A high performance filtered and configurable spdlog sink for dear imgui - (TODO: Add filter double buffering and deuglify)

ImguiSpdLog.cc

// TODO: work on filters, they are really needed, did optimize the memory storage quite a bit tho
class ImGuiSpdLogAdaptor 
	: public spdlog::sinks::base_sink<std::mutex> {
	using sink_t = spdlog::sinks::base_sink<std::mutex>;

	class SinkLineContent {
	public:
		spdlog::level::level_enum LogLevel;   // If n_levels, the message pushed counts to the previous pushed line
		int32_t                   BeginIndex; // Base offset into the text buffer

		struct ColorDataRanges {
			uint32_t SubStringBegin : 12;
			uint32_t SubStringEnd   : 12;
			uint32_t FormatTag      : 8;
		};
		ImVector<ColorDataRanges> FormattedStringRanges;
	};

public:
	void DrawLogWindow(
		IN    GLFWwindow* ClipBoardOwner,
		INOUT bool&       ShowWindow
	) {
		TRACE_FUNCTION_PROTO;

		if (ImGui::Begin("Singularity Log", &ShowWindow)) {

			// Options submenu menu
			if (ImGui::BeginPopup("Options")) {

				ImGui::Checkbox("Auto-scroll", &EnableAutoScrolling);
				ImGui::EndPopup();
			}
			if (ImGui::Button("Options"))
				ImGui::OpenPopup("Options");
			ImGui::SameLine();
			if (ImGui::Button("Copy"))
				glfwSetClipboardString(ClipBoardOwner, LoggedContent.c_str());
			ImGui::SameLine();
			if (ImGui::Button("Clear"))
				ClearLogBuffers();
			ImGui::SameLine();
			ImGui::Text("%d messages logged, using %dmb memory",
				NumberOfLogEntries,
				(LoggedContent.size() + IndicesInBytes) / (1024 * 1024));

			// Filter out physical messgaes through logger
			static const char* LogLevels[] = SPDLOG_LEVEL_NAMES;
			static const auto LogSelectionWidth = []() -> float {
				TRACE_FUNCTION_PROTO;

				float LongestTextWidth = 0;
				for (auto LogLevelText : LogLevels) {

					auto TextWidth = ImGui::CalcTextSize(LogLevelText).x;
					if (TextWidth > LongestTextWidth)
						LongestTextWidth = TextWidth;
				}

				return LongestTextWidth +
					ImGui::GetStyle().FramePadding.x * 2 +
					ImGui::GetFrameHeight();
			}();
			auto ComboBoxRightAlignment = ImGui::GetWindowSize().x -
				(LogSelectionWidth + ImGui::GetStyle().WindowPadding.x);
			auto ActiveLogLevel = spdlog::get_level();
			ImGui::SetNextItemWidth(LogSelectionWidth);
			ImGui::SameLine(ComboBoxRightAlignment);
			ImGui::Combo("##ActiveLogLevel",
				reinterpret_cast<int32_t*>(&ActiveLogLevel),
				LogLevels,
				sizeof(LogLevels) / sizeof(LogLevels[0]));
			spdlog::set_level(ActiveLogLevel);

			// Filter out messages on display
			FilterTextMatch.Draw("##LogFilter",
				ImGui::GetWindowSize().x - (LogSelectionWidth + ImGui::GetStyle().WindowPadding.x * 2 +
					ImGui::GetStyle().FramePadding.x));
			ImGui::SetNextItemWidth(LogSelectionWidth);
			ImGui::SameLine(ComboBoxRightAlignment);
			ImGui::Combo("##FilterLogLevel",
				&FilterLogLevel,
				LogLevels,
				sizeof(LogLevels) / sizeof(LogLevels[0]));

			// Draw main log window
			ImGui::Separator();
			ImGui::BeginChild("LogTextView", ImVec2(0, 0), false,
				ImGuiWindowFlags_AlwaysVerticalScrollbar | ImGuiWindowFlags_AlwaysHorizontalScrollbar);
			ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(0, 0));
			const std::lock_guard LogLock(sink_t::mutex_);
			RebuildFilterWithPreviousStates();
			ImGuiListClipper ViewClipper;
			ViewClipper.Begin(FilteredView.size());
			while (ViewClipper.Step()) {

				int32_t StylesPushedToStack = 0;
				for (auto ClipperLineNumber = ViewClipper.DisplayStart;
					ClipperLineNumber < ViewClipper.DisplayEnd;
					++ClipperLineNumber) {

					auto& LogMetaDataEntry = LogMetaData[FilteredView[ClipperLineNumber]];
					if (LogMetaDataEntry.LogLevel == spdlog::level::n_levels)
						ImGui::Indent();

					for (auto i = 0; i < LogMetaDataEntry.FormattedStringRanges.size(); ++i) {

						switch (LogMetaDataEntry.FormattedStringRanges[i].FormatTag) {
						case FORMAT_RESET_COLORS:
							ImGui::PopStyleColor(StylesPushedToStack);
							StylesPushedToStack = 0;
							break;

						case COLOR_BLACK:
						case COLOR_RED:
						case COLOR_GREEN:
						case COLOR_YELLOW:
						case COLOR_BLUE:
						case COLOR_MAGENTA:
						case COLOR_CYAN:
						case COLOR_WHITE: {
							static const ImVec4 BasicColorsToVec[]{
								{ 0.0f, 0.0f, 0.0f, 1 }, // COLOR_BLACK
								{ 0.5f, 0.0f, 0.0f, 1 }, // COLOR_RED
								{ 0.0f, 0.7f, 0.0f, 1 }, // COLOR_GREEN
								{ 0.7f, 0.7f, 0.0f, 1 }, // COLOR_YELLOW
								{ 0.0f, 0.0f, 0.7f, 1 }, // COLOR_BLUE
								{ 0.7f, 0.0f, 0.7f, 1 }, // COLOR_MAGENTA
								{ 0.0f, 0.7f, 0.7f, 1 }, // COLOR_CYAN
								{ 0.7f, 0.7f, 0.7f, 1 }  // COLOR_WHITE
							};
							ImGui::PushStyleColor(ImGuiCol_Text,
								BasicColorsToVec[LogMetaDataEntry.FormattedStringRanges[i].FormatTag - COLOR_BLACK]);
							++StylesPushedToStack;
						} break;

						case COLOR_BRIGHTBLACK:
						case COLOR_BRIGHTRED:
						case COLOR_BRIGHTGREEN:
						case COLOR_BRIGHTYELLOW:
						case COLOR_BRIGHTBLUE:
						case COLOR_BRIGHTMAGENTA:
						case COLOR_BRIGHTCYAN:
						case COLOR_BRIGHTWHITE: {
							static const ImVec4 BrightColorsToVec[]{
								{ 0, 0, 0, 1 }, // COLOR_BRIGHTBLACK
								{ 1, 0, 0, 1 }, // COLOR_BRIGHTRED
								{ 0, 1, 0, 1 }, // COLOR_BRIGHTGREEN
								{ 1, 1, 0, 1 }, // COLOR_BRIGHTYELLOW
								{ 0, 0, 1, 1 }, // COLOR_BRIGHTBLUE
								{ 1, 0, 1, 1 }, // COLOR_BRIGHTMAGENTA
								{ 0, 1, 1, 1 }, // COLOR_BRIGHTCYAN
								{ 1, 1, 1, 1 }  // COLOR_BRIGHTWHITE
							};
							ImGui::PushStyleColor(ImGuiCol_Text,
								BrightColorsToVec[LogMetaDataEntry.FormattedStringRanges[i].FormatTag - COLOR_BRIGHTBLACK]);
							++StylesPushedToStack;
						}}

						auto FormatRangeBegin = LoggedContent.begin() +
							LogMetaDataEntry.BeginIndex +
						LogMetaDataEntry.FormattedStringRanges[i].SubStringBegin;
						auto FormatRangeEnd = LoggedContent.begin() +
							LogMetaDataEntry.BeginIndex +
							LogMetaDataEntry.FormattedStringRanges[i].SubStringEnd;
						ImGui::TextUnformatted(FormatRangeBegin, FormatRangeEnd);
						if (LogMetaDataEntry.FormattedStringRanges.size() - (i + 1))
							ImGui::SameLine();
					}

					if (LogMetaDataEntry.LogLevel == spdlog::level::n_levels)
						ImGui::Unindent();
				}
				ImGui::PopStyleColor(StylesPushedToStack);
			}
			ViewClipper.End();
			ImGui::PopStyleVar();

			if (EnableAutoScrolling &&
				ImGui::GetScrollY() >= ImGui::GetScrollMaxY())
				ImGui::SetScrollHereY(1.0f);

			ImGui::EndChild();
		}

		ImGui::End();
	}

	void ClearLogBuffers(
		IN bool DisableLock = false
	) {
		TRACE_FUNCTION_PROTO;

		if (!DisableLock)
			sink_t::mutex_.lock();

		LoggedContent.clear();
		LogMetaData.clear();
		NumberOfLogEntries = 0;
		IndicesInBytes = 0;
		
		if (!DisableLock)
			sink_t::mutex_.unlock();
	}

protected:

	// Writing version 2, this will accept ansi escape sequences for colors
	void sink_it_(
		IN const spdlog::details::log_msg& LogMessage
	) noexcept {
		// This is all protected by the base sink under a mutex
		TRACE_FUNCTION_PROTO;
		++NumberOfLogEntries;

		// Format the logged message and push it into the text buffer
		spdlog::memory_buf_t FormattedBuffer;
		sink_t::formatter_->format(
			LogMessage, FormattedBuffer);
		std::string FormattedText = fmt::to_string(FormattedBuffer);
		
		// Process string by converting the color range passed to an escape sequence first,
		// yes may not be the nicest way of doing this but its way easier to process later.
		const char* ColorToEscapeSequence[]{
			ESC_BRIGHTMAGENTA,
			ESC_CYAN,
			ESC_BRIGHTGREEN,
			ESC_BRIGHTYELLOW,
			ESC_BRIGHTRED,
			ESC_RED
		};
		FormattedText.insert(LogMessage.color_range_start,
			ColorToEscapeSequence[LogMessage.level]);
		FormattedText.insert(LogMessage.color_range_end + 5,
			"\x1b[0m");
		bool FilterPassing = LogMessage.level >= FilterLogLevel;
		FilterPassing &= FilterTextMatch.PassFilter(FormattedText.c_str(),
			FormattedText.c_str() + FormattedText.size());

		// Parse formatted logged string for ansi escape sequences
		auto OldTextBufferSize = LoggedContent.size();
		SinkLineContent MessageData2 {
			LogMessage.level,
			OldTextBufferSize
		};
		AnsiEscapeSequenceTag LastSequenceTagSinceBegin = FORMAT_RESET_COLORS;
		
		// Prematurely filter out immediately starting non default formats,
		// and then enter the main processing loop
		switch (FormattedText[0]) {
		case '\x1b':
		case '\n':
			break;
		default: {

			SinkLineContent::ColorDataRanges FormatPush{
				0, 0, LastSequenceTagSinceBegin
			};
			MessageData2.FormattedStringRanges.push_back(FormatPush);
		}}
		for (auto i = 0; i < FormattedText.size(); ++i)
			switch (FormattedText[i]) {
			case '\n': {

				// Handle new line bullshit, spdlog will terminate any logged message witha  new line
				// we can also assume this may not be the last line, so we continue the previous sequence into
				// the next logically text line if necessary and reconfigure pushstate
				if (MessageData2.FormattedStringRanges.size())
					MessageData2.FormattedStringRanges.back().SubStringEnd = i;
				if (FilterPassing)
					FilteredView.push_back(LogMetaData.size());
				LogMetaData.push_back(MessageData2);

				IndicesInBytes += MessageData2.FormattedStringRanges.size() *
					sizeof(SinkLineContent::ColorDataRanges) +
					sizeof(SinkLineContent);
				MessageData2.LogLevel = spdlog::level::n_levels;
				MessageData2.BeginIndex = OldTextBufferSize + i + 1;
				MessageData2.FormattedStringRanges.clear();

				// Continue previous escape sequences pushed in the previous line
				SinkLineContent::ColorDataRanges FormatPush{
					i + 1, 0, LastSequenceTagSinceBegin
				};
				MessageData2.FormattedStringRanges.push_back(FormatPush);
			} break;
			case '\x1b': {

				// Handle ansi escape sequence, convert textual to operand
				if (FormattedText[i + 1] != '[')
					throw std::runtime_error("Invalid ansi escape sequence passed");

				size_t PositionProcessed = 0;
				auto EscapeSequenceCode = static_cast<AnsiEscapeSequenceTag>(
					std::stoi(&FormattedText[i + 2],
						&PositionProcessed)); // this may throw, in which case we let it pass down

				if (FormattedText[i + 2 + PositionProcessed] != 'm')
					throw std::runtime_error("Invalid ansi escape sequence operand was passed");
				++PositionProcessed;
				LastSequenceTagSinceBegin = EscapeSequenceCode;

				SinkLineContent::ColorDataRanges FormatPush{
					i, 0, EscapeSequenceCode
				};
				if (MessageData2.FormattedStringRanges.size())
					MessageData2.FormattedStringRanges.back().SubStringEnd = FormatPush.SubStringBegin;
				MessageData2.FormattedStringRanges.push_back(FormatPush);

				// Now the escape code has to be removed from the string,
				// the iterator has to be kept stable, otherwise the next round could skip a char
				FormattedText.erase(FormattedText.begin() + i--,
					FormattedText.begin() + (i + 2 + PositionProcessed));
			}}

		// Append processed string to log text buffer
		LoggedContent.append(FormattedText.c_str(),
			FormattedText.c_str() + FormattedText.size());
	}
	void flush_() { TRACE_FUNCTION_PROTO; }

private:

	// TODO: Need to implement double buffering for the filter
	void RebuildFilterWithPreviousStates() {
		TRACE_FUNCTION_PROTO;

		int32_t RebuildType = PreviousFilterLevel != FilterLogLevel;
		RebuildType |= memcmp(PreviousFilterText,
			FilterTextMatch.InputBuf,
			sizeof(PreviousFilterText));

		if (RebuildType) {

			// Filter was completely changed, have to rebuild array (very expensive,
			//	this may result in short freezes or stuttering on really large logs,
			//	one way to solve this could be to defer the calculation of the filter view
			//	to a thread pool and use a double buffering mechanism)

			auto NewLinePasses = false;
			FilteredView.clear();
			for (auto i = 0; i < LogMetaData.size(); ++i) {

				if (LogMetaData[i].LogLevel == spdlog::level::n_levels) {

					if (NewLinePasses)
						FilteredView.push_back(i);
					continue;
				}

				if (LogMetaData[i].LogLevel < FilterLogLevel) {
					NewLinePasses = false; continue;
				}

				auto LineBegin = LoggedContent.begin() +
					LogMetaData[i].BeginIndex +
					LogMetaData[i].FormattedStringRanges.front().SubStringBegin;
				auto LineEnd = LoggedContent.begin() +
					LogMetaData[i].BeginIndex +
					LogMetaData[i].FormattedStringRanges.back().SubStringEnd;
				if (!FilterTextMatch.PassFilter(LineBegin, LineEnd)) {
					NewLinePasses = false; continue;
				}

				NewLinePasses = true;
				FilteredView.push_back(i);
			}
		}
		
		PreviousFilterLevel = FilterLogLevel;
		memcpy(PreviousFilterText,
			FilterTextMatch.InputBuf,
			sizeof(PreviousFilterText));
	}

	// Using faster more efficient replacements of stl types for rendering
	ImGuiTextBuffer            LoggedContent;
	std::vector<SinkLineContent> LogMetaData; // Cannot use ImVetctor here as the type is not trivially copyable 
											  // the type has to be moved into, slightly more expensive
											  // but overall totally fine, at least no weird hacks
	ImGuiTextFilter   FilterTextMatch;
	ImVector<int32_t> FilteredView;           // A filtered array of indexes into the LogMetaData vector
											  // this view is calculated once any filter changes
	int32_t  FilterLogLevel = spdlog::level::trace;
	uint32_t NumberOfLogEntries = 0;          // Counts the number of entries logged
	uint32_t IndicesInBytes = 0;              // Keeps track of the amount of memory allocated by indices
	bool     EnableAutoScrolling = true;

	// Previous Frame's filterdata, if any of these change to the new values the filter has to be recalculated
	int32_t PreviousFilterLevel = spdlog::level::trace;
	decltype(ImGuiTextFilter::InputBuf)
		PreviousFilterText{};
};

Hey, I'm currently playing with spdlog and how to integrate it into my imgui based app. What license do you consider your code to be?

@irieger
i consider the code to be MIT

as for how to call it, you need a instance of the class and will need to call it in your main loop (DrawLogWindow), sink_it_ will have to be added to your spdlog pipeline
as this was ripped from another project of mine you will need to figure out a solution for GLFW yourself if you dont use that, note that the code isnt optimal

@Lima-X Thank you. I had a quick look and then decided to implement a reduced version of your idea from scratch only taking a few basic ideas over, as getting everything ready would likely have been more work than I needed now. But it was a nice inspiration.