Plot: Internals: Added hovered index to PlotEx() function. (#2670)

imgui_internal.h

@@ -1887,7 +1887,7 @@ namespace ImGui
     IMGUI_API void          ColorPickerOptionsPopup(const float* ref_col, ImGuiColorEditFlags flags);
 
     // Plot
-    IMGUI_API void          PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_getter)(void* data, int idx), void* data, int values_count, int values_offset, const char* overlay_text, float scale_min, float scale_max, ImVec2 frame_size);
+    IMGUI_API int           PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_getter)(void* data, int idx), void* data, int values_count, int values_offset, const char* overlay_text, float scale_min, float scale_max, ImVec2 frame_size);
 
     // Shade functions (write over already created vertices)
     IMGUI_API void          ShadeVertsLinearColorGradientKeepAlpha(ImDrawList* draw_list, int vert_start_idx, int vert_end_idx, ImVec2 gradient_p0, ImVec2 gradient_p1, ImU32 col0, ImU32 col1);

imgui_widgets.cpp

@@ -5835,13 +5835,13 @@ bool ImGui::ListBox(const char* label, int* current_item, bool (*items_getter)(v
 // - PlotHistogram()
 //-------------------------------------------------------------------------
 
-void ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_getter)(void* data, int idx), void* data, int values_count, int values_offset, const char* overlay_text, float scale_min, float scale_max, ImVec2 frame_size)
+int ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_getter)(void* data, int idx), void* data, int values_count, int values_offset, const char* overlay_text, float scale_min, float scale_max, ImVec2 frame_size)
 {
+    ImGuiContext& g = *GImGui;
     ImGuiWindow* window = GetCurrentWindow();
     if (window->SkipItems)
-        return;
+        return -1;
 
-    ImGuiContext& g = *GImGui;
     const ImGuiStyle& style = g.Style;
     const ImGuiID id = window->GetID(label);
 
@@ -5856,7 +5856,7 @@ void ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_ge
     const ImRect total_bb(frame_bb.Min, frame_bb.Max + ImVec2(label_size.x > 0.0f ? style.ItemInnerSpacing.x + label_size.x : 0.0f, 0));
     ItemSize(total_bb, style.FramePadding.y);
     if (!ItemAdd(total_bb, 0, &frame_bb))
-        return;
+        return -1;
     const bool hovered = ItemHoverable(frame_bb, id);
 
     // Determine scale from values if not specified
@@ -5881,13 +5881,13 @@ void ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_ge
     RenderFrame(frame_bb.Min, frame_bb.Max, GetColorU32(ImGuiCol_FrameBg), true, style.FrameRounding);
 
     const int values_count_min = (plot_type == ImGuiPlotType_Lines) ? 2 : 1;
+    int idx_hovered = -1;
     if (values_count >= values_count_min)
     {
         int res_w = ImMin((int)frame_size.x, values_count) + ((plot_type == ImGuiPlotType_Lines) ? -1 : 0);
         int item_count = values_count + ((plot_type == ImGuiPlotType_Lines) ? -1 : 0);
 
         // Tooltip on hover
-        int v_hovered = -1;
         if (hovered && inner_bb.Contains(g.IO.MousePos))
         {
             const float t = ImClamp((g.IO.MousePos.x - inner_bb.Min.x) / (inner_bb.Max.x - inner_bb.Min.x), 0.0f, 0.9999f);
@@ -5900,7 +5900,7 @@ void ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_ge
                 SetTooltip("%d: %8.4g\n%d: %8.4g", v_idx, v0, v_idx+1, v1);
             else if (plot_type == ImGuiPlotType_Histogram)
                 SetTooltip("%d: %8.4g", v_idx, v0);
-            v_hovered = v_idx;
+            idx_hovered = v_idx;
         }
 
         const float t_step = 1.0f / (float)res_w;
@@ -5927,13 +5927,13 @@ void ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_ge
             ImVec2 pos1 = ImLerp(inner_bb.Min, inner_bb.Max, (plot_type == ImGuiPlotType_Lines) ? tp1 : ImVec2(tp1.x, histogram_zero_line_t));
             if (plot_type == ImGuiPlotType_Lines)
             {
-                window->DrawList->AddLine(pos0, pos1, v_hovered == v1_idx ? col_hovered : col_base);
+                window->DrawList->AddLine(pos0, pos1, idx_hovered == v1_idx ? col_hovered : col_base);
             }
             else if (plot_type == ImGuiPlotType_Histogram)
             {
                 if (pos1.x >= pos0.x + 2.0f)
                     pos1.x -= 1.0f;
-                window->DrawList->AddRectFilled(pos0, pos1, v_hovered == v1_idx ? col_hovered : col_base);
+                window->DrawList->AddRectFilled(pos0, pos1, idx_hovered == v1_idx ? col_hovered : col_base);
             }
 
             t0 = t1;
@@ -5947,6 +5947,10 @@ void ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_ge
 
     if (label_size.x > 0.0f)
         RenderText(ImVec2(frame_bb.Max.x + style.ItemInnerSpacing.x, inner_bb.Min.y), label);
+
+    // Return hovered index or -1 if none are hovered. 
+    // This is currently not exposed in the public API because we need a larger redesign of the whole thing, but in the short-term we are making it available in PlotEx().
+    return idx_hovered;
 }
 
 struct ImGuiPlotArrayGetterData