Fix incorrect gradient rotation.

app/src/main/java/org/thoughtcrime/securesms/components/RotatableGradientDrawable.java

@@ -8,6 +8,7 @@ import android.graphics.PixelFormat;
 import android.graphics.Point;
 import android.graphics.Rect;
 import android.graphics.Shader;
+import android.graphics.Xfermode;
 import android.graphics.drawable.Drawable;
 
 import androidx.annotation.NonNull;
@@ -100,8 +101,8 @@ public final class RotatableGradientDrawable extends Drawable {
     fillPaint.setShader(new LinearGradient(fillRect.left, fillRect.top, fillRect.right, fillRect.bottom, colors, positions, Shader.TileMode.CLAMP));
   }
 
-  public @Nullable Shader getShader() {
-    return fillPaint.getShader();
+  public void setXfermode(@NonNull Xfermode xfermode) {
+    fillPaint.setXfermode(xfermode);
   }
 
   private static Point cornerPrime(@NonNull Point origin, @NonNull Point corner, float degrees) {

app/src/main/java/org/thoughtcrime/securesms/conversation/colors/ChatColors.kt

@@ -5,7 +5,6 @@ import android.graphics.ColorFilter
 import android.graphics.Path
 import android.graphics.PorterDuff
 import android.graphics.PorterDuffColorFilter
-import android.graphics.Shader
 import android.graphics.drawable.ColorDrawable
 import android.graphics.drawable.Drawable
 import android.graphics.drawable.ShapeDrawable
@@ -32,6 +31,8 @@ class ChatColors private constructor(
   private val singleColor: Int?
 ) {
 
+  fun isGradient(): Boolean = Build.VERSION.SDK_INT >= 21 && linearGradient != null
+
   /**
    * Returns the Drawable to render the linear gradient, or null if this ChatColors is a single color.
    */
@@ -54,18 +55,6 @@ class ChatColors private constructor(
       }
     }
 
-  fun asShader(left: Int, top: Int, right: Int, bottom: Int): Shader? {
-    return linearGradient?.let {
-      RotatableGradientDrawable(
-        linearGradient.degrees,
-        linearGradient.colors,
-        linearGradient.positions
-      ).apply {
-        setBounds(left, top, right, bottom)
-      }
-    }?.shader
-  }
-
   /**
    * Returns the ColorFilter to apply to a conversation bubble or other relevant piece of UI.
    */

app/src/main/java/org/thoughtcrime/securesms/conversation/colors/RecyclerViewColorizer.kt

@@ -10,6 +10,7 @@ import android.view.View
 import android.widget.EdgeEffect
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import org.thoughtcrime.securesms.components.RotatableGradientDrawable
 
 /**
  * Draws the ChatColors color or gradient following this procedure:
@@ -77,7 +78,6 @@ class RecyclerViewColorizer(private val recyclerView: RecyclerView) {
       color = Color.BLACK
     }
 
-    private val shaderPaint = Paint()
     private val colorPaint = Paint()
 
     override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
@@ -107,24 +107,25 @@ class RecyclerViewColorizer(private val recyclerView: RecyclerView) {
 
     private fun drawShaderMask(canvas: Canvas, parent: RecyclerView, chatColors: ChatColors) {
       if (useLayer) {
-        shaderPaint.xfermode = layerXfermode
         colorPaint.xfermode = layerXfermode
       } else {
-        shaderPaint.xfermode = noLayerXfermode
         colorPaint.xfermode = noLayerXfermode
       }
 
-      val shader = chatColors.asShader(0, 0, parent.width, parent.height)
-      shaderPaint.shader = shader
-      colorPaint.color = chatColors.asSingleColor()
-
-      canvas.drawRect(
-        0f,
-        0f,
-        parent.width.toFloat(),
-        parent.height.toFloat(),
-        if (shader == null) colorPaint else shaderPaint
-      )
+      if (chatColors.isGradient()) {
+        val mask = chatColors.chatBubbleMask as RotatableGradientDrawable
+        mask.setXfermode(colorPaint.xfermode)
+        mask.setBounds(0, 0, parent.width, parent.height)
+        mask.draw(canvas)
+      } else {
+        canvas.drawRect(
+          0f,
+          0f,
+          parent.width.toFloat(),
+          parent.height.toFloat(),
+          colorPaint
+        )
+      }
     }
   }