Pixel-accurate (vertical) list scrolling for touchscreen targets.

Looks much smoother now as you don't scroll by whole lines anymore.
Add some functions lcd driver to enable the line based scrolling engine to draw the lines with a pixel-based y-offset.
This should also allow for a sensible kinetic scrolling mechanism (still a todo).

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28214 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 95 insertions, 30 deletions

diff --git a/apps/gui/bitmap/list.c b/apps/gui/bitmap/list.c
index 6ce8972944..cb59dbe88d 100644
--- a/apps/gui/bitmap/list.c
+++ b/apps/gui/bitmap/list.c
@@ -48,11 +48,16 @@
 static struct viewport list_text[NB_SCREENS], title_text[NB_SCREENS];
 
 #ifdef HAVE_TOUCHSCREEN
+/* difference in pixels between draws, above it means enough to start scrolling */
+#define SCROLL_BEGIN_THRESHOLD 3 
+
 static enum {
     SCROLL_NONE,    /* no scrolling */
     SCROLL_BAR,     /* scroll by using the scrollbar */
     SCROLL_SWIPE,   /* scroll by wiping over the screen */
 } scroll_mode;
+
+static int y_offset;
 #endif
 
 int gui_list_get_item_offset(struct gui_synclist * gui_list, int item_width,
@@ -157,9 +162,30 @@ void list_draw(struct screen *display, struct gui_synclist *list)
         list_text_vp->height -= line_height;
     }
 
+
     start = list_start_item;
     end = start + viewport_get_nb_lines(list_text_vp);
 
+#ifdef HAVE_TOUCHSCREEN
+    if (list->selected_item == 0)
+        y_offset = 0; /* reset in case it's a new list */
+
+    int draw_offset = y_offset;
+    /* draw some extra items to not have empty lines at the top and bottom */
+    if (y_offset > 0)
+    {
+        /* make it negative for more consistent apparence when switching
+         * directions */
+        draw_offset -= line_height;
+        if (start > 0)
+            start--;
+    }
+    else if (y_offset < 0)
+        end++;
+#else
+    #define draw_offset 0
+#endif
+
     /* draw the scrollbar if its needed */
     if (global_settings.scrollbar &&
         viewport_get_nb_lines(list_text_vp) < list->nb_items)
@@ -216,6 +242,7 @@ void list_draw(struct screen *display, struct gui_synclist *list)
         char entry_buffer[MAX_PATH];
         unsigned char *entry_name;
         int text_pos = 0;
+        int line = i - start;
         s = list->callback_get_item_name(i, list->data, entry_buffer,
                                          sizeof(entry_buffer));
         entry_name = P2STR(s);
@@ -285,36 +312,36 @@ void list_draw(struct screen *display, struct gui_synclist *list)
             if (item_offset> item_width - (list_text_vp->width - text_pos))
             {
                 /* don't scroll */
-                display->puts_style_offset(0, i-start, entry_name,
-                        style, item_offset);
+                display->puts_style_xyoffset(0, line, entry_name,
+                        style, item_offset, draw_offset);
             }
             else
             {
-                display->puts_scroll_style_offset(0, i-start, entry_name,
-                        style, item_offset);
+                display->puts_scroll_style_xyoffset(0, line, entry_name,
+                        style, item_offset, draw_offset);
             }
         }
         else
         {
             if (list->scroll_all)
-                display->puts_scroll_style_offset(0, i-start, entry_name,
-                        style, item_offset);
+                display->puts_scroll_style_xyoffset(0, line, entry_name,
+                        style, item_offset, draw_offset);
             else
-                display->puts_style_offset(0, i-start, entry_name,
-                        style, item_offset);
+                display->puts_style_xyoffset(0, line, entry_name,
+                        style, item_offset, draw_offset);
         }
         /* do the icon */
         display->set_viewport(&list_icons);
         if (list->callback_get_item_icon && global_settings.show_icons)
         {
             screen_put_icon_with_offset(display, show_cursor?1:0,
-                                    (i-start),show_cursor?ICON_PADDING:0,0,
+                                    (line),show_cursor?ICON_PADDING:0,draw_offset,
                                     list->callback_get_item_icon(i, list->data));
         }
         if (show_cursor && i >= list->selected_item &&
                 i <  list->selected_item + list->selected_size)
         {
-            screen_put_icon(display, 0, i-start, Icon_Cursor);
+            screen_put_icon_with_offset(display, 0, line, 0, draw_offset, Icon_Cursor);
         }
     }
     display->set_viewport(parent);
@@ -343,6 +370,8 @@ static int gui_synclist_touchscreen_scrollbar(struct gui_synclist * gui_list,
     if (nb_lines <  gui_list->nb_items)
     {
         scroll_mode = SCROLL_BAR;
+        /* scrollbar scrolling is still line based */
+        y_offset = 0;
         int scrollbar_size = nb_lines*
             font_get(gui_list->parent[screen]->font)->height;
         int actual_y = y - list_text[screen].y;
@@ -365,17 +394,49 @@ static int gui_synclist_touchscreen_scrollbar(struct gui_synclist * gui_list,
 }
 
 /*
- * returns the number of scrolled items since the last call
+ * returns the number of pixel scrolled since the last call
  **/
-static int gui_synclist_touchscreen_scrolling(struct gui_synclist * gui_list, int position)
+static int gui_synclist_touchscreen_scrolling(struct gui_synclist * gui_list, int line_height, int position)
 {
-    const int screen = screens[SCREEN_MAIN].screen_type;
-    const int difference = position - last_position;
+    /* fixme */
+    const enum screen_type screen = screens[SCREEN_MAIN].screen_type;
     const int nb_lines = viewport_get_nb_lines(&list_text[screen]);
-    if(nb_lines < gui_list->nb_items && difference != 0) /* only scroll if needed */
+    /* in pixels */
+    const int difference = position - last_position;
+
+    /* make selecting items easier */
+    if (abs(difference) < SCROLL_BEGIN_THRESHOLD && scroll_mode == SCROLL_NONE)
+        return 0;
+
+    /* does the list even scroll? if no, return but still show
+     * the caller that we would scroll */
+    if (nb_lines >= gui_list->nb_items)
+        return difference;
+
+    const int old_start = gui_list->start_item[screen];
+    int new_start_item = -1;
+    int line_diff = 0;
+
+    /* don't scroll at the edges of the list */
+    if ((old_start == 0 && difference > 0)
+     || (old_start == (gui_list->nb_items - nb_lines) && difference < 0))
+    {
+        y_offset = 0;
+        return difference;
+    }
+
+    /* add up y_offset over time and translate to lines
+     * if scrolled enough */
+    y_offset += difference;
+    if (abs(y_offset) > line_height)
+    {
+        line_diff = y_offset/line_height;
+        y_offset -= line_diff * line_height;
+    }
+
+    if(line_diff != 0)
     {
-        int new_start_item;
-        new_start_item = gui_list->start_item[screen] - difference;
+        new_start_item = old_start - line_diff;
         /* check if new_start_item is bigger than list item count */
         if(new_start_item > gui_list->nb_items - nb_lines)
             new_start_item = gui_list->nb_items - nb_lines;
@@ -384,22 +445,23 @@ static int gui_synclist_touchscreen_scrolling(struct gui_synclist * gui_list, in
             new_start_item = 0;
         gui_list->start_item[screen] = new_start_item;
     }
+
     return difference;
 }
 
 unsigned gui_synclist_do_touchscreen(struct gui_synclist * gui_list)
 {
     short x, y;
-    const int button = action_get_touchscreen_press(&x, &y);
-    const int screen = SCREEN_MAIN;
+    const enum screen_type screen = SCREEN_MAIN;
+    struct viewport *info_vp = sb_skin_get_info_vp(screen);
+    const int button = action_get_touchscreen_press_in_vp(&x, &y, info_vp);
     const int list_start_item = gui_list->start_item[screen];
     const struct viewport *list_text_vp = &list_text[screen];
     const bool old_released = released;
     int line, list_width = list_text_vp->width;
 
-    /* make sure it is inside the UI viewport */    
-    if (!viewport_point_within_vp(sb_skin_get_info_vp(screen), x, y))
-        return BUTTON_NONE;
+    if (button == ACTION_NONE || button == ACTION_UNKNOWN)
+        return ACTION_NONE;
 
     released = (button&BUTTON_REL) != 0;
 
@@ -473,15 +535,18 @@ unsigned gui_synclist_do_touchscreen(struct gui_synclist * gui_list)
             int actual_y;
 
             actual_y = y - list_text_vp->y;
-            line = actual_y / line_height;
+            /* selection needs to be corrected if an items are only
+             * partly visible */
+            line = (actual_y - y_offset) / line_height;
             
             /* Pressed below the list*/
             if (list_start_item + line >= gui_list->nb_items)
+            {
+                /* don't collect last_position outside of the list area
+                 * it'd break selecting after such a situation */
+                last_position = 0;
                 return ACTION_NONE;
-            
-            /* Pressed a border */
-            if(UNLIKELY(actual_y % line_height == 0))
-                return ACTION_NONE;
+            }
 
             if (released)
             {
@@ -524,9 +589,9 @@ unsigned gui_synclist_do_touchscreen(struct gui_synclist * gui_list)
                 /* select current item */
                 gui_synclist_select_item(gui_list, list_start_item+line);
                 if (last_position == 0)
-                    last_position = line;
+                    last_position = actual_y;
                 else
-                    result = gui_synclist_touchscreen_scrolling(gui_list, line);
+                    result = gui_synclist_touchscreen_scrolling(gui_list, line_height, actual_y);
 
                 /* Start scrolling once the pen is moved without
                  * releasing it inbetween */
@@ -536,7 +601,7 @@ unsigned gui_synclist_do_touchscreen(struct gui_synclist * gui_list)
                     scroll_mode = SCROLL_SWIPE;
                 }
 
-                last_position = line;
+                last_position = actual_y;
 
                 return redraw ? ACTION_REDRAW:ACTION_NONE;
             }