File indexing completed on 2024-05-19 05:31:56

 /*
     KWin - the KDE window manager
     This file is part of the KDE project.
 
     SPDX-FileCopyrightText: 2006-2007 Rivo Laks <rivolaks@hot.ee>
     SPDX-FileCopyrightText: 2010, 2011 Martin Gräßlin <mgraesslin@kde.org>
     SPDX-FileCopyrightText: 2023 Xaver Hugl <xaver.hugl@kde.org>
 
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 #include "glvertexbuffer.h"
 #include "glframebuffer.h"
 #include "glplatform.h"
 #include "glshader.h"
 #include "glshadermanager.h"
 #include "glutils.h"
 #include "utils/common.h"
 
 #include <QVector4D>
 #include <bitset>
 #include <deque>
 
 namespace KWin
 {
 
 // Certain GPUs, especially mobile, require the data copied to the GPU to be aligned to a
 // certain amount of bytes. For example, the Mali GPU requires data to be aligned to 8 bytes.
 // This function helps ensure that the data is aligned.
 template<typename T>
 T align(T value, int bytes)
 {
     return (value + bytes - 1) & ~T(bytes - 1);
 }
 
 class IndexBuffer
 {
 public:
     IndexBuffer();
     ~IndexBuffer();
 
     void accommodate(size_t count);
     void bind();
 
 private:
     GLuint m_buffer;
     size_t m_count = 0;
     std::vector<uint16_t> m_data;
 };
 
 IndexBuffer::IndexBuffer()
 {
     // The maximum number of quads we can render with 16 bit indices is 16,384.
     // But we start with 512 and grow the buffer as needed.
     glGenBuffers(1, &m_buffer);
     accommodate(512);
 }
 
 IndexBuffer::~IndexBuffer()
 {
     glDeleteBuffers(1, &m_buffer);
 }
 
 void IndexBuffer::accommodate(size_t count)
 {
     // Check if we need to grow the buffer.
     if (count <= m_count) {
         return;
     }
     Q_ASSERT(m_count * 2 < std::numeric_limits<uint16_t>::max() / 4);
     const size_t oldCount = m_count;
     m_count *= 2;
     m_data.reserve(m_count * 6);
     for (size_t i = oldCount; i < m_count; i++) {
         const uint16_t offset = i * 4;
         m_data[i * 6 + 0] = offset + 1;
         m_data[i * 6 + 1] = offset + 0;
         m_data[i * 6 + 2] = offset + 3;
         m_data[i * 6 + 3] = offset + 3;
         m_data[i * 6 + 4] = offset + 2;
         m_data[i * 6 + 5] = offset + 1;
     }
     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
     glBufferData(GL_ELEMENT_ARRAY_BUFFER, m_count * sizeof(uint16_t), m_data.data(), GL_STATIC_DRAW);
 }
 
 void IndexBuffer::bind()
 {
     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_buffer);
 }
 
 // ------------------------------------------------------------------
 
 struct VertexAttrib
 {
     int size;
     GLenum type;
     int offset;
 };
 
 // ------------------------------------------------------------------
 
 struct BufferFence
 {
     GLsync sync;
     intptr_t nextEnd;
 
     bool signaled() const
     {
         GLint value;
         glGetSynciv(sync, GL_SYNC_STATUS, 1, nullptr, &value);
         return value == GL_SIGNALED;
     }
 };
 
 static void deleteAll(std::deque<BufferFence> &fences)
 {
     for (const BufferFence &fence : fences) {
         glDeleteSync(fence.sync);
     }
 
     fences.clear();
 }
 
 // ------------------------------------------------------------------
 
 template<size_t Count>
 struct FrameSizesArray
 {
 public:
     FrameSizesArray()
     {
         m_array.fill(0);
     }
 
     void push(size_t size)
     {
         m_array[m_index] = size;
         m_index = (m_index + 1) % Count;
     }
 
     size_t average() const
     {
         size_t sum = 0;
         for (size_t size : m_array) {
             sum += size;
         }
         return sum / Count;
     }
 
 private:
     std::array<size_t, Count> m_array;
     int m_index = 0;
 };
 
 //*********************************
 // GLVertexBufferPrivate
 //*********************************
 class GLVertexBufferPrivate
 {
 public:
     GLVertexBufferPrivate(GLVertexBuffer::UsageHint usageHint)
         : vertexCount(0)
         , persistent(false)
         , bufferSize(0)
         , bufferEnd(0)
         , mappedSize(0)
         , frameSize(0)
         , nextOffset(0)
         , baseAddress(0)
         , map(nullptr)
     {
         glGenBuffers(1, &buffer);
 
         switch (usageHint) {
         case GLVertexBuffer::Dynamic:
             usage = GL_DYNAMIC_DRAW;
             break;
         case GLVertexBuffer::Static:
             usage = GL_STATIC_DRAW;
             break;
         default:
             usage = GL_STREAM_DRAW;
             break;
         }
     }
 
     ~GLVertexBufferPrivate()
     {
         deleteAll(fences);
 
         if (buffer != 0) {
             glDeleteBuffers(1, &buffer);
             map = nullptr;
         }
     }
 
     void bindArrays();
     void unbindArrays();
     void reallocateBuffer(size_t size);
     GLvoid *mapNextFreeRange(size_t size);
     void reallocatePersistentBuffer(size_t size);
     bool awaitFence(intptr_t offset);
     GLvoid *getIdleRange(size_t size);
 
     GLuint buffer;
     GLenum usage;
     int vertexCount;
     static std::unique_ptr<GLVertexBuffer> streamingBuffer;
     static bool haveBufferStorage;
     static bool haveSyncFences;
     static bool hasMapBufferRange;
     static bool supportsIndexedQuads;
     QByteArray dataStore;
     bool persistent;
     size_t bufferSize;
     intptr_t bufferEnd;
     size_t mappedSize;
     size_t frameSize;
     intptr_t nextOffset;
     intptr_t baseAddress;
     uint8_t *map;
     std::deque<BufferFence> fences;
     FrameSizesArray<4> frameSizes;
     std::array<VertexAttrib, VertexAttributeCount> attrib;
     size_t attribStride = 0;
     std::bitset<32> enabledArrays;
     static std::unique_ptr<IndexBuffer> s_indexBuffer;
 };
 
 bool GLVertexBufferPrivate::hasMapBufferRange = false;
 bool GLVertexBufferPrivate::supportsIndexedQuads = false;
 std::unique_ptr<GLVertexBuffer> GLVertexBufferPrivate::streamingBuffer;
 bool GLVertexBufferPrivate::haveBufferStorage = false;
 bool GLVertexBufferPrivate::haveSyncFences = false;
 std::unique_ptr<IndexBuffer> GLVertexBufferPrivate::s_indexBuffer;
 
 void GLVertexBufferPrivate::bindArrays()
 {
     glBindBuffer(GL_ARRAY_BUFFER, buffer);
 
     for (size_t i = 0; i < enabledArrays.size(); i++) {
         if (enabledArrays[i]) {
             glVertexAttribPointer(i, attrib[i].size, attrib[i].type, GL_FALSE, attribStride,
                                   (const GLvoid *)(baseAddress + attrib[i].offset));
             glEnableVertexAttribArray(i);
         }
     }
 }
 
 void GLVertexBufferPrivate::unbindArrays()
 {
     for (size_t i = 0; i < enabledArrays.size(); i++) {
         if (enabledArrays[i]) {
             glDisableVertexAttribArray(i);
         }
     }
 }
 
 void GLVertexBufferPrivate::reallocatePersistentBuffer(size_t size)
 {
     if (buffer != 0) {
         // This also unmaps and unbinds the buffer
         glDeleteBuffers(1, &buffer);
         buffer = 0;
 
         deleteAll(fences);
     }
 
     if (buffer == 0) {
         glGenBuffers(1, &buffer);
     }
 
     // Round the size up to 64 kb
     size_t minSize = std::max<size_t>(frameSizes.average() * 3, 128 * 1024);
     bufferSize = std::max(size, minSize);
 
     const GLbitfield storage = GL_DYNAMIC_STORAGE_BIT;
     const GLbitfield access = GL_MAP_WRITE_BIT | GL_MAP_PERSISTENT_BIT | GL_MAP_COHERENT_BIT;
 
     glBindBuffer(GL_ARRAY_BUFFER, buffer);
     glBufferStorage(GL_ARRAY_BUFFER, bufferSize, nullptr, storage | access);
 
     map = (uint8_t *)glMapBufferRange(GL_ARRAY_BUFFER, 0, bufferSize, access);
 
     nextOffset = 0;
     bufferEnd = bufferSize;
 }
 
 bool GLVertexBufferPrivate::awaitFence(intptr_t end)
 {
     // Skip fences until we reach the end offset
     while (!fences.empty() && fences.front().nextEnd < end) {
         glDeleteSync(fences.front().sync);
         fences.pop_front();
     }
 
     Q_ASSERT(!fences.empty());
 
     // Wait on the next fence
     const BufferFence &fence = fences.front();
 
     if (!fence.signaled()) {
         qCDebug(KWIN_OPENGL) << "Stalling on VBO fence";
         const GLenum ret = glClientWaitSync(fence.sync, GL_SYNC_FLUSH_COMMANDS_BIT, 1000000000);
 
         if (ret == GL_TIMEOUT_EXPIRED || ret == GL_WAIT_FAILED) {
             qCCritical(KWIN_OPENGL) << "Wait failed";
             return false;
         }
     }
 
     glDeleteSync(fence.sync);
 
     // Update the end pointer
     bufferEnd = fence.nextEnd;
     fences.pop_front();
 
     return true;
 }
 
 GLvoid *GLVertexBufferPrivate::getIdleRange(size_t size)
 {
     if (size > bufferSize) {
         reallocatePersistentBuffer(size * 2);
     }
 
     // Handle wrap-around
     if ((nextOffset + size > bufferSize)) {
         nextOffset = 0;
         bufferEnd -= bufferSize;
 
         for (BufferFence &fence : fences) {
             fence.nextEnd -= bufferSize;
         }
 
         // Emit a fence now
         if (auto sync = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0)) {
             fences.push_back(BufferFence{
                 .sync = sync,
                 .nextEnd = intptr_t(bufferSize)});
         }
     }
 
     if (nextOffset + intptr_t(size) > bufferEnd) {
         if (!awaitFence(nextOffset + size)) {
             return nullptr;
         }
     }
 
     return map + nextOffset;
 }
 
 void GLVertexBufferPrivate::reallocateBuffer(size_t size)
 {
     // Round the size up to 4 Kb for streaming/dynamic buffers.
     const size_t minSize = 32768; // Minimum size for streaming buffers
     const size_t alloc = usage != GL_STATIC_DRAW ? std::max(size, minSize) : size;
 
     glBufferData(GL_ARRAY_BUFFER, alloc, nullptr, usage);
 
     bufferSize = alloc;
 }
 
 GLvoid *GLVertexBufferPrivate::mapNextFreeRange(size_t size)
 {
     GLbitfield access = GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_RANGE_BIT | GL_MAP_UNSYNCHRONIZED_BIT;
 
     if ((nextOffset + size) > bufferSize) {
         // Reallocate the data store if it's too small.
         if (size > bufferSize) {
             reallocateBuffer(size);
         } else {
             access |= GL_MAP_INVALIDATE_BUFFER_BIT;
             access ^= GL_MAP_UNSYNCHRONIZED_BIT;
         }
 
         nextOffset = 0;
     }
 
     return glMapBufferRange(GL_ARRAY_BUFFER, nextOffset, size, access);
 }
 
 GLVertexBuffer::GLVertexBuffer(UsageHint hint)
     : d(std::make_unique<GLVertexBufferPrivate>(hint))
 {
 }
 
 GLVertexBuffer::~GLVertexBuffer() = default;
 
 void GLVertexBuffer::setData(const void *data, size_t size)
 {
     GLvoid *ptr = map(size);
     if (!ptr) {
         return;
     }
     memcpy(ptr, data, size);
     unmap();
 }
 
 GLvoid *GLVertexBuffer::map(size_t size)
 {
     d->mappedSize = size;
     d->frameSize += size;
 
     if (d->persistent) {
         return d->getIdleRange(size);
     }
 
     glBindBuffer(GL_ARRAY_BUFFER, d->buffer);
 
     bool preferBufferSubData = GLPlatform::instance()->preferBufferSubData();
 
     if (GLVertexBufferPrivate::hasMapBufferRange && !preferBufferSubData) {
         return (GLvoid *)d->mapNextFreeRange(size);
     }
 
     // If we can't map the buffer we allocate local memory to hold the
     // buffer data and return a pointer to it.  The data will be submitted
     // to the actual buffer object when the user calls unmap().
     if (size_t(d->dataStore.size()) < size) {
         d->dataStore.resize(size);
     }
 
     return (GLvoid *)d->dataStore.data();
 }
 
 void GLVertexBuffer::unmap()
 {
     if (d->persistent) {
         d->baseAddress = d->nextOffset;
         d->nextOffset += align(d->mappedSize, 8);
         d->mappedSize = 0;
         return;
     }
 
     bool preferBufferSubData = GLPlatform::instance()->preferBufferSubData();
 
     if (GLVertexBufferPrivate::hasMapBufferRange && !preferBufferSubData) {
         glUnmapBuffer(GL_ARRAY_BUFFER);
 
         d->baseAddress = d->nextOffset;
         d->nextOffset += align(d->mappedSize, 8);
     } else {
         // Upload the data from local memory to the buffer object
         if (preferBufferSubData) {
             if ((d->nextOffset + d->mappedSize) > d->bufferSize) {
                 d->reallocateBuffer(d->mappedSize);
                 d->nextOffset = 0;
             }
 
             glBufferSubData(GL_ARRAY_BUFFER, d->nextOffset, d->mappedSize, d->dataStore.constData());
 
             d->baseAddress = d->nextOffset;
             d->nextOffset += align(d->mappedSize, 8);
         } else {
             glBufferData(GL_ARRAY_BUFFER, d->mappedSize, d->dataStore.data(), d->usage);
             d->baseAddress = 0;
         }
 
         // Free the local memory buffer if it's unlikely to be used again
         if (d->usage == GL_STATIC_DRAW) {
             d->dataStore = QByteArray();
         }
     }
 
     d->mappedSize = 0;
 }
 
 void GLVertexBuffer::setVertexCount(int count)
 {
     d->vertexCount = count;
 }
 
 void GLVertexBuffer::setAttribLayout(std::span<const GLVertexAttrib> attribs, size_t stride)
 {
     d->enabledArrays.reset();
     for (const auto &attrib : attribs) {
         Q_ASSERT(attrib.attributeIndex < d->attrib.size());
         d->attrib[attrib.attributeIndex].size = attrib.componentCount;
         d->attrib[attrib.attributeIndex].type = attrib.type;
         d->attrib[attrib.attributeIndex].offset = attrib.relativeOffset;
         d->enabledArrays[attrib.attributeIndex] = true;
     }
     d->attribStride = stride;
 }
 
 void GLVertexBuffer::render(GLenum primitiveMode)
 {
     render(infiniteRegion(), primitiveMode, false);
 }
 
 void GLVertexBuffer::render(const QRegion &region, GLenum primitiveMode, bool hardwareClipping)
 {
     d->bindArrays();
     draw(region, primitiveMode, 0, d->vertexCount, hardwareClipping);
     d->unbindArrays();
 }
 
 void GLVertexBuffer::bindArrays()
 {
     d->bindArrays();
 }
 
 void GLVertexBuffer::unbindArrays()
 {
     d->unbindArrays();
 }
 
 void GLVertexBuffer::draw(GLenum primitiveMode, int first, int count)
 {
     draw(infiniteRegion(), primitiveMode, first, count, false);
 }
 
 void GLVertexBuffer::draw(const QRegion &region, GLenum primitiveMode, int first, int count, bool hardwareClipping)
 {
     if (primitiveMode == GL_QUADS) {
         if (!GLVertexBufferPrivate::s_indexBuffer) {
             GLVertexBufferPrivate::s_indexBuffer = std::make_unique<IndexBuffer>();
         }
 
         GLVertexBufferPrivate::s_indexBuffer->bind();
         GLVertexBufferPrivate::s_indexBuffer->accommodate(count / 4);
 
         count = count * 6 / 4;
 
         if (!hardwareClipping) {
             glDrawElementsBaseVertex(GL_TRIANGLES, count, GL_UNSIGNED_SHORT, nullptr, first);
         } else {
             // Clip using scissoring
             const GLFramebuffer *current = GLFramebuffer::currentFramebuffer();
             for (const QRect &r : region) {
                 glScissor(r.x(), current->size().height() - (r.y() + r.height()), r.width(), r.height());
                 glDrawElementsBaseVertex(GL_TRIANGLES, count, GL_UNSIGNED_SHORT, nullptr, first);
             }
         }
         return;
     }
 
     if (!hardwareClipping) {
         glDrawArrays(primitiveMode, first, count);
     } else {
         // Clip using scissoring
         const GLFramebuffer *current = GLFramebuffer::currentFramebuffer();
         for (const QRect &r : region) {
             glScissor(r.x(), current->size().height() - (r.y() + r.height()), r.width(), r.height());
             glDrawArrays(primitiveMode, first, count);
         }
     }
 }
 
 bool GLVertexBuffer::supportsIndexedQuads()
 {
     return GLVertexBufferPrivate::supportsIndexedQuads;
 }
 
 void GLVertexBuffer::reset()
 {
     d->vertexCount = 0;
 }
 
 void GLVertexBuffer::endOfFrame()
 {
     if (!d->persistent) {
         return;
     }
 
     // Emit a fence if we have uploaded data
     if (d->frameSize > 0) {
         d->frameSizes.push(d->frameSize);
         d->frameSize = 0;
 
         // Force the buffer to be reallocated at the beginning of the next frame
         // if the average frame size is greater than half the size of the buffer
         if (d->frameSizes.average() > d->bufferSize / 2) {
             deleteAll(d->fences);
             glDeleteBuffers(1, &d->buffer);
 
             d->buffer = 0;
             d->bufferSize = 0;
             d->nextOffset = 0;
             d->map = nullptr;
         } else {
             if (auto sync = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0)) {
                 d->fences.push_back(BufferFence{
                     .sync = sync,
                     .nextEnd = intptr_t(d->nextOffset + d->bufferSize)});
             }
         }
     }
 }
 
 void GLVertexBuffer::beginFrame()
 {
     if (!d->persistent) {
         return;
     }
 
     // Remove finished fences from the list and update the bufferEnd offset
     while (d->fences.size() > 1 && d->fences.front().signaled()) {
         const BufferFence &fence = d->fences.front();
         glDeleteSync(fence.sync);
 
         d->bufferEnd = fence.nextEnd;
         d->fences.pop_front();
     }
 }
 
 void GLVertexBuffer::initStatic()
 {
     if (GLPlatform::instance()->isGLES()) {
         bool haveBaseVertex = hasGLExtension(QByteArrayLiteral("GL_OES_draw_elements_base_vertex"));
         bool haveCopyBuffer = hasGLVersion(3, 0);
         bool haveMapBufferRange = hasGLExtension(QByteArrayLiteral("GL_EXT_map_buffer_range"));
 
         GLVertexBufferPrivate::hasMapBufferRange = haveMapBufferRange;
         GLVertexBufferPrivate::supportsIndexedQuads = haveBaseVertex && haveCopyBuffer && haveMapBufferRange;
         GLVertexBufferPrivate::haveBufferStorage = hasGLExtension("GL_EXT_buffer_storage");
         GLVertexBufferPrivate::haveSyncFences = hasGLVersion(3, 0);
     } else {
         bool haveBaseVertex = hasGLVersion(3, 2) || hasGLExtension(QByteArrayLiteral("GL_ARB_draw_elements_base_vertex"));
         bool haveCopyBuffer = hasGLVersion(3, 1) || hasGLExtension(QByteArrayLiteral("GL_ARB_copy_buffer"));
         bool haveMapBufferRange = hasGLVersion(3, 0) || hasGLExtension(QByteArrayLiteral("GL_ARB_map_buffer_range"));
 
         GLVertexBufferPrivate::hasMapBufferRange = haveMapBufferRange;
         GLVertexBufferPrivate::supportsIndexedQuads = haveBaseVertex && haveCopyBuffer && haveMapBufferRange;
         GLVertexBufferPrivate::haveBufferStorage = hasGLVersion(4, 4) || hasGLExtension("GL_ARB_buffer_storage");
         GLVertexBufferPrivate::haveSyncFences = hasGLVersion(3, 2) || hasGLExtension("GL_ARB_sync");
     }
     GLVertexBufferPrivate::s_indexBuffer.reset();
     GLVertexBufferPrivate::streamingBuffer = std::make_unique<GLVertexBuffer>(GLVertexBuffer::Stream);
 
     if (GLVertexBufferPrivate::haveBufferStorage && GLVertexBufferPrivate::haveSyncFences) {
         if (qgetenv("KWIN_PERSISTENT_VBO") != QByteArrayLiteral("0")) {
             GLVertexBufferPrivate::streamingBuffer->d->persistent = true;
         }
     }
 }
 
 void GLVertexBuffer::cleanup()
 {
     GLVertexBufferPrivate::s_indexBuffer.reset();
     GLVertexBufferPrivate::hasMapBufferRange = false;
     GLVertexBufferPrivate::supportsIndexedQuads = false;
     GLVertexBufferPrivate::streamingBuffer.reset();
 }
 
 GLVertexBuffer *GLVertexBuffer::streamingBuffer()
 {
     return GLVertexBufferPrivate::streamingBuffer.get();
 }
 
 }