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impr: Implement a better algorithm to determine if the frame content has changed

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This commit is contained in:
WerWolv 2024-02-27 18:55:09 +01:00
parent 607f7cba8d
commit e1795d687f
1 changed files with 28 additions and 8 deletions
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36
main/gui/source/window/window.cpp
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@ -567,27 +567,47 @@ namespace hex {
// Finalize ImGui frame
ImGui::Render();
// Hash the draw data to determine if anything changed on the screen
// Compare the previous frame buffer to the current one to determine if the window content has changed
// If not, there's no point in sending the draw data off to the GPU and swapping buffers
// NOTE: For anybody looking at this code and thinking "why not just hash the buffer and compare the hashes",
// the reason is that hashing the buffer is significantly slower than just comparing the buffers directly.
// The buffer might become quite large if there's a lot of vertices on the screen but it's still usually less than
// 10MB (out of which only the active portion needs to actually be compared) which is worth the ~60x speedup.
bool shouldRender = false;
{
u32 drawDataHash = 0;
static u32 previousDrawDataHash = 0;
static std::vector<u8> previousVtxData;
static size_t previousVtxDataSize = 0;
size_t offset = 0;
size_t vtxDataSize = 0;
for (const auto viewPort : ImGui::GetPlatformIO().Viewports) {
auto drawData = viewPort->DrawData;
for (int n = 0; n < drawData->CmdListsCount; n++) {
const ImDrawList *cmdList = drawData->CmdLists[n];
drawDataHash = ImHashData(cmdList->VtxBuffer.Data, cmdList->VtxBuffer.Size * sizeof(ImDrawVert), drawDataHash);
vtxDataSize += drawData->CmdLists[n]->VtxBuffer.size() * sizeof(ImDrawVert);
}
}
for (const auto viewPort : ImGui::GetPlatformIO().Viewports) {
auto drawData = viewPort->DrawData;
for (int n = 0; n < drawData->CmdListsCount; n++) {
const ImDrawList *cmdList = drawData->CmdLists[n];
drawDataHash = ImHashData(cmdList->IdxBuffer.Data, cmdList->IdxBuffer.Size * sizeof(ImDrawIdx), drawDataHash);
if (vtxDataSize == previousVtxDataSize) {
shouldRender = shouldRender || std::memcmp(previousVtxData.data() + offset, cmdList->VtxBuffer.Data, cmdList->VtxBuffer.size() * sizeof(ImDrawVert)) != 0;
} else {
shouldRender = true;
}
if (previousVtxData.size() < offset + cmdList->VtxBuffer.size() * sizeof(ImDrawVert)) {
previousVtxData.resize(offset + cmdList->VtxBuffer.size() * sizeof(ImDrawVert));
}
std::memcpy(previousVtxData.data() + offset, cmdList->VtxBuffer.Data, cmdList->VtxBuffer.size() * sizeof(ImDrawVert));
offset += cmdList->VtxBuffer.size() * sizeof(ImDrawVert);
}
}
shouldRender = drawDataHash != previousDrawDataHash;
previousDrawDataHash = drawDataHash;
previousVtxDataSize = vtxDataSize;
}
if (shouldRender) {