confirm and cancel gestures in cropping dialog are replaced by OK/Cancel buttons

Now only "tap" and "pan" gestures are allowed in cropping dialog.

frontend/ui/button.lua

@@ -3,27 +3,37 @@ require "ui/widget"
 --[[
 a button widget
 ]]
-Button = WidgetContainer:new{
+Button = InputContainer:new{
 	text = nil, -- mandatory
-	preselect = false
+	preselect = false,
+	callback = nil,
+	margin = 0,
+	bordersize = 3,
+	background = 0,
+	radius = 15,
+	padding = 2,
+	width = nil,
+	text_font_face = "cfont",
+	text_font_size = 20,
 }
 
 function Button:init()
+	local text_widget = TextWidget:new{
+		text = self.text,
+		face = Font:getFace(self.text_font_face, self.text_font_size)
+	}
+	local text_size = text_widget:getSize()
 	-- set FrameContainer content
 	self[1] = FrameContainer:new{
-		margin = 0,
-		bordersize = 3,
-		background = 0,
-		radius = 15,
-		padding = 2,
-
+		margin = self.margin,
+		bordersize = self.bordersize,
+		background = self.background,
+		radius = self.radius,
+		padding = self.padding,
 		HorizontalGroup:new{
-			HorizontalSpan:new{ width = 8 },
-			TextWidget:new{
-				text = self.text,
-				face = Font:getFace("cfont", 20)
-			},
-			HorizontalSpan:new{ width = 8 },
+			HorizontalSpan:new{ width = (self.width - text_size.w)/2 },
+			text_widget,
+			HorizontalSpan:new{ width = (self.width - text_size.w)/2 },
 		}
 	}
 	if self.preselect then
@@ -31,6 +41,18 @@ function Button:init()
 	else
 		self[1].color = 5
 	end
+	self.dimen = self[1]:getSize()
+	if Device:isTouchDevice() then
+		self.ges_events = {
+			TapSelect = {
+				GestureRange:new{
+					ges = "tap",
+					range = self.dimen,
+				},
+				doc = "Tap Button",
+			},
+		}
+	end
 end
 
 function Button:onFocus()
@@ -43,3 +65,7 @@ function Button:onUnfocus()
 	return true
 end
 
+function Button:onTapSelect()
+	self.callback()
+	return true
+end