitmap */
 	if (dest_bmp->bpp == 8)
-	{
-		if( gfx )
 	{
 		UINT32 palbase = gfx->color_base + gfx->color_granularity * (color % gfx->total_colors);
 		UINT8 *source_base = gfx->gfxdata + (code % gfx->total_elements) * gfx->char_modulo;
@@ -1409,7 +1407,7 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 			int x_index_base;
 			int y_index;
 
-				if( flipx )
+			if (flipx )
 			{
 				x_index_base = (sprite_screen_width-1)*dx;
 				dx = -dx;
@@ -1740,6 +1738,8 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 					pen_t *palette_shadow_table = Machine->shadow_table;
 					if (pri_buffer)
 					{
+						UINT8 al = (pdrawgfx_shadow_lowpri) ? 0 : 0x80;
+
 						for( y=sy; y<ey; y++ )
 						{
 							UINT8 *source = source_base + (y_index>>16) * gfx->line_modulo;
@@ -1810,12 +1810,9 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 			}
 		}
 	}
-	}
 
 	/* 16-bit destination bitmap */
 	else if (dest_bmp->bpp == 16)
-	{
-		if( gfx )
 	{
 		const pen_t *pal = &Machine->pens[gfx->color_base + gfx->color_granularity * (color % gfx->total_colors)];
 		UINT8 *source_base = gfx->gfxdata + (code % gfx->total_elements) * gfx->char_modulo;
@@ -2167,6 +2164,8 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 					pen_t *palette_shadow_table = Machine->shadow_table;
 					if (pri_buffer)
 					{
+						UINT8 al = (pdrawgfx_shadow_lowpri) ? 0 : 0x80;
+
 						for( y=sy; y<ey; y++ )
 						{
 							UINT8 *source = source_base + (y_index>>16) * gfx->line_modulo;
@@ -2179,6 +2178,8 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 								int c = source[x_index>>16];
 								if( c != transparent_color )
 								{
+									UINT8 ah;
+
 									switch(gfx_drawmode_table[c])
 									{
 									case DRAWMODE_SOURCE:
@@ -2344,12 +2345,9 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 			}
 		}
 	}
-	}
 
 	/* 32-bit destination bitmap */
 	else
-	{
-		if( gfx )
 	{
 		const pen_t *pal = &Machine->pens[gfx->color_base + gfx->color_granularity * (color % gfx->total_colors)];
 		UINT8 *source_base = gfx->gfxdata + (code % gfx->total_elements) * gfx->char_modulo;
@@ -2611,6 +2609,7 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 					UINT8 *source, *pri;
 					UINT32 *dest;
 					int c, x, x_index;
+					UINT8 al, ah;
 
 					if (pri_buffer)
 					{
@@ -2786,7 +2785,6 @@ INLINE void common_drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
 			}
 		}
 	}
-	}
 }
 
 void drawgfxzoom( mame_bitmap *dest_bmp,const gfx_element *gfx,
@@ -3766,6 +3764,9 @@ DECLARE(drawgfx_core,(
 	int ex;
 	int ey;
 
+	/* verify arguments */
+	assert(dest != NULL);
+	assert(gfx != NULL);
 
 	/* check bounds */
 	ox = sx;