[Impeller] use BufferSubData to update gles device buffer.

impeller/core/allocator_unittests.cc

@@ -79,5 +79,52 @@ TEST(AllocatorTest, TextureDescriptorCompatibility) {
   }
 }
 
+TEST(AllocatorTest, RangeTest) {
+  {
+    Range a = Range{0, 10};
+    Range b = Range{10, 20};
+    auto merged = a.Merge(b);
+
+    EXPECT_EQ(merged.offset, 0u);
+    EXPECT_EQ(merged.length, 30u);
+  }
+
+  {
+    Range a = Range{0, 10};
+    Range b = Range{100, 20};
+    auto merged = a.Merge(b);
+
+    EXPECT_EQ(merged.offset, 0u);
+    EXPECT_EQ(merged.length, 120u);
+  }
+
+  {
+    Range a = Range{0, 10};
+    Range b = Range{100, 20};
+    auto merged = b.Merge(a);
+
+    EXPECT_EQ(merged.offset, 0u);
+    EXPECT_EQ(merged.length, 120u);
+  }
+
+  {
+    Range a = Range{0, 10};
+    Range b = Range{100, 0};
+    auto merged = b.Merge(a);
+
+    EXPECT_EQ(merged.offset, 0u);
+    EXPECT_EQ(merged.length, 10u);
+  }
+
+  {
+    Range a = Range{0, 10};
+    Range b = Range{0, 10};
+    auto merged = b.Merge(a);
+
+    EXPECT_EQ(merged.offset, 0u);
+    EXPECT_EQ(merged.length, 10u);
+  }
+}
+
 }  // namespace testing
 }  // namespace impeller

impeller/core/range.h

@@ -5,6 +5,7 @@
 #ifndef FLUTTER_IMPELLER_CORE_RANGE_H_
 #define FLUTTER_IMPELLER_CORE_RANGE_H_
 
+#include <algorithm>
 #include <cstddef>
 
 namespace impeller {
@@ -21,6 +22,19 @@ struct Range {
   constexpr bool operator==(const Range& o) const {
     return offset == o.offset && length == o.length;
   }
+
+  /// @brief Create a new range that is a union of this range and other.
+  constexpr Range Merge(const Range& other) {
+    if (other.length == 0) {
+      return *this;
+    }
+    if (length == 0) {
+      return other;
+    }
+    auto end_offset = std::max(offset + length, other.offset + other.length);
+    auto start_offset = std::min(offset, other.offset);
+    return Range{start_offset, end_offset - start_offset};
+  }
 };
 
 }  // namespace impeller

impeller/renderer/backend/gles/device_buffer_gles.cc

@@ -7,10 +7,8 @@
 #include <cstring>
 #include <memory>
 
-#include "flutter/fml/trace_event.h"
 #include "impeller/base/allocation.h"
 #include "impeller/base/config.h"
-#include "impeller/base/validation.h"
 
 namespace impeller {
 
@@ -53,13 +51,22 @@ bool DeviceBufferGLES::OnCopyHostBuffer(const uint8_t* source,
 
   std::memmove(backing_store_->GetBuffer() + offset,
                source + source_range.offset, source_range.length);
-  ++generation_;
+  Flush(Range{offset, source_range.length});
 
   return true;
 }
 
 void DeviceBufferGLES::Flush(std::optional<Range> range) const {
-  generation_++;
+  if (!range.has_value()) {
+    dirty_range_ = Range{
+        0, static_cast<size_t>(backing_store_->GetLength().GetByteSize())};
+  } else {
+    if (dirty_range_.has_value()) {
+      dirty_range_ = dirty_range_->Merge(range.value());
+    } else {
+      dirty_range_ = range.value();
+    }
+  }
 }
 
 static GLenum ToTarget(DeviceBufferGLES::BindingType type) {
@@ -86,14 +93,17 @@ bool DeviceBufferGLES::BindAndUploadDataIfNecessary(BindingType type) const {
   const auto& gl = reactor_->GetProcTable();
 
   gl.BindBuffer(target_type, buffer.value());
-
-  if (upload_generation_ != generation_) {
-    TRACE_EVENT1(
-        "impeller", "BufferData", "Bytes",
-        std::to_string(backing_store_->GetLength().GetByteSize()).c_str());
+  if (!initialized_) {
     gl.BufferData(target_type, backing_store_->GetLength().GetByteSize(),
-                  backing_store_->GetBuffer(), GL_STATIC_DRAW);
-    upload_generation_ = generation_;
+                  nullptr, GL_DYNAMIC_DRAW);
+    initialized_ = true;
+  }
+
+  if (dirty_range_.has_value()) {
+    auto range = dirty_range_.value();
+    gl.BufferSubData(target_type, range.offset, range.length,
+                     backing_store_->GetBuffer() + range.offset);
+    dirty_range_ = std::nullopt;
   }
 
   return true;
@@ -122,7 +132,8 @@ void DeviceBufferGLES::UpdateBufferData(
   if (update_buffer_data) {
     update_buffer_data(backing_store_->GetBuffer(),
                        backing_store_->GetLength().GetByteSize());
-    ++generation_;
+    Flush(Range{
+        0, static_cast<size_t>(backing_store_->GetLength().GetByteSize())});
   }
 }
 

impeller/renderer/backend/gles/device_buffer_gles.h

@@ -44,8 +44,8 @@ class DeviceBufferGLES final
   ReactorGLES::Ref reactor_;
   HandleGLES handle_;
   mutable std::shared_ptr<Allocation> backing_store_;
-  mutable uint32_t generation_ = 0;
-  mutable uint32_t upload_generation_ = 0;
+  mutable std::optional<Range> dirty_range_ = std::nullopt;
+  mutable bool initialized_ = false;
 
   // |DeviceBuffer|
   uint8_t* OnGetContents() const override;

impeller/renderer/backend/gles/proc_table_gles.h

@@ -104,6 +104,7 @@ struct GLProc {
   PROC(BlendEquationSeparate);               \
   PROC(BlendFuncSeparate);                   \
   PROC(BufferData);                          \
+  PROC(BufferSubData);                       \
   PROC(CheckFramebufferStatus);              \
   PROC(Clear);                               \
   PROC(ClearColor);                          \