[cache] Optimize SBit copying.

* src/cache/ftcsbits.c (ftc_snode_load): Do not initialize the buffer.
(ftc_sbit_copy_bitmap): Accept zero size, s/FT_ALLOC/FT_QALLOC/.

ChangeLog

@@ -1,3 +1,10 @@
+2021-04-22  Alexei Podtelezhnikov  <apodtele@gmail.com>
+
+	[cache] Optimize SBit copying.
+
+	* src/cache/ftcsbits.c (ftc_snode_load): Do not initialize the buffer.
+	(ftc_sbit_copy_bitmap): Accept zero size, s/FT_ALLOC/FT_QALLOC/.
+
 2021-04-22  Alexei Podtelezhnikov  <apodtele@gmail.com>
 
 	[gxvalid,otvalid] s/FT_ALLOC/FT_QALLOC/ for initialized buffers.

src/cache/ftcsbits.c

@@ -52,10 +52,8 @@
       pitch = -pitch;
 
     size = (FT_ULong)pitch * bitmap->rows;
-    if ( !size )
-      return FT_Err_Ok;
 
-    if ( !FT_ALLOC( sbit->buffer, size ) )
+    if ( !FT_QALLOC( sbit->buffer, size ) )
       FT_MEM_COPY( sbit->buffer, bitmap->buffer, size );
 
     return error;
@@ -122,8 +120,6 @@
     sbit  = snode->sbits + ( gindex - gnode->gindex );
     clazz = (FTC_SFamilyClass)family->clazz;
 
-    sbit->buffer = NULL;
-
     error = clazz->family_load_glyph( family, gindex, manager, &face );
     if ( error )
       goto BadGlyph;