[feat] Implement fulltext search direction (#5283)

Closes <https://github.com/koreader/koreader/issues/5054>.

frontend/apps/reader/modules/readersearch.lua

@@ -30,15 +30,36 @@ end
 function ReaderSearch:onShowFulltextSearchInput()
     self:onInput{
         title = _("Enter text to search for"),
-        ok_text = _("Search all text"),
         type = "text",
-        callback = function(input)
-            self:onShowSearchDialog(input)
-        end,
+        buttons = {
+            {
+                {
+                    text = _("Cancel"),
+                    callback = function()
+                        self:closeInputDialog()
+                    end,
+                },
+                {
+                    text = "◁",
+                    callback = function()
+                        self:onShowSearchDialog(self.input_dialog:getInputText(), 1)
+                        self:closeInputDialog()
+                    end,
+                },
+                {
+                    text = "▷",
+                    is_enter_default = true,
+                    callback = function()
+                        self:onShowSearchDialog(self.input_dialog:getInputText(), 0)
+                        self:closeInputDialog()
+                    end,
+                },
+            },
+        },
     }
 end
 
-function ReaderSearch:onShowSearchDialog(text)
+function ReaderSearch:onShowSearchDialog(text, direction)
     local neglect_current_location = false
     local current_page
     local do_search = function(search_func, _text, param)
@@ -122,19 +143,19 @@ function ReaderSearch:onShowSearchDialog(text)
         buttons = {
             {
                 {
-                    text = "|<",
+                    text = "▕◁",
                     callback = do_search(self.searchFromStart, text),
                 },
                 {
-                    text = "<",
+                    text = "◁",
                     callback = do_search(self.searchNext, text, 1),
                 },
                 {
-                    text = ">",
+                    text = "▷",
                     callback = do_search(self.searchNext, text, 0),
                 },
                 {
-                    text = ">|",
+                    text = "▷▏",
                     callback = do_search(self.searchFromEnd, text),
                 },
             }
@@ -145,7 +166,7 @@ function ReaderSearch:onShowSearchDialog(text)
             UIManager:setDirty(self.dialog, "ui")
         end,
     }
-    do_search(self.searchFromCurrent, text, 0)()
+    do_search(self.searchFromCurrent, text, direction)()
     UIManager:show(self.search_dialog)
     --- @todo regional
     UIManager:setDirty(self.dialog, "partial")