PocketBook: Open links in the on-device web browser

Many PocketBook devices include a web browser, but when clicking a link
in KOReader, there was no option to open the link in the browser, there
was only an option to show a QR code (which can then be scanned by a
smartphone).

This commit implements `canOpenLink`/`openLink` on PocketBook using the
"browser.app", if available.

Tested on PB740 (InkPad 3) and PB624 (Basic Touch).
On the older device (PB624) it doesn't work quite as well—an already
running browser ignores the request to switch URL, but it doesn't work
with the built-in book reader software either.

Fixes: https://github.com/koreader/koreader/issues/11782
Related: https://github.com/koreader/koreader/issues/6597

frontend/device/pocketbook/device.lua

@@ -428,6 +428,56 @@ function PocketBook:setEventHandlers(uimgr)
     end
 end
 
+local function getBrowser()
+    if util.pathExists("/usr/bin/browser.app") then
+        return true, "/usr/bin/browser.app"
+    elseif util.pathExists("/ebrmain/bin/browser.app") then
+        return true, "/ebrmain/bin/browser.app"
+    end
+    return false
+end
+
+function PocketBook:canOpenLink()
+    return inkview.MultitaskingSupported() and getBrowser()
+end
+
+function PocketBook:openLink(link)
+    if not link or type(link) ~= "string" then return end
+
+    -- SendRequestToNoWait only available in PocketBook SDK since 5.17
+    local inkview_SendRequestTo
+    if pcall(function() local _ = inkview.SendRequestToNoWait end) then
+        inkview_SendRequestTo = function(t, r, d, l) inkview.SendRequestToNoWait(t, r, d, l, 0) end
+    else
+        inkview_SendRequestTo = function(t, r, d, l) inkview.SendRequestTo(t, r, d, l, 0, 2000) end
+    end
+
+    local appname = "browser.app"
+    local task = inkview.FindTaskByAppName(appname)
+    if task > 0 then
+        local data = ffi.new("void *[1]")
+        local len = ffi.new("int[1]")
+        inkview.PackParameters(1, ffi.new("const char *[1]", {link}), data, len)
+        inkview_SendRequestTo(task, C.REQ_OPENBOOK2, data[0], len[0])
+        C.free(data[0])
+        inkview.SetActiveTask(task, 0)
+    else
+        local _, bin = getBrowser()
+        local args = ffi.new("const char *[3]", {bin, link, nil})
+        inkview.NewTask(bin, ffi.cast("char **", args), appname, appname, nil, C.TASK_MAKEACTIVE)
+    end
+    -- the above logic is available in newer PocketBook SDKs [1] as OpenTask:
+    --
+    --     ffi.cdef[[ int OpenTask(const char *, int, const char **, int); ]]
+    --
+    --     local argv = ffi.new("const char *[1]", {link})
+    --     inkview.OpenTask("/usr/bin/browser.app", 1, argv, C.TASK_MAKEACTIVE)
+    --
+    -- we're using an older SDK for compatibility, so we need to handle this manually
+    --
+    -- [1]: https://github.com/pocketbook/SDK_6.3.0/blob/6.5/SDK-B288/usr/arm-obreey-linux-gnueabi/sysroot/usr/local/include/inkview.h
+end
+
 -- Pocketbook HW rotation modes start from landsape, CCW
 local function landscape_ccw() return {
     1, 0, 3, 2,         -- PORTRAIT, LANDSCAPE, PORTRAIT_180, LANDSCAPE_180