DeskTop: Increase buffer overlay size to 16k

Allows preview DAs (Font, Electric Duet) and Find Files to have bigger
buffers for files.

desk.acc/API.md

@@ -183,7 +183,7 @@ highlighted in DeskTop. This can be done by copying the full path to
 * If the DA uses the text or lores screens, it *must* save the visible
   bytes on entry and restore them on exit, and *must not* modify the
   screen holes.
-* DAs can overwrite 10k of Main memory normally used for DeskTop code
+* DAs can overwrite 16k of Main memory normally used for DeskTop code
   that isn't used while a DA is running (e.g. command logic). This is
   at `OVERLAY_BUFFER` and the size is `kOverlayBufferSize`. To
   restore DeskTop, the DA *must* call DeskTop's `JUMP_TABLE_RESTORE_OVL`

desk.acc/show.duet.file.s

@@ -50,7 +50,7 @@
 ;;;
 
 ;;; There is not enough room in the DA load area to hold 6k of audio
-;;; data. A 10k buffer is available in DeskTop itself, in an area
+;;; data. A larger buffer is available in DeskTop itself, in an area
 ;;; that can be restored after use.
 data_buf        := OVERLAY_BUFFER
 kReadLength      = kOverlayBufferSize

desk.acc/show.image.file.s

@@ -226,13 +226,13 @@ slideshow_counter:
 
 ;;; ============================================================
 
-restore_10k_overlay_flag:
+restore_buffer_overlay_flag:
         .byte   0
 
 .proc Exit
         jsr     MaybeCallExitHook
 
-        bit     restore_10k_overlay_flag
+        bit     restore_buffer_overlay_flag
     IF_NS
         lda     #kDynamicRoutineRestoreBuffer
         jsr     JUMP_TABLE_RESTORE_OVL
@@ -394,7 +394,7 @@ signature:
 .proc ShowLZ4FHFile
         sta     PAGE2OFF
 
-        copy    #$80, restore_10k_overlay_flag
+        copy    #$80, restore_buffer_overlay_flag
         copy16  #OVERLAY_BUFFER, read_params::data_buffer
         JUMP_TABLE_MLI_CALL READ, read_params
         copy16  #$2000, read_params::data_buffer

desk.acc/sort.directory.s

@@ -59,7 +59,7 @@
         MLIEntry := MLI
 
 ;;; There is not enough room in the DA load area to a directory with
-;;; 127 entries, the maximum number of icons DeskTop can handle. A 10k
+;;; 127 entries, the maximum number of icons DeskTop can handle. A
 ;;; buffer is available in DeskTop itself, in an area that can be
 ;;; restored after use.
 dir_data_buffer         := OVERLAY_BUFFER

desktop/desktop.inc

@@ -27,11 +27,11 @@ kDAMaxSize      = DA_IO_BUFFER - DA_LOAD_ADDRESS
 ;;; Used by DAs for window definitions
 DEFAULT_FONT    := $8600
 
-;;; A 10k buffer that can be restored using overlays; load
+;;; A 16k buffer that can be restored using overlays; load
 ;;; `kDynamicRoutineRestoreBuffer` and call `JUMP_TABLE_RESTORE_OVL`
 ;;; to restore DeskTop afterwards.
 OVERLAY_BUFFER      := $5000
-kOverlayBufferSize   = $2800
+kOverlayBufferSize   = $4000
 
 ;;; DAs must start with a header declaring sizes of the two
 ;;; segments (aux and main).