plot_var_example

Helper to store values so they can be plotted over time.

Usage

// Call once a frame with current value
ImGui::PlotVar("Speed", current_speed);

.h

// Plot value over time
// Pass FLT_MAX value to draw without adding a new value
void	PlotVar(const char* label, float value, float scale_min = FLT_MAX, float scale_max = FLT_MAX, size_t buffer_size = 120);

// Call this periodically to discard old/unused data
void	PlotVarFlushOldEntries();

.cpp

#include <map>
struct PlotVarData
{
	ImGuiID        ID;
	Vector<float>  Data;
	int            DataInsertIdx;
	int            LastFrame;

	PlotVarData() : ID(0), DataInsertIdx(0), LastFrame(-1) {}
};

typedef std::map<ImGuiID, PlotVarData> PlotVarsMap;
static PlotVarsMap	g_PlotVarsMap;

// Plot value over time
// Call with 'value == FLT_MAX' to draw without adding new value to the buffer
void ImGui::PlotVar(const char* label, float value, float scale_min, float scale_max, size_t buffer_size)
{
	ASSERT(label);
	if (buffer_size == 0)
		buffer_size = 120;

	ImGui::PushID(label);
	ImGuiID id = ImGui::GetID("");

	// Lookup O(log N)
	PlotVarData& pvd = g_PlotVarsMap[id];

	// Setup
	if (pvd.Data.capacity() != buffer_size)
	{
		pvd.Data.resize(buffer_size);
		memset(&pvd.Data[0], 0, sizeof(float) * buffer_size);
		pvd.DataInsertIdx = 0;
		pvd.LastFrame = -1;
	}

	// Insert (avoid unnecessary modulo operator)
	if (pvd.DataInsertIdx == buffer_size)
		pvd.DataInsertIdx = 0;
	int display_idx = pvd.DataInsertIdx;
	if (value != FLT_MAX)
		pvd.Data[pvd.DataInsertIdx++] = value;

	// Draw
	int current_frame = ImGui::GetFrameCount();
	if (pvd.LastFrame != current_frame)
	{
		ImGui::PlotLines("##plot", &pvd.Data[0], buffer_size, pvd.DataInsertIdx, NULL, scale_min, scale_max, ImVec2(0, 40));
		ImGui::SameLine();
		ImGui::Text("%s\n%-3.4f", label, pvd.Data[display_idx]);	// Display last value in buffer
		pvd.LastFrame = current_frame;
	}
	
	ImGui::PopID();
}

void ImGui::PlotVarFlushOldEntries()
{
	int current_frame = ImGui::GetFrameCount();
	for (PlotVarsMap::iterator it = g_PlotVarsMap.begin(); it != g_PlotVarsMap.end(); )
	{
		PlotVarData& pvd = it->second;
		if (pvd.LastFrame < current_frame - MAX(400,(int)pvd.Data.size()))
			it = g_PlotVarsMap.erase(it);
		else
			++it;
	}
}