Fix oppia#206: Remove color-darkening computation. (oppia#3100)

* Remove the color darkening computation.

* Remove backgroundColor from TopicSummaryViewModel.

* Add more properties to the walkthrough_lesson_count_text_view.

app/src/main/java/org/oppia/android/app/home/topiclist/TopicSummaryViewModel.kt

@@ -1,20 +1,11 @@
 package org.oppia.android.app.home.topiclist
 
-import android.graphics.Color
-import androidx.annotation.ColorInt
 import androidx.appcompat.app.AppCompatActivity
 import org.oppia.android.R
 import org.oppia.android.app.home.HomeItemViewModel
 import org.oppia.android.app.model.TopicSummary
 import java.util.Objects
 
-// TODO(#206): Remove the color darkening computation and properly set up the topic thumbnails.
-// These values were roughly computed based on the mocks. They won't produce the same colors since darker colors in the
-// mocks were not consistently darker. An alternative would be to specify both background colors together to ensure
-// proper contrast with readable elements.
-const val DARKEN_VALUE_MULTIPLIER: Float = 0.9f
-const val DARKEN_SATURATION_MULTIPLIER: Float = 1.2f
-
 /** The view model corresponding to individual topic summaries in the topic summary RecyclerView. */
 class TopicSummaryViewModel(
  private val activity: AppCompatActivity,
@@ -26,11 +17,6 @@ class TopicSummaryViewModel(
  val name: String = topicSummary.name
  val totalChapterCount: Int = topicSummary.totalChapterCount
 
- @ColorInt
- val backgroundColor: Int = retrieveBackgroundColor()
-
- @ColorInt
- val darkerBackgroundOverlayColor: Int = computeDarkerBackgroundColor()
  private val outerMargin by lazy {
  activity.resources.getDimensionPixelSize(R.dimen.home_outer_margin)
  }
@@ -114,20 +100,6 @@ class TopicSummaryViewModel(
  }
  }
 
- @ColorInt
- private fun retrieveBackgroundColor(): Int {
- return topicSummary.topicThumbnail.backgroundColorRgb
- }
-
- /** Returns a version of [backgroundColor] that is slightly darker. */
- private fun computeDarkerBackgroundColor(): Int {
- val hsv = floatArrayOf(0f, 0f, 0f)
- Color.colorToHSV(backgroundColor, hsv)
- hsv[1] = (hsv[1] * DARKEN_SATURATION_MULTIPLIER).coerceIn(0f, 1f)
- hsv[2] = (hsv[2] * DARKEN_VALUE_MULTIPLIER).coerceIn(0f, 1f)
- return Color.HSVToColor(hsv)
- }
-
  // Overriding equals is needed so that DataProvider combine functions used in the HomeViewModel
  // will only rebind when the actual data in the data list changes, rather than when the ViewModel
  // object changes.

app/src/main/java/org/oppia/android/app/walkthrough/topiclist/topiclistviewmodel/WalkthroughTopicSummaryViewModel.kt

@@ -1,19 +1,11 @@
 package org.oppia.android.app.walkthrough.topiclist.topiclistviewmodel
 
-import android.graphics.Color
 import androidx.annotation.ColorInt
 import androidx.lifecycle.ViewModel
 import org.oppia.android.app.home.topiclist.TopicSummaryClickListener
 import org.oppia.android.app.model.TopicSummary
 import org.oppia.android.app.walkthrough.topiclist.WalkthroughTopicItemViewModel
 
-// TODO(#206): Remove the color darkening computation and properly set up the topic thumbnails.
-// These values were roughly computed based on the mocks. They won't produce the same colors since darker colors in the
-// mocks were not consistently darker. An alternative would be to specify both background colors together to ensure
-// proper contrast with readable elements.
-private const val DARKEN_VALUE_MULTIPLIER: Float = 0.9f
-private const val DARKEN_SATURATION_MULTIPLIER: Float = 1.2f
-
 /** The view model corresponding to topic summaries in the topic summary RecyclerView. */
 
 /** [ViewModel] corresponding to topic summaries in [WalkthroughTopicListFragment] RecyclerView.. */
@@ -28,9 +20,6 @@ class WalkthroughTopicSummaryViewModel(
  @ColorInt
  val backgroundColor: Int = retrieveBackgroundColor()
 
- @ColorInt
- val darkerBackgroundOverlayColor: Int = computeDarkerBackgroundColor()
-
  /** Callback from data-binding for when the summary tile is clicked. */
  fun clickOnSummaryTile() {
  topicSummaryClickListener.onTopicSummaryClicked(topicSummary)
@@ -40,13 +29,4 @@ class WalkthroughTopicSummaryViewModel(
  private fun retrieveBackgroundColor(): Int {
  return topicSummary.topicThumbnail.backgroundColorRgb
  }
-
- /** Returns a version of [backgroundColor] that is slightly darker. */
- private fun computeDarkerBackgroundColor(): Int {
- val hsv = floatArrayOf(0f, 0f, 0f)
- Color.colorToHSV(backgroundColor, hsv)
- hsv[1] = (hsv[1] * DARKEN_SATURATION_MULTIPLIER).coerceIn(0f, 1f)
- hsv[2] = (hsv[2] * DARKEN_VALUE_MULTIPLIER).coerceIn(0f, 1f)
- return Color.HSVToColor(hsv)
- }
 }

app/src/main/res/layout/walkthrough_topic_summary_view.xml

@@ -22,8 +22,8 @@
 
  <org.oppia.android.app.customview.LessonThumbnailImageView
  android:id="@+id/walkthrough_topic_thumbnail_image_view"
- android:layout_width="match_parent"
- android:layout_height="92dp"
+ android:layout_width="0dp"
+ android:layout_height="0dp"
  android:importantForAccessibility="no"
  android:scaleType="centerInside"
  app:entityId="@{viewModel.topicSummary.topicId}"
@@ -46,7 +46,7 @@
  android:id="@+id/bottom_topic_bar"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
- app:bottomRoundedRectDrawableWithColor="@{viewModel.darkerBackgroundOverlayColor}"
+ android:background="@color/topicTitleBackground"
  app:layout_constraintBottom_toBottomOf="parent"
  app:layout_constraintStart_toStartOf="parent" />
 
@@ -76,7 +76,9 @@
  android:id="@+id/walkthrough_lesson_count_text_view"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
+ android:ellipsize="end"
  android:fontFamily="sans-serif-light"
+ android:lines="1"
  android:text="@{@plurals/lesson_count(viewModel.totalChapterCount, viewModel.totalChapterCount)}"
  android:textColor="@color/white_80"
  android:textSize="14sp"