Text: add a DistanceFieldGlyphCache*GL::radius() getter.

Without it's rather impossible to reason about properties of the
generated distance field for consistent rendering.

src/Magnum/Text/DistanceFieldGlyphCacheGL.cpp

@@ -88,6 +88,10 @@ DistanceFieldGlyphCacheGL::DistanceFieldGlyphCacheGL(const Vector2i& size, const
 
 DistanceFieldGlyphCacheGL::DistanceFieldGlyphCacheGL(NoCreateT) noexcept: GlyphCacheGL{NoCreate} {}
 
+UnsignedInt DistanceFieldGlyphCacheGL::radius() const {
+    return static_cast<const State&>(*_state).distanceField.radius();
+}
+
 #ifdef MAGNUM_BUILD_DEPRECATED
 Vector2i DistanceFieldGlyphCacheGL::distanceFieldTextureSize() const {
     return processedSize().xy();
@@ -238,6 +242,10 @@ DistanceFieldGlyphCacheArrayGL::DistanceFieldGlyphCacheArrayGL(const Vector3i& s
 
 DistanceFieldGlyphCacheArrayGL::DistanceFieldGlyphCacheArrayGL(NoCreateT) noexcept: GlyphCacheArrayGL{NoCreate} {}
 
+UnsignedInt DistanceFieldGlyphCacheArrayGL::radius() const {
+    return static_cast<const State&>(*_state).distanceField.radius();
+}
+
 GlyphCacheFeatures DistanceFieldGlyphCacheArrayGL::doFeatures() const {
     return GlyphCacheFeature::ImageProcessing
         #ifndef MAGNUM_TARGET_GLES

src/Magnum/Text/DistanceFieldGlyphCacheGL.h

@@ -147,6 +147,12 @@ class MAGNUM_TEXT_EXPORT DistanceFieldGlyphCacheGL: public GlyphCacheGL {
          */
         explicit DistanceFieldGlyphCacheGL(NoCreateT) noexcept;
 
+        /**
+         * @brief Distance field calculation radius
+         * @m_since_latest
+         */
+        UnsignedInt radius() const;
+
         #ifdef MAGNUM_BUILD_DEPRECATED
         /**
          * @brief Distance field texture size
@@ -247,6 +253,9 @@ class MAGNUM_TEXT_EXPORT DistanceFieldGlyphCacheArrayGL: public GlyphCacheArrayG
          */
         explicit DistanceFieldGlyphCacheArrayGL(NoCreateT) noexcept;
 
+        /** @brief Distance field calculation radius */
+        UnsignedInt radius() const;
+
     private:
         struct State;
 

src/Magnum/Text/Test/DistanceFieldGlyphCacheGLTest.cpp

@@ -252,7 +252,7 @@ DistanceFieldGlyphCacheGLTest::DistanceFieldGlyphCacheGLTest() {
 }
 
 void DistanceFieldGlyphCacheGLTest::construct() {
-    DistanceFieldGlyphCacheGL cache{{256, 512}, {64, 128}, 16};
+    DistanceFieldGlyphCacheGL cache{{256, 512}, {64, 128}, 13};
     MAGNUM_VERIFY_NO_GL_ERROR();
 
     #ifndef MAGNUM_TARGET_GLES
@@ -284,6 +284,7 @@ void DistanceFieldGlyphCacheGLTest::construct() {
     #ifndef MAGNUM_TARGET_GLES
     CORRADE_COMPARE(cache.texture().imageSize(0), (Vector2i{64, 128}));
     #endif
+    CORRADE_COMPARE(cache.radius(), 13);
 }
 
 #ifndef MAGNUM_TARGET_GLES2
@@ -293,7 +294,7 @@ void DistanceFieldGlyphCacheGLTest::constructArray() {
         CORRADE_SKIP(GL::Extensions::EXT::texture_array::string() << "is not supported.");
     #endif
 
-    DistanceFieldGlyphCacheArrayGL cache{{256, 512, 7}, {64, 128}, 16};
+    DistanceFieldGlyphCacheArrayGL cache{{256, 512, 7}, {64, 128}, 17};
     MAGNUM_VERIFY_NO_GL_ERROR();
 
     #ifndef MAGNUM_TARGET_GLES
@@ -309,6 +310,7 @@ void DistanceFieldGlyphCacheGLTest::constructArray() {
     #ifndef MAGNUM_TARGET_GLES
     CORRADE_COMPARE(cache.texture().imageSize(0), (Vector3i{64, 128, 7}));
     #endif
+    CORRADE_COMPARE(cache.radius(), 17);
 }
 #endif