Demo: PlotLine example displays the average value. (#2759) + extra comments

imgui_demo.cpp

@@ -1043,6 +1043,8 @@ static void ShowDemoWindowWidgets()
         ImGui::TreePop();
     }
 
+    // Plot/Graph widgets are currently fairly limited.
+    // Consider writing your own plotting widget, or using a third-party one (see "Wiki->Useful Widgets", or github.com/ocornut/imgui/issues/2747)
     if (ImGui::TreeNode("Plots Widgets"))
     {
         static bool animate = true;
@@ -1066,7 +1068,18 @@ static void ShowDemoWindowWidgets()
             phase += 0.10f*values_offset;
             refresh_time += 1.0f/60.0f;
         }
-        ImGui::PlotLines("Lines", values, IM_ARRAYSIZE(values), values_offset, "avg 0.0", -1.0f, 1.0f, ImVec2(0,80));
+
+        // Plots can display overlay texts
+        // (in this example, we will display an average value)
+        {
+            float average = 0.0f;
+            for (int n = 0; n < IM_ARRAYSIZE(values); n++)
+                average += values[n];
+            average /= (float)IM_ARRAYSIZE(values);
+            char overlay[32];
+            sprintf(overlay, "avg %f", average);
+            ImGui::PlotLines("Lines", values, IM_ARRAYSIZE(values), values_offset, overlay, -1.0f, 1.0f, ImVec2(0,80));
+        }
         ImGui::PlotHistogram("Histogram", arr, IM_ARRAYSIZE(arr), 0, NULL, 0.0f, 1.0f, ImVec2(0,80));
 
         // Use functions to generate output