ImageViewer: start with image fullscreen with no buttons shown (#5446)

Tap any part of screen to toggle bottom buttons visibility.
Swipe south to quickly close it (as long as image is scaled
to fit, and there's no need for panning).

frontend/ui/widget/imageviewer.lua

@@ -54,6 +54,8 @@ local ImageViewer = InputContainer:new{
     caption = nil,
     caption_visible = true, -- caption visible by default
     caption_tap_area = nil,
+    -- Start with buttons hidden (tap on screen will toggle their visibility)
+    buttons_visible = false,
 
     width = nil,
     height = nil,
@@ -81,6 +83,7 @@ local ImageViewer = InputContainer:new{
     _image_wg = nil,
     _images_list = nil,
     _images_list_disposable = nil,
+
 }
 
 function ImageViewer:init()
@@ -165,52 +168,57 @@ function ImageViewer:update()
         self.width = Screen:getWidth() - Screen:scaleBySize(40)
     end
 
-    local buttons = {
-        {
+    local button_table_size = 0
+    local button_container
+    if self.buttons_visible then
+        local buttons = {
             {
-                text = self._scale_to_fit and _("Original size") or _("Scale"),
-                callback = function()
-                    self.scale_factor = self._scale_to_fit and 1 or 0
-                    self._scale_to_fit = not self._scale_to_fit
-                    -- Reset center ratio (may have been modified if some panning was done)
-                    self._center_x_ratio = 0.5
-                    self._center_y_ratio = 0.5
-                    self:update()
-                end,
+                {
+                    text = self._scale_to_fit and _("Original size") or _("Scale"),
+                    callback = function()
+                        self.scale_factor = self._scale_to_fit and 1 or 0
+                        self._scale_to_fit = not self._scale_to_fit
+                        -- Reset center ratio (may have been modified if some panning was done)
+                        self._center_x_ratio = 0.5
+                        self._center_y_ratio = 0.5
+                        self:update()
+                    end,
+                },
+                {
+                    text = self.rotated and _("No rotation") or _("Rotate"),
+                    callback = function()
+                        self.rotated = not self.rotated and true or false
+                        self:update()
+                    end,
+                },
+                {
+                    text = _("Close"),
+                    callback = function()
+                        UIManager:close(self)
+                    end,
+                },
             },
-            {
-                text = self.rotated and _("No rotation") or _("Rotate"),
-                callback = function()
-                    self.rotated = not self.rotated and true or false
-                    self:update()
-                end,
+        }
+        local button_table = ButtonTable:new{
+            width = self.width - 2*self.button_padding,
+            button_font_face = "cfont",
+            button_font_size = 20,
+            buttons = buttons,
+            zero_sep = true,
+            show_parent = self,
+        }
+        button_container = CenterContainer:new{
+            dimen = Geom:new{
+                w = self.width,
+                h = button_table:getSize().h,
             },
-            {
-                text = _("Close"),
-                callback = function()
-                    UIManager:close(self)
-                end,
-            },
-        },
-    }
-    local button_table = ButtonTable:new{
-        width = self.width - 2*self.button_padding,
-        button_font_face = "cfont",
-        button_font_size = 20,
-        buttons = buttons,
-        zero_sep = true,
-        show_parent = self,
-    }
-    local button_container = CenterContainer:new{
-        dimen = Geom:new{
-            w = self.width,
-            h = button_table:getSize().h,
-        },
-        button_table,
-    }
+            button_table,
+        }
+        button_table_size = button_table:getSize().h
+    end
 
     -- height available to our image
-    local img_container_h = self.height - button_table:getSize().h
+    local img_container_h = self.height - button_table_size
 
     local title_bar, title_sep
     if self.with_title_bar then
@@ -328,8 +336,14 @@ function ImageViewer:update()
         img_container_h = img_container_h - progress_container:getSize().h
     end
 
-    local max_image_h = img_container_h - self.image_padding*2
-    local max_image_w = self.width - self.image_padding*2
+    -- If no buttons and no title are shown, use the full screen
+    local max_image_h = img_container_h
+    local max_image_w = self.width
+    -- Otherwise, add paddings around image
+    if self.buttons_visible or self.with_title_bar then
+        max_image_h = img_container_h - self.image_padding*2
+        max_image_w = self.width - self.image_padding*2
+    end
 
     local rotation_angle = 0
     if self.rotated then
@@ -374,7 +388,9 @@ function ImageViewer:update()
     if progress_container then
         table.insert(frame_elements, progress_container)
     end
-    table.insert(frame_elements, button_container)
+    if self.buttons_visible then
+        table.insert(frame_elements, button_container)
+    end
 
     self.main_frame = FrameContainer:new{
         radius = not self.fullscreen and 8 or nil,
@@ -439,13 +455,26 @@ function ImageViewer:onTap(_, ges)
     if self.caption_tap_area and ges.pos:intersectWith(self.caption_tap_area.dimen) then
         self.caption_visible = not self.caption_visible
         self:update()
+        return true
     end
     if self._images_list then
-        if ges.pos.x < Screen:getWidth()/2 and self._images_list_cur > 1 then
-            self:switchToImageNum(self._images_list_cur - 1)
-        elseif ges.pos.x > Screen:getWidth()/2 and self._images_list_cur < self._images_list_nb then
-            self:switchToImageNum(self._images_list_cur + 1)
+        -- If it's a list of image (e.g. animated gifs), tap left/right 1/3 of screen to navigate
+        if ges.pos.x < Screen:getWidth()/3 then
+            if self._images_list_cur > 1 then
+                self:switchToImageNum(self._images_list_cur - 1)
+            end
+        elseif ges.pos.x > Screen:getWidth()*2/3 then
+            if self._images_list_cur < self._images_list_nb then
+                self:switchToImageNum(self._images_list_cur + 1)
+            end
+        else -- toggle buttons when tap on middle 1/3 of screen width
+            self.buttons_visible = not self.buttons_visible
+            self:update()
         end
+    else
+        -- No image list: tap on any part of screen toggles buttons visibility
+        self.buttons_visible = not self.buttons_visible
+        self:update()
     end
     return true
 end
@@ -479,6 +508,11 @@ function ImageViewer:onSwipe(_, ges)
             -- allow for zooming with vertical swipe on screen sides
             local dec = ges.distance / Screen:getHeight()
             self:onZoomOut(dec)
+        elseif self.scale_factor == 0 then
+            -- When scaled to fit (on initial launch, or after one has tapped
+            -- "Scale"), as we are then sure that there is no use for panning,
+            -- allow swipe south to close the widget.
+            self:onClose()
         else
             self:panBy(0, -distance)
         end