Touchscreen: Improved scroll threshold

Remove the hardcoded (and way too small) scroll threshold (the distance moved in pixels before we think the users wants to scroll) and replace it with something based on the actual DPI of the screen.
On Android we call the API for that, on other touchscreens we reimplemented Android's formula (as of 2.2) and calculate it.

Flyspray: 11727

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28548 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 10 insertions, 0 deletions

diff --git a/firmware/export/lcd.h b/firmware/export/lcd.h
index 79231d198e..e6e19b1597 100644
--- a/firmware/export/lcd.h
+++ b/firmware/export/lcd.h
@@ -549,4 +549,14 @@ extern void lcd_bitmap_transparent(const fb_data *src, int x, int y,
 
 #endif /* HAVE_LCD_BITMAP */
 
+
+#ifdef HAVE_TOUCHSCREEN
+/* only needed for touchscreen for now, feel free to implement it for others
+ * once needed
+ */
+
+/* returns the pixel density of the display */
+extern int lcd_get_dpi(void);
+#endif
+
 #endif /* __LCD_H__ */