PDF free zoom mode revisit

this should implement feature request of zoom mode for multi-columns
page in #501
This PR depends on koreader/koreader-base#435

How to use?
1. Tap the top left corner of a PDF/Djvu page to get into the flipping
mode
2. Double-tap on text block will zoom in to that column
3. Double-tap on any area will zoom out to an overview of the page
4. repeat step 2 to focus to another page block

How does it work?
1. We first find the mask of text blocks in the page. (Pic 1)
2. Then we intersect page boxes with user tap to form a page block. (Pic 2)
3. Finally we zoom the page to the page block and center current view to
that block. (Pic 3)

defaults.lua

@@ -136,9 +136,6 @@ DMINIBAR_HEIGHT = 7             -- Should be smaller than DMINIBAR_CONTAINER_HEI
 DMINIBAR_CONTAINER_HEIGHT = 14  -- Larger means more padding at the bottom, at the risk of eating into the last line
 DMINIBAR_FONT_SIZE = 14
 
--- gesture detector defaults
-DGESDETECT_DISABLE_DOUBLE_TAP = true
-
 -- change this to any numerical value if you want to antomatically save settings when turning pages
 DAUTO_SAVE_PAGING_COUNT = nil
 

frontend/apps/reader/modules/readerpaging.lua

@@ -267,30 +267,24 @@ function ReaderPaging:onToggleBookmarkFlipping()
 end
 
 function ReaderPaging:enterFlippingMode()
-    self.ui:handleEvent(Event:new("EnterFlippingMode"))
     self.orig_reflow_mode = self.view.document.configurable.text_wrap
     self.orig_scroll_mode = self.view.page_scroll
     self.orig_zoom_mode = self.view.zoom_mode
     DEBUG("store zoom mode", self.orig_zoom_mode)
-    self.DGESDETECT_DISABLE_DOUBLE_TAP = DGESDETECT_DISABLE_DOUBLE_TAP
-
     self.view.document.configurable.text_wrap = 0
     self.view.page_scroll = self.flipping_scroll_mode
     Input.disable_double_tap = false
-    DGESDETECT_DISABLE_DOUBLE_TAP = false
-    self.ui:handleEvent(Event:new("SetZoomMode", self.flipping_zoom_mode))
+    self.ui:handleEvent(Event:new("EnterFlippingMode", self.flipping_zoom_mode))
 end
 
 function ReaderPaging:exitFlippingMode()
-    self.ui:handleEvent(Event:new("ExitFlippingMode"))
     self.view.document.configurable.text_wrap = self.orig_reflow_mode
     self.view.page_scroll = self.orig_scroll_mode
-    DGESDETECT_DISABLE_DOUBLE_TAP = self.DGESDETECT_DISABLE_DOUBLE_TAP
-    Input.disable_double_tap = DGESDETECT_DISABLE_DOUBLE_TAP
+    Input.disable_double_tap = true
     self.flipping_zoom_mode = self.view.zoom_mode
     self.flipping_scroll_mode = self.view.page_scroll
     DEBUG("restore zoom mode", self.orig_zoom_mode)
-    self.ui:handleEvent(Event:new("SetZoomMode", self.orig_zoom_mode))
+    self.ui:handleEvent(Event:new("ExitFlippingMode", self.orig_zoom_mode))
 end
 
 function ReaderPaging:updateOriginalPage(page)

frontend/apps/reader/modules/readerzooming.lua

@@ -113,7 +113,7 @@ function ReaderZooming:onReadSettings(config)
 end
 
 function ReaderZooming:onSaveSettings()
-    self.ui.doc_settings:saveSetting("zoom_mode", self.zoom_mode)
+    self.ui.doc_settings:saveSetting("zoom_mode", self.orig_zoom_mode or self.zoom_mode)
 end
 
 function ReaderZooming:onSpread(arg, ges)
@@ -141,7 +141,6 @@ end
 function ReaderZooming:onToggleFreeZoom(arg, ges)
     if self.zoom_mode ~= "free" then
         self.orig_zoom = self.zoom
-        self.orig_zoom_mode = self.zoom_mode
         local xpos, ypos
         self.zoom, xpos, ypos = self:getRegionalZoomCenter(self.current_page, ges.pos)
         DEBUG("zoom center", self.zoom, xpos, ypos)
@@ -152,7 +151,7 @@ function ReaderZooming:onToggleFreeZoom(arg, ges)
         end
         self.view:SetZoomCenter(xpos, ypos)
     else
-        self.ui:handleEvent(Event:new("SetZoomMode", self.orig_zoom_mode or "page"))
+        self.ui:handleEvent(Event:new("SetZoomMode", "page"))
     end
 end
 
@@ -207,6 +206,20 @@ function ReaderZooming:onReZoom()
     return true
 end
 
+function ReaderZooming:onEnterFlippingMode(zoom_mode)
+    self.orig_zoom_mode = self.zoom_mode
+    if zoom_mode == "free" then
+        self.ui:handleEvent(Event:new("SetZoomMode", "page"))
+    else
+        self.ui:handleEvent(Event:new("SetZoomMode", zoom_mode))
+    end
+end
+
+function ReaderZooming:onExitFlippingMode(zoom_mode)
+    self.orig_zoom_mode = nil
+    self.ui:handleEvent(Event:new("SetZoomMode", zoom_mode))
+end
+
 function ReaderZooming:getZoom(pageno)
     -- check if we're in bbox mode and work on bbox if that's the case
     local zoom = nil
@@ -254,22 +267,19 @@ end
 function ReaderZooming:getRegionalZoomCenter(pageno, pos)
     local p_pos = self.view:getSinglePagePosition(pos)
     local page_size = self.ui.document:getNativePageDimensions(pageno)
-    local pos_x = p_pos.x / page_size.w / p_pos.zoom
-    local pos_y = p_pos.y / page_size.h / p_pos.zoom
-    local regions = self.ui.document:getPageRegions(pageno)
-    DEBUG("get page regions", regions)
+    local pos_x = p_pos.x / page_size.w
+    local pos_y = p_pos.y / page_size.h
+    local block = self.ui.document:getPageBlock(pageno, pos_x, pos_y)
     local margin = self.ui.document.configurable.page_margin * Screen:getDPI()
-    for i = 1, #regions do
-        if regions[i].x0 <= pos_x and pos_x <= regions[i].x1
-            and regions[i].y0 <= pos_y and pos_y <= regions[i].y1 then
-            local zoom = 1/(regions[i].x1 - regions[i].x0)
-            zoom = zoom/(1 + 3*margin/zoom/page_size.w)
-            local xpos = (regions[i].x0 + regions[i].x1)/2 * zoom * page_size.w
-            local ypos = p_pos.y / p_pos.zoom * zoom
-            return zoom, xpos, ypos
-        end
+    if block then
+        local zoom = self.dimen.w / page_size.w / (block.x1 - block.x0)
+        zoom = zoom/(1 + 3*margin/zoom/page_size.w)
+        local xpos = (block.x0 + block.x1)/2 * zoom * page_size.w
+        local ypos = p_pos.y / p_pos.zoom * zoom
+        return zoom, xpos, ypos
     end
-    return 2
+    local zoom = 2*self.dimen.w / page_size.w
+    return zoom/(1 + 3*margin/zoom/page_size.w)
 end
 
 function ReaderZooming:setZoom()

frontend/device/input.lua

@@ -88,7 +88,7 @@ local Input = {
     },
 
     timer_callbacks = {},
-    disable_double_tap = DGESDETECT_DISABLE_DOUBLE_TAP,
+    disable_double_tap = true,
 
     -- keyboard state:
     modifiers = {

frontend/document/djvudocument.lua

@@ -69,8 +69,8 @@ function DjvuDocument:getOCRText(pageno, tboxes)
     return self.koptinterface:getOCRText(self, pageno, tboxes)
 end
 
-function DjvuDocument:getPageRegions(pageno)
-    return self.koptinterface:getPageRegions(self, pageno)
+function DjvuDocument:getPageBlock(pageno, x, y)
+    return self.koptinterface:getPageBlock(self, pageno, x, y)
 end
 
 function DjvuDocument:getUsedBBox(pageno)

frontend/document/koptinterface.lua

@@ -540,10 +540,11 @@ end
 --[[
 get page regions in native page via optical method,
 --]]
-function KoptInterface:getPageRegions(doc, pageno)
+function KoptInterface:getPageBlock(doc, pageno, x, y)
+    local kctx = nil
     local bbox = doc:getPageBBox(pageno)
     local context_hash = self:getContextHash(doc, pageno, bbox)
-    local hash = "pageregions|"..context_hash
+    local hash = "pageblocks|"..context_hash
     local cached = Cache:check(hash)
     if not cached then
         local page_size = Document.getNativePageDimensions(doc, pageno)
@@ -553,17 +554,19 @@ function KoptInterface:getPageRegions(doc, pageno)
             y1 = page_size.h,
         }
         local kc = self:createContext(doc, pageno, bbox)
-        kc:setZoom(1.0)
+        local screen_size = Screen:getSize()
+        -- leptonica needs a source image of at least 300dpi
+        kc:setZoom(screen_size.w / page_size.w * 300 / self.screen_dpi)
         local page = doc._document:openPage(pageno)
         page:getPagePix(kc)
-        local regions = kc:getPageRegions()
-        Cache:insert(hash, CacheItem:new{ pageregions = regions })
+        kc:findPageBlocks()
+        Cache:insert(hash, CacheItem:new{ kctx = kc })
         page:close()
-        kc:free()
-        return regions
+        kctx = kc
     else
-        return cached.pageregions
+        kctx = cached.kctx
     end
+    return kctx:getPageBlock(x, y)
 end
 
 --[[

frontend/document/pdfdocument.lua

@@ -77,8 +77,8 @@ function PdfDocument:getOCRText(pageno, tboxes)
     return self.koptinterface:getOCRText(self, pageno, tboxes)
 end
 
-function PdfDocument:getPageRegions(pageno)
-    return self.koptinterface:getPageRegions(self, pageno)
+function PdfDocument:getPageBlock(pageno, x, y)
+    return self.koptinterface:getPageBlock(self, pageno, x, y)
 end
 
 function PdfDocument:getUsedBBox(pageno)

frontend/ui/uimanager.lua

@@ -181,8 +181,6 @@ function UIManager:close(widget, refreshtype, refreshregion)
         return
     end
     dbg("close widget", widget.id)
-    -- TODO: Why do we the following?
-    Input.disable_double_tap = DGESDETECT_DISABLE_DOUBLE_TAP
     local dirty = false
     for i = #self._window_stack, 1, -1 do
         if self._window_stack[i].widget == widget then