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[MG_Backend, MG_IntegrationTest] (P7): the default draw framebuffer is asked the multisample depth/stencil shape question before any aspect runs, so a scaled COLOR|DEPTH resolve onto the window writes nothing

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- BlitWireFramebuffers' round-2 pre-pass left a default DRAW framebuffer to the per-aspect lambdas on the belief that a default draw behind a multisample read was ResolveWireDepthStencil's region Fatal whatever the shape. It is not: that arm calls DeclineWireDepthStencilResolveShape BEFORE its destination.isDefault region check, so a scaled (or X-mirrored) COLOR|DEPTH blit out of a multisample framebuffer onto the window ran the colour lambda first (BlitWireColorToDefault wrote the swapchain image) and then recorded INVALID_OPERATION on its depth - the partial effect magma-b2.md §2.9 item 3 declared closed.
- The guard drops !draw->IsDefault, and the pre-pass resolves both sides as READS (isWriteTarget=false): only their format and samples are consulted, and DefaultFramebufferReadIndex is const, so nothing re-points the default framebuffer at the acquired image before a write.
- The flipped-resolve case gains a leg: the window is primed blue at depth 0.5, the multisample source (red below, green above) is blown up over the whole of it with COLOR|DEPTH, the call must be INVALID_OPERATION, and three probes (corner, centre, far corner) must read the priming on both aspects through glReadPixels - the only way the harness's pbuffer default framebuffer can be looked at.
- Red-once (split + spawn, restored): the round-2 guard (&& !draw->IsDefault) put back -> DirectVulkan.{Split,Spawn}.MsFlip. fail "the declined COLOR|DEPTH scale onto the window must not have written its colour at (1, 1)" reading {255,0,0,255} (the source's bottom band), and {0,255,0,255} at (64, 48) and (126, 94), for {0,0,255,255}; the INVALID_OPERATION assertion still held, which is the partial effect exactly.
- Verified: the 107 multisample blit/resolve and depth/stencil readback entries on the three wire arms (MsFlip/MsFlip1/MsBlit/MsResolve0/1, Full x3 for both readback scenarios) and the monolith DirectVulkan.DepthStencilReadback* entries pass, pre-existing skips unchanged.
This commit is contained in:
swung0x48
2026-09-22 21:36:08 -04:00
parent 6f1c6d26ee
commit 24da1e0f6d
2 changed files with 66 additions and 6 deletions
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MobileGL/MG_Backend/DirectVulkan/Renderer/WireFramebuffer.inc
+13 -6
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@@ -819,16 +819,23 @@
// images, so it is asked here, before any aspect runs, for every depth/stencil aspect
// the mask names that would take the multisample resolve arm.
//
// A default READ framebuffer is never multisampled here, and a default DRAW one behind a
// multisample read is ResolveWireDepthStencil's region Fatal whatever the shape - and
// resolving the default draw image early would move its write index - so both are left
// to the lambda.
if ((mask & (GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT)) && !read->IsDefault && !draw->IsDefault) {
// A default READ framebuffer is never multisampled here, so it is left to the lambda. A
// default DRAW framebuffer is asked like any other (review round 3): round 2 left it out
// on the belief that a default draw behind a multisample read was ResolveWireDepthStencil's
// region Fatal whatever the shape, but that arm asks DeclineWireDepthStencilResolveShape
// BEFORE its region check - so a scaled (or X-mirrored) COLOR|DEPTH blit out of a
// multisample framebuffer onto the window scaled and wrote its colour through
// BlitWireColorToDefault and then recorded INVALID_OPERATION on its depth, the very
// partial effect this block exists to close. Both sides are resolved as READS
// (isWriteTarget=false): only their format and samples are consulted here, and a write
// resolve of the default framebuffer would re-point it at the acquired swapchain image
// before anything had been written to it.
if ((mask & (GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT)) && !read->IsDefault) {
const auto declines = [&](const MG_Pipe::MGPSurface& src, const MG_Pipe::MGPSurface& dst,
VkImageAspectFlags aspect) -> Bool {
const WireImage source = ResolveWireImage(*read, src, aspect, /*isWriteTarget=*/false);
if (!source.image || source.samples == VK_SAMPLE_COUNT_1_BIT) return false;
const WireImage destination = ResolveWireImage(*draw, dst, aspect, /*isWriteTarget=*/true);
const WireImage destination = ResolveWireImage(*draw, dst, aspect, /*isWriteTarget=*/false);
if (!destination.image || destination.samples != VK_SAMPLE_COUNT_1_BIT) return false;
return DeclineWireDepthStencilResolveShape(source, destination, sx0, sy0, sx1, sy1,
dx0, dy0, dx1, dy1);
MobileGL/MG_IntegrationTest/Scenarios/DepthStencilReadbackMatrixScenario.cpp
+53
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@@ -614,6 +614,59 @@ namespace MGITest {
"the empty-destination decline must have left the depth alone");
EXPECT_EQ(FirstGLError(), 0u) << "the session survived the empty-destination decline";
// THE SAME SCALE ONTO THE WINDOW (review round 3). The default framebuffer was the one
// destination the round-2 pre-pass left to the per-aspect lambdas, on the belief that a
// default draw framebuffer behind a multisample read was the resolve arm's region Fatal
// whatever the shape - but that arm asks the shape question BEFORE its region check, so
// a scaled COLOR|DEPTH resolve onto the window scaled and wrote its colour through the
// swapchain blit and then recorded INVALID_OPERATION on its depth: the partial effect
// the previous leg pins for a user framebuffer, reproduced on the only other kind of
// destination there is. The window is primed blue at depth 0.5, the source (red below,
// green above) is blown up over the whole of it, and three probes - a corner, the
// centre, the far corner - must all still read the priming on both aspects. The
// harness's pbuffer default framebuffer has no other way of being looked at than
// glReadPixels, which is what both probes use.
{
HeadlessGL& gl = Gl();
const int windowWidth = gl.Width();
const int windowHeight = gl.Height();
ASSERT_GE(windowWidth, 4);
ASSERT_GE(windowHeight, 4);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glDisable(GL_SCISSOR_TEST);
glViewport(0, 0, windowWidth, windowHeight);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(GL_TRUE);
glClearColor(0, 0, 1, 1);
glClearDepth(0.5);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
ASSERT_EQ(FirstGLError(), 0u) << "priming the default framebuffer";
glBindFramebuffer(GL_READ_FRAMEBUFFER, multisampled.fbo);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
glBlitFramebuffer(0, 0, kWidth, kHeight, 0, 0, windowWidth, windowHeight,
GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT, GL_NEAREST);
glFinish();
EXPECT_EQ(FirstGLError(), GLenum(GL_INVALID_OPERATION))
<< "a scaled multisample COLOR|DEPTH blit onto the default framebuffer is INVALID_OPERATION as a whole";
glBindFramebuffer(GL_FRAMEBUFFER, 0);
const int probeX[3] = {1, windowWidth / 2, windowWidth - 2};
const int probeY[3] = {1, windowHeight / 2, windowHeight - 2};
for (int i = 0; i < 3; ++i) {
const int x = probeX[i], y = probeY[i];
std::array<GLubyte, 4> window{};
glReadPixels(x, y, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, window.data());
EXPECT_EQ(window, (std::array<GLubyte, 4>{0, 0, 255, 255}))
<< "the declined COLOR|DEPTH scale onto the window must not have written its colour at ("
<< x << ", " << y << ")";
float depth = kDepthPoison;
glReadPixels(x, y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &depth);
EXPECT_NEAR(depth, 0.5f, 1.0f / 4096.0f)
<< "the declined COLOR|DEPTH scale onto the window must have left its depth alone at ("
<< x << ", " << y << ")";
}
EXPECT_EQ(FirstGLError(), 0u) << "the session survived the default-framebuffer decline";
}
DestroySource(resolved);
DestroySource(multisampled);
glBindFramebuffer(GL_FRAMEBUFFER, 0);