Change how scrolling is done

- All functions involved return a boolean, and the core function use
  that value to determine if a refresh is needed or not. (avoids useless
  refreshs)

- Scrolling with PGUP/DOWN on the roster now only does _one_ action, an
  not a range corresponding to the screen size (should be way faster)

3 files changed, 100 insertions, 46 deletions

diff --git a/src/core.py b/src/core.py
index 7af9e628..9de580b8 100644
--- a/src/core.py
+++ b/src/core.py
@@ -934,34 +934,67 @@ class Core(object):
         self.doupdate()
 
     def refresh_tab_win(self):
+        """
+        Refresh the window containing the tab list
+        """
         self.current_tab().refresh_tab_win()
         if self.current_tab().input:
             self.current_tab().input.refresh()
         self.doupdate()
 
     def scroll_page_down(self, args=None):
-        self.current_tab().on_scroll_down()
-        self.refresh_window()
+        """
+        Scroll a page down, if possible.
+        Returns True on success, None on failure.
+        """
+        if self.current_tab().on_scroll_down():
+            self.refresh_window()
+            return True
 
     def scroll_page_up(self, args=None):
-        self.current_tab().on_scroll_up()
-        self.refresh_window()
+        """
+        Scroll a page up, if possible.
+        Returns True on success, None on failure.
+        """
+        if self.current_tab().on_scroll_up():
+            self.refresh_window()
+            return True
 
     def scroll_line_up(self, args=None):
-        self.current_tab().on_line_up()
-        self.refresh_window()
+        """
+        Scroll a line up, if possible.
+        Returns True on success, None on failure.
+        """
+        if self.current_tab().on_line_up():
+            self.refresh_window()
+            return True
 
     def scroll_line_down(self, args=None):
-        self.current_tab().on_line_down()
-        self.refresh_window()
+        """
+        Scroll a line down, if possible.
+        Returns True on success, None on failure.
+        """
+        if self.current_tab().on_line_down():
+            self.refresh_window()
+            return True
 
     def scroll_half_up(self, args=None):
-        self.current_tab().on_half_scroll_up()
-        self.refresh_window()
+        """
+        Scroll half a screen down, if possible.
+        Returns True on success, None on failure.
+        """
+        if self.current_tab().on_half_scroll_up():
+            self.refresh_window()
+            return True
 
     def scroll_half_down(self, args=None):
-        self.current_tab().on_half_scroll_down()
-        self.refresh_window()
+        """
+        Scroll half a screen down, if possible.
+        Returns True on success, None on failure.
+        """
+        if self.current_tab().on_half_scroll_down():
+            self.refresh_window()
+            return True
 
     def grow_information_win(self, nb=1):
         if self.information_win_size >= self.current_tab().height -5 or \
diff --git a/src/tabs.py b/src/tabs.py
index 7eed1790..74475779 100644
--- a/src/tabs.py
+++ b/src/tabs.py
@@ -543,22 +543,22 @@ class ChatTab(Tab):
         raise NotImplementedError
 
     def on_line_up(self):
-        self.text_win.scroll_up(1)
+        return self.text_win.scroll_up(1)
 
     def on_line_down(self):
-        self.text_win.scroll_down(1)
+        return self.text_win.scroll_down(1)
 
     def on_scroll_up(self):
-        self.text_win.scroll_up(self.text_win.height-1)
+        return self.text_win.scroll_up(self.text_win.height-1)
 
     def on_scroll_down(self):
-        self.text_win.scroll_down(self.text_win.height-1)
+        return self.text_win.scroll_down(self.text_win.height-1)
 
     def on_half_scroll_up(self):
-        self.text_win.scroll_up((self.text_win.height-1) // 2)
+        return self.text_win.scroll_up((self.text_win.height-1) // 2)
 
     def on_half_scroll_down(self):
-        self.text_win.scroll_down((self.text_win.height-1) // 2)
+        return self.text_win.scroll_down((self.text_win.height-1) // 2)
 
     def scroll_separator(self):
         self.text_win.scroll_to_separator()
@@ -2359,14 +2359,10 @@ class RosterInfoTab(Tab):
         self.core.doupdate()
 
     def on_scroll_down(self):
-        for i in range(self.height-1):
-            self.roster_win.move_cursor_down()
-        return True
+        return self.roster_win.move_cursor_down(self.height // 2)
 
     def on_scroll_up(self):
-        for i in range(self.height-1):
-            self.roster_win.move_cursor_up()
-        return True
+        return self.roster_win.move_cursor_up(self.height // 2)
 
     def on_space(self):
         selected_row = self.roster_win.get_selected_row()
@@ -2858,10 +2854,10 @@ class MucListTab(Tab):
         curses.curs_set(0)
 
     def on_scroll_up(self):
-        self.listview.scroll_up()
+        return self.listview.scroll_up()
 
     def on_scroll_down(self):
-        self.listview.scroll_down()
+        return self.listview.scroll_down()
 
 class XMLTab(Tab):
 
@@ -2943,10 +2939,10 @@ class XMLTab(Tab):
         return True
 
     def on_scroll_up(self):
-        self.text_win.scroll_up(self.text_win.height-1)
+        return self.text_win.scroll_up(self.text_win.height-1)
 
     def on_scroll_down(self):
-        self.text_win.scroll_down(self.text_win.height-1)
+        return self.text_win.scroll_down(self.text_win.height-1)
 
     def command_clear(self, args):
         """
diff --git a/src/windows.py b/src/windows.py
index 03905d4b..a46edb1e 100644
--- a/src/windows.py
+++ b/src/windows.py
@@ -212,11 +212,14 @@ class UserList(Win):
                }
     def scroll_up(self):
         self.pos += self.height-1
+        return True
 
     def scroll_down(self):
+        pos = self.pos
         self.pos -= self.height-1
         if self.pos < 0:
             self.pos = 0
+        return self.pos != pos
 
     def draw_plus(self, y):
         self.addstr(y, self.width-2, '++', to_curses_attr(get_theme().COLOR_MORE_INDICATOR))
@@ -714,16 +717,20 @@ class TextWin(Win):
             self.pos = 0
 
     def scroll_up(self, dist=14):
+        pos = self.pos
         self.pos += dist
         if self.pos + self.height > len(self.built_lines):
             self.pos = len(self.built_lines) - self.height
             if self.pos < 0:
                 self.pos = 0
+        return self.pos != pos
 
     def scroll_down(self, dist=14):
+        pos = self.pos
         self.pos -= dist
         if self.pos <= 0:
             self.pos = 0
+        return self.pos != pos
 
     def scroll_to_separator(self):
         """
@@ -1540,35 +1547,53 @@ class RosterWin(Win):
         self.roster_len = 0
         self.selected_row = None
 
-    def move_cursor_down(self):
+    def move_cursor_down(self, number=1):
         """
         Return True if we scrolled, False otherwise
         """
-        if self.pos < self.roster_len-1:
-            self.pos += 1
+        pos = self.pos
+        if self.pos < self.roster_len-number:
+            self.pos += number
         else:
-            return False
-        if self.pos == self.start_pos-1 + self.height-1:
-            self.scroll_down()
-        return True
+            self.pos = self.roster_len - 1
+        if self.pos >= self.start_pos-1 + self.height-1:
+            if number == 1:
+                self.scroll_down(8)
+            else:
+                self.scroll_down(self.pos-self.start_pos - self.height // 2)
+        return pos != self.pos
 
-    def move_cursor_up(self):
+    def move_cursor_up(self, number=1):
         """
         Return True if we scrolled, False otherwise
         """
-        if self.pos > 0:
-            self.pos -= 1
+        pos = self.pos
+        if self.pos-number >= 0:
+            self.pos -= number
         else:
-            return False
-        if self.pos == self.start_pos-2:
-            self.scroll_up()
-        return True
+            self.pos = 0
+        if self.pos <= self.start_pos:
+            if number == 1:
+                self.scroll_up(8)
+            else:
+                self.scroll_up(self.start_pos-self.pos + self.height // 2)
+        return pos != self.pos
 
-    def scroll_down(self):
-        self.start_pos += 8
+    def scroll_down(self, number=8):
+        pos = self.start_pos
+        if self.start_pos + number <= self.roster_len-1:
+            self.start_pos += number
+        else:
+            self.start_pos = self.roster_len-1
+        return self.start_pos != pos
 
-    def scroll_up(self):
-        self.start_pos -= 8
+    def scroll_up(self, number=8):
+        pos = self.start_pos
+        if self.start_pos - number > 0:
+            self.start_pos -= number
+        else:
+            self.start_pos = 1
+        return self.start_pos != pos
 
     def refresh(self, roster):
         """