remove redundancy: new framebuffer supports rotation, multi-bpp

We can get rid of shadow blitbuffers. Screen.bb is now fb.bb.
All bpp conversion is now done by the blitbuffer abstraction layer.
Rotation mechanism is adapted to this.

frontend/ui/device/screen.lua

@@ -29,10 +29,8 @@ Codes for rotation modes:
 
 
 local Screen = {
-	width = 0,
-	height = 0,
-	native_rotation_mode = nil,
 	cur_rotation_mode = 0,
+	native_rotation_mode = nil,
 
 	bb = nil,
 	saved_bb = nil,
@@ -43,19 +41,10 @@ local Screen = {
 }
 
 function Screen:init()
-	-- for unknown strange reason, pitch*2 is 10 px more than screen width in KPW
-	self.width, self.height = self.fb:getSize()
-	-- Blitbuffer still uses inverted 4bpp bitmap, so pitch should be
-	-- (self.width / 2)
-	self.bb = Blitbuffer.new(self.width, self.height, self.width/2)
-	if self.width > self.height then
-		-- For another unknown strange reason, self.fb:getOrientation always
-		-- return 0 in KPW, even though we are in landscape mode.
-		-- Seems like the native framework change framebuffer on the fly when
-		-- starting booklet. Starting KPV from ssh and KPVBooklet will get
-		-- different framebuffer height and width.
-		--
-		--self.native_rotation_mode = self.fb:getOrientation()
+	self.bb = self.fb.bb
+	-- asking the framebuffer for orientation is error prone,
+	-- so we do this simple heuristic (for now)
+	if self:getWidth() > self:getHeight() then
 		self.native_rotation_mode = 1
 	else
 		self.native_rotation_mode = 0
@@ -63,50 +52,20 @@ function Screen:init()
 	self.cur_rotation_mode = self.native_rotation_mode
 end
 
-function Screen:refresh(refesh_type, waveform_mode, x, y, w, h)
-	if x then x = x < 0 and 0 or math.floor(x) end
-    if y then y = y < 0 and 0 or math.floor(y) end
-    if w then w = w + x > self.width and self.width - x or math.ceil(w) end
-    if h then h = h + y > self.height and self.height - y or math.ceil(h) end
-	if self.native_rotation_mode == self.cur_rotation_mode then
-        self.fb.bb:blitFrom(self.bb, 0, 0, 0, 0, self.width, self.height)
-    elseif self.native_rotation_mode == 0 and self.cur_rotation_mode == 1 then
-        self.fb.bb:blitFromRotate(self.bb, 270)
-        if x and y and w and h then
-        	x, y = y, self.width - w - x
-        	w, h = h, w
-        end
-    elseif self.native_rotation_mode == 0 and self.cur_rotation_mode == 3 then
-        self.fb.bb:blitFromRotate(self.bb, 90)
-        if x and y and w and h then
-        	x, y = self.height - h - y, x
-        	w, h = h, w
-        end
-    elseif self.native_rotation_mode == 1 and self.cur_rotation_mode == 0 then
-        self.fb.bb:blitFromRotate(self.bb, 90)
-        if x and y and w and h then
-        	x, y = self.height - h - y, x
-        	w, h = h, w
-        end
-    elseif self.native_rotation_mode == 1 and self.cur_rotation_mode == 3 then
-        self.fb.bb:blitFromRotate(self.bb, 180)
-        if x and y and w and h then
-        	x, y = self.width - w - x, self.height - h - y
-        end
-    end
-	self.fb:refresh(refesh_type, waveform_mode, x, y, w, h)
+function Screen:refresh(refresh_type, waveform_mode, x, y, w, h)
+	self.fb:refresh(refresh_type, waveform_mode, x, y, w, h)
 end
 
 function Screen:getSize()
-	return Geom:new{w = self.width, h = self.height}
+	return Geom:new{w = self.bb:getWidth(), h = self.bb:getHeight()}
 end
 
 function Screen:getWidth()
-	return self.width
+	return self.bb:getWidth()
 end
 
 function Screen:getHeight()
-	return self.height
+	return self.bb:getHeight()
 end
 
 function Screen:getDPI()
@@ -131,21 +90,12 @@ function Screen:rescaleByDPI(px)
 	return math.ceil(px * 167/self:getDPI())
 end
 
-function Screen:getPitch()
-	return self.fb:getPitch()
-end
-
-function Screen:getNativeRotationMode()
-	-- in EMU mode, you will always get 0 from getOrientation()
-	return self.fb:getOrientation()
-end
-
 function Screen:getRotationMode()
 	return self.cur_rotation_mode
 end
 
 function Screen:getScreenMode()
-	if self.width > self.height then
+	if self:getWidth() > self:getHeight() then
 		return "landscape"
 	else
 		return "portrait"
@@ -153,17 +103,8 @@ function Screen:getScreenMode()
 end
 
 function Screen:setRotationMode(mode)
-	if mode > 3 or mode < 0 then
-		return
-	end
-
-	-- mode 0 and mode 2 has the same width and height, so do mode 1 and 3
-	if (self.cur_rotation_mode % 2) ~= (mode % 2) then
-		self.width, self.height = self.height, self.width
-	end
+	self.fb.bb:rotateAbsolute(-90 * (mode - self.native_rotation_mode))
 	self.cur_rotation_mode = mode
-	self.bb:free()
-	self.bb = Blitbuffer.new(self.width, self.height, self.width/2)
 end
 
 function Screen:setScreenMode(mode)
@@ -184,17 +125,19 @@ function Screen:saveCurrentBB()
 	local width, height = self:getWidth(), self:getHeight()
 
 	if not self.saved_bb then
-		self.saved_bb = Blitbuffer.new(width, height, self.width/2)
+		self.saved_bb = Blitbuffer.new(width, height)
 	end
 	if self.saved_bb:getWidth() ~= width then
 		self.saved_bb:free()
-		self.saved_bb = Blitbuffer.new(width, height, self.width/2)
+		self.saved_bb = Blitbuffer.new(width, height)
 	end
 	self.saved_bb:blitFullFrom(self.bb)
 end
 
 function Screen:restoreFromSavedBB()
 	self:restoreFromBB(self.saved_bb)
+	-- free data
+	self.saved_bb = nil
 end
 
 function Screen:getCurrentScreenBB()