Better tracking, management and freeing of BlitBuffers

This should fix the most obvious memory leaks (noticable when
using images as screensaver).
ImageWidget: added a few more options needed by ImageViewer,
and removed 'overflow' option as logic was wrong.

frontend/ui/screensaver.lua

@@ -30,6 +30,7 @@ local function createWidgetFromFile(file)
         return createWidgetFromImage(
                    ImageWidget:new{
                        file = file,
+                       file_do_cache = false,
                        height = Screen:getHeight(),
                        width = Screen:getWidth(),
                        autostretch = true,

frontend/ui/widget/container/alphacontainer.lua

@@ -29,6 +29,9 @@ function AlphaContainer:paintTo(bb, x, y)
     or private_bb:getWidth() ~= contentSize.w
     or private_bb:getHeight() ~= contentSize.h
     then
+        if private_bb then
+            private_bb:free() -- free the one we're going to replace
+        end
         -- create private blitbuffer for our child widget to paint to
         private_bb = BlitBuffer.new(contentSize.w, contentSize.h, bb:getType())
         self.private_bb = private_bb
@@ -38,6 +41,9 @@ function AlphaContainer:paintTo(bb, x, y)
         or self.background_bb:getWidth() ~= contentSize.w
         or self.background_bb:getHeight() ~= contentSize.h
         then
+            if self.background_bb then
+                self.background_bb:free() -- free the one we're going to replace
+            end
             self.background_bb = BlitBuffer.new(contentSize.w, contentSize.h, bb:getType())
         end
         self.background_bb:blitFrom(bb, 0, 0, x, y)
@@ -51,4 +57,16 @@ function AlphaContainer:paintTo(bb, x, y)
     bb:addblitFrom(private_bb, x, y, nil, nil, nil, nil, self.alpha)
 end
 
+function AlphaContainer:onCloseWidget()
+    if self.private_bb then
+        self.private_bb:free()
+        self.private_bb = nil
+    end
+    if self.background_bb then
+        self.background_bb:free()
+        self.background_bb = nil
+    end
+end
+
+
 return AlphaContainer

frontend/ui/widget/imagewidget.lua

@@ -46,8 +46,17 @@ function ImageCacheItem:onFree()
 end
 
 local ImageWidget = Widget:new{
+    -- Can be provided with a path to a file
     file = nil,
+    -- or an already made BlitBuffer (ie: made by Mupdf.renderImage())
     image = nil,
+
+    -- Whether BlitBuffer rendered from file should be cached
+    file_do_cache = true,
+    -- Whether provided BlitBuffer can be modified by us and SHOULD be free() by us,
+    -- normally true unless our caller wants to reuse it's provided image
+    image_disposable = true,
+
     invert = nil,
     dim = nil,
     hide = nil,
@@ -62,15 +71,19 @@ local ImageWidget = Widget:new{
     -- widget size. i.e. either fit the width or fit the height according to the
     -- original image size.
     autostretch = false,
-    -- when overflow is set to true, image will be stretched to fit the widget
-    -- size vertically and horizontally, without impact original aspect ratio.
-    -- But overflow part will be ignored.
-    overflow = false,
-    _bb = nil
+    -- when pre_rotate is not 0, native image is rotated by this angle
+    -- before applying the other autostretch/autoscale settings
+    pre_rotate = 0,
+    -- former 'overflow' setting removed, as logic was wrong
+
+    _bb = nil,
+    _bb_disposable = true -- whether we should free() our _bb
 }
 
 function ImageWidget:_loadimage()
     self._bb = self.image
+    -- don't touch or free if caller doesn't want that
+    self._bb_disposable = self.image_disposable
 end
 
 function ImageWidget:_loadfile()
@@ -82,9 +95,11 @@ function ImageWidget:_loadfile()
         if cache then
             -- hit cache
             self._bb = cache.bb
+            self._bb_disposable = false -- don't touch or free a cached _bb
         else
-            if self.height and self.height > 200 then -- don't cache big images
+            if not self.file_do_cache then
                 self._bb = Mupdf.renderImageFile(self.file, self.width, self.height)
+                self._bb_disposable = true -- we made it, we can modify and free it
             else
                 -- cache this image
                 logger.dbg("cache", hash)
@@ -94,6 +109,7 @@ function ImageWidget:_loadfile()
                 cache.size = cache.bb.pitch * cache.bb.h * cache.bb:getBpp() / 8
                 ImageCache:insert(hash, cache)
                 self._bb = cache.bb
+                self._bb_disposable = false -- don't touch or free a cached _bb
             end
         end
     else
@@ -112,6 +128,14 @@ function ImageWidget:_render()
     else
         error("cannot render image")
     end
+    if self.pre_rotate ~= 0 then
+        if not self._bb_disposable then
+            -- we can't modify _bb, make a copy
+            self._bb = self._bb:copy()
+            self._bb_disposable = true -- new object will have to be freed
+        end
+        self._bb:rotate(self.pre_rotate) -- rotate in-place
+    end
     local native_w, native_h = self._bb:getWidth(), self._bb:getHeight()
     local w, h = self.width, self.height
     if self.autoscale then
@@ -126,22 +150,20 @@ function ImageWidget:_render()
                 h = self.height
                 w = self.width * ratio
             else
-                h = self.height * ratio
-                w = self.width
-            end
-        elseif self.overflow then
-            local ratio = native_w / self.width / native_h * self.height
-            if ratio < 1 then
                 h = self.height / ratio
                 w = self.width
-            else
-                h = self.height
-                w = self.width / ratio
             end
         end
     end
     if (w and w ~= native_w) or (h and h ~= native_h) then
-        self._bb = self._bb:scale(w or native_w, h or native_h)
+        -- We're making a new blitbuffer, we need to explicitely free
+        -- the old one to not leak memory
+        local new_bb = self._bb:scale(w or native_w, h or native_h)
+        if self._bb_disposable then
+            self._bb:free()
+        end
+        self._bb = new_bb
+        self._bb_disposable = true -- new object will have to be freed
     end
 end
 
@@ -177,11 +199,20 @@ function ImageWidget:paintTo(bb, x, y)
     end
 end
 
+-- This will normally be called by our WidgetContainer:free()
+-- But it SHOULD explicitely be called if we are getting replaced
+-- (ie: in some other widget's update()), to not leak memory with
+-- BlitBuffer zombies
 function ImageWidget:free()
-    if self.image then
-        self.image:free()
-        self.image = nil
+    if self._bb and self._bb_disposable and self._bb.free then
+        self._bb:free()
+        self._bb = nil
     end
 end
 
+function ImageWidget:onCloseWidget()
+    -- free when UIManager:close() was called
+    self:free()
+end
+
 return ImageWidget