[feat] Add Device:hasClipboard() (#3465)

References https://github.com/koreader/koreader/issues/3441

frontend/apps/reader/modules/readerhighlight.lua

@@ -383,8 +383,11 @@ function ReaderHighlight:onHoldRelease()
                 },
                 {
                     {
-                        text = "-",
+                        text = "Copy",
-                        enabled = false,
+                        enabled = Device:hasClipboard(),
+                        callback = function()
+                            Device.input.setClipboardText(self.selected_text.text)
+                        end,
                     },
                     {
                         text = _("Translate"),

frontend/device/generic/device.lua

@@ -24,6 +24,7 @@ local Device = {
     isTouchDevice = no,
     hasFrontlight = no,
     needsTouchScreenProbe = no,
+    hasClipboard = no,
     hasColorScreen = no,
 
     -- use these only as a last resort. We should abstract the functionality

frontend/device/sdl/device.lua

@@ -34,10 +34,22 @@ function Device:init()
     end
 
     if util.haveSDL2() then
+        self.hasClipboard = yes
         self.screen = require("ffi/framebuffer_SDL2_0"):new{device = self, debug = logger.dbg}
+
+        local input = require("ffi/input")
         self.input = require("device/input"):new{
             device = self,
             event_map = require("device/sdl/event_map_sdl2"),
+            hasClipboardText = function()
+                return input.hasClipboardText()
+            end,
+            getClipboardText = function()
+                return input.getClipboardText()
+            end,
+            setClipboardText = function(text)
+                return input.setClipboardText(text)
+            end,
         }
     else
         self.screen = require("ffi/framebuffer_SDL1_2"):new{device = self, debug = logger.dbg}