Tame some ButtonTable users into re-using Buttontable instances if possible (#7166)

* QuickDictLookup, ImageViewer, NumberPicker: Smarter `update` that will re-use most of the widget's layout instead of re-instantiating all the things.
* SpinWidget/DoubleSpinWidget: The NumberPicker change above renders a hack to preserve alpha on these widgets almost unnecessary. Also fixed said hack to also apply to the center, value button.

* Button: Don't re-instantiate the frame in setText/setIcon when unnecessary (e.g., no change at all, or no layout change).
* Button: Add a refresh method that repaints and refreshes a *specific* Button (provided it's been painted once) all on its lonesome.

* ConfigDialog: Free everything that's going to be re-instatiated on update
 
* A few more post #7118 fixes:
  * SkimTo: Always flag the chapter nav buttons as vsync
  * Button: Fix the highlight on rounded buttons when vsync is enabled (e.g., it's now entirely visible, instead of showing a weird inverted corner glitch).
  * Some more heuristic tweaks in Menu/TouchMenu/Button/IconButton
* ButtonTable: fix the annoying rounding issue I'd noticed in #7054 ;).

* Enable dithering in TextBoxWidget (e.g., in the Wikipedia full view). This involved moving the HW dithering align fixup to base, where it always ought to have been ;).

* Switch a few widgets that were using "partial" on close to "ui", or, more rarely, "flashui". The intent being to limit "partial" purely to the Reader, because it has a latency cost when mixed with other refreshes, which happens often enough in UI ;).

* Minor documentation tweaks around UIManager's `setDirty` to reflect that change.

* ReaderFooter: Force a footer repaint on resume if it is visible (otherwise, just update it).
* ReaderBookmark: In the same vein, don't repaint an invisible footer on bookmark count changes.

frontend/ui/widget/spinwidget.lua

@@ -72,14 +72,15 @@ function SpinWidget:init()
             },
          }
     end
+
+    -- Actually the widget layout
     self:update()
 end
 
 function SpinWidget:update()
-    -- This picker_update_callback will be redefined later. It is needed
-    -- so we can have our MovableContainer repainted on NumberPickerWidgets
-    -- update. It is needed if we have enabled transparency on MovableContainer,
-    -- otherwise the NumberPicker area gets opaque on update.
+    -- This picker_update_callback will be redefined later.
+    -- It's a hack to restore transparency after a Button unhighlight in NumberPicker,
+    -- in case the MovableContainer was actually made transparent.
     local picker_update_callback = function() end
     local value_widget = NumberPickerWidget:new{
         show_parent = self,
@@ -242,9 +243,25 @@ function SpinWidget:update()
         return "ui", self.spin_frame.dimen
     end)
     picker_update_callback = function()
-        UIManager:setDirty("all", function()
-            return "ui", self.movable.dimen
-        end)
+        -- If we're actually transparent, force an alpha-aware repaint.
+        if self.movable.alpha then
+            if G_reader_settings:nilOrTrue("flash_ui") then
+                -- It's delayed to the next tick to actually catch a Button unhighlight.
+                UIManager:nextTick(function()
+                    UIManager:setDirty("all", function()
+                        return "ui", self.movable.dimen
+                    end)
+                end)
+            else
+                -- This should only really be necessary for the up/down buttons here,
+                -- because they repaint the center value button & text, unlike said button,
+                -- which just pops up the VK.
+                -- On the upside, we shouldn't need to delay anything without flash_ui ;).
+                UIManager:setDirty("all", function()
+                    return "ui", self.movable.dimen
+                end)
+            end
+        end
     end
 end
 
@@ -255,7 +272,7 @@ end
 
 function SpinWidget:onCloseWidget()
     UIManager:setDirty(nil, function()
-        return "partial", self.spin_frame.dimen
+        return "ui", self.spin_frame.dimen
     end)
     return true
 end