[Perf] (MG_Backend/DirectVulkan, MG_IntegrationTest/Scenarios): defer window clears while a window pass is open

- A whole-window clear with a window pass open ends that pass and folds
  into the next one, instead of running a load-clear-store pass of its own
- A present drops the depth/stencil half of a pending window clear

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRendererPresent.cpp

@@ -16,12 +16,15 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         // Present has its own submit path. Tag its last wire pass before that
         // submission, rather than retaining it until a draw in the next frame.
         RetireWireDrawPass();
-        // A window clear no pass drew after still has to reach the presented image; a frame that
-        // cannot be presented drops it with the rest of the frame.
-        if (m_swapchainObject.GetHandle() == VK_NULL_HANDLE || m_presentSuspended)
+        // A window color clear no pass drew after still has to reach the presented image. Its
+        // depth/stencil half is dropped: a swap leaves those undefined (see the content flags
+        // reset below). A frame that cannot be presented drops the whole clear.
+        if (m_swapchainObject.GetHandle() == VK_NULL_HANDLE || m_presentSuspended) {
             m_defaultWirePendingClear = {};
-        else
+        } else {
+            m_defaultWirePendingClear.depthStencil = 0;
             MaterializeDefaultWirePendingClear();
+        }
 #endif
         if (m_swapchainObject.GetHandle() == VK_NULL_HANDLE || m_presentSuspended) {
             // No usable swapchain: the window was zero-area at initialization, or

MobileGL/MG_Backend/DirectVulkan/Renderer/WireDraw.cpp

@@ -1407,18 +1407,17 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         return variant;
     }
 
-    // The default framebuffer's half of the deferred clears: a whole-window glClear with no pass
-    // open on the window waits for the next pass that draws into it, which loads it with
-    // LOAD_OP_CLEAR (BeginWireDrawPassFolding) instead of storing a cleared window and loading it
-    // back. Returns the buffers it did not take.
+    // The default framebuffer's half of the deferred clears: a whole-window glClear waits for the
+    // next pass that draws into the window, which loads it with LOAD_OP_CLEAR
+    // (BeginWireDrawPassFolding) instead of storing a cleared window and loading it back. A pass
+    // open on the window ends first, since the in-pass clear does not take the window
+    // (MagmaInPassClearDefault); a present drops the depth/stencil half (Present). Returns the
+    // buffers it did not take.
     GLbitfield VulkanRenderer::DeferDefaultWireClear(const MG_Pipe::MGPFramebufferState& fbo,
                                                      const ClearAttachmentPayload& payload, GLint drawbuffer) {
         GLbitfield remaining = payload.mask & (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
         if (!remaining || !fbo.IsDefault || drawbuffer >= 0 || m_wirePreparationDepth != 0) return remaining;
         if (GLScissorTestClips()) return remaining;
-        // A pass open on the window takes the clear itself (ClearWireAttachmentsOfOpenPass).
-        if (VkRenderPassManager::GetActiveRenderPass() != nullptr && m_wireDrawPass && m_wireDrawPassKey.isDefault)
-            return remaining;
         GLbitfield handled = 0;
         Bool color = false;
         VkImageAspectFlags depthStencil = 0;
@@ -1452,6 +1451,8 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             }
         }
         if (!color && depthStencil == 0) return remaining & ~handled;
+        if (VkRenderPassManager::GetActiveRenderPass() != nullptr && m_wireDrawPass && m_wireDrawPassKey.isDefault)
+            RetireWireDrawPass();
         // The index the next drawing pass on the window will address (WireDraw.cpp's pass key).
         const Uint32 index = DefaultFramebufferWriteIndex(true);
         auto& pending = m_defaultWirePendingClear;

MobileGL/MG_IntegrationTest/Scenarios/InPassClearScenario.cpp

@@ -357,4 +357,35 @@ void main() { o0 = texture(uPalette, vec2(0.5, 0.5)); }
         glDeleteProgram(paletteProgram);
     }
 
+    // A depth clear of the DEFAULT framebuffer while a pass is open on it (a game clearing depth
+    // before its hand or GUI): the in-pass clear does not take the window, so the clear ends the
+    // pass and becomes the load op of the next one, which the farther draw must see.
+    TEST_F(InPassClearScenario, ADefaultFramebufferDepthClearBetweenTestedDrawsDecidesTheSecondDraw) {
+        if (!Ready()) return;
+        HeadlessGL& gl = Gl();
+        const int width = gl.Width(), height = gl.Height();
+        Build();
+        for (int frame = 0; frame < 2; ++frame) {
+            BindDefaultFramebuffer();
+            glViewport(0, 0, width, height);
+            glDisable(GL_SCISSOR_TEST);
+            glDisable(GL_BLEND);
+            glDepthMask(GL_TRUE);
+            glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+            glClearDepth(1.0);
+            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+            glEnable(GL_DEPTH_TEST);
+            glDepthFunc(GL_LESS);
+            Quad(1.0f, 0.0f, 0.0f, 1.0f, -0.5f);
+            glClear(GL_DEPTH_BUFFER_BIT);
+            Quad(0.0f, 1.0f, 0.0f, 1.0f, 0.0f);
+            glDisable(GL_DEPTH_TEST);
+            EXPECT_EQ(FirstGLError(), 0u);
+            const Image image = ReadPixels(width, height);
+            EXPECT_TRUE(Near(image.At(width / 2, height / 2), 0, 255, 0, 255))
+                << "frame " << frame << ": the depth clear between the draws let the farther draw pass";
+            gl.EndFrame();
+        }
+    }
+
 } // namespace MGITest