Font zooming more than 1 (#2989)

frontend/apps/reader/modules/readerfont.lua

@@ -19,6 +19,8 @@ local ReaderFont = InputContainer:new{
     face_table = nil,
     -- default gamma from crengine's lvfntman.cpp
     gamma_index = nil,
+    steps = {0,1,1,1,1,1,2,2,2,3,3,3,4,4,5},
+    gestureScale = Screen:getWidth() * FRONTLIGHT_SENSITIVITY_DECREASE,
 }
 
 function ReaderFont:init()
@@ -78,7 +80,7 @@ function ReaderFont:setupTouchZones()
                 screen_zone = {
                     ratio_x = 0, ratio_y = 0, ratio_w = 1, ratio_h = 1,
                 },
-                handler = function() return self:onSpread() end
+                handler = function(ges) return self:onAdjustSpread(ges) end
             },
             {
                 id = "id_pinch",
@@ -86,7 +88,7 @@ function ReaderFont:setupTouchZones()
                 screen_zone = {
                     ratio_x = 0, ratio_y = 0, ratio_w = 1, ratio_h = 1,
                 },
-                handler = function() return self:onPinch() end
+                handler = function(ges) return self:onAdjustPinch(ges) end
             },
         })
     end
@@ -160,9 +162,13 @@ end
 --[[
     UpdatePos event is used to tell ReaderRolling to update pos.
 --]]
-function ReaderFont:onChangeSize(direction)
+function ReaderFont:onChangeSize(direction, font_delta)
     local delta = direction == "decrease" and -1 or 1
-    self.font_size = self.font_size + delta
+    if font_delta then
+        self.font_size = self.font_size + font_delta * delta
+    else
+        self.font_size = self.font_size + delta
+    end
     self.ui:handleEvent(Event:new("SetFontSize", self.font_size))
     return true
 end
@@ -258,20 +264,24 @@ function ReaderFont:addToMainMenu(menu_items)
     }
 end
 
-function ReaderFont:onPinch()
-    local info = Notification:new{text = _("Decreasing font size…")}
+function ReaderFont:onAdjustSpread(ges)
+    local step = math.ceil(2 * #self.steps * ges.distance / self.gestureScale)
+    local delta_int = self.steps[step] or self.steps[#self.steps]
+    local info = Notification:new{text = _("Increasing font size…")}
     UIManager:show(info)
     UIManager:forceRePaint()
-    self:onChangeSize("decrease")
+    self:onChangeSize("increase", delta_int)
     UIManager:close(info)
     return true
 end
 
-function ReaderFont:onSpread()
-    local info = Notification:new{text = _("Increasing font size…")}
+function ReaderFont:onAdjustPinch(ges)
+    local step = math.ceil(2 * #self.steps * ges.distance / self.gestureScale)
+    local delta_int = self.steps[step] or self.steps[#self.steps]
+    local info = Notification:new{text = _("Decreasing font size…")}
     UIManager:show(info)
     UIManager:forceRePaint()
-    self:onChangeSize("increase")
+    self:onChangeSize("decrease", delta_int)
     UIManager:close(info)
     return true
 end