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[Fix] (Backend): resolve primitive restart per draw - never for a non-indexed one, and never on an index the type cannot hold

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Swung0x48
2026-08-27 03:18:09 -04:00
parent e69e939d1a
commit 90b7a689c5
8 changed files with 486 additions and 131 deletions
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MobileGL/MG_Backend/DirectGLES/MultiDraw.cpp
+28 -13
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@@ -29,20 +29,21 @@ namespace MobileGL::MG_Backend::DirectGLES::MultiDrawImpl {
}
}
// The index value this batch restarts on, in the SOURCE index type's width. Normally
// the all-ones value of that type, which is what GL_PRIMITIVE_RESTART_FIXED_INDEX and
// GLES both restart on; with desktop GL_PRIMITIVE_RESTART it is instead whatever
// glPrimitiveRestartIndex named. The rebased tier turns whichever it is into
// 0xFFFFFFFF in its widened stream, which is what the driver restarts on.
// The index value this batch restarts on, compared at 32 bits against the zero-extended
// source index. Normally the all-ones value of the source type, which is what
// GL_PRIMITIVE_RESTART_FIXED_INDEX and GLES both restart on; with desktop
// GL_PRIMITIVE_RESTART it is instead whatever glPrimitiveRestartIndex named. The rebased
// tier turns whichever it is into 0xFFFFFFFF in its widened stream, which is what the
// driver restarts on.
//
// No truncation, deliberately, and the same rule ResolveRestartSubstitution applies: a
// restart index the source type cannot hold simply matches nothing, so returning it
// verbatim is already "this batch restarts nowhere".
Uint32 RestartSentinelFor(GLenum type) {
if (NeedsArbitraryRestartSubstitution(type)) {
if (ResolveRestartSubstitution(type) != RestartSubstitutionKind::None) {
return MG_State::pGLContext->GetPrimitiveRestartIndex();
}
switch (type) {
case GL_UNSIGNED_BYTE: return 0xFFu;
case GL_UNSIGNED_SHORT: return 0xFFFFu;
default: return 0xFFFFFFFFu;
}
return MG_Util::FixedRestartIndexForGLType(type);
}
Bool RestartActive() {
@@ -502,6 +503,16 @@ namespace MobileGL::MG_Backend::DirectGLES::MultiDrawImpl {
const Bool restartActive = RestartActive();
const Uint32 restartSentinel = RestartSentinelFor(type);
// Widening to GL_UNSIGNED_INT gives a UBYTE/USHORT source a sentinel it can never
// spell, so those batches are lossless. A UINT source that already uses 0xFFFFFFFF as
// a real vertex index while restarting on a different one is the one shape 32 bits
// cannot express - the same corner the single-draw substitution reports.
if (restartActive && indexSize == 4 && restartSentinel != 0xFFFFFFFFu) {
MGLOG_E_ONCE("GL_PRIMITIVE_RESTART with restart index %u over GL_UNSIGNED_INT multi-draw indices: "
"any index that is already 0xFFFFFFFF will restart too, because the rewritten stream "
"has no wider sentinel to move to.",
restartSentinel);
}
g_indexStaging.resize(total);
SizeT cursor = 0;
for (GLsizei i = 0; i < drawcount; ++i) {
@@ -868,8 +879,12 @@ void main() {
if (drawcount <= 0 || !count || !indices) return;
// Read before any GL work, because it decides the tier below: a desktop restart index
// the driver does not know about can only be honoured by the tier that rewrites the
// index stream (see ResolveTierForBatch).
const Bool arbitraryRestart = NeedsArbitraryRestartSubstitution(type);
// index stream (see ResolveTierForBatch). A restart index this index type cannot hold
// needs no rewrite at all - nothing can match it - but it does need the driver's own
// fixed-index restart held off for the batch, which is what the scope below does.
const RestartSubstitutionKind restartKind = ResolveRestartSubstitution(type);
const Bool arbitraryRestart = restartKind == RestartSubstitutionKind::RewriteIndices;
const ScopedSuppressedPrimitiveRestart restartCapOverride(restartKind);
const Bool hasIndexBuffer = BoundIndexBuffer() != nullptr;