Notifications: stack them instead of overdrawing them

frontend/ui/widget/notification.lua

@@ -10,9 +10,11 @@ local FrameContainer = require("ui/widget/container/framecontainer")
 local Geom = require("ui/geometry")
 local GestureRange = require("ui/gesturerange")
 local InputContainer = require("ui/widget/container/inputcontainer")
+local RectSpan = require("ui/widget/rectspan")
 local Size = require("ui/size")
 local TextWidget = require("ui/widget/textwidget")
 local UIManager = require("ui/uimanager")
+local VerticalGroup = require("ui/widget/verticalgroup")
 local Input = Device.input
 local Screen = Device.screen
 
@@ -23,6 +25,8 @@ local Notification = InputContainer:new{
     padding = Size.padding.default,
     timeout = 2, -- default to 2 seconds
     toast = true, -- closed on any event, and let the event propagate to next top widget
+
+    _nums_shown = {}, -- array of stacked notifications
 }
 
 function Notification:init()
@@ -48,18 +52,12 @@ function Notification:init()
         end
     end
 
-    -- we construct the actual content here because self.text is only available now
     local text_widget = TextWidget:new{
         text = self.text,
         face = self.face,
     }
     local widget_size = text_widget:getSize()
-    self[1] = CenterContainer:new{
-        dimen = Geom:new{
-            w = Screen:getWidth(),
-            h = math.floor(Screen:getHeight() / 10),
-        },
-        FrameContainer:new{
+    self.frame = FrameContainer:new{
         background = Blitbuffer.COLOR_WHITE,
         radius = 0,
         margin = self.margin,
@@ -72,12 +70,51 @@ function Notification:init()
             text_widget,
         }
     }
+    local notif_height = self.frame:getSize().h
+
+    self:_cleanShownStack()
+    table.insert(Notification._nums_shown, os.time())
+    self.num = #Notification._nums_shown
+
+    self[1] = VerticalGroup:new{
+        align = "center",
+        -- We use a span to properly position this notification:
+        RectSpan:new{
+            -- have this VerticalGroup full width, to ensure centering
+            width = Screen:getWidth(),
+            -- push this frame at its y=self.num position
+            height = notif_height * (self.num - 1),
+        },
+        self.frame,
     }
 end
 
+function Notification:_cleanShownStack(num)
+    -- Clean stack of shown notifications
+    if num then
+        -- This notification is no longer displayed
+        Notification._nums_shown[num] = false
+    end
+    -- We remove from the stack tail all slots no longer displayed.
+    -- Even if slots at top are available, we'll keep adding new
+    -- notifications only at the tail/bottom (easier for the eyes
+    -- to follow what is happening).
+    -- As a sanity check, we also forget those shown for
+    -- more than 30s in case no close event was received.
+    local expire_ts = os.time() - 30
+    for i=#Notification._nums_shown, 1, -1 do
+        if Notification._nums_shown[i] and Notification._nums_shown[i] > expire_ts then
+            break -- still shown (or not yet expired)
+        end
+        table.remove(Notification._nums_shown, i)
+    end
+end
+
 function Notification:onCloseWidget()
+    self:_cleanShownStack(self.num)
+    self.num = nil -- avoid mess in case onCloseWidget is called multiple times
     UIManager:setDirty(nil, function()
-        return "ui", self[1][1].dimen
+        return "ui", self.frame.dimen
     end)
     return true
 end
@@ -85,7 +122,7 @@ end
 function Notification:onShow()
     -- triggered by the UIManager after we got successfully shown (not yet painted)
     UIManager:setDirty(self, function()
-        return "ui", self[1][1].dimen
+        return "ui", self.frame.dimen
     end)
     if self.timeout then
         UIManager:scheduleIn(self.timeout, function() UIManager:close(self) end)