Empty command list when imgui.ini present

[lwjglgamedev]

Hi,

I'm facing a strange issue with this library. I'm doing some tests, and it seems that once the imgui.ini file is created, the commands list is always 0 and the buffers are not populated. I've tried to create a simple sample to show this. The folloing code just initializes Imgui, creates the demo window, renders it and then tries to get the commands list.

package org.vulkanb;

import imgui.*;
import imgui.type.ImInt;

public class TestImGui {
    public static void main(String[] args) {
        try {
            ImGui.createContext();

            ImGuiIO imGuiIO = ImGui.getIO();
            imGuiIO.setDisplaySize(1280, 720);
            imGuiIO.setDisplayFramebufferScale(1.0f, 1.0f);

            ImInt outWidth = new ImInt();
            ImInt outHeight = new ImInt();
            imGuiIO.getFonts().getTexDataAsAlpha8(outWidth, outHeight);

            ImGui.newFrame();
            ImGui.showDemoWindow();
            ImGui.render();

            ImDrawData imDrawData = ImGui.getDrawData();

            System.out.println("Cmd Lists=" + imDrawData.getCmdListsCount());
            System.out.println("Total vertices count=" + imDrawData.getTotalVtxCount());
            System.out.println("Total indices count=" + imDrawData.getTotalIdxCount());
            System.out.println("Draw data valid=" + imDrawData.getValid());

            ImGui.destroyContext();
        } catch (Exception excp) {
            excp.printStackTrace();
        }
    }
}

The first time it ies ececuted, no imgui.ini file is present, I get the following result:

Cmd Lists=1
Total vertices count=814
Total indices count=1365
Draw data valid=true

However, if I execute the example again, the imgui.ini is present, I get the following output:

Cmd Lists=0
Total vertices count=0
Total indices count=0
Draw data valid=true

I'm using openjdk 15.0.2 2021-01-19 and version 1.81.2 of the imgui-java library.

Any idea of what I am missing? In addition to that, it seems to mee that the vertex coordinates have quite small values (the display size seems not to be applied). I don't know if this related to this issue or not.

Any guidance is very much appreciated.

[SpaiR]

Hi. Thanks for your detailed explanation and code example. I've didn't meet such problem. I never tried to experiment with things in such way though.

It seems you have the same issue described here: ocornut/imgui#1905
Specificaly, in another issue there is a comment: ocornut/imgui#1893 (comment)

I see. Dear ImGui can't give you guarantee that things will appear on the first frame unless you explicitly size them. If you want to hold on a pre-recorded command buffer (which seems a little odd) maybe you can call the imgui NewFrame/Render set twice before turning the ImDrawData structure into a command buffer?

Is it related?

[lwjglgamedev]

Thanks a lot!

Thanks to your comments, I've first being able to disable imgui.ini file generation (I don't want this), and the first problema solved. Woth the #1893 issue, I now set the size and the values of the vertex buffer start to make sense. Now I hope to start seeing something in Vulkan.

I will close the issue. Thanks again.