BookMap/PageBrowser: allow mousewheel scrolling

Also fix SDL to use sendEvent() instead of broadcastEvent(),
so such BookMap scrolling doesn't also scroll pages in the
book below.

frontend/device/sdl/device.lua

@@ -230,12 +230,12 @@ function Device:init()
                 local fake_release_ev = Event:new("Gesture", fake_ges_release)
                 if scrolled_y == down then
                     fake_ges.direction = "north"
-                    UIManager:broadcastEvent(fake_pan_ev)
-                    UIManager:broadcastEvent(fake_release_ev)
+                    UIManager:sendEvent(fake_pan_ev)
+                    UIManager:sendEvent(fake_release_ev)
                 elseif scrolled_y == up then
                     fake_ges.direction = "south"
-                    UIManager:broadcastEvent(fake_pan_ev)
-                    UIManager:broadcastEvent(fake_release_ev)
+                    UIManager:sendEvent(fake_pan_ev)
+                    UIManager:sendEvent(fake_release_ev)
                 end
             elseif ev.code == SDL_MULTIGESTURE then
                 -- no-op for now

frontend/ui/widget/bookmapwidget.lua

@@ -639,6 +639,12 @@ function BookMapWidget:init()
                     range = self.dimen,
                 }
             },
+            Pan = { -- (for mousewheel scrolling support)
+                GestureRange:new{
+                    ges = "pan",
+                    range = self.dimen,
+                }
+            },
             Tap = {
                 GestureRange:new{
                     ges = "tap",
@@ -1608,6 +1614,16 @@ function BookMapWidget:onSwipe(arg, ges)
     end
 end
 
+function BookMapWidget:onPan(arg, ges)
+    if ges.mousewheel_direction then
+        if ges.direction == "north" then
+            return self:onScrollRowDown()
+        elseif ges.direction == "south" then
+            return self:onScrollRowUp()
+        end
+    end
+end
+
 function BookMapWidget:onPinch(arg, ges)
     if self.overview_mode then
         return true

frontend/ui/widget/pagebrowserwidget.lua

@@ -76,6 +76,12 @@ function PageBrowserWidget:init()
                     range = self.dimen,
                 }
             },
+            Pan = { -- (for mousewheel scrolling support)
+                GestureRange:new{
+                    ges = "pan",
+                    range = self.dimen,
+                }
+            },
             Tap = {
                 GestureRange:new{
                     ges = "tap",
@@ -1176,6 +1182,17 @@ function PageBrowserWidget:onSwipe(arg, ges)
     end
 end
 
+function PageBrowserWidget:onPan(arg, ges)
+    if ges.mousewheel_direction then
+        if ges.direction == "north" then
+            self:onScrollRowDown()
+        elseif ges.direction == "south" then
+            self:onScrollRowUp()
+        end
+    end
+    return true
+end
+
 function PageBrowserWidget:onPinch(arg, ges)
     if ges.direction == "horizontal" then
         if self:updateNbCols(1, true) then