[core] Use optional where SpriteAtlas return values might not exist

Fixes #3162

2 files changed, 18 insertions, 14 deletions

diff --git a/src/mbgl/sprite/sprite_atlas.cpp b/src/mbgl/sprite/sprite_atlas.cpp
index ae71f18f03..6ebebb9507 100644
--- a/src/mbgl/sprite/sprite_atlas.cpp
+++ b/src/mbgl/sprite/sprite_atlas.cpp
@@ -47,17 +47,17 @@ Rect<SpriteAtlas::dimension> SpriteAtlas::allocateImage(const size_t pixel_width
     return rect;
 }
 
-SpriteAtlasElement SpriteAtlas::getImage(const std::string& name, const bool wrap) {
+mapbox::util::optional<SpriteAtlasElement> SpriteAtlas::getImage(const std::string& name, const bool wrap) {
     std::lock_guard<std::recursive_mutex> lock(mtx);
 
     auto rect_it = images.find({ name, wrap });
     if (rect_it != images.end()) {
-        return { rect_it->second.pos, rect_it->second.texture };
+        return SpriteAtlasElement { rect_it->second.pos, rect_it->second.texture };
     }
 
     auto sprite = store.getSprite(name);
     if (!sprite) {
-        return { Rect<dimension> { 0, 0, 0, 0 }, nullptr };
+        return {};
     }
 
     Rect<dimension> rect = allocateImage(sprite->width, sprite->height);
@@ -65,19 +65,24 @@ SpriteAtlasElement SpriteAtlas::getImage(const std::string& name, const bool wra
         if (debug::spriteWarnings) {
             Log::Warning(Event::Sprite, "sprite atlas bitmap overflow");
         }
-        return { Rect<dimension> { 0, 0, 0, 0 }, nullptr };
+        return {};
     }
 
     const Holder& holder = images.emplace(Key{ name, wrap }, Holder{ sprite, rect }).first->second;
     copy(holder, wrap);
 
-    return { rect, sprite };
+    return SpriteAtlasElement { rect, sprite };
 }
 
-SpriteAtlasPosition SpriteAtlas::getPosition(const std::string& name, bool repeating) {
+mapbox::util::optional<SpriteAtlasPosition> SpriteAtlas::getPosition(const std::string& name, bool repeating) {
     std::lock_guard<std::recursive_mutex> lock(mtx);
 
-    auto rect = getImage(name, repeating).pos;
+    auto img = getImage(name, repeating);
+    if (!img) {
+        return {};
+    }
+
+    auto rect = (*img).pos;
     if (repeating) {
         // When the image is repeating, get the correct position of the image, rather than the
         // one rounded up to 4 pixels.
diff --git a/src/mbgl/sprite/sprite_atlas.hpp b/src/mbgl/sprite/sprite_atlas.hpp
index 0e3e8cf225..0d1e52cf81 100644
--- a/src/mbgl/sprite/sprite_atlas.hpp
+++ b/src/mbgl/sprite/sprite_atlas.hpp
@@ -6,6 +6,8 @@
 #include <mbgl/util/noncopyable.hpp>
 #include <mbgl/util/ptr.hpp>
 
+#include <mapbox/optional.hpp>
+
 #include <string>
 #include <map>
 #include <mutex>
@@ -41,15 +43,12 @@ public:
     SpriteAtlas(dimension width, dimension height, float pixelRatio, SpriteStore& store);
     ~SpriteAtlas();
 
-    // Returns the coordinates of an image that is sourced from the sprite image.
-    // This getter attempts to read the image from the sprite if it is already loaded.
-    // In that case, it copies it into the sprite atlas and returns the dimensions.
-    // Otherwise, it returns a 0/0/0/0 rect.
-    // This function is used during bucket creation.
-    SpriteAtlasElement getImage(const std::string& name, const bool wrap);
+    // If the sprite is loaded, copies the requsted image from it into the atlas and returns
+    // the resulting icon measurements. If not, returns an empty optional.
+    mapbox::util::optional<SpriteAtlasElement> getImage(const std::string& name, const bool wrap);
 
     // This function is used for getting the position during render time.
-    SpriteAtlasPosition getPosition(const std::string& name, bool repeating = false);
+    mapbox::util::optional<SpriteAtlasPosition> getPosition(const std::string& name, bool repeating = false);
 
     // Binds the atlas texture to the GPU, and uploads data if it is out of date.
     void bind(bool linear = false);