From 17abc7482f5da8f104fb57c2e5d592636d3770c3 Mon Sep 17 00:00:00 2001
From: Fabian Kozynski <kozynski@google.com>
Date: Fri, 14 May 2021 10:35:44 -0400
Subject: [PATCH] Use padding in pages instead of pageMargin

ViewPager pageMargin does some rounding when calculating the offset of
each page, leading to positions that are not integers at the snapping
points. This is usually not an issue, except that we use those positions
to drive the PageIndicator.

Instead, set padding on the pages and negative margin in
PagedTileLayout. As everything has clip false, this produces the exact
same effect.

Test: manual
Fixes: 187954110
Change-Id: Ie1055a34c26214b012e96e3ec032ce4db576694d
---
 packages/SystemUI/res/layout/qs_paged_page.xml |  6 +++++-
 .../android/systemui/qs/PagedTileLayout.java   | 18 ++++++++++++++++--
 .../android/systemui/qs/QSContainerImpl.java   |  2 +-
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/packages/SystemUI/res/layout/qs_paged_page.xml b/packages/SystemUI/res/layout/qs_paged_page.xml
index a4f0a0c85d411..98804fc80b50e 100644
--- a/packages/SystemUI/res/layout/qs_paged_page.xml
+++ b/packages/SystemUI/res/layout/qs_paged_page.xml
@@ -18,4 +18,8 @@
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/tile_page"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"/>
+    android:layout_height="match_parent"
+    android:paddingStart="@dimen/notification_side_paddings"
+    android:paddingEnd="@dimen/notification_side_paddings"
+    android:clipChildren="false"
+    android:clipToPadding="false" />
diff --git a/packages/SystemUI/src/com/android/systemui/qs/PagedTileLayout.java b/packages/SystemUI/src/com/android/systemui/qs/PagedTileLayout.java
index e0c8af6b89776..ce1066ee41c25 100644
--- a/packages/SystemUI/src/com/android/systemui/qs/PagedTileLayout.java
+++ b/packages/SystemUI/src/com/android/systemui/qs/PagedTileLayout.java
@@ -80,8 +80,22 @@ public class PagedTileLayout extends ViewPager implements QSTileLayout {
 
     @Override
     public void setPageMargin(int marginPixels) {
-        if (marginPixels != getPageMargin()) {
-            super.setPageMargin(marginPixels);
+        // Using page margins creates some rounding issues that interfere with the correct position
+        // in the onPageChangedListener and therefore present bad positions to the PageIndicator.
+        // Instead, we use negative margins in the container and positive padding in the pages,
+        // matching the margin set from QSContainerImpl (note that new pages will always be inflated
+        // with the correct value.
+        // QSContainerImpl resources are set onAttachedView, so this view will always have the right
+        // values when attached.
+        MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();
+        lp.setMarginStart(-marginPixels);
+        lp.setMarginEnd(-marginPixels);
+        setLayoutParams(lp);
+
+        int nPages = mPages.size();
+        for (int i = 0; i < nPages; i++) {
+            View v = mPages.get(i);
+            v.setPadding(marginPixels, v.getPaddingTop(), marginPixels, v.getPaddingBottom());
         }
     }
 
diff --git a/packages/SystemUI/src/com/android/systemui/qs/QSContainerImpl.java b/packages/SystemUI/src/com/android/systemui/qs/QSContainerImpl.java
index cd97f976540d5..edfbed04f70da 100644
--- a/packages/SystemUI/src/com/android/systemui/qs/QSContainerImpl.java
+++ b/packages/SystemUI/src/com/android/systemui/qs/QSContainerImpl.java
@@ -295,7 +295,7 @@ public class QSContainerImpl extends FrameLayout {
                 qsPanelController.setContentMargins(mContentPadding, mContentPadding);
                 // Set it as double the side margin (to simulate end margin of current page +
                 // start margin of next page).
-                qsPanelController.setPageMargin(2 * mSideMargins);
+                qsPanelController.setPageMargin(mSideMargins);
             } else if (view == mHeader) {
                 // No content padding for the header.
             } else {