Fix #4845: Dark mode support to Equations Text (#4866)

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check off every point from the Essential Checklist! -->
## Explanation

Fixes #4845 : Dark mode support to Equations Text

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- Explain what your PR does. If this PR fixes an existing bug, please
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- "Fixes #bugnum:" in the explanation so that GitHub can auto-close the
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  - when this PR is merged.
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## Essential Checklist
<!-- Please tick the relevant boxes by putting an "x" in them. -->
- [x] The PR title and explanation each start with "Fix #bugnum: " (If
this PR fixes part of an issue, prefix the title with "Fix part of
#bugnum: ...".)
- [x] Any changes to
[scripts/assets](https://github.com/oppia/oppia-android/tree/develop/scripts/assets)
files have their rationale included in the PR explanation.
- [x] The PR follows the [style
guide](https://github.com/oppia/oppia-android/wiki/Coding-style-guide).
- [x] The PR does not contain any unnecessary code changes from Android
Studio
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#undo-unnecessary-changes)).
- [x] The PR is made from a branch that's **not** called "develop" and
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([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#clarification-regarding-assignees-and-reviewers-section)).

## For UI-specific PRs only

### Equation Text Screenshots

<img
src="https://user-images.githubusercontent.com/76530270/216761443-21a973e8-20f9-4fbb-a19d-595530dfebb9.jpg"
height="400" style="max-width: 100%"> <img
src="https://user-images.githubusercontent.com/76530270/216761463-b4a49932-7b9c-4b2a-b3e6-96a5a693f058.jpg"
height="400" style="max-width: 100%">


### Equation Text Screen Recording


https://user-images.githubusercontent.com/76530270/216761782-027744b7-a0df-41ca-8547-2e7f52eaea0c.mp4



## Equation Color Test

#### Day Mode Test


![image](https://user-images.githubusercontent.com/76530270/222653431-05f7e726-c8f0-4677-a48e-8ca37c5ea8e4.png)

#### Night Mode Test


![image](https://user-images.githubusercontent.com/76530270/222653513-458e25ce-9508-480e-bdfc-a4ede5e8a0ed.png)


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changes. -->
If your PR includes UI-related changes, then:
- Add screenshots for portrait/landscape for both a tablet & phone of
the before & after UI changes
- For the screenshots above, include both English and pseudo-localized
(RTL) screenshots (see [RTL
guide](https://github.com/oppia/oppia-android/wiki/RTL-Guidelines))
- Add a video showing the full UX flow with a screen reader enabled (see
[accessibility
guide](https://github.com/oppia/oppia-android/wiki/Accessibility-(A11y)-Guide))
- Add a screenshot demonstrating that you ran affected Espresso tests
locally & that they're passing

---------

Co-authored-by: Ben Henning <ben@oppia.org>

WORKSPACE

@@ -141,7 +141,7 @@ git_repository(
 # min target SDK version to be compatible with Oppia.
 git_repository(
     name = "kotlitex",
-    commit = "6b7db8ff9e0f4a70bdaa25f482143e038fd0c301",
+    commit = "43139c140833c7120f351d63d74b42c253d2b213",
     remote = "https://github.com/oppia/kotlitex",
     shallow_since = "1647554845 -0700",
 )

utility/BUILD.bazel

@@ -33,6 +33,7 @@ android_library(
     custom_package = "org.oppia.android.util",
     manifest = "src/main/AndroidManifest.xml",
     resource_files = glob(["src/main/res/**/*.xml"]),
+    visibility = ["//visibility:public"],
 )
 
 # Visibility for migrated utility tests.

utility/build.gradle

@@ -83,7 +83,7 @@ dependencies {
       'androidx.lifecycle:lifecycle-livedata-ktx:2.2.0-alpha03',
       'androidx.work:work-runtime-ktx:2.4.0',
       'com.github.oppia:androidsvg:4bc1d26412f0fb9fd4ef263fa93f6a64f4d4dbcf',
-      'com.github.oppia:kotlitex:6b7db8ff9e0f4a70bdaa25f482143e038fd0c301',
+      'com.github.oppia:kotlitex:43139c140833c7120f351d63d74b42c253d2b213',
       'com.github.bumptech.glide:glide:4.11.0',
       'com.google.dagger:dagger:2.24',
       'com.google.firebase:firebase-analytics-ktx:17.5.0',

utility/src/main/java/org/oppia/android/util/parser/html/HtmlParser.kt

@@ -1,5 +1,6 @@
 package org.oppia.android.util.parser.html
 
+import android.app.Application
 import android.content.Context
 import android.text.Spannable
 import android.text.SpannableStringBuilder
@@ -134,7 +135,8 @@ class HtmlParser private constructor(
         consoleLogger,
         context.assets,
         htmlContentTextView.lineHeight.toFloat(),
-        cacheLatexRendering
+        cacheLatexRendering,
+        context as? Application ?: context.applicationContext as Application
       )
     if (supportsConceptCards) {
       handlersMap[CUSTOM_CONCEPT_CARD_TAG] = conceptCardTagHandler

utility/src/main/java/org/oppia/android/util/parser/html/MathTagHandler.kt

@@ -1,11 +1,14 @@
 package org.oppia.android.util.parser.html
 
+import android.app.Application
 import android.content.res.AssetManager
 import android.text.Editable
 import android.text.Spannable
 import android.text.style.ImageSpan
+import androidx.core.content.res.ResourcesCompat
 import io.github.karino2.kotlitex.view.MathExpressionSpan
 import org.json.JSONObject
+import org.oppia.android.util.R
 import org.oppia.android.util.logging.ConsoleLogger
 import org.oppia.android.util.parser.html.CustomHtmlContentHandler.ImageRetriever.Type.BLOCK_IMAGE
 import org.oppia.android.util.parser.html.CustomHtmlContentHandler.ImageRetriever.Type.INLINE_TEXT_IMAGE
@@ -24,7 +27,8 @@ class MathTagHandler(
   private val consoleLogger: ConsoleLogger,
   private val assetManager: AssetManager,
   private val lineHeight: Float,
-  private val cacheLatexRendering: Boolean
+  private val cacheLatexRendering: Boolean,
+  private val application: Application
 ) : CustomHtmlContentHandler.CustomTagHandler {
   override fun handleTag(
     attributes: Attributes,
@@ -65,7 +69,15 @@ class MathTagHandler(
           )
         } else {
           MathExpressionSpan(
-            content.rawLatex, lineHeight, assetManager, isMathMode = !useInlineRendering
+            content.rawLatex,
+            lineHeight,
+            assetManager,
+            isMathMode = !useInlineRendering,
+            ResourcesCompat.getColor(
+              application.resources,
+              R.color.component_color_shared_equation_color,
+              /* theme = */ null
+            )
           )
         }
       }

utility/src/main/java/org/oppia/android/util/parser/math/BUILD.bazel

@@ -28,6 +28,7 @@ kt_android_library(
         ":math_latex_model",
         "//third_party:com_github_bumptech_glide_glide",
         "//third_party:io_github_karino2_kotlitex",
+        "//utility:resources",
         "//utility/src/main/java/org/oppia/android/util/logging:console_logger_injector_provider",
         "//utility/src/main/java/org/oppia/android/util/threading:dispatcher_injector_provider",
     ],

utility/src/main/java/org/oppia/android/util/parser/math/MathBitmapModelLoader.kt

@@ -12,6 +12,7 @@ import android.text.Spannable
 import android.text.SpannableStringBuilder
 import android.text.StaticLayout
 import android.text.TextPaint
+import androidx.core.content.res.ResourcesCompat
 import com.bumptech.glide.Priority
 import com.bumptech.glide.load.DataSource
 import com.bumptech.glide.load.Options
@@ -26,6 +27,7 @@ import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
+import org.oppia.android.util.R
 import org.oppia.android.util.logging.ConsoleLogger
 import org.oppia.android.util.logging.ConsoleLoggerInjectorProvider
 import org.oppia.android.util.threading.DispatcherInjectorProvider
@@ -109,7 +111,16 @@ class MathBitmapModelLoader private constructor(
         // creation can still happen in parallel, and those are the more expensive steps.
         val span = withContext(CoroutineScope(blockingDispatcher).coroutineContext) {
           MathExpressionSpan(
-            model.rawLatex, model.lineHeight, application.assets, !model.useInlineRendering
+            model.rawLatex,
+            model.lineHeight,
+            application.assets,
+            !model.useInlineRendering,
+            // TODO(#1523): Test color parameter in MathBitmapModelLoader
+            ResourcesCompat.getColor(
+              application.resources,
+              R.color.component_color_shared_equation_color,
+              /* theme = */null
+            )
           ).also { it.ensureDrawable() }
         }
         val renderableText = SpannableStringBuilder("\uFFFC").apply {
@@ -121,6 +132,7 @@ class MathBitmapModelLoader private constructor(
         // since the width isn't necessarily known ahead of time).
         // Any TextPaint can be used since the span will use its own.
         val textPaint = TextPaint()
+
         @Suppress("DEPRECATION") // This call is necessary for the supported min API version.
         val staticTextLayout =
           StaticLayout(

utility/src/main/res/values-night/color_palette.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- TODO(#59): Consolidate color resource files once Bazel migration is done -->
+<resources>
+  <color name="color_palette_shared_equation_color">@color/color_def_white</color>
+</resources>

utility/src/main/res/values/color_defs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- TODO(#59): Consolidate color resource files once Bazel migration is done -->
+<resources>
+  <color name="color_def_black">#000000</color>
+  <color name="color_def_white">#FFFFFF</color>
+</resources>

utility/src/main/res/values/color_palette.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- TODO(#59): Consolidate color resource files once Bazel migration is done -->
+<resources>
+  <color name="color_palette_shared_equation_color">@color/color_def_black</color>
+</resources>

utility/src/main/res/values/component_colors.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- TODO(#59): Consolidate color resource files once Bazel migration is done -->
+<resources>
+  <color name="component_color_shared_equation_color">@color/color_palette_shared_equation_color</color>
+</resources>

utility/src/test/java/org/oppia/android/util/parser/html/MathTagHandlerTest.kt

@@ -2,6 +2,7 @@ package org.oppia.android.util.parser.html
 
 import android.app.Application
 import android.content.Context
+import android.graphics.Color
 import android.text.Html
 import android.text.Spannable
 import android.text.style.ImageSpan
@@ -34,6 +35,7 @@ import org.oppia.android.util.logging.ConsoleLogger
 import org.oppia.android.util.logging.LoggerModule
 import org.oppia.android.util.parser.html.CustomHtmlContentHandler.CustomTagHandler
 import org.oppia.android.util.parser.html.CustomHtmlContentHandler.ImageRetriever
+import org.robolectric.annotation.Config
 import org.robolectric.annotation.LooperMode
 import javax.inject.Inject
 import javax.inject.Singleton
@@ -246,6 +248,33 @@ class MathTagHandlerTest {
     verifyNoMoreInteractions(mockImageRetriever) // No cached image loading.
   }
 
+  @Test
+  fun testParseHtmlDayColor_withMathMarkup_cachingOff_getEquationDayColor() {
+    val parsedHtml =
+      CustomHtmlContentHandler.fromHtml(
+        html = MATH_WITHOUT_FILENAME_MARKUP,
+        imageRetriever = mockImageRetriever,
+        customTagHandlers = tagHandlersWithUncachedMathSupport
+      )
+
+    val equationColor = parsedHtml.getSpansFromWholeString(MathExpressionSpan::class)
+    assertThat(equationColor[0].equationColor).isEqualTo(Color.BLACK)
+  }
+
+  @Config(qualifiers = "night")
+  @Test
+  fun testParseHtmlNightColor_withMathMarkup_cachingOff_getEquationNightColor() {
+    val parsedHtml =
+      CustomHtmlContentHandler.fromHtml(
+        html = MATH_WITHOUT_FILENAME_MARKUP,
+        imageRetriever = mockImageRetriever,
+        customTagHandlers = tagHandlersWithUncachedMathSupport
+      )
+
+    val equationColor = parsedHtml.getSpansFromWholeString(MathExpressionSpan::class)
+    assertThat(equationColor[0].equationColor).isEqualTo(Color.WHITE)
+  }
+
   @Test
   fun testParseHtml_noTagHandler_withMathMarkup_doesNotIncludeImageSpan() {
     val parsedHtml =
@@ -306,7 +335,13 @@ class MathTagHandlerTest {
 
   private fun createMathTagHandler(cacheLatexRendering: Boolean): MathTagHandler {
     // Pick an arbitrary line height since rendering doesn't actually happen in tests.
-    return MathTagHandler(consoleLogger, context.assets, lineHeight = 10.0f, cacheLatexRendering)
+    return MathTagHandler(
+      consoleLogger,
+      context.assets,
+      lineHeight = 10.0f,
+      cacheLatexRendering,
+      application = context.applicationContext as Application
+    )
   }
 
   private fun <T : Any> Spannable.getSpansFromWholeString(spanClass: KClass<T>): Array<T> =