RESTRICT AUTOMERGE Add 1/16th pixel offset when drawing non-AA points/lines

This nudge ensures that pixel-aligned non-AA'd draws fill the desired
fragment.

Coupled with http://review.skia.org/665816, we're moving this logic from
Skia to Android so that the prerotation matrix can be properly accounted
for. Offseting only in Skia without accounting for prerotation  meant
the device-space Y offset could be applied in the wrong direction when
using Vulkan.

Equivalent change in T: Idfb5027fe3230f2c2b0cad224f2c7640e147ce4a

Bug: 254771190
Test: android.uirendering.cts.testclasses.ExactCanvasTests#testDrawLine
Change-Id: I975b62510a36312a395d1e254474bca726a9445d
(cherry picked from commit 7f785ebd57cf129bb39e89237fba541912ce3649)

libs/hwui/renderthread/VulkanSurface.cpp

diff --git a/libs/hwui/renderthread/VulkanSurface.cpp b/libs/hwui/renderthread/VulkanSurface.cpp
index 21b6c44e..a8da04b 100644
--- a/libs/hwui/renderthread/VulkanSurface.cpp
+++ b/libs/hwui/renderthread/VulkanSurface.cpp
@@ -63,6 +63,18 @@
     return SkMatrix::I();
 }
 
+static SkM44 GetPixelSnapMatrix(SkISize windowSize, int transform) {
+    // Small (~1/16th) nudge to ensure that pixel-aligned non-AA'd draws fill the
+    // desired fragment
+    static const SkScalar kOffset = 0.063f;
+    SkMatrix preRotation = GetPreTransformMatrix(windowSize, transform);
+    SkMatrix invert;
+    LOG_ALWAYS_FATAL_IF(!preRotation.invert(&invert));
+    return SkM44::Translate(kOffset, kOffset)
+            .postConcat(SkM44(preRotation))
+            .preConcat(SkM44(invert));
+}
+
 static bool ConnectAndSetWindowDefaults(ANativeWindow* window) {
     ATRACE_CALL();
 
@@ -178,6 +190,8 @@
 
     outWindowInfo->preTransform =
             GetPreTransformMatrix(outWindowInfo->size, outWindowInfo->transform);
+    outWindowInfo->pixelSnapMatrix =
+            GetPixelSnapMatrix(outWindowInfo->size, outWindowInfo->transform);
 
     err = window->query(window, NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS, &query_value);
     if (err != 0 || query_value < 0) {
@@ -413,6 +427,7 @@
         }
 
         mWindowInfo.preTransform = GetPreTransformMatrix(mWindowInfo.size, mWindowInfo.transform);
+        mWindowInfo.pixelSnapMatrix = GetPixelSnapMatrix(mWindowInfo.size, mWindowInfo.transform);
     }
 
     uint32_t idx;