A ImGui::TabLabels(...) that supports line wrapping, tab reordering through drag'n'drop and tab closing through MMB press.

imguitablabel.h

#pragma once
#include <imgui.h>

// USAGE EXAMPLE
/*
ImGui::Text("Tabs (based on the code by krys-spectralpixel):");
static const char* tabNames[] = {"Render","Layers","Scene","World","Object","Constraints","Modifiers","Data","Material","Texture","Particle","Physics"};
static const int numTabs = sizeof(tabNames)/sizeof(tabNames[0]);
static const char* tabTooltips[numTabs] = {"Render Tab Tooltip","","","","Object Type Tooltip","","","","","Tired to add tooltips...",""};
static int tabItemOrdering[numTabs] = {0,1,2,3,4,5,6,7,8,9,10,11};
static int selectedTab = 0;
static int optionalHoveredTab = 0;
/*const bool tabSelectedChanged =*/ ImGui::TabLabels(numTabs,tabNames,selectedTab,tabTooltips,true,&optionalHoveredTab,&tabItemOrdering[0],true,true);
ImGui::Text("\nTab Page For Tab: \"%s\" here.\n",tabNames[selectedTab]);
if (optionalHoveredTab>=0) ImGui::Text("Mouse is hovering Tab Label: \"%s\".\n\n",tabNames[optionalHoveredTab]);
*/


namespace ImGui {

// Based on the code by krys-spectralpixel (https://github.com/krys-spectralpixel), posted here: https://github.com/ocornut/imgui/issues/261
/* pOptionalHoveredIndex: a ptr to an optional int that is set to -1 if no tab label is hovered by the mouse.
 * pOptionalItemOrdering: an optional static array of unique integers from 0 to numTabs-1 that maps the tab label order. If one of the numbers is replaced by -1 the tab label is not visible (closed). It can be read/modified at runtime.
 * allowTabReorder (requires pOptionalItemOrdering): allows tab reordering through drag and drop (it modifies pOptionalItemOrdering).
 * allowTabClosingThroughMMB (requires pOptionalItemOrdering): closes the tabs when MMB is clicked on them, by setting the tab value in pOptionalItemOrdering to -1.
 * pOptionalClosedTabIndex (requires allowTabClosingThroughMMB): out variable (int pointer) that returns the index of the closed tab in last call or -1.
 * pOptionalClosedTabIndexInsideItemOrdering: same as above, but index of the pOptionalItemOrdering array.
*/
IMGUI_API bool TabLabels(int numTabs, const char** tabLabels, int& selectedIndex, const char** tabLabelTooltips=NULL, bool wrapMode=true, int *pOptionalHoveredIndex=NULL, int* pOptionalItemOrdering=NULL, bool allowTabReorder=true, bool allowTabClosingThroughMMB=true, int *pOptionalClosedTabIndex=NULL, int *pOptionalClosedTabIndexInsideItemOrdering=NULL) {
    ImGuiStyle& style = ImGui::GetStyle();

    const ImVec2 itemSpacing =  style.ItemSpacing;
    const ImVec4 color =        style.Colors[ImGuiCol_Button];
    const ImVec4 colorActive =  style.Colors[ImGuiCol_ButtonActive];
    const ImVec4 colorHover =   style.Colors[ImGuiCol_ButtonHovered];
    const ImVec4 colorText =   style.Colors[ImGuiCol_Text];
    style.ItemSpacing.x =       1;
    style.ItemSpacing.y =       1;
    const ImVec4 colorSelectedTab(color.x,color.y,color.z,color.w*0.5f);
    const ImVec4 colorSelectedTabHovered(colorHover.x,colorHover.y,colorHover.z,colorHover.w*0.5f);
    const ImVec4 colorSelectedTabText(colorText.x*0.8f,colorText.y*0.8f,colorText.z*0.6f,colorText.w*0.8f);
    //ImGui::ClampColor(colorSelectedTabText);

    if (numTabs>0 && (selectedIndex<0 || selectedIndex>=numTabs)) {
        if (!pOptionalItemOrdering)  selectedIndex = 0;
        else selectedIndex = -1;
    }
    if (pOptionalHoveredIndex) *pOptionalHoveredIndex = -1;
    if (pOptionalClosedTabIndex) *pOptionalClosedTabIndex = -1;
    if (pOptionalClosedTabIndexInsideItemOrdering) *pOptionalClosedTabIndexInsideItemOrdering = -1;

    float windowWidth = 0.f,sumX=0.f;
    if (wrapMode) windowWidth = ImGui::GetWindowWidth() - style.WindowPadding.x - (ImGui::GetScrollMaxY()>0 ? style.ScrollbarSize : 0.f);

    static int draggingTabIndex = -1;int draggingTabTargetIndex = -1;   // These are indices inside pOptionalItemOrdering
    static ImVec2 draggingTabSize(0,0);
    static ImVec2 draggingTabOffset(0,0);

    const bool isMMBreleased = ImGui::IsMouseReleased(2);
    const bool isMouseDragging = ImGui::IsMouseDragging(0,2.f);
    int justClosedTabIndex = -1,newSelectedIndex = selectedIndex;


    bool selection_changed = false;bool noButtonDrawn = true;
    for (int j = 0,i; j < numTabs; j++)
    {
        i = pOptionalItemOrdering ? pOptionalItemOrdering[j] : j;
        if (i==-1) continue;

        if (!wrapMode) {if (!noButtonDrawn) ImGui::SameLine();}
        else if (sumX > 0.f) {
            sumX+=style.ItemSpacing.x;   // Maybe we can skip it if we use SameLine(0,0) below
            sumX+=ImGui::CalcTextSize(tabLabels[i]).x+2.f*style.FramePadding.x;
            if (sumX>windowWidth) sumX = 0.f;
            else ImGui::SameLine();
        }

        if (i == selectedIndex) {
            // Push the style
            style.Colors[ImGuiCol_Button] =         colorSelectedTab;
            style.Colors[ImGuiCol_ButtonActive] =   colorSelectedTab;
            style.Colors[ImGuiCol_ButtonHovered] =  colorSelectedTabHovered;
            style.Colors[ImGuiCol_Text] =           colorSelectedTabText;
        }
        // Draw the button
        ImGui::PushID(i);   // otherwise two tabs with the same name would clash.
        if (ImGui::Button(tabLabels[i]))   {selection_changed = (selectedIndex!=i);newSelectedIndex = i;}
        ImGui::PopID();
        if (i == selectedIndex) {
            // Reset the style
            style.Colors[ImGuiCol_Button] =         color;
            style.Colors[ImGuiCol_ButtonActive] =   colorActive;
            style.Colors[ImGuiCol_ButtonHovered] =  colorHover;
            style.Colors[ImGuiCol_Text] =           colorText;
        }
        noButtonDrawn = false;

        if (wrapMode) {
            if (sumX==0.f) sumX = style.WindowPadding.x + ImGui::GetItemRectSize().x; // First element of a line
        }
        else if (isMouseDragging && allowTabReorder && pOptionalItemOrdering) {
            // We still need sumX
            if (sumX==0.f) sumX = style.WindowPadding.x + ImGui::GetItemRectSize().x; // First element of a line
            else sumX+=style.ItemSpacing.x + ImGui::GetItemRectSize().x;

        }

        if (ImGui::IsItemHoveredRect()) {
            if (pOptionalHoveredIndex) *pOptionalHoveredIndex = i;
            if (tabLabelTooltips && tabLabelTooltips[i] && strlen(tabLabelTooltips[i])>0)  ImGui::SetTooltip("%s",tabLabelTooltips[i]);

            if (pOptionalItemOrdering)  {
                if (allowTabReorder)  {
                    if (isMouseDragging) {
                        if (draggingTabIndex==-1) {
                            draggingTabIndex = j;
                            draggingTabSize = ImGui::GetItemRectSize();
                            const ImVec2& mp = ImGui::GetIO().MousePos;
                            const ImVec2 draggingTabCursorPos = ImGui::GetCursorPos();
                            draggingTabOffset=ImVec2(
                                        mp.x+draggingTabSize.x*0.5f-sumX+ImGui::GetScrollX(),
                                        mp.y+draggingTabSize.y*0.5f-draggingTabCursorPos.y+ImGui::GetScrollY()
                                        );

                        }
                    }
                    else if (draggingTabIndex>=0 && draggingTabIndex<numTabs && draggingTabIndex!=j){
                        draggingTabTargetIndex = j; // For some odd reasons this seems to get called only when draggingTabIndex < i ! (Probably during mouse dragging ImGui owns the mouse someway and sometimes ImGui::IsItemHovered() is not getting called)
                    }
                }
                if (allowTabClosingThroughMMB)  {
                    if (isMMBreleased) {
                        justClosedTabIndex = i;
                        if (pOptionalClosedTabIndex) *pOptionalClosedTabIndex = i;
                        if (pOptionalClosedTabIndexInsideItemOrdering) *pOptionalClosedTabIndexInsideItemOrdering = j;
                        pOptionalItemOrdering[j] = -1;
                    }
                }
            }
        }

    }

    selectedIndex = newSelectedIndex;

    // Draw tab label while mouse drags it
    if (draggingTabIndex>=0 && draggingTabIndex<numTabs) {
        const ImVec2& mp = ImGui::GetIO().MousePos;
        const ImVec2 wp = ImGui::GetWindowPos();
        ImVec2 start(wp.x+mp.x-draggingTabOffset.x-draggingTabSize.x*0.5f,wp.y+mp.y-draggingTabOffset.y-draggingTabSize.y*0.5f);
        const ImVec2 end(start.x+draggingTabSize.x,start.y+draggingTabSize.y);
        ImDrawList* drawList = ImGui::GetWindowDrawList();
        const float draggedBtnAlpha = 0.65f;
        const ImVec4& btnColor = style.Colors[ImGuiCol_Button];
        drawList->AddRectFilled(start,end,ImColor(btnColor.x,btnColor.y,btnColor.z,btnColor.w*draggedBtnAlpha),style.FrameRounding);
        start.x+=style.FramePadding.x;start.y+=style.FramePadding.y;
        const ImVec4& txtColor = style.Colors[ImGuiCol_Text];
        drawList->AddText(start,ImColor(txtColor.x,txtColor.y,txtColor.z,txtColor.w*draggedBtnAlpha),tabLabels[pOptionalItemOrdering[draggingTabIndex]]);

        ImGui::SetMouseCursor(ImGuiMouseCursor_Move);
    }

    // Drop tab label
    if (draggingTabTargetIndex!=-1) {
        // swap draggingTabIndex and draggingTabTargetIndex in pOptionalItemOrdering
        const int tmp = pOptionalItemOrdering[draggingTabTargetIndex];
        pOptionalItemOrdering[draggingTabTargetIndex] = pOptionalItemOrdering[draggingTabIndex];
        pOptionalItemOrdering[draggingTabIndex] = tmp;
        //fprintf(stderr,"%d %d\n",draggingTabIndex,draggingTabTargetIndex);
        draggingTabTargetIndex = draggingTabIndex = -1;
    }

    // Reset draggingTabIndex if necessary
    if (!isMouseDragging) draggingTabIndex = -1;

    // Change selected tab when user closes the selected tab
    if (selectedIndex == justClosedTabIndex && selectedIndex>=0)    {
        selectedIndex = -1;
        for (int j = 0,i; j < numTabs; j++) {
            i = pOptionalItemOrdering ? pOptionalItemOrdering[j] : j;
            if (i==-1) continue;
            selectedIndex = i;
            break;
        }
    }

    // Restore the style
    style.Colors[ImGuiCol_Button] =         color;
    style.Colors[ImGuiCol_ButtonActive] =   colorActive;
    style.Colors[ImGuiCol_ButtonHovered] =  colorHover;
    style.Colors[ImGuiCol_Text] =           colorText;
    style.ItemSpacing =                     itemSpacing;

    return selection_changed;
}


} // namespace ImGui