add negative y config

packages/grafana-data/src/field/overrides/processors.ts

@@ -65,6 +65,8 @@ export const valueMappingsOverrideProcessor = (
 export interface SelectFieldConfigSettings<T> {
   allowCustomValue?: boolean;
 
+  isClearable?: boolean;
+
   /** The default options */
   options: Array<SelectableValue<T>>;
 

packages/grafana-schema/src/schema/graph.cue

@@ -7,6 +7,7 @@ LineInterpolation:  "linear" | "smooth" | "stepBefore" | "stepAfter"        @cue
 ScaleDistribution:  "linear" | "log" | "ordinal"                            @cuetsy(kind="enum")
 GraphGradientMode:  "none" | "opacity" | "hue" | "scheme"                   @cuetsy(kind="enum")
 StackingMode:       "none" | "normal" | "percent"                           @cuetsy(kind="enum")
+GraphTransform:     "constant" | "negative-Y"                               @cuetsy(kind="enum")
 BarAlignment:       -1 | 0 | 1                                              @cuetsy(kind="enum",memberNames="Before|Center|After")
 ScaleOrientation:   0 | 1                                                   @cuetsy(kind="enum",memberNames="Horizontal|Vertical")
 ScaleDirection:     1 | 1 | -1 | -1                                         @cuetsy(kind="enum",memberNames="Up|Right|Down|Left")
@@ -84,4 +85,5 @@ GraphFieldConfig: {
 	drawStyle?:       GraphDrawStyle
 	gradientMode?:    GraphGradientMode
 	thresholdsStyle?: GraphThresholdsStyleConfig
+	transform?:       GraphTransform
 } @cuetsy(kind="interface")

packages/grafana-schema/src/schema/graph.gen.ts

@@ -24,6 +24,11 @@ export enum GraphDrawStyle {
   Points = 'points',
 }
 
+export enum GraphTransform {
+  Constant = 'constant',
+  NegativeY = 'negative-Y',
+}
+
 export enum LineInterpolation {
   Linear = 'linear',
   Smooth = 'smooth',
@@ -250,6 +255,7 @@ export interface GraphFieldConfig
   drawStyle?: GraphDrawStyle;
   gradientMode?: GraphGradientMode;
   thresholdsStyle?: GraphThresholdsStyleConfig;
+  transform?: GraphTransform;
 }
 
 export interface VizLegendOptions {

packages/grafana-ui/src/components/OptionsUI/select.tsx

@@ -67,7 +67,8 @@ export class SelectValueEditor<T> extends React.PureComponent<Props<T>, State<T>
         value={current}
         defaultValue={value}
         allowCustomValue={settings?.allowCustomValue}
-        onChange={(e) => onChange(e.value)}
+        isClearable={settings?.isClearable}
+        onChange={(e) => onChange(e?.value)}
         options={options}
       />
     );

public/app/plugins/panel/timeseries/config.ts

@@ -16,6 +16,7 @@ import {
   VisibilityMode,
   StackingMode,
   GraphTresholdsStyleMode,
+  GraphTransform,
 } from '@grafana/schema';
 
 import { graphFieldOptions, commonOptionsBuilder } from '@grafana/ui';
@@ -181,6 +182,28 @@ export function getGraphFieldConfig(cfg: GraphFieldConfig): SetFieldConfigOption
         });
 
       commonOptionsBuilder.addStackingConfig(builder, cfg.stacking, categoryStyles);
+
+      builder.addSelect({
+        category: categoryStyles,
+        name: 'Transform',
+        path: 'transform',
+        settings: {
+          options: [
+            {
+              label: 'Constant',
+              value: GraphTransform.Constant,
+              description: 'The first value will be shown as a constant line',
+            },
+            {
+              label: 'Negative Y',
+              value: GraphTransform.NegativeY,
+              description: 'Flip the results to negative values on the y axis',
+            },
+          ],
+          isClearable: true,
+        },
+      });
+
       commonOptionsBuilder.addAxisConfig(builder, cfg);
       commonOptionsBuilder.addHideFrom(builder);