Allow toggling CRe's new dithering & scaling (#4922)

Smooth scaling toggle is per document, in the gear tab.
Dithering is in the Dev top menu ;).

frontend/document/credocument.lua

@@ -5,6 +5,7 @@ local Document = require("document/document")
 local FontList = require("fontlist")
 local Geom = require("ui/geometry")
 local RenderImage = require("ui/renderimage")
+local Screen = require("device").screen
 local ffi = require("ffi")
 local C = ffi.C
 local lfs = require("libs/libkoreader-lfs")
@@ -21,6 +22,7 @@ local CreDocument = Document:new{
     _document = false,
     _loaded = false,
     _view_mode = nil,
+    _smooth_scaling = false,
 
     line_space_percent = 100,
     default_font = "Noto Serif",
@@ -368,14 +370,15 @@ function CreDocument:drawCurrentView(target, x, y, rect, pos)
     -- same buffer. And it could only change when some other methods
     -- from here are called
 
-    -- If in night mode, ask crengine to invert all images, so they
+    -- If in night mode, we ask crengine to invert all images, so they
     -- get displayed in their original colors when the whole screen
     -- is inverted by night mode
-    local invert_images = G_reader_settings:isTrue("night_mode")
+    -- We also honor the current smooth scaling setting,
+    -- as well as the global SW dithering setting.
 
     -- local start_clock = os.clock()
     self._drawn_images_count, self._drawn_images_surface_ratio =
-        self._document:drawCurrentPage(self.buffer, self.render_color, invert_images)
+        self._document:drawCurrentPage(self.buffer, self.render_color, Screen.night_mode, self._smooth_scaling, Screen.sw_dithering)
     -- print(string.format("CreDocument:drawCurrentView: Rendering took %9.3f ms", (os.clock() - start_clock) * 1000))
 
     -- start_clock = os.clock()
@@ -728,6 +731,11 @@ function CreDocument:setPageMargins(left, top, right, bottom)
     self._document:setIntProperty("crengine.page.margin.bottom", bottom)
 end
 
+function CreDocument:setImageScaling(toggle)
+    logger.dbg("CreDocument: set smooth scaling", toggle)
+    self._smooth_scaling = toggle
+end
+
 function CreDocument:setFloatingPunctuation(enabled)
     -- FIXME: occasional segmentation fault when toggling floating punctuation
     logger.dbg("CreDocument: set floating punctuation", enabled)