Vulkan: drawArrays followed by drawElements bugfix

src/libANGLE/renderer/vulkan/VertexArrayVk.cpp

@@ -464,7 +464,11 @@ gl::Error VertexArrayVk::onDraw(const gl::Context *context,
             updateArrayBufferReadDependencies(drawNode, activeAttribs,
                                               renderer->getCurrentQueueSerial());
         }
+
         mVertexBuffersDirty = false;
+
+        // This forces the binding to happen if we follow a drawElement call from a drawArrays call.
+        mIndexBufferDirty = true;
     }
 
     return gl::NoError();

src/tests/gl_tests/StateChangeTest.cpp

@@ -15,6 +15,18 @@ using namespace angle;
 
 namespace
 {
+constexpr char kBasicVertexShader[] =
+    R"(attribute vec3 position;
+void main()
+{
+    gl_Position = vec4(position, 1);
+})";
+
+constexpr char kGreenFragmentShader[] =
+    R"(void main()
+{
+    gl_FragColor = vec4(0, 1, 0, 1);
+})";
 
 class StateChangeTest : public ANGLETest
 {
@@ -1008,6 +1020,61 @@ void SimpleStateChangeTest::simpleDrawWithColor(const GLColor &color)
     simpleDrawWithBuffer(&colorBuffer);
 }
 
+// Test that we can do a drawElements call successfully after making a drawArrays call in the same
+// frame.
+TEST_P(SimpleStateChangeTest, DrawArraysThenDrawElement)
+{
+    ANGLE_GL_PROGRAM(program, kBasicVertexShader, kGreenFragmentShader);
+    glUseProgram(program);
+
+    // We expect to draw a triangle with the first 3 points to the left, then another triangle with
+    // the last 3 vertices using a drawElements call.
+    auto vertices = std::vector<Vector3>{{-1.0f, -1.0f, 0.0f},
+                                         {-1.0f, 1.0f, 0.0f},
+                                         {0.0f, 0.0f, 0.0f},
+                                         {1.0f, 1.0f, 0.0f},
+                                         {1.0f, -1.0f, 0.0f}};
+
+    // If we use these indices to draw we'll be using the last 2 vertex only to draw.
+    auto indices = std::vector<GLushort>{2, 3, 4};
+
+    GLint positionLocation = glGetAttribLocation(program, "position");
+    ASSERT_NE(-1, positionLocation);
+
+    GLBuffer vertexBuffer;
+    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices[0]) * vertices.size(), vertices.data(),
+                 GL_STATIC_DRAW);
+
+    GLBuffer indexBuffer;
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
+    glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size() * sizeof(GLushort), &indices[0],
+                 GL_STATIC_DRAW);
+
+    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
+    glEnableVertexAttribArray(positionLocation);
+
+    for (int i = 0; i < 10; i++)
+    {
+        glClear(GL_COLOR_BUFFER_BIT);
+        glDrawArrays(GL_TRIANGLES, 0, 3);                             // triangle to the left
+        glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_SHORT, nullptr);  // triangle to the right
+        swapBuffers();
+    }
+    glDisableVertexAttribArray(positionLocation);
+
+    ASSERT_GL_NO_ERROR();
+
+    int quarterWidth = getWindowWidth() / 4;
+    int halfHeight   = getWindowHeight() / 2;
+
+    // Validate triangle to the left
+    EXPECT_PIXEL_COLOR_EQ(quarterWidth, halfHeight, GLColor::green);
+
+    // Validate triangle to the right
+    EXPECT_PIXEL_COLOR_EQ((quarterWidth * 3), halfHeight, GLColor::green);
+}
+
 // Handles deleting a Buffer when it's being used.
 TEST_P(SimpleStateChangeTest, DeleteBufferInUse)
 {