[MaterialCardView] Stroke not correctly overlapping corners

Description: When using MaterialCardView with a StrokeColor and StrokeWidth set, the rendered stroke does not fully overlap rounded corners. Expected behavior: The stroke should correctly overlap all corners

Source code: layout:

<?xml version="1.0" encoding="utf-8"?>
<com.google.android.material.card.MaterialCardView xmlns:android="http://schemas.android.com/apk/res/android"
    style="@style/AppCard"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="16dp">

    <View
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/colorPrimary" />
</com.google.android.material.card.MaterialCardView>

styles:

    <style name="AppCard" parent="Widget.MaterialComponents.CardView">
        <item name="cardCornerRadius">32dp</item>
        <item name="cardBackgroundColor">#ffffff</item>
        <item name="strokeColor">#efefef</item>
        <item name="strokeWidth">1dp</item>
        <item name="cardElevation">0dp</item>
    </style>

Android API version: Reproducible with API 29 to 21.

Material Library version: Reproducible with 1.1.0-rc1 and 1.2.0-alpha03

Device: Emulator and real devices (Pixel 1 e.g.)

[ymarian]

@G00fY2 Hi this is due to Anti aliasing. The background and the stroke are drawn on the same pixels but depending on the color of the stroke the transparent pixels added by the AA can cause the bleed through. That’s why you won’t see it if you invert the colors here.

We fixed this in the past by adding another layout inside the card and drawing the stroke outside that layout. We decided this wasn’t worth it because it caused many problems. https://github.com/material-components/material-components-android/commit/0f8fa7e6c9f7e44407c4bde0a6e800c17c2781e6#diff-54cfea65201fdba3911acbc81d757c37

We have been talking about moving the stroke to the background of the card instead of the foreground so I think that’s the only way we will get this fixed, but it’s a complicated change to make.

[ALXKAY]

@G00fY2 @KlassenKonstantin @nicusorflorin I created the Gist with a workaround to fix this bug. Maybe it will work for someone. https://gist.github.com/ALXKAY/681ee1e5ad9ad204cfd8896ccdcc2303