[core] Simplify and fix sprite atlas coordinate calculations

* Always return image metrics exclusive of padding
* Work with integer coordinates whenever possible
* Eliminate redundant SpriteAtlasElement members
* Fix asymmetric re-padding in getIconQuad when pixelRatio != 1
* Add explanatory comments

6 files changed, 7 insertions, 8 deletions

diff --git a/src/mbgl/renderer/bucket_parameters.hpp b/src/mbgl/renderer/bucket_parameters.hpp
index 1774ba2bbe..50ec4cf521 100644
--- a/src/mbgl/renderer/bucket_parameters.hpp
+++ b/src/mbgl/renderer/bucket_parameters.hpp
@@ -9,6 +9,7 @@ class BucketParameters {
 public:
     const OverscaledTileID tileID;
     const MapMode mode;
+    const float pixelRatio;
 };
 
 } // namespace mbgl
diff --git a/src/mbgl/renderer/painters/painter_background.cpp b/src/mbgl/renderer/painters/painter_background.cpp
index 9c6df06094..9cbc3d516c 100644
--- a/src/mbgl/renderer/painters/painter_background.cpp
+++ b/src/mbgl/renderer/painters/painter_background.cpp
@@ -42,7 +42,7 @@ void Painter::renderBackground(PaintParameters& parameters, const RenderBackgrou
                 FillPatternUniforms::values(
                     matrixForTile(tileID),
                     context.viewport.getCurrentValue().size,
-                    spriteAtlas->getSize(),
+                    spriteAtlas->getPixelSize(),
                     *imagePosA,
                     *imagePosB,
                     background.get<BackgroundPattern>(),
diff --git a/src/mbgl/renderer/painters/painter_fill.cpp b/src/mbgl/renderer/painters/painter_fill.cpp
index e34b4107a9..d15a871d98 100644
--- a/src/mbgl/renderer/painters/painter_fill.cpp
+++ b/src/mbgl/renderer/painters/painter_fill.cpp
@@ -49,7 +49,7 @@ void Painter::renderFill(PaintParameters& parameters,
                                           properties.get<FillTranslateAnchor>(),
                                           state),
                     context.viewport.getCurrentValue().size,
-                    spriteAtlas->getSize(),
+                    spriteAtlas->getPixelSize(),
                     *imagePosA,
                     *imagePosB,
                     properties.get<FillPattern>(),
diff --git a/src/mbgl/renderer/painters/painter_fill_extrusion.cpp b/src/mbgl/renderer/painters/painter_fill_extrusion.cpp
index c7aede3aa6..c28cb76bff 100644
--- a/src/mbgl/renderer/painters/painter_fill_extrusion.cpp
+++ b/src/mbgl/renderer/painters/painter_fill_extrusion.cpp
@@ -46,7 +46,7 @@ void Painter::renderFillExtrusion(PaintParameters& parameters,
                 tile.translatedClipMatrix(properties.get<FillExtrusionTranslate>(),
                                           properties.get<FillExtrusionTranslateAnchor>(),
                                           state),
-                spriteAtlas->getSize(),
+                spriteAtlas->getPixelSize(),
                 *imagePosA,
                 *imagePosB,
                 properties.get<FillExtrusionPattern>(),
diff --git a/src/mbgl/renderer/painters/painter_line.cpp b/src/mbgl/renderer/painters/painter_line.cpp
index df627a76aa..40076726af 100644
--- a/src/mbgl/renderer/painters/painter_line.cpp
+++ b/src/mbgl/renderer/painters/painter_line.cpp
@@ -75,7 +75,7 @@ void Painter::renderLine(PaintParameters& parameters,
                  tile,
                  state,
                  pixelsToGLUnits,
-                 spriteAtlas->getSize(),
+                 spriteAtlas->getPixelSize(),
                  *posA,
                  *posB));
 
diff --git a/src/mbgl/renderer/painters/painter_symbol.cpp b/src/mbgl/renderer/painters/painter_symbol.cpp
index 45094777c6..a89e7db28d 100644
--- a/src/mbgl/renderer/painters/painter_symbol.cpp
+++ b/src/mbgl/renderer/painters/painter_symbol.cpp
@@ -68,13 +68,11 @@ void Painter::renderSymbol(PaintParameters& parameters,
         auto paintPropertyValues = layer.iconPaintProperties();
 
         SpriteAtlas& atlas = *bucket.spriteAtlas;
-        const bool iconScaled = layout.get<IconSize>().constantOr(1.0) != 1.0 ||
-            frame.pixelRatio != atlas.getPixelRatio() ||
-            bucket.iconsNeedLinear;
+        const bool iconScaled = layout.get<IconSize>().constantOr(1.0) != 1.0 || bucket.iconsNeedLinear;
         const bool iconTransformed = values.rotationAlignment == AlignmentType::Map || state.getPitch() != 0;
         atlas.bind(bucket.sdfIcons || state.isChanging() || iconScaled || iconTransformed, context, 0);
 
-        const Size texsize = atlas.getSize();
+        const Size texsize = atlas.getPixelSize();
 
         if (bucket.sdfIcons) {
             if (values.hasHalo) {