Text input fixes and enhancements (#4084)

InputText, ScrollTextWidget, TextBoxWidget:
- proper line scrolling when moving cursor or inserting/deleting text
  to behave like most text editors do
- fix cursor navigation, optimize refreshes when moving only the cursor,
  don't recreate the textwidget when moving cursor up/down
- optimize refresh areas, stick to "ui" to avoid a "partial" black
  flash every 6 appended or deleted chars

InputText:
- fix issue when toggling Show password multiple times
- new option: InputText.cursor_at_end (default: true)
- if no InputText.height provided, measure the text widget height
  that we would start with, and use a ScrollTextWidget with that
  fixed height, so widget does not overflow container if we extend
  the text and increase the number of lines
- as we are using "ui" refreshes while text editing, allows refreshing
  the InputText with a diagonal swipe on it (actually, refresh the
  whole screen, which allows refreshing the keyboard too if needed)

ScrollTextWidget:
- properly align scrollbar with its TextBoxWidget

TextBoxWidget:
- some cleanup (added new properties to avoid many method calls), added
  proxy methods for upper widgets to get them
- reordered/renamed/refactored the *CharPos* methods for easier reading
  (sorry for the diff that won't help reviewing, but that was needed)

InputDialog:
- new options:
   allow_newline = false, -- allow entering new lines
   cursor_at_end = true, -- starts with cursor at end of text, ready to append
   fullscreen = false, -- adjust to full screen minus keyboard
   condensed = false, -- true will prevent adding air and balance between elements
   add_scroll_buttons = false, -- add scroll Up/Down buttons to first row of buttons
   add_nav_bar = false, -- append a row of page navigation buttons
- find the most adequate text height, when none provided or fullscreen, to
  not overflow screen (and not be stuck with Cancel/Save buttons hidden)
- had to disable the use of a MovableContainer (many issues like becoming
  transparent when a PathChooser comes in front, Hold to paste from
  clipboard, moving the InputDialog under the keyboard and getting stuck...)

GestureRange: fix possible crash (when event processed after widget
destruction ?)

LoginDialog: fix some ui stack increase and possible crash when switching
focus many times.

frontend/ui/widget/scrolltextwidget.lua

@@ -19,6 +19,7 @@ local ScrollTextWidget = InputContainer:new{
     text = nil,
     charlist = nil,
     charpos = nil,
+    top_line_num = nil,
     editable = false,
     justified = false,
     face = nil,
@@ -36,6 +37,8 @@ function ScrollTextWidget:init()
         text = self.text,
         charlist = self.charlist,
         charpos = self.charpos,
+        top_line_num = self.top_line_num,
+        dialog = self.dialog,
         editable = self.editable,
         justified = self.justified,
         face = self.face,
@@ -52,9 +55,10 @@ function ScrollTextWidget:init()
         low = 0,
         high = visible_line_count / total_line_count,
         width = self.scroll_bar_width,
-        height = self.height,
+        height = self.text_widget:getTextHeight(),
     }
-    local horizontal_group = HorizontalGroup:new{}
+    self:updateScrollBar()
+    local horizontal_group = HorizontalGroup:new{ align = "top" }
     table.insert(horizontal_group, self.text_widget)
     table.insert(horizontal_group, HorizontalSpan:new{width=self.text_scroll_span})
     table.insert(horizontal_group, self.v_scroll_bar)
@@ -92,38 +96,93 @@ function ScrollTextWidget:focus()
     self.text_widget:focus()
 end
 
-function ScrollTextWidget:moveCursor(x, y)
-    return self.text_widget:moveCursor(x, y)
+function ScrollTextWidget:getTextHeight()
+    return self.text_widget:getTextHeight()
+end
+
+function ScrollTextWidget:getLineHeight()
+    return self.text_widget:getLineHeight()
+end
+
+function ScrollTextWidget:getCharPos()
+    return self.text_widget:getCharPos()
+end
+
+function ScrollTextWidget:updateScrollBar()
+    local low, high = self.text_widget:getVisibleHeightRatios()
+    if low ~= self.prev_low or high ~= self.prev_high then
+        self.prev_low = low
+        self.prev_high = high
+        self.v_scroll_bar:set(low, high)
+        UIManager:setDirty(self.dialog, function()
+            return "partial", self.dimen
+        end)
+    end
+end
+
+function ScrollTextWidget:moveCursorToCharPos(charpos)
+    self.text_widget:moveCursorToCharPos(charpos)
+    self:updateScrollBar()
+end
+
+function ScrollTextWidget:moveCursorToXY(x, y, no_overflow)
+    self.text_widget:moveCursorToXY(x, y, no_overflow)
+    self:updateScrollBar()
+end
+
+function ScrollTextWidget:moveCursorLeft()
+    self.text_widget:moveCursorLeft();
+    self:updateScrollBar()
+end
+
+function ScrollTextWidget:moveCursorRight()
+    self.text_widget:moveCursorRight();
+    self:updateScrollBar()
 end
 
 function ScrollTextWidget:moveCursorUp()
-    return self.text_widget:moveCursorUp();
+    self.text_widget:moveCursorUp();
+    self:updateScrollBar()
 end
 
 function ScrollTextWidget:moveCursorDown()
-    return self.text_widget:moveCursorDown();
+    self.text_widget:moveCursorDown();
+    self:updateScrollBar()
+end
+
+function ScrollTextWidget:scrollDown()
+    self.text_widget:scrollDown();
+    self:updateScrollBar()
+end
+
+function ScrollTextWidget:scrollUp()
+    self.text_widget:scrollUp();
+    self:updateScrollBar()
+end
+
+function ScrollTextWidget:scrollToTop()
+    self.text_widget:scrollToTop();
+    self:updateScrollBar()
+end
+
+function ScrollTextWidget:scrollToBottom()
+    self.text_widget:scrollToBottom();
+    self:updateScrollBar()
 end
 
 function ScrollTextWidget:scrollText(direction)
     if direction == 0 then return end
-    local low, high
     if direction > 0 then
-        low, high = self.text_widget:scrollDown()
+        self.text_widget:scrollDown()
     else
-        low, high = self.text_widget:scrollUp()
+        self.text_widget:scrollUp()
     end
-    self.v_scroll_bar:set(low, high)
-    UIManager:setDirty(self.dialog, function()
-        return "partial", self.dimen
-    end)
+    self:updateScrollBar()
 end
 
 function ScrollTextWidget:scrollToRatio(ratio)
-    local low, high = self.text_widget:scrollToRatio(ratio)
-    self.v_scroll_bar:set(low, high)
-    UIManager:setDirty(self.dialog, function()
-        return "partial", self.dimen
-    end)
+    self.text_widget:scrollToRatio(ratio)
+    self:updateScrollBar()
 end
 
 function ScrollTextWidget:onScrollText(arg, ges)
@@ -139,6 +198,10 @@ function ScrollTextWidget:onScrollText(arg, ges)
 end
 
 function ScrollTextWidget:onTapScrollText(arg, ges)
+    if self.editable then
+        -- Tap is used to position cursor
+        return false
+    end
     -- same tests as done in TextBoxWidget:scrollUp/Down
     if ges.pos.x < Screen:getWidth()/2 then
         if self.text_widget.virtual_line_num > 1 then