Revert 5772 revert 5534 css gradients (#5779)

* Revert "Revert "Css gradients" (#5772)"

This reverts commit 7edf56197a179b13e1afe4c706aea4a99ac62aca.

* chore(): fix LinearGradient circular dependency

apps/app/ui-tests-app/button/border-playground.ts

@@ -34,6 +34,11 @@ export function onToggle(args: EventData) {
         target.backgroundImage = target.backgroundImage ? undefined : `~/ui-tests-app/resources/images/test2.png`; 
         debugConsole.text += `> background-image: ${target.backgroundImage}\n`;
     }
+    else if (button.text === "BGGradient") {
+        const gradient = "linear-gradient(to right, purple, red)";
+        target.backgroundImage = typeof target.backgroundImage === "object" ? undefined :  gradient;
+        debugConsole.text += `> background-image: ${gradient} \n`;
+    }
 
     scrollView.scrollToVerticalOffset(scrollView.scrollableHeight, true);
 }

apps/app/ui-tests-app/button/border-playground.xml

@@ -17,6 +17,7 @@
         <StackLayout id="target" row="1" col="1">
             <Button text="BGColor" tap="onToggle"/>
             <Button text="BGImage" tap="onToggle"/>
+            <Button text="BGGradient" tap="onToggle"/>
         </StackLayout>
         <StackLayout id="right" class="button-container" row="1" col="2">
             <Button text="Color" id="borderRightColor" tap="onToggle"/>

apps/app/ui-tests-app/css/background-image-linear-gradient.ts

@@ -0,0 +1,41 @@
+import * as pages from "tns-core-modules/ui/page";
+import { EventData } from "tns-core-modules/data/observable";
+import * as button from "tns-core-modules/ui/button";
+
+import { GridLayout } from "tns-core-modules/ui/layouts/grid-layout";
+
+let testIndex = 0;
+const tests = [
+    { name: "black-blue only", backgroundImage: "linear-gradient(to bottom, black, blue)"},
+    { name: "to bottom green-blue", backgroundImage: "linear-gradient(to bottom, green, blue)"},
+    { name: "to left yellow-blue", backgroundImage: "linear-gradient(to left, yellow, green)"},
+    { name: "to right yellow-blue", backgroundImage: "linear-gradient(to right, yellow, green)"},
+    { name: "-45deg green-blue", backgroundImage: "linear-gradient(-45deg, green, blue)"},
+    { name: "45deg green-blue", backgroundImage: "linear-gradient(45deg, green, blue)"},
+
+    { name: "black-blue-pink only", backgroundImage: "linear-gradient(to bottom, black, blue, pink)"},
+    { name: "to bottom green-blue-pink", backgroundImage: "linear-gradient(to bottom, green, blue, pink)"},
+    { name: "to left yellow-blue-pink", backgroundImage: "linear-gradient(to left, yellow, green, pink)"},
+    { name: "to right yellow-blue-pink", backgroundImage: "linear-gradient(to right, yellow, green, pink)"},
+    { name: "-45deg green-blue-pink", backgroundImage: "linear-gradient(-45deg, green, blue, pink)"},
+    { name: "45deg green-blue-pink", backgroundImage: "linear-gradient(45deg, green, blue, pink)"},
+]
+
+export function onLoaded(args) {
+    applyNextStyle(args);
+}
+
+export function onButtonTap(args) {
+    applyNextStyle(args);
+}
+
+function applyNextStyle(args) {
+    let page = <pages.Page>args.object.page;
+    let btn = <button.Button>args.object;
+    let gridElement = <GridLayout>page.getViewById("Container");
+
+    btn.text = tests[testIndex].name;
+    gridElement.backgroundImage = tests[testIndex].backgroundImage;
+
+    testIndex = testIndex < tests.length - 1 ? ++testIndex : 0;
+}

apps/app/ui-tests-app/css/background-image-linear-gradient.xml

@@ -0,0 +1,7 @@
+<Page xmlns="http://schemas.nativescript.org/tns.xsd" loaded="onLoaded">
+  <GridLayout rows="*, 7*">
+     <Button row="0" text="a1" tap="onButtonTap"/>
+
+    <GridLayout id="Container" fontSize="12" borderColor="black" margin="5" borderWidth="1" row="1"/>
+  </GridLayout>
+</Page>

apps/app/ui-tests-app/css/background-shorthand.ts

@@ -9,7 +9,9 @@ const tests = [
     { name: "black hex color only", background: "#000000" },
     { name: "yellow hex color only", background: "#ffff00" },
     { name: "blue color only", background: "blue" },
+
     { name: "repeat image only", background: "url(\"~/ui-tests-app/resources/images/icon.png\")" },
+    { name: "linear gradient red-blue only", background: "linear-gradient(to bottom, red, blue)"},
 
     { name: "[straight] image only, no-repeat ", background: "url(\"~/ui-tests-app/resources/images/icon.png\") no-repeat" },
     { name: "[straight] green color, image, no-repeat", background: "green url(\"~/ui-tests-app/resources/images/icon.png\") no-repeat" },

apps/app/ui-tests-app/css/gradient-border.css

@@ -0,0 +1,77 @@
+StackLayout {
+    width: 80;
+    height: 80;
+    background: linear-gradient(to top, green, blue);
+}
+
+#s0 {
+    border-width: 5;
+}
+
+#s1 {
+    border-width: 5; border-color: red;
+}
+
+#s2 {
+    border-width: 5; border-color: red red red green;
+}
+
+#s3 {
+    border-width: 5; border-color: red; border-radius: 5;
+}
+
+#s4 {
+    border-width: 5; border-color: red; border-radius: 50;
+}
+
+#s5 {
+    border-width: 5 10 15 20; border-color: red;
+}
+
+#s6 {
+    border-width: 5; border-color: red green blue yellow;
+}
+
+#s7 {
+    border-width: 5 10 15 20; border-color: red green blue yellow;
+}
+
+#s8 {
+    border-width: 5 10; border-color: red green;
+}
+
+#s9 {
+    border-width: 15 10 5; border-color: red green blue;
+}
+
+#s10 {
+    border-width: 5 0; border-color: black;
+}
+
+#s11 {
+    background-color: magenta;
+}
+
+#s12 {
+    border-width: 5 10 15 20; border-color: red green blue yellow; border-radius: 5 10 15 20;
+}
+
+#s13 {
+    border-width: 5 10 15 20; border-color: red green blue yellow; border-radius: 5;
+}
+
+#s14 {
+    border-width: 5 10 15 20; border-color: red green blue yellow; background-color: magenta;
+}
+
+#s15 {
+    border-width: 5 10 15 20; border-color: red green blue yellow; background-image: url('~/ui-tests-app/resources/images/test2.png');
+}
+
+#s16 {
+    border-width: 5; border-color: red; padding: 5;
+}
+
+#s17 {
+    border-width: 5 6 7 8; border-color: red green blue yellow; padding: 5 6 7 8;
+}

apps/app/ui-tests-app/css/gradient-border.xml

@@ -0,0 +1,22 @@
+<Page>
+    <GridLayout rows="*,*,*,*,*,*" columns="*,*,*">
+        <StackLayout  id="s0" row="0" col="0"/>
+        <StackLayout  id="s1" row="0" col="1"/>
+        <StackLayout  id="s2" row="0" col="2"/>
+        <StackLayout  id="s3" row="1" col="0"/>
+        <StackLayout  id="s4" row="1" col="1"/>
+        <StackLayout  id="s5" row="1" col="2"/>
+        <StackLayout  id="s6" row="2" col="0"/>
+        <StackLayout  id="s7" row="2" col="1"/>
+        <StackLayout  id="s8" row="2" col="2"/>
+        <StackLayout  id="s9" row="3" col="0"/>
+        <StackLayout id="s10" row="3" col="1"/>
+        <StackLayout id="s11" row="3" col="2"/>
+        <StackLayout id="s12" row="4" col="0"/>
+        <StackLayout id="s13" row="4" col="1"/>
+        <StackLayout id="s14" row="4" col="2"/>
+        <StackLayout id="s15" row="5" col="0"/>
+        <StackLayout id="s16" row="5" col="1"/>
+        <StackLayout id="s17" row="5" col="2"/>
+    </GridLayout>
+</Page>

apps/app/ui-tests-app/css/main-page.ts

@@ -30,6 +30,7 @@ export function loadExamples() {
     examples.set("label-border", "css/label-border");
     examples.set("text-view-border", "css/text-view-border");
     examples.set("image-border", "css/image-border");
+    examples.set("gradient-border", "css/gradient-border");
     examples.set("layouts-border-overlap", "css/layouts-border-overlap");
     examples.set("measure-tests", "css/measure-tests");
     examples.set("all-uniform-border", "css/all-uniform-border");
@@ -41,5 +42,6 @@ export function loadExamples() {
     examples.set("non-uniform-radius", "css/non-uniform-radius");
     examples.set("missing-background-image", "css/missing-background-image");
     examples.set("background-shorthand", "css/background-shorthand");
+    examples.set("background-image-linear-gradient", "css/background-image-linear-gradient");
     return examples;
 }

tns-core-modules/ui/core/view/view-common.ts

@@ -21,9 +21,11 @@ import {
 
 import { createViewFromEntry } from "../../builder";
 import { StyleScope } from "../../styling/style-scope";
+import { LinearGradient } from "../../styling/linear-gradient";
 
 export * from "../../styling/style-properties";
 export * from "../view-base";
+export { LinearGradient };
 
 import * as am from "../../animation";
 let animationModule: typeof am;
@@ -435,10 +437,10 @@ export abstract class ViewCommon extends ViewBase implements ViewDefinition {
         this.style.backgroundColor = value;
     }
 
-    get backgroundImage(): string {
+    get backgroundImage(): string | LinearGradient {
         return this.style.backgroundImage;
     }
-    set backgroundImage(value: string) {
+    set backgroundImage(value: string | LinearGradient) {
         this.style.backgroundImage = value;
     }
 

tns-core-modules/ui/core/view/view.d.ts

@@ -7,9 +7,11 @@ import { ViewBase, Property, EventData, Color } from "../view-base";
 import { Animation, AnimationDefinition, AnimationPromise } from "../../animation";
 import { HorizontalAlignment, VerticalAlignment, Visibility, Length, PercentLength } from "../../styling/style-properties";
 import { GestureTypes, GestureEventData, GesturesObserver } from "../../gestures";
+import { LinearGradient } from "../../styling/linear-gradient";
 
 export * from "../view-base";
 export * from "../../styling/style-properties";
+export { LinearGradient };
 
 export function PseudoClassHandler(...pseudoClasses: string[]): MethodDecorator;
 
@@ -219,7 +221,7 @@ export abstract class View extends ViewBase {
     /**
      * Gets or sets the background image of the view.
      */
-    backgroundImage: string;
+    backgroundImage: string | LinearGradient;
 
     /**
      * Gets or sets the minimum width the view may grow to.

tns-core-modules/ui/styling/background-common.ts

@@ -1,7 +1,7 @@
 // Deifinitions.
 import { Background as BackgroundDefinition } from "./background";
 import { BackgroundRepeat } from "../core/view";
-
+import { LinearGradient } from "./linear-gradient";
 // Types.
 import { Color } from "../../color";
 
@@ -9,7 +9,7 @@ export class Background implements BackgroundDefinition {
     public static default = new Background();
 
     public color: Color;
-    public image: string;
+    public image: string | LinearGradient;
     public repeat: BackgroundRepeat;
     public position: string;
     public size: string;
@@ -58,7 +58,7 @@ export class Background implements BackgroundDefinition {
         return clone;
     }
 
-    public withImage(value: string): Background {
+    public withImage(value: string | LinearGradient): Background {
         const clone = this.clone();
         clone.image = value;
         return clone;
@@ -179,8 +179,15 @@ export class Background implements BackgroundDefinition {
             return false;
         }
 
+        let imagesEqual = false;
+        if (value1 instanceof LinearGradient && value2 instanceof LinearGradient) {
+            imagesEqual = LinearGradient.equals(value1, value2);
+        } else {
+            imagesEqual = value1.image === value2.image;
+        }
+
         return Color.equals(value1.color, value2.color)
-            && value1.image === value2.image
+            && imagesEqual
             && value1.position === value2.position
             && value1.repeat === value2.repeat
             && value1.size === value2.size

tns-core-modules/ui/styling/background.android.ts

@@ -1,4 +1,6 @@
 import { View } from "../core/view";
+import { LinearGradient } from "./linear-gradient";
+
 import { isDataURI, isFileOrResourcePath, layout, RESOURCE_PREFIX, FILE_PREFIX } from "../../utils/utils";
 import { parse } from "../../css-value";
 import { path, knownFolders } from "../../file-system";
@@ -104,6 +106,38 @@ function fromBase64(source: string): android.graphics.Bitmap {
     return android.graphics.BitmapFactory.decodeByteArray(bytes, 0, bytes.length)
 }
 
+function fromGradient(gradient: LinearGradient): org.nativescript.widgets.LinearGradientDefinition {
+    const colors = Array.create("int", gradient.colorStops.length);
+    const stops = Array.create("float", gradient.colorStops.length);
+    let hasStops = false;
+    gradient.colorStops.forEach((stop, index) => {
+        colors[index] = stop.color.android;
+        if (stop.offset) {
+            stops[index] = stop.offset.value;
+            hasStops = true;
+        }
+    });
+
+    const alpha = gradient.angle / (Math.PI * 2);
+    const startX = Math.pow(
+      Math.sin(Math.PI * (alpha + 0.75)),
+      2
+    );
+    const startY = Math.pow(
+      Math.sin(Math.PI * (alpha + 0.5)),
+      2
+    );
+    const endX = Math.pow(
+      Math.sin(Math.PI * (alpha + 0.25)),
+      2
+    );
+    const endY = Math.pow(
+      Math.sin(Math.PI * alpha),
+      2
+    );
+    return new org.nativescript.widgets.LinearGradientDefinition(startX, startY, endX, endY, colors, hasStops ? stops : null);
+}
+
 const pattern: RegExp = /url\(('|")(.*?)\1\)/;
 function refreshBorderDrawable(this: void, view: View, borderDrawable: org.nativescript.widgets.BorderDrawable) {
     const nativeView = <android.view.View>view.nativeViewProtected;
@@ -115,8 +149,9 @@ function refreshBorderDrawable(this: void, view: View, borderDrawable: org.nativ
         const backgroundSizeParsedCSSValues = createNativeCSSValueArray(background.size);
         const blackColor = -16777216; //android.graphics.Color.BLACK;
 
-        let imageUri = background.image;
-        if (imageUri) {
+        let imageUri: string;
+        if (background.image && typeof background.image === "string") {
+            imageUri = background.image;
             const match = imageUri.match(pattern);
             if (match && match[2]) {
                 imageUri = match[2];
@@ -141,6 +176,11 @@ function refreshBorderDrawable(this: void, view: View, borderDrawable: org.nativ
             }
         }
 
+        let gradient: org.nativescript.widgets.LinearGradientDefinition = null;
+        if (background.image && background.image instanceof LinearGradient) {
+            gradient = fromGradient(background.image);
+        }
+
         borderDrawable.refresh(
             background.borderTopColor ? background.borderTopColor.android : blackColor,
             background.borderRightColor ? background.borderRightColor.android : blackColor,
@@ -162,6 +202,7 @@ function refreshBorderDrawable(this: void, view: View, borderDrawable: org.nativ
             background.color ? background.color.android : 0,
             imageUri,
             bitmap,
+            gradient,
             context,
             background.repeat,
             background.position,

tns-core-modules/ui/styling/background.d.ts

@@ -3,12 +3,12 @@
  */ /** */
 
 import { Color } from "../../color";
-import { View, BackgroundRepeat } from "../core/view";
+import { View, BackgroundRepeat, LinearGradient } from "../core/view";
 
 export class Background {
     public static default: Background;
     public color: Color;
-    public image: string;
+    public image: string | LinearGradient;
     public repeat: BackgroundRepeat;
     public position: string;
     public size: string;
@@ -27,7 +27,7 @@ export class Background {
     public clipPath: string;
 
     public withColor(value: Color): Background;
-    public withImage(value: string): Background;
+    public withImage(value: string | LinearGradient): Background;
     public withRepeat(value: BackgroundRepeat): Background;
     public withPosition(value: string): Background;
     public withSize(value: string): Background;

tns-core-modules/ui/styling/background.ios.ts

@@ -2,6 +2,7 @@ import { ScrollEventData } from "../scroll-view";
 
 import { Background as BackgroundDefinition } from "./background";
 import { View, Point } from "../core/view";
+import { LinearGradient } from "./linear-gradient";
 import { Color } from "../../color";
 import { ios as utilsIos, isDataURI, isFileOrResourcePath, layout } from "../../utils/utils";
 import { fromFileOrResource, fromBase64, fromUrl } from "../../image-source";
@@ -21,6 +22,8 @@ interface NativeView extends UIView {
     rightBorderLayer: CALayer;
     bottomBorderLayer: CALayer;
     leftBorderLayer: CALayer;
+
+    gradientLayer: CAGradientLayer;
 }
 
 interface Rect {
@@ -43,6 +46,11 @@ export module ios {
             clearNonUniformBorders(nativeView);
         }
 
+        clearGradient(nativeView);
+        if (background.image instanceof LinearGradient) {
+            drawGradient(nativeView, background.image);
+        }
+
         const hasNonUniformBorderWidths = background.hasBorderWidth() && !background.hasUniformBorder();
         const hasNonUniformBorderRadiuses = background.hasBorderRadius() && !background.hasUniformBorderRadius();
         if (background.hasUniformBorderColor() && (hasNonUniformBorderWidths || hasNonUniformBorderRadiuses)) {
@@ -67,7 +75,7 @@ export module ios {
             drawClipPath(nativeView, background);
         }
 
-        if (!background.image) {
+        if (!background.image || background.image instanceof LinearGradient) {
             const uiColor = background.color ? background.color.ios : undefined;
             callback(uiColor);
         } else {
@@ -151,7 +159,7 @@ function setUIColorFromImage(view: View, nativeView: UIView, callback: (uiColor:
 
     const style = view.style;
     const background = style.backgroundInternal;
-    let imageUri = background.image;
+    let imageUri = background.image as string;
     if (imageUri) {
         const match = imageUri.match(pattern);
         if (match && match[2]) {
@@ -663,6 +671,60 @@ function drawNoRadiusNonUniformBorders(nativeView: NativeView, background: Backg
     nativeView.hasNonUniformBorder = hasNonUniformBorder;
 }
 
+function drawGradient(nativeView: NativeView, gradient: LinearGradient) {
+
+    const gradientLayer = CAGradientLayer.layer();
+    gradientLayer.frame = nativeView.bounds;
+    nativeView.gradientLayer = gradientLayer;
+
+    const iosColors = NSMutableArray.alloc().initWithCapacity(gradient.colorStops.length);
+    const iosStops = NSMutableArray.alloc<number>().initWithCapacity(gradient.colorStops.length);
+    let hasStops = false;
+
+    gradient.colorStops.forEach(stop => {
+       iosColors.addObject(stop.color.ios.CGColor);
+       if (stop.offset) {
+           iosStops.addObject(stop.offset.value);
+           hasStops = true;
+       }
+    });
+
+    gradientLayer.colors = iosColors;
+
+    if (hasStops) {
+        gradientLayer.locations = iosStops;
+    }
+
+    const alpha = gradient.angle / (Math.PI * 2);
+    const startX = Math.pow(
+      Math.sin(Math.PI * (alpha + 0.75)),
+      2
+    );
+    const startY = Math.pow(
+      Math.sin(Math.PI * (alpha + 0.5)),
+      2
+    );
+    const endX = Math.pow(
+      Math.sin(Math.PI * (alpha + 0.25)),
+      2
+    );
+    const endY = Math.pow(
+      Math.sin(Math.PI * alpha),
+      2
+    );
+    gradientLayer.startPoint = {x: startX, y: startY};
+    gradientLayer.endPoint = {x: endX, y: endY};
+
+    nativeView.layer.insertSublayerAtIndex(gradientLayer, 0);
+
+}
+
+function clearGradient(nativeView: NativeView): void {
+    if (nativeView.gradientLayer) {
+        nativeView.gradientLayer.removeFromSuperlayer();
+    }
+}
+
 function drawClipPath(nativeView: UIView, background: BackgroundDefinition) {
     const layer = nativeView.layer;
     const layerBounds = layer.bounds;

tns-core-modules/ui/styling/linear-gradient.ts

@@ -0,0 +1,64 @@
+import { LengthPercentUnit } from "./style-properties";
+import * as parser from "../../css/parser";
+import { Color } from "../../color";
+
+export class LinearGradient {
+    public angle: number;
+    public colorStops: ColorStop[];
+
+    static parse(value: parser.LinearGradient): LinearGradient {
+        const result = new LinearGradient();
+        result.angle = value.angle;
+        result.colorStops = value.colors.map(color => {
+            const offset = color.offset || null;
+            let offsetUnit: LengthPercentUnit;
+
+            if (offset && offset.unit === "%") {
+                offsetUnit = {
+                    unit: "%",
+                    value: offset.value
+                };
+            }
+
+            return {
+                color: new Color(color.argb),
+                offset: offsetUnit
+            }
+        });
+        return result;
+    }
+
+    static equals(first: LinearGradient, second: LinearGradient): boolean {
+        if (!first && !second) {
+            return true;
+        } else if (!first || !second) {
+            return false
+        }
+
+        if (first.angle !== second.angle) {
+            return false;
+        }
+
+        if (first.colorStops.length !== second.colorStops.length) {
+            return false;
+        }
+
+        for (let i = 0; i < first.colorStops.length; i++) {
+            const firstStop = first.colorStops[i];
+            const secondStop = second.colorStops[i];
+            if (firstStop.offset !== secondStop.offset) {
+                return false;
+            }
+            if (!Color.equals(firstStop.color, secondStop.color)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+
+export interface ColorStop {
+    color: Color;
+    offset?: LengthPercentUnit;
+}

tns-core-modules/ui/styling/style-properties.ts

@@ -27,6 +27,7 @@ import {
 } from "../../matrix";
 
 import * as parser from "../../css/parser";
+import { LinearGradient } from "./linear-gradient";
 
 export type LengthDipUnit = { readonly unit: "dip", readonly value: dip };
 export type LengthPxUnit = { readonly unit: "px", readonly value: px };
@@ -563,10 +564,28 @@ export const backgroundInternalProperty = new CssProperty<Style, Background>({
 backgroundInternalProperty.register(Style);
 
 // const pattern: RegExp = /url\(('|")(.*?)\1\)/;
-export const backgroundImageProperty = new CssProperty<Style, string>({
+export const backgroundImageProperty = new CssProperty<Style, string | LinearGradient>({
     name: "backgroundImage", cssName: "background-image", valueChanged: (target, oldValue, newValue) => {
         const background = target.backgroundInternal.withImage(newValue);
         target.backgroundInternal = background;
+    },
+    equalityComparer: (value1, value2) => {
+        if (value1 instanceof LinearGradient && value2 instanceof LinearGradient) {
+            return LinearGradient.equals(value1, value2)
+        } else {
+            return value1 === value2;
+        }
+    },
+    valueConverter: (value: any) => {
+        if (typeof value === "string") {
+            const parsed = parser.parseBackground(value);
+            if (parsed) {
+                const background = parsed.value;
+                value = (typeof background.image === "object") ? LinearGradient.parse(background.image) : value;
+            }
+        }
+
+        return value;
     }
 });
 backgroundImageProperty.register(Style);
@@ -618,7 +637,14 @@ function convertToBackgrounds(this: void, value: string): [CssProperty<any, any>
     if (typeof value === "string") {
         const backgrounds = parser.parseBackground(value).value;
         const backgroundColor = backgrounds.color ? new Color(backgrounds.color) : unsetValue;
-        const backgroundImage = backgrounds.image || unsetValue;
+
+        let backgroundImage: string | LinearGradient;
+        if (typeof backgrounds.image === "object" && backgrounds.image) {
+            backgroundImage = LinearGradient.parse(backgrounds.image);
+        } else {
+            backgroundImage = backgrounds.image || unsetValue;
+        }
+
         const backgroundRepeat = backgrounds.repeat || unsetValue;
         const backgroundPosition = backgrounds.position ? backgrounds.position.text : unsetValue;
 

tns-core-modules/ui/styling/style/style.d.ts

@@ -11,6 +11,7 @@ import {
     FlexDirection, FlexWrap, JustifyContent, AlignItems, AlignContent,
     Order, FlexGrow, FlexShrink, FlexWrapBefore, AlignSelf
 } from "../../layouts/flexbox-layout";
+import { LinearGradient } from "../linear-gradient";
 
 export interface Thickness {
     left: number;
@@ -64,7 +65,7 @@ export class Style extends Observable {
 
     public background: string;
     public backgroundColor: Color;
-    public backgroundImage: string;
+    public backgroundImage: string | LinearGradient;
     public backgroundRepeat: BackgroundRepeat;
     public backgroundSize: string;
     public backgroundPosition: string;

tns-core-modules/ui/styling/style/style.ts

@@ -2,7 +2,8 @@ import { Style as StyleDefinition } from ".";
 import { Color } from "../../../color";
 import { Font, FontStyle, FontWeight } from "../font";
 import { Background } from "../background";
-import { Length, PercentLength, ViewBase, BackgroundRepeat, Visibility, HorizontalAlignment, VerticalAlignment, dip } from "../../core/view";
+import { Length, PercentLength, ViewBase, BackgroundRepeat, Visibility,
+    HorizontalAlignment, VerticalAlignment, dip, LinearGradient } from "../../core/view";
 import { Observable } from "../../../data/observable";
 
 import {
@@ -37,7 +38,7 @@ export class Style extends Observable implements StyleDefinition {
 
     public background: string;
     public backgroundColor: Color;
-    public backgroundImage: string;
+    public backgroundImage: string | LinearGradient;
     public backgroundRepeat: BackgroundRepeat;
     public backgroundSize: string;
     public backgroundPosition: string;

tns-platform-declarations/android/org.nativescript.widgets.d.ts

@@ -73,6 +73,7 @@
                     backgroundColor: number,
                     backgroundImage: string,
                     backgroundBitmap: android.graphics.Bitmap,
+                    backgroundGradient: LinearGradientDefinition,
                     context: android.content.Context,
                     backgroundRepeat: string,
                     backgroundPosition: string,
@@ -117,6 +118,18 @@
                 public toDebugString(): string;
             }
 
+            export class LinearGradientDefinition {
+                constructor(startX: number, endX: number, startY: number,
+                            endY: number, colors: number[], stops?: number[]);
+
+                public getStartX(): number;
+                public getStartY(): number;
+                public getEndX(): number;
+                public getEndY(): number;
+                public getColors(): number[];
+                public getStops(): number[];
+            }
+
             export class CSSValue {
                 constructor(type: string, str: string, unit: string, value: number);
                 public getType(): string;