put_line/scrolling: Make the scroll engine inform custom scrollers about start/stop of scrolling.

With the new lcd_putsxy_scroll_func() code can register custom scroll functions
(put_line() makes use of that). In order for the custom scroller to be able
to properly manage its userdata pointer (set via struct scrollinfo::userdata)
the scroll engine must inform the scroller about start and stop of scrolling.

To inform about start the lcd_scroll_* functions now return true when
the line will scroll. To inform about stop the scroll engine calls into the
scroller one last time, with the text set to NULL.

put_line() can use this to release the userdata registered per scrolling line
so that it can be recycled.

This fixes that some scrolling lines became glitchy after some time because
the userdata was recycled too early.

Change-Id: Iff0a6ce2a4f9ae2bada1b8e62f4f5950224942a9

1 files changed, 2 insertions, 2 deletions

diff --git a/apps/screen_access.h b/apps/screen_access.h
index 7efc38b174..c4a87849b8 100644
--- a/apps/screen_access.h
+++ b/apps/screen_access.h
@@ -126,8 +126,8 @@ struct screen
     void (*putsxy)(int x, int y, const unsigned char *str);
     void (*puts)(int x, int y, const unsigned char *str);
     void (*putsf)(int x, int y, const unsigned char *str, ...);
-    void (*puts_scroll)(int x, int y, const unsigned char *string);
-    void (*putsxy_scroll_func)(int x, int y, const unsigned char *string,
+    bool (*puts_scroll)(int x, int y, const unsigned char *string);
+    bool (*putsxy_scroll_func)(int x, int y, const unsigned char *string,
                                void (*scroll_func)(struct scrollinfo *),
                                void *data, int x_offset);
     void (*scroll_speed)(int speed);