Dict lookups: have them always interruptible

They should be now interruptible when fuzzy search is disabled
and on Android.

frontend/apps/reader/modules/readerdictionary.lua

@@ -673,41 +673,29 @@ function ReaderDictionary:startSdcv(word, dict_names, fuzzy_search)
             end
         end
 
-        local results_str = nil
-        if Device:isAndroid() then
-            local A = require("android")
-            results_str = A.stdout(unpack(args))
-        else
-            local cmd = util.shell_escape(args)
-            -- cmd = "sleep 7 ; " .. cmd     -- uncomment to simulate long lookup time
-
-            if self.lookup_progress_msg then
-                -- Some sdcv lookups, when using fuzzy search with many dictionaries
-                -- and a really bad selected text, can take up to 10 seconds.
-                -- It is nice to be able to cancel it when noticing wrong text was selected.
-                -- As we have a lookup_progress_msg (that can be used to catch a tap
-                -- and trigger cancellation), and because sdcv starts outputing its
-                -- output only at the end when it has done its work, we can
-                -- use Trapper:dismissablePopen() to cancel it as long as we are waiting
-                -- for output.
-                -- We must ensure we will have some output to be readable (if no
-                -- definition found, sdcv will output some message on stderr, and
-                -- let stdout empty) by appending an "echo":
-                cmd = cmd .. "; echo"
-                local completed
-                completed, results_str = Trapper:dismissablePopen(cmd, self.lookup_progress_msg)
-                lookup_cancelled = not completed
-            else
-                -- Fuzzy search disabled, usual option for people who don't want
-                -- a "Looking up..." InfoMessage and usually fast: do a classic
-                -- blocking io.popen()
-                local std_out = io.popen(cmd, "r")
-                if std_out then
-                    results_str = std_out:read("*all")
-                    std_out:close()
-                end
-            end
-        end
+        local cmd = util.shell_escape(args)
+        -- cmd = "sleep 7 ; " .. cmd     -- uncomment to simulate long lookup time
+
+        -- Some sdcv lookups, when using fuzzy search with many dictionaries
+        -- and a really bad selected text, can take up to 10 seconds.
+        -- It is nice to be able to cancel it when noticing wrong text was
+        -- selected.
+        -- Because sdcv starts outputing its output only at the end when it has
+        -- done its work, we can use Trapper:dismissablePopen() to cancel it as
+        -- long as we are waiting for output.
+        -- When fuzzy search is enabled, we have a lookup_progress_msg that can
+        -- be used to catch a tap and trigger cancellation.
+        -- When fuzzy search is disabled, we provide false instead so an
+        -- invisible non-event-forwarding TrapWidget is used to catch a tap
+        -- and trigger cancellation (invisible so there's no need for repaint
+        -- and refresh with the usually fast non-fuzzy search lookups).
+        -- We must ensure we will have some output to be readable (if no
+        -- definition found, sdcv will output some message on stderr, and
+        -- let stdout empty) by appending an "echo":
+        cmd = cmd .. "; echo"
+        local completed, results_str = Trapper:dismissablePopen(cmd, self.lookup_progress_msg or false)
+        lookup_cancelled = not completed
+
         if results_str and results_str ~= "\n" then -- \n is when lookup was cancelled
             local ok, results = pcall(JSON.decode, results_str)
             if ok and results then

frontend/ui/trapper.lua

@@ -314,8 +314,9 @@ Notes and limitations:
 3) We need a @{ui.widget.trapwidget|TrapWidget} or @{ui.widget.infomessage|InfoMessage},
    that, as a modal, will catch any @{ui.event|Tap event} happening during
    `cmd` execution. This can be an existing already displayed widget, or
-   provided as a string (a new TrapWidget will be created). If nil, an invisible
-   TrapWidget will be used instead.
+   provided as a string (a new TrapWidget will be created). If nil, true or false,
+   an invisible TrapWidget will be used instead (if nil or true, the event will be
+   resent; if false, the event will not be resent).
 
 If we really need to have more control, we would need to use `select()` via `ffi`
 or do low level non-blocking reading on the file descriptor.
@@ -324,7 +325,7 @@ collect indefinitely, the best option would be to compile any `timeout.c`
 and use it as a wrapper.
 
 @string cmd shell `cmd` to execute and get output from
-@param trap_widget_or_string already shown widget, string or nil
+@param trap_widget_or_string already shown widget, string, or nil, true or false
 @treturn boolean completed (`true` if not interrupted, `false` if dismissed)
 @treturn string output of command
 ]]
@@ -358,10 +359,15 @@ function Trapper:dismissablePopen(cmd, trap_widget_or_string)
             UIManager:show(trap_widget)
             UIManager:forceRePaint()
         else
-            -- Use an invisible TrapWidget that resend event
+            -- Use an invisible TrapWidget that resend event, but not if
+            -- trap_widget_or_string is false (rather than nil or true)
+            local resend_event = true
+            if trap_widget_or_string == false then
+                resend_event = false
+            end
             trap_widget = TrapWidget:new{
                 text = nil,
-                resend_event = true,
+                resend_event = resend_event,
             }
             UIManager:show(trap_widget)
             own_trap_widget_invisible = true
@@ -472,11 +478,12 @@ Notes and limitations:
 4) We need a @{ui.widget.trapwidget|TrapWidget} or @{ui.widget.infomessage|InfoMessage},
    that, as a modal, will catch any @{ui.event|Tap event} happening during
    `cmd` execution. This can be an existing already displayed widget, or
-   provided as a string (a new TrapWidget will be created). If nil, an invisible
-   TrapWidget will be used instead.
+   provided as a string (a new TrapWidget will be created). If nil, true or false,
+   an invisible TrapWidget will be used instead (if nil or true, the event will be
+   resent; if false, the event will not be resent).
 
 @function task lua function to execute and get return values from
-@param trap_widget_or_string already shown widget, string or nil
+@param trap_widget_or_string already shown widget, string, or nil, true or false
 @boolean task_returns_simple_string[opt=false] true if task returns a single string
 @treturn boolean completed (`true` if not interrupted, `false` if dismissed)
 @return ... return values of task
@@ -504,10 +511,15 @@ function Trapper:dismissableRunInSubprocess(task, trap_widget_or_string, task_re
             UIManager:show(trap_widget)
             UIManager:forceRePaint()
         else
-            -- Use an invisible TrapWidget that resend event
+            -- Use an invisible TrapWidget that resend event, but not if
+            -- trap_widget_or_string is false (rather than nil or true)
+            local resend_event = true
+            if trap_widget_or_string == false then
+                resend_event = false
+            end
             trap_widget = TrapWidget:new{
                 text = nil,
-                resend_event = true,
+                resend_event = resend_event,
             }
             UIManager:show(trap_widget)
             own_trap_widget_invisible = true

frontend/ui/widget/trapwidget.lua

@@ -115,16 +115,13 @@ function TrapWidget:_dismissAndResent(evtype, ev)
     self.dismiss_callback()
     UIManager:close(self)
     if self.resend_event and evtype and ev then
-        -- XXX There may be timing problems that could cause crashes, as we
+        -- There may be some timing issues that could cause crashes, as we
         -- use nextTick, if the dismiss_callback uses UIManager:scheduleIn()
         -- or has set up some widget that may catch that event while not being
         -- yet fully initialiazed.
-        -- It happened mostly when I had some bug somewhere, and it was a quite
+        -- (It happened mostly when I had some bug somewhere, and it was a quite
         -- reliable sign of a bug somewhere, but the stacktrace was unrelated
-        -- to the bug location.
-        -- Fix to avoid crashes: in GestureRange:match(), check that self.range()
-        -- does not return nil before using it:
-        --   if not range or not range:contains(gs.pos) then return false
+        -- to the bug location.)
         UIManager:nextTick(function() UIManager:handleInputEvent(Event:new(evtype, ev)) end)
     end
     return true