Flexline width exceeds container width (#521)

In this PR I am trying to address an issue that occurs when the calculation of flexlines exceeds the permitted size of their container and some items can be shrunk.

After successfully calculating the number of flexline the FlexboxLayout proceeds its measurement by determining the main size through the determineMainSize() method. In certain situations, the width of some flexlines might be bigger than the size of their container. In this cases, we need to restrict their calculated width by retriggering a second layout calculation and enforcing their width as the one of their containers.

Author: AlexBalo

flexbox/src/androidTest/java/com/google/android/flexbox/FlexboxHelperTest.kt

@@ -17,6 +17,7 @@
 package com.google.android.flexbox
 
 import android.view.View
+import android.widget.TextView
 import androidx.test.rule.ActivityTestRule
 import androidx.test.runner.AndroidJUnit4
 import com.google.android.flexbox.test.FlexboxTestActivity
@@ -36,6 +37,13 @@ import org.junit.runner.RunWith
 @RunWith(AndroidJUnit4::class)
 class FlexboxHelperTest {
 
+    private val LONG_TEXT = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do " +
+            "eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim " +
+            "veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo " +
+            "consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum " +
+            "dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, " +
+            "sunt in culpa qui officia deserunt mollit anim id est laborum."
+
     @JvmField
     @Rule
     var activityRule = ActivityTestRule(FlexboxTestActivity::class.java)
@@ -325,6 +333,72 @@ class FlexboxHelperTest {
         assertThat(view4.measuredHeight, `is`(125))
     }
 
+    @Test
+    @Throws(Throwable::class)
+    fun testDetermineMainSize_directionRow_fixedSizeViewAndShrinkable_doNotExceedMaxMainSize() {
+        val activity = activityRule.activity
+        val lp1 = FlexboxLayout.LayoutParams(100, 100)
+        val view1 = View(activity)
+        lp1.flexShrink = 0f
+        view1.layoutParams = lp1
+        val lp2 = FlexboxLayout.LayoutParams(
+                FlexboxLayout.LayoutParams.WRAP_CONTENT,
+                FlexboxLayout.LayoutParams.WRAP_CONTENT)
+        val view2 = TextView(activity)
+        view2.layoutParams = lp2
+        view2.text = LONG_TEXT
+        flexContainer.addView(view1)
+        flexContainer.addView(view2)
+        flexContainer.flexWrap = FlexWrap.NOWRAP
+        val widthMeasureSpec = View.MeasureSpec.makeMeasureSpec(500, View.MeasureSpec.AT_MOST)
+        val heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(1000, View.MeasureSpec.UNSPECIFIED)
+        val result = FlexboxHelper.FlexLinesResult()
+        flexboxHelper.calculateHorizontalFlexLines(result, widthMeasureSpec, heightMeasureSpec)
+        flexContainer.flexLines = result.mFlexLines
+        flexboxHelper.determineMainSize(widthMeasureSpec, heightMeasureSpec)
+
+        // Container with WRAP_CONTENT and a max width forces resizable children to shrink
+        // to avoid exceeding max available space.
+        assertThat(view1.measuredWidth, `is`(100))
+        assertThat(view2.measuredWidth, `is`(400))
+    }
+
+    @Test
+    @Throws(Throwable::class)
+    fun testDetermineMainSize_directionRow_twoFixedSizeViewsAndShrinkable_doNotExceedMaxMainSize() {
+        val activity = activityRule.activity
+        val lp1 = FlexboxLayout.LayoutParams(100, 100)
+        val view1 = View(activity)
+        lp1.flexShrink = 0f
+        view1.layoutParams = lp1
+        val lp2 = FlexboxLayout.LayoutParams(
+                FlexboxLayout.LayoutParams.WRAP_CONTENT,
+                FlexboxLayout.LayoutParams.WRAP_CONTENT)
+        val view2 = TextView(activity)
+        view2.layoutParams = lp2
+        view2.text = LONG_TEXT
+        val lp3 = FlexboxLayout.LayoutParams(100, 100)
+        val view3 = View(activity)
+        lp3.flexShrink = 0f
+        view3.layoutParams = lp3
+        flexContainer.addView(view1)
+        flexContainer.addView(view2)
+        flexContainer.addView(view3)
+        flexContainer.flexWrap = FlexWrap.NOWRAP
+        val widthMeasureSpec = View.MeasureSpec.makeMeasureSpec(500, View.MeasureSpec.AT_MOST)
+        val heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(1000, View.MeasureSpec.UNSPECIFIED)
+        val result = FlexboxHelper.FlexLinesResult()
+        flexboxHelper.calculateHorizontalFlexLines(result, widthMeasureSpec, heightMeasureSpec)
+        flexContainer.flexLines = result.mFlexLines
+        flexboxHelper.determineMainSize(widthMeasureSpec, heightMeasureSpec)
+
+        // Container with WRAP_CONTENT and a max width forces resizable children to shrink
+        // to avoid exceeding max available space.
+        assertThat(view1.measuredWidth, `is`(100))
+        assertThat(view2.measuredWidth, `is`(300))
+        assertThat(view3.measuredWidth, `is`(100))
+    }
+
     @Test
     @Throws(Throwable::class)
     fun testDetermineCrossSize_direction_row_alignContent_stretch() {

flexbox/src/main/java/com/google/android/flexbox/FlexboxHelper.java

@@ -946,10 +946,11 @@ void determineMainSize(int widthMeasureSpec, int heightMeasureSpec, int fromInde
             case FlexDirection.ROW_REVERSE:
                 int widthMode = View.MeasureSpec.getMode(widthMeasureSpec);
                 int widthSize = View.MeasureSpec.getSize(widthMeasureSpec);
+                int largestMainSize = mFlexContainer.getLargestMainSize();
                 if (widthMode == View.MeasureSpec.EXACTLY) {
                     mainSize = widthSize;
                 } else {
-                    mainSize = mFlexContainer.getLargestMainSize();
+                    mainSize = largestMainSize > widthSize ? widthSize : largestMainSize;
                 }
                 paddingAlongMainAxis = mFlexContainer.getPaddingLeft()
                         + mFlexContainer.getPaddingRight();