improve scrollbar

src/ltui/scrollbar.lua

@@ -149,30 +149,30 @@ function scrollbar:on_draw(transparent)
     -- draw background
     view.on_draw(self, transparent)
 
-    -- compute bar range
+    -- draw bar
     local char      = self:char()
     local charattr  = self:charattr_val()
-    local progress  = self:progress()
-    local stepwidth = self:stepwidth()
-    local pb = progress
-    local pe = progress + stepwidth
-    if pe > 1 then
-        pb = 1 - stepwidth
-        pe = 1
-    end
-
-    -- draw bar
     if self:vertical() then
-        local sb = math.floor(self:height() * pb)
-        local se = math.ceil(self:height() * pe)
+        local sn = math.ceil(self:height() * self:stepwidth())
+        local sb = math.floor(self:height() * self:progress())
+        local se = sb + sn
+        if se > self:height() then
+            sb = self:height() - sn
+            se = self:height()
+        end
         if se > sb and se - sb <= self:height() then
             for x = 0, self:width() - 1 do
                 self:canvas():attr(charattr):move(x, sb):putchar(char, se - sb, true)
             end
         end
     else
-        local sb = math.floor(self:width() * pb)
-        local se = math.ceil(self:width() * pe)
+        local sn = math.ceil(self:width() * self:stepwidth())
+        local sb = math.floor(self:width() * self:progress())
+        local se = sb + sn
+        if se > self:width() then
+            sb = self:width() - sn
+            se = self:width()
+        end
         if se > sb and se - sb <= self:width() then
             for y = 0, self:height() - 1 do
                 self:canvas():attr(charattr):move(sb, y):putchar(char, se - sb)

src/ltui/textarea.lua

@@ -74,9 +74,11 @@ function textarea:scroll(lines)
         if self._STARTLINE < 0 then
             self._STARTLINE = 0
         end
-        if self._STARTLINE > self._LINECOUNT - self:height() then
-            self._STARTLINE = self._LINECOUNT - self:height()
+        local startline_end = self._LINECOUNT - self:height()
+        if self._STARTLINE > startline_end then
+            self._STARTLINE = startline_end
         end
+        self:action_on(action.ac_on_scrolled, self._STARTLINE / startline_end)
         self:invalidate()
     end
 end
@@ -84,7 +86,9 @@ end
 -- scroll to end
 function textarea:scroll_to_end()
     if self._LINECOUNT > self:height() then
-        self._STARTLINE = self._LINECOUNT - self:height()
+        local startline_end = self._LINECOUNT - self:height()
+        self._STARTLINE = startline_end
+        self:action_on(action.ac_on_scrolled, self._STARTLINE / startline_end)
         self:invalidate()
     end
 end

src/ltui/textdialog.lua

@@ -58,6 +58,11 @@ function textdialog:init(name, bounds, title)
             self:text():bounds_set(rect:new(0, 0, v:width(), v:height() - 1))
         end
     end)
+
+    -- on scroll for text and scrollbar
+    self:text():action_set(action.ac_on_scrolled, function (v, progress)
+        self:scrollbar():progress_set(progress)
+    end)
 end
 
 -- enable or disable scrollbar