Using vector with Dear Imgui

[DaBigBoy01]

Hi folks,

I've dabbled with programming for so many years but have never built a complete project before. I started working on my own midi controller for my music. It's going pretty well so far, but I'm stumped right now.

I have buttons that will send my midi data out(I do not have any midi code yet). They are stored in std::vector. No problems adding these to the vector. The issue is searching for these buttons. Basically when I click on a button inside my canvas, it will find the item and tell the code what the last selected button is and send it to my Inspector Panel. I've been using an iterator to find the element in the vector based on the Button last selected's name. The iterator index is always out of range. My program has no problems counting the number of elements or adding elements to the vector, it just cannot find the Button element I'm looking for.

Plain C++ has no problems finding elements so I bet I have a misunderstanding of Dear Imgui. I've been going at this issue for a week now and have researched quite a bit on using std::find_if without any luck. I hope I added my code correctly.

Thanks!

Global Declarations:

vector<Button> button_macros;

Button* last_selected;

Button* button_01 = new Button();
Button* button_02 = new Button();`

class Object
{
public:
	Object();
	~Object();

	void SetIDName(std::string id_name);
	void SetLabelName(std::string label_name);
	void SetPitch(int value)
	{
		this->pitch = value;
	}
	void SetEditorValue(int editor_value)
	{
		this->editor_id_value = editor_value;
	}

	const char * GetName() {
		return label_name.c_str();
	}

	int GetEditorIDValue()
	{
		return this->editor_id_value;
	}
	//Midi info

	
	
protected:
	std::string id_name;
	std::string label_name; //Name in GUI

	int editor_id_value;

	int pitch;

};

Button.h

int x, y;
int Width;
int Height;

int channel_message;
int control_change;

void SetMidiValues(int channel_message, int control_change);
void SetPositionInGrid(int x, int y);
void SetSize(int Width, int Height);


std::string get_idName()
{
	return this->id_name;
}

friend bool operator==(Button& obj, Button& robj)
{
	return obj.id_name == robj.id_name;
}

Inspector Window:

 ImGui::Begin("Inspector Window");
 ImDrawList* draw = ImGui::GetWindowDrawList();

 ImVec2 p = ImGui::GetCursorScreenPos();

 std::vector<Button>::iterator& button_finder = button_macros.end();
 if (last_selected != nullptr)
 {
     button_finder = std::find_if(button_macros.begin(), button_macros.end() - 1, [&](Button& button) {return button.get_idName() == last_selected->get_idName(); });
 }
 else
 {
     spdlog::error("Could not find control in list! Index out of range!");

 }

 if (button_finder != button_macros.end())
 {
     int index = std::distance(button_macros.begin(), button_finder);
     int buf1 = button_macros.at(index).x, buf2 = button_macros.at(index).y;
     int buf3 = 0, buf4 = 0;
     int input_cm = 0, input_cc = 0;
     static int last_cm = button_macros.at(index).channel_message, last_cc = button_macros.at(index).control_change;

     if (ImGui::CollapsingHeader("Control Info"))
     {
             ImGui::Text("Name: %s", button_macros.at(index).get_idName().c_str());
             ImGui::SameLine();
             ImGui::Text("Label: %s", button_macros.at(index).GetName());
             ImGui::Spacing();
             static char input_name[255] = {};
             ImGui::InputText("Name: ", &input_name[0], IM_ARRAYSIZE(input_name));

             static char input_id_name[255] = {};
             ImGui::InputText("Label: ", &input_id_name[0], IM_ARRAYSIZE(input_id_name));

             ImGui::PushItemWidth(100);
             ImGui::Text("Channel: %d Control Change: %d", button_macros.at(index).channel_message, button_macros.at(index).control_change);
             ImGui::InputInt("Channel: ", &input_cm);
             ImGui::SameLine();
             ImGui::PushItemWidth(100);
             ImGui::InputInt("CC: ", &input_cc);

             ImGui::SameLine();

             if (ImGui::Button("New CC"))
             {
                 //TODO: Assign next available control change value
             }

             ImGui::Spacing();
             ImGui::Text("Position X: %d Position Y: %d", button_macros.at(index).x, button_macros.at(index).y);
             ImGui::PushItemWidth(100);
             ImGui::InputInt("Input X: ", &buf1);
             ImGui::SameLine();
             ImGui::PushItemWidth(100);
             ImGui::InputInt("Input Y: ", &buf2);

             ImGui::Spacing();
             ImGui::Text("Width: %d Height: %d", button_macros.at(index).Width, button_macros.at(index).Height);
             ImGui::PushItemWidth(100);
             ImGui::InputInt("Width: ", &buf3);
             ImGui::SameLine();
             ImGui::PushItemWidth(100);
             ImGui::InputInt("Height: ", &buf4);


         if (ImGui::Button("Save Changes"))
         {
             if (button_finder != button_macros.end())
             {
                 button_macros.at(index).channel_message = input_cm;
                 button_macros.at(index).control_change = input_cc;

                 for (size_t i = 0; i < button_macros.size(); i++)
                 {
                     spdlog::info("Button 1 Name: {} Channel: {} CC: {}", button_macros.at(index).GetName(), button_macros.at(index).channel_message, button_macros.at(index).control_change);

                 }
             }

             else
             {
                 spdlog::error("Could not find control in list! Index out of range!");
             }




         }
        
     }
     else
     {
         //spdlog::error("Could not find control in list! Index out of range!");
     }
 }

Control List Panel:

void Controls_List_Panel()
{
    ImGui::Begin("Controls List");

    static int item_selected_idx = 0;

    static bool item_highlight = false;
    int item_highlighted_idx = -1;

    if(ImGui::BeginListBox(" "))
    {
        for (int n = 0; n < button_macros.size(); n++)
        {
            ImGui::PushID(n);
            const bool is_selected = (item_selected_idx == n);
            if (ImGui::Selectable(button_macros[n].GetName(), is_selected))
                item_selected_idx = n;

            if (item_highlight && ImGui::IsItemHovered())
                item_highlighted_idx = n;

            if (is_selected)
            {
                ImGui::SetItemDefaultFocus();
                last_selected = &button_macros[n];
            }

            ImGui::PopID();
        }
        ImGui::EndListBox();
    }

    ImGui::End();
}

[DaBigBoy01]

I do believe I know the basics of Dear ImGui though.

I need the last selected button to be known every frame, because another frame, it could be another button or control, but the iterator never seems to figure out where the last selected button is in the vector, even if I assign it by reference.

I forgot to share how I call the panels in order. I call the Canvas first, then the Controls List Panel, then the inspector window panel.

[DaBigBoy01]

Okay, so on debugging, I figured out, the iterator knows where the index is based on the last selected button, so when I go to actually
change the values of the selected button:
button_macros.at(index).channel_message = input_cm; button_macros.at(index).control_change = input_cc;

It does access the correct index, but for some reason the inputs in my program editor just don't save.

[DaBigBoy01]

I fixed it, although it doesn't make much sense to me.

Instead of initializing the iterator to std::find_if, I needed to initialize it to std::button_macros.begin(), then I assign the iterator to std::find_if later. I don't quite understand because the iterator should have been initializing correctly, since there is a last selected button. I am doing this now:

auto button_finder = button_macros.begin();

if (last_selected == nullptr)
{
    spdlog::info("Nothing Selected...");
}
else
{
    button_finder = std::find_if(button_macros.begin(), button_macros.end(), [&](Button& button) {return button.get_idName() == last_selected->get_idName(); });
}

I also needed to make my input_cc and input_cm static for my inputs to save.

The only issue that I'm have now is that my inputs aren't exactly saving. They "save", but the values reset soon after choose another object.

[ocornut]

I have fixed the formatting in your posts to make them less discouraging to read (the code seems abnormally complex), but TL;DR nothing in your problem has anything to do with Dear ImGui, this is a general C++ question.

[DaBigBoy01]

Thanks - I had a tough time with it.

So my code actually works fine- The iterator works properly, the problem is where I go to calculate the distance.

auto button_finder = std::find_if(button_macros.begin(), button_macros.end(), [&](Button& button) {return button.get_idName() == last_selected->get_idName(); });

int index = std::distance(button_macros.begin(), button_finder);

button_finder works, it's just the index is always zero, making my inputs not saving and incorrect readouts.

[PathogenDavid]

Thanks - I had a tough time with it.

For future reference.

button_finder works, it's just the index is always zero, making my inputs not saving and incorrect readouts.

As Omar said this feels like a C++ usage issue rather than a Dear ImGui one, and your code is quite long and contains a lot of irrelevant cruft.

It'd be helpful if you reduced it to a minimal snippet that reproduces your problem, chances are you'd find the issue while reducing things down.