Blacklist the C BB on devices where it cannot be used (#4989)

Either at all, or because it would impose reduced functionality.

Meaning:
* On 4bpp fb, because those are completely unsupported by the C BB
* On 24bpp fb, because it has limited support for that target format (no alpha blending).
* On 8bpp Linux eInk fb with an inverted palette (that's basically only the K4 ;)).
* On Linux eInk devices w/ no HW inversion support, as that would render NightMode inoperable.

That last point means that it's currently *always* blacklisted on PocketBook, because I don't have a PB device, so I don't know how safe HW inversion would be, meaning none of them are marked as being HW invert capable.

(I was a tiny bit hasty with https://github.com/koreader/koreader-base/pull/912 ;).)

base

@@ -1 +1 @@
-Subproject commit b525cb490ea83e1c4be2eed9e4a2e165fa03c32e
+Subproject commit 531e4bc685f099716170849a10c67dd5966c9e3a

frontend/device/generic/device.lua

@@ -34,6 +34,7 @@ local Device = {
     hasEinkScreen = yes,
     canHWDither = no,
     canHWInvert = no,
+    canUseCBB = yes, -- The C BB maintains a 1:1 feature parity with the Lua BB, except that is has NO support for BB4, and limited support for BBRGB24
     hasColorScreen = no,
     hasBGRFrameBuffer = no,
     canToggleGSensor = no,

frontend/device/kindle/device.lua

@@ -202,6 +202,24 @@ function Kindle:ambientBrightnessLevel()
     return 4
 end
 
+-- Make sure the C BB cannot be used on devices with a 4bpp fb
+function Kindle:blacklistCBB()
+    local ffi = require("ffi")
+    local dummy = require("ffi/posix_h")
+    local C = ffi.C
+
+    -- As well as on those than can't do HW inversion, as otherwise NightMode would be ineffective.
+    if not self:canUseCBB() or not self:canHWInvert() then
+        logger.info("Blacklisting the C BB on this device")
+        if ffi.os == "Windows" then
+            C._putenv("KO_NO_CBB=true")
+        else
+            C.setenv("KO_NO_CBB", "true", 1)
+        end
+        -- Enforce the global setting, too, so the Dev menu is accurate...
+        G_reader_settings:saveSetting("dev_no_c_blitter", true)
+    end
+end
 
 local Kindle2 = Kindle:new{
     model = "Kindle2",
@@ -209,6 +227,7 @@ local Kindle2 = Kindle:new{
     hasKeys = yes,
     hasDPad = yes,
     canHWInvert = no,
+    canUseCBB = no, -- 4bpp
 }
 
 local KindleDXG = Kindle:new{
@@ -217,6 +236,7 @@ local KindleDXG = Kindle:new{
     hasKeys = yes,
     hasDPad = yes,
     canHWInvert = no,
+    canUseCBB = no, -- 4bpp
 }
 
 local Kindle3 = Kindle:new{
@@ -225,6 +245,7 @@ local Kindle3 = Kindle:new{
     hasKeys = yes,
     hasDPad = yes,
     canHWInvert = no,
+    canUseCBB = no, -- 4bpp
 }
 
 local Kindle4 = Kindle:new{
@@ -232,6 +253,8 @@ local Kindle4 = Kindle:new{
     hasKeys = yes,
     hasDPad = yes,
     canHWInvert = no,
+    -- NOTE: It could *technically* use the C BB, as it's running @ 8bpp, but it's expecting an inverted palette...
+    canUseCBB = no,
 }
 
 local KindleTouch = Kindle:new{
@@ -319,6 +342,9 @@ local KindlePaperWhite4 = Kindle:new{
 }
 
 function Kindle2:init()
+    -- Blacklist the C BB before the first BB require...
+    self:blacklistCBB()
+
     self.screen = require("ffi/framebuffer_einkfb"):new{device = self, debug = logger.dbg}
     self.powerd = require("device/kindle/powerd"):new{
         device = self,
@@ -334,6 +360,9 @@ function Kindle2:init()
 end
 
 function KindleDXG:init()
+    -- Blacklist the C BB before the first BB require...
+    self:blacklistCBB()
+
     self.screen = require("ffi/framebuffer_einkfb"):new{device = self, debug = logger.dbg}
     self.powerd = require("device/kindle/powerd"):new{
         device = self,
@@ -350,6 +379,9 @@ function KindleDXG:init()
 end
 
 function Kindle3:init()
+    -- Blacklist the C BB before the first BB require...
+    self:blacklistCBB()
+
     self.screen = require("ffi/framebuffer_einkfb"):new{device = self, debug = logger.dbg}
     self.powerd = require("device/kindle/powerd"):new{
         device = self,
@@ -367,6 +399,9 @@ function Kindle3:init()
 end
 
 function Kindle4:init()
+    -- Blacklist the C BB before the first BB require...
+    self:blacklistCBB()
+
     self.screen = require("ffi/framebuffer_einkfb"):new{device = self, debug = logger.dbg}
     self.powerd = require("device/kindle/powerd"):new{
         device = self,

frontend/device/kobo/device.lua

@@ -249,7 +249,29 @@ probeEvEpochTime = function(self, ev)
     end
 end
 
+-- Make sure the C BB cannot be used on devices with unsafe HW inversion, as otherwise NightMode would be ineffective.
+function Kobo:blacklistCBB()
+    local ffi = require("ffi")
+    local dummy = require("ffi/posix_h")
+    local C = ffi.C
+
+    -- NOTE: canUseCBB is never no on Kobo ;).
+    if not self:canUseCBB() or not self:canHWInvert() then
+        logger.info("Blacklisting the C BB on this device")
+        if ffi.os == "Windows" then
+            C._putenv("KO_NO_CBB=true")
+        else
+            C.setenv("KO_NO_CBB", "true", 1)
+        end
+        -- Enforce the global setting, too, so the Dev menu is accurate...
+        G_reader_settings:saveSetting("dev_no_c_blitter", true)
+    end
+end
+
 function Kobo:init()
+    -- Blacklist the C BB before the first BB require...
+    self:blacklistCBB()
+
     self.screen = require("ffi/framebuffer_mxcfb"):new{device = self, debug = logger.dbg}
     if self.screen.fb_bpp == 32 then
         -- Ensure we decode images properly, as our framebuffer is BGRA...

frontend/device/pocketbook/device.lua

@@ -62,7 +62,30 @@ local PocketBook = Generic:new{
     hasWifiToggle = yes,
 }
 
+-- Make sure the C BB cannot be used on devices with a 24bpp fb
+function PocketBook:blacklistCBB()
+    local dummy = require("ffi/posix_h")
+    local C = ffi.C
+
+    -- As well as on those than can't do HW inversion, as otherwise NightMode would be ineffective.
+    -- FIXME: Either relax the HWInvert check, or actually enable HWInvert on PB if it's safe and it works,
+    --        as, currently, no PB device is marked as canHWInvert, so, the C BB is essentially *always* blacklisted.
+    if not self:canUseCBB() or not self:canHWInvert() then
+        logger.info("Blacklisting the C BB on this device")
+        if ffi.os == "Windows" then
+            C._putenv("KO_NO_CBB=true")
+        else
+            C.setenv("KO_NO_CBB", "true", 1)
+        end
+        -- Enforce the global setting, too, so the Dev menu is accurate...
+        G_reader_settings:saveSetting("dev_no_c_blitter", true)
+    end
+end
+
 function PocketBook:init()
+    -- Blacklist the C BB before the first BB require...
+    self:blacklistCBB()
+
     self.screen = require("ffi/framebuffer_mxcfb"):new{device = self, debug = logger.dbg}
     self.powerd = require("device/pocketbook/powerd"):new{device = self}
     self.input = require("device/input"):new{
@@ -292,6 +315,7 @@ local PocketBookColorLux = PocketBook:new{
     hasFrontlight = yes,
     hasColorScreen = yes,
     has3BytesWideFrameBuffer = yes,
+    canUseCBB = no, -- 24bpp
     isAlwaysPortrait = no,
     emu_events_dev = "/var/dev/shm/emu_events",
 }