[core] Add a few conveniences to Color

include/mbgl/annotation/annotation.hpp

@@ -30,14 +30,14 @@ public:
     ShapeAnnotationGeometry geometry;
     float opacity = 1;
     float width = 1;
-    Color color = { 0, 0, 0, 1 };
+    Color color = Color::black();
 };
 
 class FillAnnotation {
 public:
     ShapeAnnotationGeometry geometry;
     float opacity = 1;
-    Color color = { 0, 0, 0, 1 };
+    Color color = Color::black();
     Color outlineColor = { 0, 0, 0, -1 };
 };
 

include/mbgl/gl/gl_values.hpp

@@ -5,6 +5,7 @@
 #include <array>
 
 #include <mbgl/gl/gl.hpp>
+#include <mbgl/util/color.hpp>
 
 namespace mbgl {
 namespace gl {
@@ -23,7 +24,7 @@ struct ClearDepth {
 };
 
 struct ClearColor {
-    struct Type { GLfloat r, g, b, a; };
+    using Type = Color;
     static const Type Default;
     inline static void Set(const Type& value) {
         MBGL_CHECK_ERROR(glClearColor(value.r, value.g, value.b, value.a));
@@ -35,10 +36,6 @@ struct ClearColor {
     }
 };
 
-inline bool operator!=(const ClearColor::Type& a, const ClearColor::Type& b) {
-    return a.r != b.r || a.g != b.g || a.b != b.b || a.a != b.a;
-}
-
 struct ClearStencil {
     using Type = GLint;
     static const Type Default;

include/mbgl/util/color.hpp

@@ -11,14 +11,26 @@ public:
     float g = 0.0f;
     float b = 0.0f;
     float a = 0.0f;
+
+    static constexpr Color black() { return { 0.0f, 0.0f, 0.0f, 1.0f }; };
+    static constexpr Color white() { return { 1.0f, 1.0f, 1.0f, 1.0f }; };
 };
 
-inline bool operator== (const Color& colorA, const Color& colorB) {
+inline bool operator==(const Color& colorA, const Color& colorB) {
     return colorA.r == colorB.r && colorA.g == colorB.g && colorA.b == colorB.b && colorA.a == colorB.a;
 }
 
-inline bool operator!= (const Color& colorA, const Color& colorB) {
-    return !(colorA.r == colorB.r && colorA.g == colorB.g && colorA.b == colorB.b && colorA.a == colorB.a);
+inline bool operator!=(const Color& colorA, const Color& colorB) {
+    return !(colorA == colorB);
+}
+
+inline Color operator*(const Color& color, float alpha) {
+    return {
+        color.r * alpha,
+        color.g * alpha,
+        color.b * alpha,
+        color.a * alpha
+    };
 }
 
 } // namespace mbgl

src/mbgl/renderer/painter.cpp

@@ -144,9 +144,9 @@ void Painter::render(const Style& style, const FrameData& frame_, SpriteAtlas& a
         config.depthMask = GL_TRUE;
         config.colorMask = { GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE };
         if (frame.debugOptions & MapDebugOptions::Wireframe) {
-            config.clearColor = { 0.0f, 0.0f, 0.0f, 1.0f };
+            config.clearColor = Color::black();
         } else {
-            config.clearColor = { background.r, background.g, background.b, background.a };
+            config.clearColor = background;
         }
         config.clearStencil = 0;
         config.clearDepth = 1;

src/mbgl/renderer/painter_background.cpp

@@ -45,7 +45,7 @@ void Painter::renderBackground(const BackgroundLayer& layer) {
 
     } else {
         if (wireframe) {
-            plainShader->u_color = { 0.0f, 0.0f, 0.0f, 1.0f };
+            plainShader->u_color = Color::black();
             plainShader->u_opacity = 1.0f;
         } else {
             plainShader->u_color = properties.backgroundColor;

src/mbgl/renderer/painter_debug.cpp

@@ -44,7 +44,7 @@ void Painter::renderDebugText(Tile& tile, const mat4 &matrix) {
     plainShader->u_matrix = matrix;
 
     // Draw white outline
-    plainShader->u_color = { 1.0f, 1.0f, 1.0f, 1.0f };
+    plainShader->u_color = Color::white();
     config.lineWidth = 4.0f * frame.pixelRatio;
     tile.debugBucket->drawLines(*plainShader, store);
 
@@ -55,7 +55,7 @@ void Painter::renderDebugText(Tile& tile, const mat4 &matrix) {
 #endif
 
     // Draw black text.
-    plainShader->u_color = { 0.0f, 0.0f, 0.0f, 1.0f };
+    plainShader->u_color = Color::black();
     config.lineWidth = 2.0f * frame.pixelRatio;
     tile.debugBucket->drawLines(*plainShader, store);
 

src/mbgl/renderer/painter_fill.cpp

@@ -38,8 +38,8 @@ void Painter::renderFill(FillBucket& bucket,
 
     bool wireframe = frame.debugOptions & MapDebugOptions::Wireframe;
     if (wireframe) {
-        fillColor = { 1.0f, 1.0f, 1.0f, 1.0f };
-        strokeColor = { 1.0f, 1.0f, 1.0f, 1.0f };
+        fillColor = Color::white();
+        strokeColor = Color::white();
         opacity = 1.0f;
         pattern = false;
         outline = true;

src/mbgl/renderer/painter_line.cpp

@@ -37,7 +37,7 @@ void Painter::renderLine(LineBucket& bucket,
 
     float blur = properties.lineBlur + antialiasing;
 
-    Color color { 1.0f, 1.0f, 1.0f, 1.0f };
+    Color color = Color::white();
     float opacity = 1.0f;
     if (!wireframe) {
         color = properties.lineColor;

src/mbgl/renderer/render_item.hpp

@@ -30,7 +30,7 @@ public:
 
 class RenderData {
 public:
-    Color backgroundColor = { 0, 0, 0, 0 };
+    Color backgroundColor;
     std::set<style::Source*> sources;
     std::vector<RenderItem> order;
 };

src/mbgl/style/style.cpp

@@ -266,11 +266,7 @@ RenderData Style::getRenderData() const {
             const BackgroundPaintProperties& paint = background->impl->paint;
             if (layer.get() == layers[0].get() && paint.backgroundPattern.value.from.empty()) {
                 // This is a solid background. We can use glClear().
-                result.backgroundColor = paint.backgroundColor;
-                result.backgroundColor.r *= paint.backgroundOpacity;
-                result.backgroundColor.g *= paint.backgroundOpacity;
-                result.backgroundColor.b *= paint.backgroundOpacity;
-                result.backgroundColor.a *= paint.backgroundOpacity;
+                result.backgroundColor = paint.backgroundColor * paint.backgroundOpacity;
             } else {
                 // This is a textured background, or not the bottommost layer. We need to render it with a quad.
                 result.order.emplace_back(*layer);