Touchscreen: Improve scrolling in absolute point mode.

* Scrolling is now done by wiping over the screen. There's no acceleration or
  kinetic scrolling yet though. But it works rather well (previously
  you held the edges of the list to scroll).
* Improve scrollbar scrolling so that it keeps scrolling even if you leave the
  scrollbar area.
* Hide selection during scrolling
* Prevent accidental hitting of the list title (which means go back) during
  scrolling
* Don't go into context menu after scrolling when leaving the screen on an item

In general, it's very much like scrolling in native lists in Android,
except there's no kinetic scrolling and everything is still line based, but with
the feature that the scrollbar enables jumping around in the list and very fast
scrolling.

Thanks to Dustin Skoracki for his ideas and half of the code for this.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28145 a1c6a512-1295-4272-9138-f99709370657

2 files changed, 127 insertions, 59 deletions

diff --git a/apps/gui/bitmap/list.c b/apps/gui/bitmap/list.c
index 87d7107950..d892bff22b 100644
--- a/apps/gui/bitmap/list.c
+++ b/apps/gui/bitmap/list.c
@@ -40,6 +40,7 @@
 #include "misc.h"
 #include "viewport.h"
 #include "statusbar-skinned.h"
+#include "debug.h"
 
 #define ICON_PADDING 1
 
@@ -230,8 +231,10 @@ void list_draw(struct screen *display, struct gui_synclist *list)
             }
         }
 #endif
-        if(i >= list->selected_item && i <  list->selected_item
-                + list->selected_size && list->show_selection_marker)
+        /* draw the selected line */
+        if(!list->hide_selection && i >= list->selected_item
+                && i <  list->selected_item + list->selected_size
+                && list->show_selection_marker)
         {/* The selected item must be displayed scrolling */
             if (global_settings.cursor_style == 1
 #ifdef HAVE_REMOTE_LCD
@@ -308,7 +311,20 @@ void list_draw(struct screen *display, struct gui_synclist *list)
 
 #if defined(HAVE_TOUCHSCREEN)
 /* This needs to be fixed if we ever get more than 1 touchscreen on a target. */
-static bool scrolling=false;
+static enum {
+    SCROLL_NONE,    /* no scrolling */
+    SCROLL_BAR,     /* scroll by using the scrollbar */
+    SCROLL_SWIPE,   /* scroll by wiping over the screen */
+} scroll_mode;
+
+static bool released = false;
+
+/* Used for kinetic scrolling as we need to know the last position to
+ * recognize the scroll direction.
+ * This gets reset to 0 at the end of scrolling
+ */
+static int last_position=0;
+
 
 static int gui_synclist_touchscreen_scrollbar(struct gui_synclist * gui_list,
                                               int y)
@@ -318,8 +334,7 @@ static int gui_synclist_touchscreen_scrollbar(struct gui_synclist * gui_list,
 
     if (nb_lines <  gui_list->nb_items)
     {
-        scrolling = true;
-
+        scroll_mode = SCROLL_BAR;
         int scrollbar_size = nb_lines*
             font_get(gui_list->parent[screen]->font)->height;
         int actual_y = y - list_text[screen].y;
@@ -334,7 +349,6 @@ static int gui_synclist_touchscreen_scrollbar(struct gui_synclist * gui_list,
             start_item = gui_list->nb_items - nb_lines;
 
         gui_list->start_item[screen] = start_item;
-        gui_synclist_select_item(gui_list, new_selection);
 
         return ACTION_REDRAW;
     }
@@ -342,16 +356,44 @@ static int gui_synclist_touchscreen_scrollbar(struct gui_synclist * gui_list,
     return ACTION_NONE;
 }
 
+/*
+ * returns the number of scrolled items since the last call
+ **/
+static int gui_synclist_touchscreen_scrolling(struct gui_synclist * gui_list, int position)
+{
+    const int screen = screens[SCREEN_MAIN].screen_type;
+    const int difference = position - last_position;
+    const int nb_lines = viewport_get_nb_lines(&list_text[screen]);
+    if(nb_lines < gui_list->nb_items && difference != 0) // only scroll if needed
+    {
+        int new_start_item;
+        new_start_item = gui_list->start_item[screen] - difference;
+        // 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;
+        // set new_start_item to 0 if it's negative
+        if(new_start_item < 0)
+            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);
-    int line;
     const int screen = SCREEN_MAIN;
     const int list_start_item = gui_list->start_item[screen];
     const struct viewport *list_text_vp = &list_text[screen];
-    int list_width = list_text_vp->width;
+    const bool old_released = released;
+    int line, list_width = list_text_vp->width;
+
+    released = (button&BUTTON_REL) != 0;
+    gui_list->hide_selection = (scroll_mode != SCROLL_NONE);
+
 
+    
     if (global_settings.scrollbar == SCROLLBAR_RIGHT)
         list_width += SCROLLBAR_WIDTH;
 
@@ -364,7 +406,7 @@ unsigned gui_synclist_do_touchscreen(struct gui_synclist * gui_list)
     /* make sure it is inside the UI viewport */
     if (list_display_title(gui_list, screen) &&
         viewport_point_within_vp(&title_text[screen], x, y) && 
-        button == BUTTON_REL)
+        button == BUTTON_REL && scroll_mode == SCROLL_NONE)
         return ACTION_STD_CANCEL;
 
     if (x < list_text_vp->x)
@@ -385,9 +427,26 @@ unsigned gui_synclist_do_touchscreen(struct gui_synclist * gui_list)
     }
     else
     {
-        if (x > list_text_vp->x + list_text_vp->width &&
-           global_settings.scrollbar == SCROLLBAR_RIGHT)
+        int line_height = font_get(gui_list->parent[screen]->font)->height;
+        /* add a small margin to prevent accidental selection */
+        int x_end = list_text_vp->x + list_text_vp->width - line_height;
+
+        /* conditions for scrollbar scrolling:
+         *    * pen is on the scrollbar (x > x_end-scrollbar width)
+         *      AND scrollbar is on the right (left case is handled above)
+         * OR * pen is in the somewhere else but we did scrollbar scrolling before
+         *
+         * scrollbar scrolling must end if the pen is released
+         * scrollbar scrolling must not happen if we're currently scrolling
+         * via swiping the screen
+         **/
+
+        if (!released && scroll_mode != SCROLL_SWIPE
+            && ((scroll_mode == SCROLL_BAR
+                || (x > x_end && global_settings.scrollbar == SCROLLBAR_RIGHT))))
+        {
             return gui_synclist_touchscreen_scrollbar(gui_list, y);
+        }
 
         /* |--------------------------------------------------------|
          * | Description of the touchscreen list interface:         |
@@ -403,10 +462,9 @@ unsigned gui_synclist_do_touchscreen(struct gui_synclist * gui_list)
          */
         if (y > list_text_vp->y || button & BUTTON_REPEAT)
         {
-            int line_height, actual_y;
-            
+            int actual_y;
+
             actual_y = y - list_text_vp->y;
-            line_height = font_get(gui_list->parent[screen]->font)->height;
             line = actual_y / line_height;
             
             /* Pressed below the list*/
@@ -416,59 +474,66 @@ unsigned gui_synclist_do_touchscreen(struct gui_synclist * gui_list)
             /* Pressed a border */
             if(UNLIKELY(actual_y % line_height == 0))
                 return ACTION_NONE;
-            
-            if (line != (gui_list->selected_item - list_start_item)
-                && button ^ BUTTON_REL)
-            {
-                if(button & BUTTON_REPEAT)
-                    scrolling = true;
-                
-                gui_synclist_select_item(gui_list, list_start_item + line);
-                
-                return ACTION_REDRAW;
-            }
-            
-            /* This has the same effect as the icons do when the scrollbar
-               is on the left (ie eliminate the chances an user enters/starts
-               an item when he wanted to use the scrollbar, due to touchscreen
-               dead zones)
-             */
-            if(global_settings.scrollbar == SCROLLBAR_RIGHT &&
-               x > list_text_vp->x + list_text_vp->width -
-                   get_icon_width(SCREEN_MAIN))
-                return ACTION_NONE;
-            
-            if (button == (BUTTON_REPEAT|BUTTON_REL))
+
+            if (released)
             {
-                if(!scrolling)
+                /* Pen was released anywhere on the screen */
+                last_position = 0;
+                if (scroll_mode == SCROLL_NONE)
                 {
-                    /* Pen was hold on the same line as the 
-                     * previously selected one
-                     * => simulate long button press
-                     */
-                    return ACTION_STD_CONTEXT;
+                    gui_synclist_select_item(gui_list, list_start_item + line);
+                    /* If BUTTON_REPEAT is set, then the pen was hold on
+                     * the same line for some time
+                     *  -> context menu
+                     * otherwise,
+                     *  -> select
+                     **/
+                    if (button & BUTTON_REPEAT)
+                        return ACTION_STD_CONTEXT;
+                    return ACTION_STD_OK;
                 }
                 else
                 {
-                    /* Pen was moved across several lines and then released on 
-                     * this one
-                     * => do nothing
-                     */
-                    scrolling = false;
+                    /* we were scrolling
+                     *  -> reset scrolling but do nothing else */
+                    scroll_mode = SCROLL_NONE;
                     return ACTION_NONE;
                 }
             }
-            else if(button == BUTTON_REL &&
-                    line == gui_list->selected_item - list_start_item)
-            {
-                /* Pen was released on either the same line as the previously
-                 *  selected one or an other one
-                 *  => simulate short press
-                 */
-                return ACTION_STD_OK;
-            }
             else
-                return ACTION_NONE;
+            {   /* pen is on the screen */
+                int result = 0;
+                bool redraw = false;
+
+                /* beginning of list interaction denoted by release in
+                 * the previous call */
+                if (old_released)
+                {
+                    scroll_mode = SCROLL_NONE;
+                    redraw = true;
+                    /* don't draw the selection during scrolling */
+                    gui_list->hide_selection = false;
+                }
+
+                /* select current item */
+                gui_synclist_select_item(gui_list, list_start_item+line);
+                if (last_position == 0)
+                    last_position = line;
+                else
+                    result = gui_synclist_touchscreen_scrolling(gui_list, line);
+
+                /* Start scrolling once the pen is moved without
+                 * releasing it inbetween */
+                if (result)
+                {
+                    redraw = true;
+                    scroll_mode = SCROLL_SWIPE;
+                }
+
+                last_position = line;
+
+                return redraw ? ACTION_REDRAW:ACTION_NONE;
+            }
         }
     }
     return ACTION_NONE;
diff --git a/apps/gui/list.h b/apps/gui/list.h
index 965a46bfc6..57ca912800 100644
--- a/apps/gui/list.h
+++ b/apps/gui/list.h
@@ -94,7 +94,10 @@ struct gui_synclist
     /* wether the text of the whole items of the list have to be
      * scrolled or only for the selected item */
     bool scroll_all;
-
+    /*
+     * if true the selection bar will not be drawn
+     */
+    bool hide_selection;
     int nb_items;
     int selected_item;
     int start_item[NB_SCREENS]; /* the item that is displayed at the top of the screen */