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

3 files changed, 8 insertions, 5 deletions

diff --git a/firmware/export/lcd-remote.h b/firmware/export/lcd-remote.h
index bc26a23..1819a4d 100644
--- a/firmware/export/lcd-remote.h
+++ b/firmware/export/lcd-remote.h
@@ -176,8 +176,8 @@ extern void lcd_remote_clear_viewport(void);
 extern void lcd_remote_puts(int x, int y, const unsigned char *str);
 extern void lcd_remote_putsf(int x, int y, const unsigned char *fmt, ...);
 extern void lcd_remote_putc(int x, int y, unsigned short ch);
-extern void lcd_remote_puts_scroll(int x, int y, const unsigned char *str);
-extern void lcd_remote_putsxy_scroll_func(int x, int y, const unsigned char *string,
+extern bool lcd_remote_puts_scroll(int x, int y, const unsigned char *str);
+extern bool lcd_remote_putsxy_scroll_func(int x, int y, const unsigned char *string,
                                           void (*scroll_func)(struct scrollinfo *),
                                           void *data, int x_offset);
 
diff --git a/firmware/export/lcd.h b/firmware/export/lcd.h
index 87476d9..386ac5a 100644
--- a/firmware/export/lcd.h
+++ b/firmware/export/lcd.h
@@ -179,8 +179,8 @@ extern void lcd_putsxy_style_offset(int x, int y, const unsigned char *str,
 extern void lcd_puts(int x, int y, const unsigned char *string);
 extern void lcd_putsf(int x, int y, const unsigned char *fmt, ...);
 extern void lcd_putc(int x, int y, unsigned long ucs);
-extern void lcd_puts_scroll(int x, int y, const unsigned char* string);
-extern void lcd_putsxy_scroll_func(int x, int y, const unsigned char *string,
+extern bool lcd_puts_scroll(int x, int y, const unsigned char* string);
+extern bool lcd_putsxy_scroll_func(int x, int y, const unsigned char *string,
                                    void (*scroll_func)(struct scrollinfo *),
                                    void *data, int x_offset);
 
diff --git a/firmware/export/scroll_engine.h b/firmware/export/scroll_engine.h
index 64e1d6d..ce230a2 100644
--- a/firmware/export/scroll_engine.h
+++ b/firmware/export/scroll_engine.h
@@ -79,7 +79,10 @@ struct scrollinfo
     bool bidir;
     long start_tick;
 
-    /* support for custom scrolling functions */
+    /* support for custom scrolling functions,
+     * must be called with ::line == NULL to indicate that the line
+     * stops scrolling or when the userdata pointer is going to be changed
+     * (the custom scroller can release the userdata then) */
     void (*scroll_func)(struct scrollinfo *s);
     void *userdata;
 };