From ac513c2fde2bd385f26f63848ff72ad85d2a4144 Mon Sep 17 00:00:00 2001
From: John Reck <jreck@google.com>
Date: Thu, 28 Mar 2019 16:57:38 -0700
Subject: [PATCH] Fix NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS handling

Fixes: 123541940
Test: CTS HardwareRendererTests#testLotsOfBuffers
Change-Id: I5d96e615f552c4faa0e6dcaaaa828c871eaf6c8e
---
 libs/hwui/renderthread/VulkanSurface.cpp | 19 ++++++++++++++-----
 libs/hwui/renderthread/VulkanSurface.h   | 12 +++++++++---
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/libs/hwui/renderthread/VulkanSurface.cpp b/libs/hwui/renderthread/VulkanSurface.cpp
index 1708d3c0e0936..3fed6b09ede26 100644
--- a/libs/hwui/renderthread/VulkanSurface.cpp
+++ b/libs/hwui/renderthread/VulkanSurface.cpp
@@ -222,7 +222,17 @@ VulkanSurface* VulkanSurface::Create(ANativeWindow* window, ColorMode colorMode,
     const SkISize maxSize = SkISize::Make(caps.maxImageExtent.width, caps.maxImageExtent.height);
     ComputeWindowSizeAndTransform(&windowInfo, minSize, maxSize);
 
-    windowInfo.bufferCount = std::max<uint32_t>(VulkanSurface::sMaxBufferCount, caps.minImageCount);
+    int query_value;
+    int err = window->query(window, NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS, &query_value);
+    if (err != 0 || query_value < 0) {
+        ALOGE("window->query failed: %s (%d) value=%d", strerror(-err), err,
+              query_value);
+        return nullptr;
+    }
+    auto min_undequeued_buffers = static_cast<uint32_t>(query_value);
+
+    windowInfo.bufferCount = min_undequeued_buffers
+            + std::max(VulkanSurface::sTargetBufferCount, caps.minImageCount);
     if (caps.maxImageCount > 0 && windowInfo.bufferCount > caps.maxImageCount) {
         // Application must settle for fewer images than desired:
         windowInfo.bufferCount = caps.maxImageCount;
@@ -357,10 +367,9 @@ bool VulkanSurface::UpdateWindow(ANativeWindow* window, const WindowInfo& window
         return false;
     }
 
-    // Lower layer insists that we have at least two buffers.
-    err = native_window_set_buffer_count(window, std::max(2, windowInfo.bufferCount));
+    err = native_window_set_buffer_count(window, windowInfo.bufferCount);
     if (err != 0) {
-        ALOGE("VulkanSurface::UpdateWindow() native_window_set_buffer_count(%d) failed: %s (%d)",
+        ALOGE("VulkanSurface::UpdateWindow() native_window_set_buffer_count(%zu) failed: %s (%d)",
               windowInfo.bufferCount, strerror(-err), err);
         return false;
     }
@@ -392,7 +401,7 @@ VulkanSurface::~VulkanSurface() {
 }
 
 void VulkanSurface::releaseBuffers() {
-    for (uint32_t i = 0; i < VulkanSurface::sMaxBufferCount; i++) {
+    for (uint32_t i = 0; i < mWindowInfo.bufferCount; i++) {
         VulkanSurface::NativeBufferInfo& bufferInfo = mNativeBuffers[i];
 
         if (bufferInfo.buffer.get() != nullptr && bufferInfo.dequeued) {
diff --git a/libs/hwui/renderthread/VulkanSurface.h b/libs/hwui/renderthread/VulkanSurface.h
index 418d40f8c056e..305483fce2d59 100644
--- a/libs/hwui/renderthread/VulkanSurface.h
+++ b/libs/hwui/renderthread/VulkanSurface.h
@@ -83,14 +83,19 @@ private:
      * as private to this class.
      *
      */
-    static constexpr int sMaxBufferCount = 3;
+
+    // How many buffers we want to be able to use ourselves. We want 1 in active rendering with
+    // 1 more queued, so 2. This will be added to NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS, which is
+    // how many buffers the consumer needs (eg, 1 for SurfaceFlinger), getting to a typically
+    // triple-buffered queue as a result.
+    static constexpr uint32_t sTargetBufferCount = 2;
 
     struct WindowInfo {
         SkISize size;
         PixelFormat pixelFormat;
         android_dataspace dataspace;
         int transform;
-        int bufferCount;
+        size_t bufferCount;
         uint64_t windowUsageFlags;
 
         // size of the ANativeWindow if the inverse of transform requires us to swap width/height
@@ -111,7 +116,8 @@ private:
                                               const SkISize& maxSize);
     void releaseBuffers();
 
-    NativeBufferInfo mNativeBuffers[VulkanSurface::sMaxBufferCount];
+    // TODO: Just use a vector?
+    NativeBufferInfo mNativeBuffers[android::BufferQueueDefs::NUM_BUFFER_SLOTS];
 
     sp<ANativeWindow> mNativeWindow;
     WindowInfo mWindowInfo;