expose runtime changes to gamma

api/current.xml

@@ -60507,6 +60507,21 @@
  visibility="public"
 >
 </method>
+<method name="setGammaForText"
+ return="void"
+ abstract="false"
+ native="true"
+ synchronized="false"
+ static="true"
+ final="false"
+ deprecated="not deprecated"
+ visibility="public"
+>
+<parameter name="blackGamma" type="float">
+</parameter>
+<parameter name="whiteGamma" type="float">
+</parameter>
+</method>
 <field name="BOLD"
  type="int"
  transient="false"

core/jni/android/graphics/Typeface.cpp

@@ -141,6 +141,25 @@ static SkTypeface* Typeface_createFromFile(JNIEnv* env, jobject, jstring jpath)
     return SkTypeface::CreateFromFile(str.c_str());
 }
 
+#define MIN_GAMMA   (0.1f)
+#define MAX_GAMMA   (10.0f)
+static float pinGamma(float gamma) {
+    if (gamma < MIN_GAMMA) {
+        gamma = MIN_GAMMA;
+    } else if (gamma > MAX_GAMMA) {
+        gamma = MAX_GAMMA;
+    }
+    return gamma;
+}
+
+extern void skia_set_text_gamma(float, float);
+
+static void Typeface_setGammaForText(JNIEnv* env, jobject, jfloat blackGamma,
+                                     jfloat whiteGamma) {
+    // Comment this out for release builds. This is only used during development
+    skia_set_text_gamma(pinGamma(blackGamma), pinGamma(whiteGamma));
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 static JNINativeMethod gTypefaceMethods[] = {
@@ -151,7 +170,8 @@ static JNINativeMethod gTypefaceMethods[] = {
     { "nativeCreateFromAsset",    "(Landroid/content/res/AssetManager;Ljava/lang/String;)I",
                                            (void*)Typeface_createFromAsset },
     { "nativeCreateFromFile",     "(Ljava/lang/String;)I",
-                                           (void*)Typeface_createFromFile }
+                                           (void*)Typeface_createFromFile },
+    { "setGammaForText", "(FF)V", (void*)Typeface_setGammaForText },
 };
 
 int register_android_graphics_Typeface(JNIEnv* env);

graphics/java/android/graphics/Typeface.java

@@ -172,4 +172,14 @@ public class Typeface {
     private static native int  nativeGetStyle(int native_instance);
     private static native int  nativeCreateFromAsset(AssetManager mgr, String path);
     private static native int nativeCreateFromFile(String path);
+
+    /**
+     * Set the global gamma coefficients for black and white text. This call is
+     * usually a no-op in shipping products, and only exists for testing during
+     * development.
+     *
+     * @param blackGamma gamma coefficient for black text
+     * @param whiteGamma gamma coefficient for white text
+     */
+    public static native void setGammaForText(float blackGamma, float whiteGamma);
 }