satdump/src-core/common/widgets/fft_plot.cpp

#include "fft_plot.h"
#include "imgui/imgui_internal.h"
#include <string>

namespace widgets
{
    FFTPlot::FFTPlot(float *v, int size, float min, float max, float scale_res)
    {
        values = v;
        values_size = size;
        scale_min = min;
        scale_max = max;
        scale_resolution = scale_res;
    }

    void FFTPlot::draw(ImVec2 size)
    {
        ImGuiWindow *window = ImGui::GetCurrentWindow();
        ImGuiContext &g = *GImGui;
        const ImGuiStyle &style = g.Style;
        const ImRect frame_bb(window->DC.CursorPos, {window->DC.CursorPos.x + size.x, window->DC.CursorPos.y + size.y});
        const ImRect inner_bb({frame_bb.Min.x + style.FramePadding.x, frame_bb.Min.y + style.FramePadding.y},
                              {frame_bb.Max.x - style.FramePadding.x, frame_bb.Max.y - style.FramePadding.y});

        int res_w = /*ImMin((int)size.x,*/ values_size /*)*/ - 1;
        int item_count = values_size - 1;
        const float t_step = 1.0f / (float)res_w;
        const float inv_scale = (scale_min == scale_max) ? 0.0f : (1.0f / (scale_max - scale_min));
        float v0 = values[0];
        float t0 = 0.0f;
        ImVec2 tp0 = ImVec2(t0, 1.0f - ImSaturate((v0 - scale_min) * inv_scale));
        const ImU32 col_base = ImGui::GetColorU32(ImGuiCol_PlotLines);

        // Background
        ImGui::RenderFrame(frame_bb.Min, frame_bb.Max, ImGui::GetColorU32(ImGuiCol_FrameBg), true, style.FrameRounding);

        // Draw lines
        float vscale = ((scale_max - scale_min) / scale_resolution);
        float step = (frame_bb.Max.y - frame_bb.Min.y) / scale_resolution;
        float value = scale_min;
        const ImU32 color_scale = ImGui::GetColorU32(ImGuiCol_Text, 0.4);
        for (float i = frame_bb.Max.y - step; i >= frame_bb.Min.y; i -= step)
        {
            ImVec2 pos0 = {frame_bb.Min.x, i};
            ImVec2 pos1 = {frame_bb.Max.x, i};
            window->DrawList->AddLine(pos0, pos1, color_scale);
            value += vscale;
            window->DrawList->AddText({pos0.x, pos0.y + 2}, color_scale, std::string(std::to_string(int(value)) + " dB").c_str());
        }

        // Draw lines
        for (int n = 0; n < res_w; n++)
        {
            const float t1 = t0 + t_step;
            const int v1_idx = (int)(t0 * item_count + 0.5f);
            const float v1 = values[v1_idx];
            const ImVec2 tp1 = ImVec2(t1, 1.0f - ImSaturate((v1 - scale_min) * inv_scale));

            ImVec2 pos0 = ImLerp(inner_bb.Min, inner_bb.Max, tp0);
            ImVec2 pos1 = ImLerp(inner_bb.Min, inner_bb.Max, tp1);

            window->DrawList->AddLine(pos0, pos1, col_base);

            t0 = t1;
            tp0 = tp1;
        }

        ImGui::Dummy(size);
    }
}