[feat, Kobo] On Kobo, drop fb to 8bpp on startup (#4637)

* The Great 8bpp Experiment

Swap to 8bpp on Kobo, because we're 'effing grayscale, for pete's sake!

* Always swap to 8bpp, no matter the launch method.

Because it turned out that, even when restarting Nickel, we had to
restore the expected bitdepth ourselves, because pickel/Nickel didn't do
the job completely.

(I'm going to guess the grayscale flag wasn't getting flipped properly).

* Dither every non-transparent icon to the eInk palette

* Make sure hasBGRFrameBuffer is only enabled when the Kobo fb actually is
@ 32bpp...

* Re-process badly grayscaled icons

* And re-grayscale that one w/ gamma correction so the squares show up
better.

* Allow the fbdepth switch to be disabled (in Developer settings).

Also, allow setting debug mode that way.

Also, forcibly disable verbose logging when disabling debug.

* Update setting name to piggyback on the existing check in reader.lua

* Update icons postprocessing info

frontend/apps/filemanager/filemanagermenu.lua

@@ -217,8 +217,52 @@ function FileManagerMenu:setUpdateItemTable()
                     })
                 end,
             },
+            {
+                text = _("Enable debug logging"),
+                checked_func = function()
+                    return G_reader_settings:isTrue("debug")
+                end,
+                callback = function()
+                    G_reader_settings:flipNilOrFalse("debug")
+                    if G_reader_settings:isTrue("debug") then
+                        dbg:turnOn()
+                    else
+                        dbg:setVerbose(false)
+                        dbg:turnOff()
+                        G_reader_settings:flipTrue("debug_verbose")
+                    end
+                end,
+            },
+            {
+                text = _("Enable verbose debug logging"),
+                enabled_func = function()
+                    return G_reader_settings:isTrue("debug")
+                end,
+                checked_func = function()
+                    return G_reader_settings:isTrue("debug_verbose")
+                end,
+                callback = function()
+                    G_reader_settings:flipNilOrFalse("debug_verbose")
+                    if G_reader_settings:isTrue("debug_verbose") then
+                        dbg:setVerbose(true)
+                    else
+                        dbg:setVerbose(false)
+                    end
+                end,
+            },
         }
     }
+    if Device:isKobo() then
+        table.insert(self.menu_items.developer_options.sub_item_table, {
+            text = _("Disable forced 8-bit color space"),
+            checked_func = function()
+                return G_reader_settings:isTrue("dev_startup_no_fbdepth")
+            end,
+            callback = function()
+                G_reader_settings:flipNilOrFalse("dev_startup_no_fbdepth")
+            end,
+        })
+    end
     self.menu_items.cloud_storage = {
         text = _("Cloud storage"),
         callback = function()

frontend/device/kobo/device.lua

@@ -23,7 +23,6 @@ local Kobo = Generic:new{
     model = "Kobo",
     isKobo = yes,
     isTouchDevice = yes, -- all of them are
-    hasBGRFrameBuffer = yes, -- True when >16bpp (i.e., on current FW)
     hasOTAUpdates = yes,
     hasWifiManager = yes,
 
@@ -260,7 +259,9 @@ function Kobo:init()
     if self.screen.fb_bpp == 16 then
         logger.info("Enabling Kobo @ 16bpp tweaks")
         jit.opt.start("loopunroll=45")
-        self.hasBGRFrameBuffer = no
+    elseif self.screen.fb_bpp == 32 then
+        -- Ensure we decode images properly, as our framebuffer is BGRA...
+        self.hasBGRFrameBuffer = yes
     end
     self.powerd = require("device/kobo/powerd"):new{device = self}
     -- NOTE: For the Forma, with the buttons on the right, 193 is Top, 194 Bottom.

platform/kobo/koreader.sh

@@ -151,6 +151,41 @@ if [ "${PRODUCT}" = "frost" ]; then
 fi
 # NOTE: We don't have to restore anything on exit, nickel's startup process will take care of everything (pickel -> nickel).
 
+# In the same vein, swap to 8bpp,
+# because 16bpp is the worst idea in the history of time, as RGB565 is generally a PITA without hardware blitting,
+# and 32bpp usually gains us nothing except a performance hit (we're not Qt5 with its QPainter constraints).
+# The reduced size & complexity should hopefully make things snappier,
+# (and hopefully prevent the JIT for going crazy on high-density screens...).
+# NOTE: Even though pickel/Nickel appear to restore their preferred fb setup, we'll have to do it ourselves,
+#       because things are a bit wonky otherwise. Plus, we get to play nice with every launch method that way.
+#       So, remember the current bitdepth, so we can restore it on exit.
+ORIG_FB_BPP="$(./fbdepth -g)"
+# Sanity check...
+case "${ORIG_FB_BPP}" in
+    16) ;;
+    32) ;;
+    *)
+        # Hu oh? Don't do anything...
+        unset ORIG_FB_BPP
+        ;;
+esac
+
+# The actual swap is done in a function, because we can disable it in the Developer settings, and we want to honor it on restart.
+ko_do_fbdepth() {
+    # Check if the swap has been disabled...
+    if grep -q '\["dev_startup_no_fbdepth"\] = true' 'settings.reader.lua' 2>/dev/null; then
+        # Swap back to the original bitdepth (in case this was a restart)
+        if [ -n "${ORIG_FB_BPP}" ]; then
+            ./fbdepth -d "${ORIG_FB_BPP}" >>crash.log 2>&1
+        fi
+    else
+        # Swap to 8bpp if things looke sane
+        if [ -n "${ORIG_FB_BPP}" ]; then
+            ./fbdepth -d 8 >>crash.log 2>&1
+        fi
+    fi
+}
+
 # Remount the SD card RW if it's inserted and currently RO
 if awk '$4~/(^|,)ro($|,)/' /proc/mounts | grep ' /mnt/sd '; then
     mount -o remount,rw /mnt/sd
@@ -166,11 +201,18 @@ RETURN_VALUE=85
 while [ $RETURN_VALUE -eq 85 ]; do
     # Do an update check now, so we can actually update KOReader via the "Restart KOReader" menu entry ;).
     ko_update_check
+    # Do the fb depth switch, unless it's been disabled
+    ko_do_fbdepth
 
     ./reader.lua "${args}" >>crash.log 2>&1
     RETURN_VALUE=$?
 done
 
+# Restore original fb bitdepth if need be...
+if [ -n "${ORIG_FB_BPP}" ]; then
+    ./fbdepth -d "${ORIG_FB_BPP}" >>crash.log 2>&1
+fi
+
 # Restore original CPUFreq governor if need be...
 if [ -n "${ORIG_CPUFREQ_GOV}" ]; then
     echo "${ORIG_CPUFREQ_GOV}" >"/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor"

reader.lua

@@ -62,7 +62,8 @@ end
 -- should check DEBUG option in arg and turn on DEBUG before loading other
 -- modules, otherwise DEBUG in some modules may not be printed.
 local dbg = require("dbg")
-if G_reader_settings:readSetting("debug") then dbg:turnOn() end
+if G_reader_settings:isTrue("debug") then dbg:turnOn() end
+if G_reader_settings:isTrue("debug") and G_reader_settings:isTrue("debug_verbose") then dbg:setVerbose(true) end
 
 local Profiler = nil
 local ARGV = arg

resources/icons/README.md

@@ -1,5 +1,11 @@
 menu-icon.png is post-processed with:
 
 ```bash
-convert menu-icon.png -set colorspace Gray -separate -average menu-icon-grayscale.png
+convert menu-icon.png -grayscale Rec709Luma -dither Riemersma -remap eink_cmap.gif -quality 75 png:menu-icon-grayscale.png
 ```
+
+The intent being to grayscale, dither down to the 16c eInk palette, and save as a 16c paletted grayscale PNG.
+Start from an RGB copy of the image if you end up with a 256c or sRGB PNG (check via IM's identify tool).
+
+See https://www.mobileread.com/forums/showpost.php?p=3728291&postcount=17 for more details ;).
+