Subplots Limits

[marhninemohammed]

Hi there!

When I add new Plot to BeginSubPlots programmatically, the Limits reset at initial state, while I want let the limits be where it is when I add new plot.

How to make BeginSubPlots not reset Limits, but still where it is?

[brenocq]

Hi @marhninemohammed! Interesting issue number. Let me make sure I understand the issue correctly. When you call BeginSubplots and add a new plot to the grid (e.g., going from 2x2 to 2x3), the axis limits of the existing plots reset to their initial values, losing any zoom/pan state. You want the existing plots to keep their current limits when the subplot layout changes. Is that correct?

[marhninemohammed]

Hello @brenocq.

Thank you for your reply. Actually, I partially solved the problem in the code by saving the current state of the x-axis (which represents the time axis), then I add a new plot, and then restoring the state to the correct position.

I will share the code when I am back at my desk.

[brenocq]

I tried to create a demo to reproduce the error that you found, but looks like the subplot axis range state is being restored correctly when adding/removing plots.

void Demo_DynamicSubplots() {
    ImGui::BulletText("Add plots dynamically and observe that existing plot limits reset.");
    ImGui::BulletText("Zoom/pan the plots, then click 'Add Plot' to see the issue.");

    static int num_plots = 2;
    static float data1[100], data2[100], data3[100], data4[100];
    static bool initialized = false;

    if (!initialized) {
        for (int i = 0; i < 100; ++i) {
            data1[i] = sinf(i * 0.1f);
            data2[i] = cosf(i * 0.1f);
            data3[i] = sinf(i * 0.1f) * cosf(i * 0.05f);
            data4[i] = cosf(i * 0.1f) * sinf(i * 0.05f);
        }
        initialized = true;
    }

    if (ImGui::Button("Add Plot") && num_plots < 4) {
        num_plots++;
    }
    ImGui::SameLine();
    if (ImGui::Button("Remove Plot") && num_plots > 1) {
        num_plots--;
    }
    ImGui::SameLine();
    ImGui::Text("Number of plots: %d", num_plots);

    // BeginSubplots with dynamic row count
    if (ImPlot::BeginSubplots("##DynamicSubplots", num_plots, 1, ImVec2(-1, 400))) {

        if (ImPlot::BeginPlot("Plot 1")) {
            ImPlot::SetupAxes("X", "Y");
            ImPlot::PlotLine("Sine", data1, 100);
            ImPlot::EndPlot();
        }

        if (num_plots >= 2) {
            if (ImPlot::BeginPlot("Plot 2")) {
                ImPlot::SetupAxes("X", "Y");
                ImPlot::PlotLine("Cosine", data2, 100);
                ImPlot::EndPlot();
            }
        }

        if (num_plots >= 3) {
            if (ImPlot::BeginPlot("Plot 3")) {
                ImPlot::SetupAxes("X", "Y");
                ImPlot::PlotLine("Mixed 1", data3, 100);
                ImPlot::EndPlot();
            }
        }

        if (num_plots >= 4) {
            if (ImPlot::BeginPlot("Plot 4")) {
                ImPlot::SetupAxes("X", "Y");
                ImPlot::PlotLine("Mixed 2", data4, 100);
                ImPlot::EndPlot();
            }
        }

        ImPlot::EndSubplots();
    }
}

Can you provide a minimal reproducible example?