screenshot with finger touch at the two corners of the diagonal

frontend/ui/gesturedetector.lua

@@ -7,7 +7,7 @@ GestureRange = {
 	-- temproal range limits the gesture emitting rate
 	rate = nil,
 	-- span limits of this gesture
-	span = nil,
+	scale = nil,
 }
 
 function GestureRange:new(o)
@@ -34,8 +34,8 @@ function GestureRange:match(gs)
 			return false
 		end
 	end
-	if self.span then
-		if self.span[1] > gs.span or self.span[2] < gs.span then
+	if self.scale then
+		if self.scale[1] > gs.span or self.scale[2] < gs.span then
 			return false
 		end
 	end
@@ -244,7 +244,7 @@ function GestureDetector:tapState(tev)
 					span = pos0:distance(pos1),
 					time = tev.timev,
 				}
-				DEBUG("two-finger tap detected")
+				DEBUG("two-finger tap detected with span", pos0:distance(pos1))
 				self:clearState(0)
 				self:clearState(1)
 				return ges_ev

frontend/ui/reader/readerscreenshot.lua

@@ -0,0 +1,25 @@
+
+ReaderScreenshot = InputContainer:new{}
+
+function ReaderScreenshot:init()
+	local diagonal = math.sqrt(
+		math.pow(Screen:getWidth(), 2) + 
+		math.pow(Screen:getHeight(), 2)
+	)
+	self.ges_events = {
+		Screenshot = {
+			GestureRange:new{
+				ges = "two_finger_tap",
+				scale = {diagonal - 80*Screen:getDPI()/167, diagonal},
+				rate = 1.0,
+			}
+		},
+	}
+end
+
+function ReaderScreenshot:onScreenshot()
+	os.execute("screenshot")
+	UIManager:setDirty(self.view.dialog, "full")
+	return true
+end
+

frontend/ui/readerui.lua

@@ -14,6 +14,7 @@ require "ui/reader/readerconfig"
 require "ui/reader/readercropping"
 require "ui/reader/readerkopt"
 require "ui/reader/readercopt"
+require "ui/reader/readerscreenshot"
 
 --[[
 This is an abstraction for a reader interface
@@ -90,6 +91,13 @@ function ReaderUI:init()
 		ui = self
 	}
 	table.insert(self, reader_bm)
+	-- screenshot controller
+	local reader_ss = ReaderScreenshot:new{
+		dialog = self.dialog,
+		view = self[1],
+		ui = self
+	}
+	table.insert(self, reader_ss)
 
 	if self.document.info.has_pages then
 		-- for page specific controller