add flipping mode in pdf/djvu reader

By tapping on the upper left corner of the reader one can toggling flipping mode on/off.
In flipping mode swiping right/down and left/up  will paging backward and forward
accordingly with pages proportional to swiping distance.

frontend/ui/reader/readerflip.lua

@@ -0,0 +1,16 @@
+
+ReaderFlipping = LeftContainer:new{}
+
+function ReaderFlipping:init()
+	local widget = ImageWidget:new{
+		file = "resources/icons/appbar.book.open.png",
+	}
+	local icon_size = widget:getSize()
+	self.dimen = Geom:new{w = Screen:getWidth(), h = icon_size.h}
+	self[1] = widget
+end
+
+function ReaderFlipping:onSetDogearVisibility(visible)
+	self.view.dogear_visible = visible
+	return true
+end

frontend/ui/reader/readermenu.lua

@@ -21,8 +21,9 @@ function ReaderMenu:initGesListener()
 			GestureRange:new{
 				ges = "tap",
 				range = Geom:new{
-					x = 0, y = 0,
-					w = Screen:getWidth()*7/8,
+					x = Screen:getWidth()/8,
+					y = 0,
+					w = Screen:getWidth()*3/4,
 					h = Screen:getHeight()/4,
 				}
 			}

frontend/ui/reader/readerpaging.lua

@@ -68,7 +68,38 @@ function ReaderPaging:initGesListener()
 					h = 5*Screen:getHeight()/8,
 				}
 			}
-		}
+		},
+		ToggleFlipping = {
+			GestureRange:new{
+				ges = "tap",
+				range = Geom:new{
+					x = 0, y = 0,
+					w = Screen:getWidth()/8,
+					h = Screen:getHeight()/8
+				}
+			}
+		},
+		Swipe = {
+			GestureRange:new{
+				ges = "swipe",
+				range = Geom:new{
+					x = 0, y = 0,
+					w = Screen:getWidth(),
+					h = Screen:getHeight(),
+				}
+			}
+		},
+		Pan = {
+			GestureRange:new{
+				ges = "pan",
+				range = Geom:new{
+					x = 0, y = 0,
+					w = Screen:getWidth(),
+					h = Screen:getHeight(),
+				},
+				rate = 4.0,
+			}
+		},
 	}
 end
 
@@ -95,6 +126,47 @@ function ReaderPaging:onTapBackward()
 	return true
 end
 
+function ReaderPaging:onToggleFlipping()
+	self.view.flipping_visible = not self.view.flipping_visible
+	self.flipping_page = self.view.flipping_visible and self.current_page or nil
+	UIManager:setDirty(self.view.dialog, "partial")
+end
+
+function ReaderPaging:onSwipe(arg, ges)
+	if self.flipping_page == nil then
+		if ges.direction == "left" or ges.direction == "up" then
+			self:onGotoPageRel(1)
+		elseif ges.direction == "right" or ges.direction == "down" then
+			self:onGotoPageRel(-1)
+		end
+	elseif self.flipping_page then
+		self:gotoPage(self.flipping_page)
+	end
+	return true
+end
+
+function ReaderPaging:onPan(arg, ges)
+	if self.flipping_page then
+		local read = self.flipping_page - 1
+		local unread = self.number_of_pages - self.flipping_page
+		local whole = self.number_of_pages
+		local rel_proportion = ges.distance / Screen:getWidth()
+		local abs_proportion = ges.distance / Screen:getHeight()
+		if ges.direction == "right" then
+			self:gotoPage(self.flipping_page - math.floor(read*rel_proportion))
+		elseif ges.direction == "left" then
+			self:gotoPage(self.flipping_page + math.floor(unread*rel_proportion))
+		elseif ges.direction == "down" then
+			self:gotoPage(self.flipping_page - math.floor(whole*abs_proportion))
+		elseif ges.direction == "up" then
+			self:gotoPage(self.flipping_page + math.floor(whole*abs_proportion))
+		end
+		
+		UIManager:setDirty(self.view.dialog, "partial")
+	end
+	return true
+end
+
 function ReaderPaging:onZoomModeUpdate(new_mode)
 	-- we need to remember zoom mode to handle page turn event
 	self.zoom_mode = new_mode

frontend/ui/reader/readerview.lua

@@ -1,3 +1,4 @@
+require "ui/reader/readerflip"
 require "ui/reader/readerfooter"
 require "ui/reader/readerdogear"
 
@@ -30,6 +31,8 @@ ReaderView = OverlapGroup:new{
 	footer_visible = false,
 	-- has dogear
 	dogear_visible = false,
+	-- in flipping state
+	flipping_visible = false,
 }
 
 function ReaderView:init()
@@ -43,8 +46,12 @@ function ReaderView:resetLayout()
 	self.footer = ReaderFooter:new{
 		view = self,
 	}
+	self.flipping = ReaderFlipping:new{
+		view = self,
+	}
 	self[1] = self.dogear
 	self[2] = self.footer
+	self[3] = self.flipping
 end
 
 function ReaderView:paintTo(bb, x, y)
@@ -109,6 +116,10 @@ function ReaderView:paintTo(bb, x, y)
 	if self.footer_visible then
 		self.footer:paintTo(bb, x, y)
 	end
+	-- paint flipping
+	if self.flipping_visible then
+		self.flipping:paintTo(bb, x, y)
+	end
 end
 
 --[[