PlotHistogram: Fixed zero-line position when manually specifying min<0 and max>0. (#4349)

+ amended demo tweaks by ocornut

imgui_demo.cpp

@@ -1561,16 +1561,17 @@ static void ShowDemoWindowWidgets()
     }
 
     // Plot/Graph widgets are not very good.
-    // Consider writing your own, or using a third-party one, see:
-    // - ImPlot https://github.com/epezent/implot
-    // - others https://github.com/ocornut/imgui/wiki/Useful-Extensions
+    // Consider using a third-party library such as ImPlot: https://github.com/epezent/implot
+    // (see others https://github.com/ocornut/imgui/wiki/Useful-Extensions)
     if (ImGui::TreeNode("Plots Widgets"))
     {
         static bool animate = true;
         ImGui::Checkbox("Animate", &animate);
 
+        // Plot as lines and plot as histogram
         static float arr[] = { 0.6f, 0.1f, 1.0f, 0.5f, 0.92f, 0.1f, 0.2f };
         ImGui::PlotLines("Frame Times", arr, IM_ARRAYSIZE(arr));
+        ImGui::PlotHistogram("Histogram", arr, IM_ARRAYSIZE(arr), 0, NULL, 0.0f, 1.0f, ImVec2(0, 80.0f));
 
         // Fill an array of contiguous float values to plot
         // Tip: If your float aren't contiguous but part of a structure, you can pass a pointer to your first float
@@ -1600,7 +1601,6 @@ static void ShowDemoWindowWidgets()
             sprintf(overlay, "avg %f", average);
             ImGui::PlotLines("Lines", values, IM_ARRAYSIZE(values), values_offset, overlay, -1.0f, 1.0f, ImVec2(0, 80.0f));
         }
-        ImGui::PlotHistogram("Histogram", arr, IM_ARRAYSIZE(arr), 0, NULL, 0.0f, 1.0f, ImVec2(0, 80.0f));
 
         // Use functions to generate output
         // FIXME: This is rather awkward because current plot API only pass in indices.