Screensaver: allow limiting stretch of covers and images (#8570)

ImageWidget: adds stretch_limit_percentage parameter.
Add support for screensaver on the emulator, for easier testing.

frontend/device/sdl/device.lua

@@ -318,22 +318,17 @@ function Device:setDateTime(year, month, day, hour, min, sec)
     end
 end
 
+function Emulator:supportsScreensaver() return true end
+
 function Emulator:simulateSuspend()
-    local InfoMessage = require("ui/widget/infomessage")
-    local UIManager = require("ui/uimanager")
-    local _ = require("gettext")
-    UIManager:show(InfoMessage:new{
-        text = _("Suspend")
-    })
+    local Screensaver = require("ui/screensaver")
+    Screensaver:setup()
+    Screensaver:show()
 end
 
 function Emulator:simulateResume()
-    local InfoMessage = require("ui/widget/infomessage")
-    local UIManager = require("ui/uimanager")
-    local _ = require("gettext")
-    UIManager:show(InfoMessage:new{
-        text = _("Resume")
-    })
+    local Screensaver = require("ui/screensaver")
+    Screensaver:close()
 end
 
 -- fake network manager for the emulator

frontend/ui/elements/screensaver_menu.lua

@@ -126,7 +126,7 @@ return {
                 text = _("Covers and images settings"),
                 sub_item_table = {
                     {
-                        text = _("Black background behind covers and images"),
+                        text = _("Black background"),
                         checked_func = function()
                             return G_reader_settings:readSetting("screensaver_img_background") == "black"
                         end,
@@ -135,7 +135,7 @@ return {
                         end,
                     },
                     {
-                        text = _("White background behind covers and images"),
+                        text = _("White background"),
                         checked_func = function()
                             return G_reader_settings:readSetting("screensaver_img_background") == "white"
                         end,
@@ -144,7 +144,7 @@ return {
                         end,
                     },
                     {
-                        text = _("Leave background as-is behind covers and images"),
+                        text = _("Leave background as-is"),
                         checked_func = function()
                             return G_reader_settings:readSetting("screensaver_img_background") == "none"
                         end,
@@ -153,12 +153,20 @@ return {
                         end,
                     },
                     {
-                        text = _("Stretch covers and images to fit screen"),
+                        text_func = function()
+                            if G_reader_settings:nilOrFalse("screensaver_stretch_images") then
+                                return _("Stretch to fit screen")
+                            elseif G_reader_settings:readSetting("screensaver_stretch_limit_percentage") then
+                                return _("Stretch to fit screen (with limit)")
+                            else
+                                return _("Stretch to fit screen")
+                            end
+                        end,
                         checked_func = function()
                             return G_reader_settings:isTrue("screensaver_stretch_images")
                         end,
-                        callback = function()
-                            G_reader_settings:toggle("screensaver_stretch_images")
+                        callback = function(touchmenu_instance)
+                            Screensaver:setStretchLimit(touchmenu_instance)
                         end,
                         separator = true,
                     },

frontend/ui/screensaver.lua

@@ -14,6 +14,7 @@ local ImageWidget = require("ui/widget/imagewidget")
 local Math = require("optmath")
 local OverlapGroup = require("ui/widget/overlapgroup")
 local ScreenSaverWidget = require("ui/widget/screensaverwidget")
+local SpinWidget = require("ui/widget/spinwidget")
 local TextBoxWidget = require("ui/widget/textboxwidget")
 local TopContainer = require("ui/widget/container/topcontainer")
 local UIManager = require("ui/uimanager")
@@ -383,6 +384,34 @@ function Screensaver:setMessage()
     self.input_dialog:onShowKeyboard()
 end
 
+function Screensaver:setStretchLimit(touchmenu_instance)
+    UIManager:show(SpinWidget:new{
+        value = G_reader_settings:readSetting("screensaver_stretch_limit_percentage", 8),
+        value_min = 0,
+        value_max = 25,
+        default_value = 8, -- percent
+        title_text = _("Set maximum stretch limit"),
+        ok_text = _("Set"),
+        ok_always_enabled = true,
+        callback = function(spin)
+            G_reader_settings:saveSetting("screensaver_stretch_limit_percentage", spin.value)
+            G_reader_settings:makeTrue("screensaver_stretch_images")
+            if touchmenu_instance then touchmenu_instance:updateItems() end
+        end,
+        extra_text = _("Disable stretch"),
+        extra_callback = function()
+            G_reader_settings:makeFalse("screensaver_stretch_images")
+            if touchmenu_instance then touchmenu_instance:updateItems() end
+        end,
+        option_text = _("Full stretch"),
+        option_callback = function()
+            G_reader_settings:makeTrue("screensaver_stretch_images")
+            G_reader_settings:delSetting("screensaver_stretch_limit_percentage")
+            if touchmenu_instance then touchmenu_instance:updateItems() end
+        end,
+    })
+end
+
 -- When called after setup(), may not match the saved settings, because it accounts for fallbacks that might have kicked in.
 function Screensaver:getMode()
    return self.screensaver_type
@@ -543,6 +572,7 @@ function Screensaver:show()
             width = Screen:getWidth(),
             height = Screen:getHeight(),
             scale_factor = G_reader_settings:isFalse("screensaver_stretch_images") and 0 or nil,
+            stretch_limit_percentage = G_reader_settings:readSetting("screensaver_stretch_limit_percentage"),
         }
     elseif self.screensaver_type == "bookstatus" then
         local ReaderUI = require("apps/reader/readerui")
@@ -565,6 +595,7 @@ function Screensaver:show()
             width = Screen:getWidth(),
             height = Screen:getHeight(),
             scale_factor = G_reader_settings:isFalse("screensaver_stretch_images") and 0 or nil,
+            stretch_limit_percentage = G_reader_settings:readSetting("screensaver_stretch_limit_percentage"),
         }
     elseif self.screensaver_type == "readingprogress" then
         widget = Screensaver.getReaderProgress()

frontend/ui/widget/imagewidget.lua

@@ -81,12 +81,18 @@ local ImageWidget = Widget:new{
     -- If scale_for_dpi is true image will be rescaled according to screen dpi
     scale_for_dpi = false,
 
-    -- When scale_factor is not nil, native image is scaled by this factor
-    -- (if scale_factor == 1, native image size is kept)
-    -- Special case : scale_factor == 0 : image will be scaled to best fit provided
-    -- width and height, keeping aspect ratio (scale_factor will be updated
-    -- from 0 to the factor used at _render() time)
+    -- When scale_factor is not nil, native image is scaled by this factor,
+    --   (if scale_factor == 1, native image size is kept)
+    --   Special case: scale_factor == 0 : image will be scaled to best fit provided
+    --   width and height, keeping aspect ratio (scale_factor will be updated
+    --   from 0 to the factor used at _render() time)
+    -- If scale_factor is nil and stretch_limit_percantage is provided:
+    --   If the aspect ratios of the image and the width/height provided don't differ by more than
+    --   stretch_limit_percentage, then stretch the image (as scale_factor=nil);
+    --   otherwise, scale to best fit (as scale_factor=0)
+    -- In all other cases the image will be stretched to best fit the container.
     scale_factor = nil,
+    stretch_limit_percentage = nil,
 
     -- Whether to use former blitbuffer:scale() (default to using MuPDF)
     use_legacy_image_scaling = G_reader_settings:isTrue("legacy_image_scaling"),
@@ -281,8 +287,18 @@ function ImageWidget:_render()
         self.scale_factor = self.scale_factor * DPI_SCALE
     end
 
-    -- scale to best fit container : compute scale_factor for that
+    if self.stretch_limit_percentage and not self.scale_factor then
+        -- stretch or scale to fit container, depending on self.stretch_limit_percentage
+        local screen_ratio = self.width / self.height
+        local image_ratio = bb_w / bb_h
+        local ratio_divergence_percent = math.abs(100 - image_ratio / screen_ratio * 100)
+        if ratio_divergence_percent > self.stretch_limit_percentage then
+            self.scale_factor = 0
+        end
+    end
+
     if self.scale_factor == 0 then
+        -- scale to best fit container: compute scale_factor for that
         if self.width and self.height then
             self.scale_factor = math.min(self.width / bb_w, self.height / bb_h)
             logger.dbg("ImageWidget: scale to fit, setting scale_factor to", self.scale_factor)

frontend/ui/widget/spinwidget.lua

@@ -47,9 +47,12 @@ local SpinWidget = InputContainer:new{
     -- Set this to add upper default button that restores number to its default value
     default_value = nil,
     default_text = nil,
-    -- Optional extra button above ok/cancel buttons row
+    -- Optional extra button
     extra_text = nil,
     extra_callback = nil,
+    -- Optional extra button above ok/cancel buttons row
+    option_text = nil,
+    option_callback = nil,
 }
 
 function SpinWidget:init()
@@ -138,21 +141,37 @@ function SpinWidget:update(numberpicker_value, numberpicker_value_index)
             },
         })
     end
-    if self.extra_text then
-        table.insert(buttons, {
-            {
-                text = self.extra_text,
-                callback = function()
-                    if self.extra_callback then
-                        self.value, self.value_index = value_widget:getValue()
-                        self.extra_callback(self)
-                    end
-                    if not self.keep_shown_on_apply then -- assume extra wants it same as ok
-                        self:onClose()
-                    end
-                end,
-            },
-        })
+
+    local extra_button = {
+        text = self.extra_text,
+        callback = function()
+            if self.extra_callback then
+                self.value, self.value_index = value_widget:getValue()
+                self.extra_callback(self)
+            end
+            if not self.keep_shown_on_apply then -- assume extra wants it same as ok
+                self:onClose()
+            end
+        end,
+    }
+    local option_button = {
+        text = self.option_text,
+        callback = function()
+            if self.option_callback then
+                self.value, self.value_index = value_widget:getValue()
+                self.option_callback(self)
+            end
+            if not self.keep_shown_on_apply then -- assume option wants it same as ok
+                self:onClose()
+            end
+        end,
+    }
+    if self.extra_text and not self.option_text then
+        table.insert(buttons, {extra_button})
+    elseif self.option_text and not self.extra_text then
+        table.insert(buttons, {option_button})
+    elseif self.extra_text and self.option_text then
+        table.insert(buttons, {extra_button, option_button})
     end
     table.insert(buttons, {
         {