Dict, Trapper: prevent dismissal by past events

Add UIManager:discardEvents(), to allow dropping events
for a period of time.
Default duration of 600ms on eInk, 300ms otherwise.
Used when showing the dict result window, so that a tap
happening just when it's being shown won't discard it.
Used with Trapper:confirm()/:info(), to avoid taps made
in a previous processing to dismiss (and so, select the
cancel action) a ConfirmBox not yet painted/visible.

frontend/apps/reader/modules/readerdictionary.lua

@@ -889,6 +889,12 @@ function ReaderDictionary:showDict(word, results, box, link)
     self:dismissLookupInfo()
     if results and results[1] then
         UIManager:show(self.dict_window)
+        if not results[1].lookup_cancelled then
+            -- Discard queued and coming up events to avoid accidental
+            -- dismissal (but not if lookup interrupted, so 2 quick
+            -- taps can discard everything)
+            UIManager:discardEvents(true)
+        end
     end
 end
 

frontend/ui/trapper.lua

@@ -165,6 +165,9 @@ function Trapper:info(text, fast_refresh)
                 ok_callback = function()
                     coroutine.resume(_coroutine, false)
                 end,
+                -- flush any pending tap, so past events won't be considered
+                -- action on the yet to be displayed widget
+                flush_events_on_show = true,
             }
             UIManager:show(abort_box)
             -- no need to forceRePaint, UIManager will do it when we yield()
@@ -186,10 +189,6 @@ function Trapper:info(text, fast_refresh)
         -- continue processing
     end
 
-    --- @todo We should try to flush any pending tap, so past
-    -- events won't be considered action on the yet to be displayed
-    -- widget
-
     -- If fast_refresh option, avoid UIManager refresh overhead
     if fast_refresh and self.current_widget and self.current_widget.is_infomessage then
         local orig_moved_offset = self.current_widget.movable:getMovedOffset()
@@ -214,7 +213,10 @@ function Trapper:info(text, fast_refresh)
             dismiss_callback = function()
                 coroutine.resume(_coroutine, false)
             end,
-            is_infomessage = true -- flag on our InfoMessages
+            is_infomessage = true, -- flag on our InfoMessages
+            -- flush any pending tap, so past events won't be considered
+            -- action on the yet to be displayed widget
+            flush_events_on_show = true,
         }
         logger.dbg("Showing InfoMessage:", text)
         UIManager:show(self.current_widget)
@@ -268,10 +270,6 @@ function Trapper:confirm(text, cancel_text, ok_text)
         return true -- always select "OK" in ConfirmBox if no UI
     end
 
-    --- @todo We should try to flush any pending tap, so past
-    -- events won't be considered action on the yet to be displayed
-    -- widget
-
     -- Close any previous widget
     if self.current_widget then
         UIManager:close(self.current_widget)
@@ -289,6 +287,9 @@ function Trapper:confirm(text, cancel_text, ok_text)
         ok_callback = function()
             coroutine.resume(_coroutine, true)
         end,
+        -- flush any pending tap, so past events won't be considered
+        -- action on the yet to be displayed widget
+        flush_events_on_show = true,
     }
     logger.dbg("Showing ConfirmBox and waiting for answer:", text)
     UIManager:show(self.current_widget)

frontend/ui/uimanager.lua

@@ -39,6 +39,7 @@ local UIManager = {
     _exit_code = nil,
     _prevent_standby_count = 0,
     _prev_prevent_standby_count = 0,
+    _discard_events_till = nil,
 
     event_hook = require("ui/hook_container"):new()
 }
@@ -797,10 +798,48 @@ function UIManager:quit()
     end
 end
 
+--- Request events to be ignored for some duration
+function UIManager:discardEvents(set_or_seconds)
+    if not set_or_seconds then -- remove any previously set
+        self._discard_events_till = nil
+        return
+    end
+    local usecs
+    if set_or_seconds == true then
+        -- Use an adequate delay to account for device refresh duration
+        -- so any events happening in this delay (ie. before a widget
+        -- is really painted on screen) are discarded.
+        if Device:hasEinkScreen() then
+            -- A screen refresh can take a few 100ms,
+            -- sometimes > 500ms on some devices/temperatures
+            usecs = 600000
+        else
+            -- On non-eInk screen, it's usually instantaneous
+            usecs = 300000
+        end
+    else -- we expect a number
+        usecs = set_or_seconds * MILLION
+    end
+    local now = { util.gettime() }
+    local now_us = now[1] * MILLION + now[2]
+    self._discard_events_till = now_us + usecs
+end
+
 --- Transmits an event to an active widget.
 function UIManager:sendEvent(event)
     if #self._window_stack == 0 then return end
 
+    -- Ensure discardEvents
+    if self._discard_events_till then
+        local now = { util.gettime() }
+        local now_us = now[1] * MILLION + now[2]
+        if now_us < self._discard_events_till then
+            return
+        else
+            self._discard_events_till = nil
+        end
+    end
+
     local top_widget = self._window_stack[#self._window_stack]
     -- top level widget has first access to the event
     if top_widget.widget:handleEvent(event) then

frontend/ui/widget/confirmbox.lua

@@ -51,6 +51,8 @@ local ConfirmBox = InputContainer:new{
     margin = Size.margin.default,
     padding = Size.padding.default,
     dismissable = true, -- set to false if any button callback is required
+    flush_events_on_show = false, -- set to true when it might be displayed after
+                                  -- some processing, to avoid accidental dismissal
 }
 
 function ConfirmBox:init()
@@ -182,6 +184,10 @@ function ConfirmBox:onShow()
     UIManager:setDirty(self, function()
         return "ui", self[1][1].dimen
     end)
+    if self.flush_events_on_show then
+        -- Discard queued and coming up events to avoid accidental dismissal
+        UIManager:discardEvents(true)
+    end
 end
 
 function ConfirmBox:onCloseWidget()

frontend/ui/widget/infomessage.lua

@@ -69,6 +69,8 @@ local InfoMessage = InputContainer:new{
     no_refresh_on_close = nil,
     -- Only have it painted after this delay (dismissing still works before it's shown)
     show_delay = nil,
+    -- Set to true when it might be displayed after some processing, to avoid accidental dismissal
+    flush_events_on_show = false,
 }
 
 function InfoMessage:init()
@@ -224,6 +226,10 @@ function InfoMessage:onShow()
     UIManager:setDirty(self, function()
         return "ui", self[1][1].dimen
     end)
+    if self.flush_events_on_show then
+        -- Discard queued and coming up events to avoid accidental dismissal
+        UIManager:discardEvents(true)
+    end
     -- schedule us to close ourself if timeout provided
     if self.timeout then
         UIManager:scheduleIn(self.timeout, function() UIManager:close(self) end)