@Config(fontScale=...) does not get applied to the default display

[hoisie]

For instance, add this to AndroidTestEnvironmentTest:

 @Test
  @Config(fontScale = 1.3f)
  public void setFontScale_updateDefaultDisplayScaledDensity() {
    Context context = ApplicationProvider.getApplicationContext();
    WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
    Display defaultDisplay = wm.getDefaultDisplay();
    DisplayMetrics defaultDisplayMetrics = new DisplayMetrics();
    defaultDisplay.getMetrics(defaultDisplayMetrics);
    assertThat(defaultDisplayMetrics.scaledDensity).isEqualTo(defaultDisplayMetrics.density * 1.3f);
  }

@utzcoz and @MGaetan89, this is related to the ShadowDisplay.setScaledDensity that was recently removed:: https://github.com/robolectric/robolectric/pull/8840/files#diff-ef2dfc7df64dc5c3c361a801fdcbaa9696e5749de52872debdba1c06f0fdf2e1L201-L203

I assumed that it was possible to set the scaled density using a combination of e.g. @Config(qualifiers="xhdpi", fontScale=1.3"), but there is a bug in Robolectric and that doesn't seem to apply to WindowManager.getDefaultDisplay().

I took a quick look and it may be related to the call to 'displayInfo.getAppMetrics' in ShadowDisplayManager.createDisplayInfo
https://github.com/robolectric/robolectric/blob/master/shadows/framework/src/main/java/org/robolectric/shadows/ShadowDisplayManager.java#L154-L156, but I was not able to do a quick fix.

We could investigate a bit more, but if there is not an easy solution we may need to restore the ShadowDisplay.setScaledDensity until this issue is fixed, and then we can remove it again. There are a few tests inside of Google that look at the value of scaledDensity from the default display.

[hoisie]

Just a bit more findings:

Display.getMetric(DisplayMetrics outMetrics) is this code:

    public void getMetrics(DisplayMetrics outMetrics) {
        synchronized (mLock) {
            updateDisplayInfoLocked();
            mDisplayInfo.getAppMetrics(outMetrics, getDisplayAdjustments());
        }
    }

I think in real Android, getDisplayAdjustments(), which returns a DisplayAdjustments class, is where the scaled density gets set. In DisplayAdjustments there is a member CompatibilityInfo which encapsulates the font scale value that the user overrides.

There is currently no logic in Robolectric that has logic to set the display adjustments.

Unfortunately the initial implementation of font scale never took into consideration DisplayAdjustments or Displays.

[hoisie]

This method may also play a role: CompatibilityInfo.setOverrideInvertedScale.

[MGaetan89]

I'll try to look into this issue. Thanks for providing all these info @hoisie

[MGaetan89]

@hoisie just to be sure, the test case you shared in the issue detail should also call bootstrapWrapper.callSetUpApplicationState();, right? Otherwise the default display doesn't get created.