The Formatting String Catastrophe

11 files changed, 66 insertions, 66 deletions

diff --git a/source/windowing/StarFuelWidget.cpp b/source/windowing/StarFuelWidget.cpp
index 43ea3d5..af51cb2 100644
--- a/source/windowing/StarFuelWidget.cpp
+++ b/source/windowing/StarFuelWidget.cpp
@@ -86,7 +86,7 @@ void FuelWidget::renderImpl() {
     guiContext.setFontColor(Color::White.toRgba());
   }
 
-  guiContext.renderInterfaceText(strf("Fuel %s/%s", std::min(m_fuelLevel + m_potential, m_maxLevel), (int)m_maxLevel),
+  guiContext.renderInterfaceText(strf("Fuel {}/{}", std::min(m_fuelLevel + m_potential, m_maxLevel), (int)m_maxLevel),
       {textPosition, HorizontalAnchor::HMidAnchor, VerticalAnchor::VMidAnchor});
 }
 
diff --git a/source/windowing/StarGuiReader.cpp b/source/windowing/StarGuiReader.cpp
index 4e02529..f44706a 100644
--- a/source/windowing/StarGuiReader.cpp
+++ b/source/windowing/StarGuiReader.cpp
@@ -38,10 +38,10 @@ WidgetConstructResult GuiReader::titleHandler(String const&, Json const& config)
         String type = iconConfig.getString("type");
         auto icon = m_constructors.get(type)("icon", iconConfig);
         if (!icon.obj)
-          throw WidgetParserException(strf("Title specified incompatible icon type: %s", type));
+          throw WidgetParserException(strf("Title specified incompatible icon type: {}", type));
         m_pane->setTitle(icon.obj, title, subtitle);
       } catch (JsonException const& e) {
-        throw WidgetParserException(strf("Malformed icon configuration data in title. %s", outputException(e, false)));
+        throw WidgetParserException(strf("Malformed icon configuration data in title. {}", outputException(e, false)));
       }
     }
   } else {
@@ -74,7 +74,7 @@ WidgetConstructResult GuiReader::backgroundHandler(String const&, Json const& co
       footer = config.getString("fileFooter", "");
     } catch (MapException const& e) {
       throw WidgetParserException(
-          strf("Malformed gui json, missing a required value in the map. %s", outputException(e, false)));
+          strf("Malformed gui json, missing a required value in the map. {}", outputException(e, false)));
     }
 
     m_pane->setBG(header, body, footer);
diff --git a/source/windowing/StarGuiTypes.cpp b/source/windowing/StarGuiTypes.cpp
index 2085426..80ac5fd 100644
--- a/source/windowing/StarGuiTypes.cpp
+++ b/source/windowing/StarGuiTypes.cpp
@@ -23,7 +23,7 @@ EnumMap<GuiDirection> const GuiDirectionNames{
 };
 
 String rarityBorder(Rarity rarity) {
-  return strf("/interface/inventory/itemborder%s.png", RarityNames.getRight(rarity).toLower());
+  return strf("/interface/inventory/itemborder{}.png", RarityNames.getRight(rarity).toLower());
 }
 
 }
diff --git a/source/windowing/StarItemGridWidget.cpp b/source/windowing/StarItemGridWidget.cpp
index 624385b..ad02c32 100644
--- a/source/windowing/StarItemGridWidget.cpp
+++ b/source/windowing/StarItemGridWidget.cpp
@@ -155,7 +155,7 @@ void ItemGridWidget::setItemBag(ItemBagConstPtr bag) {
   m_slots.clear();
   for (size_t i = 0; i < m_bag->size() - m_bagOffset && i < (unsigned)m_dimensions[0] * m_dimensions[1]; ++i) {
     auto itemSlot = make_shared<ItemSlotWidget>(m_bag->at(i), m_backingImage);
-    addChild(strf("%d", i), itemSlot);
+    addChild(strf("{}", i), itemSlot);
     m_slots.append(itemSlot);
     itemSlot->setBackingImageAffinity(m_drawBackingImageWhenFull, m_drawBackingImageWhenEmpty);
     itemSlot->setProgress(m_progress);
diff --git a/source/windowing/StarItemSlotWidget.cpp b/source/windowing/StarItemSlotWidget.cpp
index a828838..cf12a8d 100644
--- a/source/windowing/StarItemSlotWidget.cpp
+++ b/source/windowing/StarItemSlotWidget.cpp
@@ -178,20 +178,20 @@ void ItemSlotWidget::renderImpl() {
     }
 
     int frame = (int)roundf(m_progress * 18); // TODO: Hardcoded lol
-    context()->drawInterfaceQuad(String(strf("/interface/cooldown.png:%d", frame)), Vec2F(screenPosition()));
+    context()->drawInterfaceQuad(String(strf("/interface/cooldown.png:{}", frame)), Vec2F(screenPosition()));
 
     if (m_item->count() > 1 && m_showCount) { // we don't need to tell people that there's only 1 of something
       context()->setFont(m_font);
       context()->setFontSize(m_fontSize);
       context()->setFontColor(m_fontColor.toRgba());
       context()->setFontMode(m_countFontMode);
-      context()->renderInterfaceText(strf("%d", m_item->count()), m_countPosition.translated(Vec2F(screenPosition())));
+      context()->renderInterfaceText(strf("{}", m_item->count()), m_countPosition.translated(Vec2F(screenPosition())));
     }
 
   } else if (m_drawBackingImageWhenEmpty && m_backingImage != "") {
     context()->drawInterfaceQuad(m_backingImage, Vec2F(screenPosition()));
     int frame = (int)roundf(m_progress * 18); // TODO: Hardcoded lol
-    context()->drawInterfaceQuad(String(strf("/interface/cooldown.png:%d", frame)), Vec2F(screenPosition()));
+    context()->drawInterfaceQuad(String(strf("/interface/cooldown.png:{}", frame)), Vec2F(screenPosition()));
   }
 
   if (m_highlightEnabled) {
diff --git a/source/windowing/StarKeyBindings.cpp b/source/windowing/StarKeyBindings.cpp
index e93a1af..969a766 100644
--- a/source/windowing/StarKeyBindings.cpp
+++ b/source/windowing/StarKeyBindings.cpp
@@ -107,10 +107,10 @@ KeyChord inputDescriptorFromJson(Json const& json) {
     } else if (value.canConvert(Json::Type::Int)) {
       key = (Key)value.toUInt();
     } else {
-      throw StarException::format("Improper key value '%s'", value);
+      throw StarException::format("Improper key value '{}'", value);
     }
   } else {
-    throw StarException::format("Improper bindings type '%s'", type);
+    throw StarException::format("Improper bindings type '{}'", type);
   }
 
   KeyMod mods = KeyMod::NoMod;
@@ -156,7 +156,7 @@ KeyBindings::KeyBindings(Json const& json) {
           auto chord = inputDescriptorFromJson(input);
           actions[chord.key].append({chord.mods, action});
         } catch (StarException const& e) {
-          Logger::warn("Could not load keybinding for %s: %s\n",
+          Logger::warn("Could not load keybinding for {}: {}\n",
               InterfaceActionNames.getRight(action),
               outputException(e, false));
         }
@@ -165,7 +165,7 @@ KeyBindings::KeyBindings(Json const& json) {
 
     m_actions = move(actions);
   } catch (StarException const& e) {
-    throw StarException(strf("Could not set keybindings from configuration. %s", outputException(e, false)));
+    throw StarException(strf("Could not set keybindings from configuration. {}", outputException(e, false)));
   }
 }
 
diff --git a/source/windowing/StarListWidget.cpp b/source/windowing/StarListWidget.cpp
index cda7f92..993fb73 100644
--- a/source/windowing/StarListWidget.cpp
+++ b/source/windowing/StarListWidget.cpp
@@ -63,14 +63,14 @@ void ListWidget::setSchema(Json const& schema) {
     m_spacing = jsonToVec2I(schema.get("spacing"));
     m_memberSize = jsonToVec2I(schema.get("memberSize"));
   } catch (JsonException const& e) {
-    throw GuiException(strf("Missing required value in map: %s", outputException(e, false)));
+    throw GuiException(strf("Missing required value in map: {}", outputException(e, false)));
   }
   updateSizeAndPosition();
 }
 
 WidgetPtr ListWidget::addItem() {
   auto newItem = constructWidget();
-  addChild(strf("%d", Random::randu64()), newItem);
+  addChild(strf("{}", Random::randu64()), newItem);
   updateSizeAndPosition();
 
   return newItem;
@@ -78,7 +78,7 @@ WidgetPtr ListWidget::addItem() {
 
 WidgetPtr ListWidget::addItem(size_t at) {
   auto newItem = constructWidget();
-  addChildAt(strf("%d", Random::randu64()), newItem, at);
+  addChildAt(strf("{}", Random::randu64()), newItem, at);
   updateSizeAndPosition();
 
   if (m_selectedItem != NPos && at <= m_selectedItem)
@@ -88,7 +88,7 @@ WidgetPtr ListWidget::addItem(size_t at) {
 }
 
 WidgetPtr ListWidget::addItem(WidgetPtr existingItem) {
-  addChild(strf("%d", Random::randu64()), existingItem);
+  addChild(strf("{}", Random::randu64()), existingItem);
   updateSizeAndPosition();
 
   return existingItem;
diff --git a/source/windowing/StarRegisteredPaneManager.hpp b/source/windowing/StarRegisteredPaneManager.hpp
index fb17ee5..4038525 100644
--- a/source/windowing/StarRegisteredPaneManager.hpp
+++ b/source/windowing/StarRegisteredPaneManager.hpp
@@ -50,7 +50,7 @@ template <typename T>
 shared_ptr<T> RegisteredPaneManager<KeyT>::registeredPane(KeyT const& paneId) const {
   if (auto v = m_registeredPanes.ptr(paneId))
     return convert<T>(v->pane);
-  throw GuiException(strf("No pane named '%s' found in RegisteredPaneManager", outputAny(paneId)));
+  throw GuiException(strf("No pane named '{}' found in RegisteredPaneManager", outputAny(paneId)));
 }
 
 template <typename KeyT>
@@ -58,7 +58,7 @@ void RegisteredPaneManager<KeyT>::registerPane(
     KeyT paneId, PaneLayer paneLayer, PanePtr pane, DismissCallback onDismiss) {
   if (!m_registeredPanes.insert(move(paneId), {move(paneLayer), move(pane), move(onDismiss)}).second)
     throw GuiException(
-        strf("Registered pane with name '%s' registered a second time in RegisteredPaneManager::registerPane",
+        strf("Registered pane with name '{}' registered a second time in RegisteredPaneManager::registerPane",
             outputAny(paneId)));
 }
 
@@ -69,7 +69,7 @@ PanePtr RegisteredPaneManager<KeyT>::deregisterPane(KeyT const& paneId) {
       dismissPane(v->pane);
     return v->pane;
   }
-  throw GuiException(strf("No pane named '%s' found in RegisteredPaneManager::deregisterPane", outputAny(paneId)));
+  throw GuiException(strf("No pane named '{}' found in RegisteredPaneManager::deregisterPane", outputAny(paneId)));
 }
 
 template <typename KeyT>
@@ -119,7 +119,7 @@ typename RegisteredPaneManager<KeyT>::PaneInfo const& RegisteredPaneManager<KeyT
     KeyT const& paneId) const {
   if (auto p = m_registeredPanes.ptr(paneId))
     return *p;
-  throw GuiException(strf("No registered pane with name '%s' found in  RegisteredPaneManager", outputAny(paneId)));
+  throw GuiException(strf("No registered pane with name '{}' found in  RegisteredPaneManager", outputAny(paneId)));
 }
 }
 
diff --git a/source/windowing/StarSliderBar.cpp b/source/windowing/StarSliderBar.cpp
index 12fb749..e25ed4f 100644
--- a/source/windowing/StarSliderBar.cpp
+++ b/source/windowing/StarSliderBar.cpp
@@ -39,17 +39,17 @@ SliderBarWidget::SliderBarWidget(String const& grid, bool showSpinner)
     // TODO: Make spinners a thing already
     Json config = Json::parse(strf(
         R"SPINNER(
-          {
-            "spinner" : {
+          {{
+            "spinner" : {{
               "type" : "spinner",
-              "leftBase" : "%s",
-              "leftHover" : "%s",
-              "rightBase" : "%s",
-              "rightHover" : "%s",
+              "leftBase" : "{}",
+              "leftHover" : "{}",
+              "rightBase" : "{}",
+              "rightHover" : "{}",
               "position" : [0, 0],
-              "upOffset" : %s
-            }
-          }
+              "upOffset" : {}
+            }}
+          }}
         )SPINNER",
         assets->json("/interface.config:slider.leftBase").toString(),
         assets->json("/interface.config:slider.leftHover").toString(),
diff --git a/source/windowing/StarWidget.cpp b/source/windowing/StarWidget.cpp
index 3189f8a..518b922 100644
--- a/source/windowing/StarWidget.cpp
+++ b/source/windowing/StarWidget.cpp
@@ -427,15 +427,15 @@ String Widget::toStringImpl(int indentLevel) const {
   for (auto child : m_members) {
     childrenString.append(child->toStringImpl(indentLevel + 4));
   }
-  String output = strf(R"OUTPUT(%s%s : {
-%s  address : %p,
-%s  visible : %s,
-%s  position : %s,
-%s  size : %s,
-%s  children : {
-%s
-%s  }
-%s}
+  String output = strf(R"OUTPUT({}{} : {
+{}  address : %p,
+{}  visible : {},
+{}  position : {},
+{}  size : {},
+{}  children : {
+{}
+{}  }
+{}}
 )OUTPUT",
       leader,
       m_name,
diff --git a/source/windowing/StarWidgetParsing.cpp b/source/windowing/StarWidgetParsing.cpp
index 4ffc921..c7bc69e 100644
--- a/source/windowing/StarWidgetParsing.cpp
+++ b/source/windowing/StarWidgetParsing.cpp
@@ -75,7 +75,7 @@ void WidgetParser::constructImpl(Json const& config, Widget* widget) {
 
 WidgetPtr WidgetParser::makeSingle(String const& name, Json const& config) {
   if (!m_constructors.contains(config.getString("type"))) {
-    throw WidgetParserException(strf("Unknown type in gui json. %s", config.getString("type")));
+    throw WidgetParserException(strf("Unknown type in gui json. {}", config.getString("type")));
   }
 
   auto constructResult = m_constructors.get(config.getString("type"))(name, config);
@@ -94,7 +94,7 @@ List<WidgetConstructResult> WidgetParser::constructor(Json const& config) {
       widgets.appendAll(constructor(Root::singleton().assets()->json(memberConfig.getString("file"))));
     } else {
       if (!m_constructors.contains(type)) {
-        throw WidgetParserException(strf("Unknown type in gui json. %s", type));
+        throw WidgetParserException(strf("Unknown type in gui json. {}", type));
       }
       auto constructResult =
           m_constructors.get(memberConfig.getString("type"))(memberConfig.getString("name"), memberConfig);
@@ -110,7 +110,7 @@ List<WidgetConstructResult> WidgetParser::constructor(Json const& config) {
     for (auto const& elem : config.iterateArray())
       addWidget(elem);
   } else {
-    throw WidgetParserException(strf("Malformed gui json, expected a Map or a List. Instead got %s", config));
+    throw WidgetParserException(strf("Malformed gui json, expected a Map or a List. Instead got {}", config));
   }
 
   return widgets;
@@ -129,7 +129,7 @@ WidgetConstructResult WidgetParser::buttonHandler(String const& name, Json const
       baseImage = config.getString("base");
   } catch (MapException const& e) {
     throw WidgetParserException(
-        strf("Malformed gui json, missing a required value in the map. %s", outputException(e, false)));
+        strf("Malformed gui json, missing a required value in the map. {}", outputException(e, false)));
   }
 
   String hoverImage = config.getString("hover", "");
@@ -144,7 +144,7 @@ WidgetConstructResult WidgetParser::buttonHandler(String const& name, Json const
   String callback = config.getString("callback", name);
 
   if (!m_callbacks.contains(callback))
-    throw WidgetParserException::format("Failed to find callback named: %s", callback);
+    throw WidgetParserException::format("Failed to find callback named: {}", callback);
   WidgetCallbackFunc callbackFunc = m_callbacks.get(callback);
 
   auto button = make_shared<ButtonWidget>(callbackFunc, baseImage, hoverImage, pressedImage, disabledImage);
@@ -177,7 +177,7 @@ WidgetConstructResult WidgetParser::buttonHandler(String const& name, Json const
     button->setTextAlign(HorizontalAnchor::LeftAnchor);
   } else {
     throw WidgetParserException(strf(
-        "Malformed gui json, expected textAlign to be one of \"left\", \"right\", or \"center\", got %s", hAnchor));
+        "Malformed gui json, expected textAlign to be one of \"left\", \"right\", or \"center\", got {}", hAnchor));
   }
 
   if (config.contains("fontSize"))
@@ -251,9 +251,9 @@ WidgetConstructResult WidgetParser::spinnerHandler(String const& name, Json cons
   String callback = config.getString("callback", name);
 
   if (!m_callbacks.contains(callback + ".up"))
-    throw WidgetParserException::format("Failed to find spinner callback named: '%s.up'", name);
+    throw WidgetParserException::format("Failed to find spinner callback named: '{}.up'", name);
   if (!m_callbacks.contains(callback + ".down"))
-    throw WidgetParserException::format("Failed to find spinner callback named: '%s.down'", name);
+    throw WidgetParserException::format("Failed to find spinner callback named: '{}.down'", name);
 
   WidgetCallbackFunc callbackDown = m_callbacks.get(callback + ".down");
   WidgetCallbackFunc callbackUp = m_callbacks.get(callback + ".up");
@@ -301,11 +301,11 @@ WidgetConstructResult WidgetParser::radioGroupHandler(String const& name, Json c
     buttons = config.getArray("buttons");
   } catch (MapException const& e) {
     throw WidgetParserException(
-        strf("Malformed gui json, missing a required value in the map. %s", outputException(e, false)));
+        strf("Malformed gui json, missing a required value in the map. {}", outputException(e, false)));
   }
 
   if (!m_callbacks.contains(callback))
-    throw WidgetParserException::format("Failed to find callback named: '%s'", callback);
+    throw WidgetParserException::format("Failed to find callback named: '{}'", callback);
 
   String baseImage = config.getString("baseImage", "");
   String hoverImage = config.getString("hoverImage", "");
@@ -360,10 +360,10 @@ WidgetConstructResult WidgetParser::radioGroupHandler(String const& name, Json c
 
       common(button, btnConfig);
 
-      buttonGroup->addChild(strf("%d", button->buttonGroupId()), button);
+      buttonGroup->addChild(strf("{}", button->buttonGroupId()), button);
     } catch (MapException const& e) {
       throw WidgetParserException(
-          strf("Malformed gui json, missing a required value in the map. %s", outputException(e, false)));
+          strf("Malformed gui json, missing a required value in the map. {}", outputException(e, false)));
     }
   }
 
@@ -390,7 +390,7 @@ WidgetConstructResult WidgetParser::textboxHandler(String const& name, Json cons
   String callback = config.getString("callback", name);
 
   if (!m_callbacks.contains(callback))
-    throw WidgetParserException::format("Failed to find textbox callback named: '%s'", name);
+    throw WidgetParserException::format("Failed to find textbox callback named: '{}'", name);
 
   WidgetCallbackFunc callbackFunc = m_callbacks.get(callback);
 
@@ -417,7 +417,7 @@ WidgetConstructResult WidgetParser::textboxHandler(String const& name, Json cons
     textbox->setTextAlign(HorizontalAnchor::HMidAnchor);
   } else if (hAnchor != "left") {
     throw WidgetParserException(strf(
-        "Malformed gui json, expected textAlign to be one of \"left\", \"right\", or \"center\", got %s", hAnchor));
+        "Malformed gui json, expected textAlign to be one of \"left\", \"right\", or \"center\", got {}", hAnchor));
   }
 
   if (config.contains("fontSize"))
@@ -477,11 +477,11 @@ WidgetConstructResult WidgetParser::itemSlotHandler(String const& name, Json con
   auto itemSlot = make_shared<ItemSlotWidget>(ItemPtr(), backingImage);
 
   if (!m_callbacks.contains(callback))
-    throw WidgetParserException::format("Failed to find itemSlot callback named: '%s'", callback);
+    throw WidgetParserException::format("Failed to find itemSlot callback named: '{}'", callback);
   itemSlot->setCallback(m_callbacks.get(callback));
 
   if (!m_callbacks.contains(rightClickCallback))
-    throw WidgetParserException::format("Failed to find itemslot rightClickCallback named: '%s'", rightClickCallback);
+    throw WidgetParserException::format("Failed to find itemslot rightClickCallback named: '{}'", rightClickCallback);
 
   itemSlot->setRightClickCallback(m_callbacks.get(rightClickCallback));
   itemSlot->setBackingImageAffinity(config.getBool("showBackingImageWhenFull", false), config.getBool("showBackingImageWhenEmpty", true));
@@ -509,7 +509,7 @@ WidgetConstructResult WidgetParser::itemGridHandler(String const& name, Json con
       columnSpacing = jsonToVec2I(config.get("columnSpacing"));
     }
   } catch (MapException const& e) {
-    throw WidgetParserException::format("Malformed gui json, missing a required value in the map. %s", outputException(e, false));
+    throw WidgetParserException::format("Malformed gui json, missing a required value in the map. {}", outputException(e, false));
   }
 
   String backingImage = config.getString("backingImage", "");
@@ -526,7 +526,7 @@ WidgetConstructResult WidgetParser::itemGridHandler(String const& name, Json con
   auto itemGrid = make_shared<ItemGridWidget>(ItemBagConstPtr(), dimensions, rowSpacing, columnSpacing, backingImage, slotOffset);
 
   if (!m_callbacks.contains(callback))
-    throw WidgetParserException::format("Failed to find itemgrid callback named: '%s'", callback);
+    throw WidgetParserException::format("Failed to find itemgrid callback named: '{}'", callback);
 
   itemGrid->setCallback(m_callbacks.get(callback));
 
@@ -535,7 +535,7 @@ WidgetConstructResult WidgetParser::itemGridHandler(String const& name, Json con
   itemGrid->showDurability(config.getBool("showDurability", false));
 
   if (!m_callbacks.contains(rightClickCallback))
-    throw WidgetParserException::format("Failed to find itemgrid rightClickCallback named: '%s'", rightClickCallback);
+    throw WidgetParserException::format("Failed to find itemgrid rightClickCallback named: '{}'", rightClickCallback);
 
   itemGrid->setRightClickCallback(m_callbacks.get(rightClickCallback));
 
@@ -550,7 +550,7 @@ WidgetConstructResult WidgetParser::listHandler(String const& name, Json const&
     schema = config.get("schema");
   } catch (MapException const& e) {
     throw WidgetParserException(
-        strf("Malformed gui json, missing a required value in the map. %s", outputException(e, false)));
+        strf("Malformed gui json, missing a required value in the map. {}", outputException(e, false)));
   }
 
   auto list = make_shared<ListWidget>(schema);
@@ -593,7 +593,7 @@ WidgetConstructResult WidgetParser::sliderHandler(String const& name, Json const
     return WidgetConstructResult(slider, name, config.getFloat("zlevel", 0));
   } catch (MapException const& e) {
     throw WidgetParserException::format(
-        "Malformed gui json, missing a required value in the map. %s", outputException(e, false));
+        "Malformed gui json, missing a required value in the map. {}", outputException(e, false));
   }
 }
 
@@ -601,7 +601,7 @@ WidgetConstructResult WidgetParser::largeCharPlateHandler(String const& name, Js
   String callback = config.getString("callback", name);
 
   if (!m_callbacks.contains(callback))
-    throw WidgetParserException::format("Failed to find callback named: '%s'", name);
+    throw WidgetParserException::format("Failed to find callback named: '{}'", name);
 
   auto charPlate = make_shared<LargeCharPlateWidget>(m_callbacks.get(callback));
   common(charPlate, config);
@@ -639,7 +639,7 @@ WidgetConstructResult WidgetParser::tabSetHandler(String const& name, Json const
       tabSet->addTab(entry.getString("tabName"), widget, entry.getString("tabTitle"));
     }
   } catch (JsonException const& e) {
-    throw WidgetParserException(strf("Malformed gui json. %s", outputException(e, false)));
+    throw WidgetParserException(strf("Malformed gui json. {}", outputException(e, false)));
   }
 
   return WidgetConstructResult(tabSet, name, config.getFloat("zlevel", 0));
@@ -673,7 +673,7 @@ WidgetConstructResult WidgetParser::layoutHandler(String const& name, Json const
     try {
       flow->setSpacing(jsonToVec2I(config.get("spacing")));
     } catch (JsonException const& e) {
-      throw WidgetParserException(strf("Parameter \"spacing\" in FlowLayout specification is invalid: %s.", outputException(e, false)));
+      throw WidgetParserException(strf("Parameter \"spacing\" in FlowLayout specification is invalid: {}.", outputException(e, false)));
     }
   } else if (type == "vertical") {
     widget = make_shared<VerticalLayout>();
@@ -685,7 +685,7 @@ WidgetConstructResult WidgetParser::layoutHandler(String const& name, Json const
   } else if (type == "basic") {
     widget = make_shared<Layout>();
   } else {
-    throw WidgetParserException(strf("Invalid layout type \"%s\".  Options are \"basic\", \"flow\", \"vertical\".", type));
+    throw WidgetParserException(strf("Invalid layout type \"{}\".  Options are \"basic\", \"flow\", \"vertical\".", type));
   }
   common(widget, config);
   if (config.contains("children"))
@@ -745,7 +745,7 @@ WidgetConstructResult WidgetParser::stackHandler(String const& name, Json const&
       auto widget = make_shared<Widget>();
       constructImpl(widgetCfg, widget.get());
       widget->determineSizeFromChildren();
-      stack->addChild(strf("%d", stack->numChildren()), widget);
+      stack->addChild(strf("{}", stack->numChildren()), widget);
     }
   }
 
@@ -811,7 +811,7 @@ ImageStretchSet WidgetParser::parseImageStretchSet(Json const& config) {
   } else if (type == "stretch") {
     res.type = ImageStretchSet::ImageStretchType::Stretch;
   } else {
-    throw WidgetParserException(strf("Could not parse Image Stretch Set, unknown type: %s"));
+    throw WidgetParserException(strf("Could not parse Image Stretch Set, unknown type: {}"));
   }
 
   return res;