Dynamic max and min zoom in the new ImageView

res/css/views/elements/_ImageView.scss

@@ -31,8 +31,7 @@ limitations under the License.
 
 .mx_ImageView_image {
     pointer-events: all;
-    max-width: 95%;
-    max-height: 95%;
+    flex-shrink: 0;
 }
 
 .mx_ImageView_panel {

src/components/views/elements/ImageView.tsx

@@ -34,15 +34,15 @@ import {RoomPermalinkCreator} from "../../../utils/permalinks/Permalinks"
 import {MatrixEvent} from "matrix-js-sdk/src/models/event";
 import {normalizeWheelEvent} from "../../../utils/Mouse";
 
-const MIN_ZOOM = 100;
-const MAX_ZOOM = 300;
+// Max scale to keep gaps around the image
+const MAX_SCALE = 0.95;
 // This is used for the buttons
-const ZOOM_STEP = 10;
+const ZOOM_STEP = 0.10;
 // This is used for mouse wheel events
-const ZOOM_COEFFICIENT = 0.5;
+const ZOOM_COEFFICIENT = 0.0025;
 // If we have moved only this much we can zoom
 const ZOOM_DISTANCE = 10;
-
+const IMAGE_WRAPPER_CLASS = "mx_ImageView_image_wrapper";
 
 interface IProps {
     src: string, // the source of the image being displayed
@@ -62,8 +62,10 @@ interface IProps {
 }
 
 interface IState {
-    rotation: number,
     zoom: number,
+    minZoom: number,
+    maxZoom: number,
+    rotation: number,
     translationX: number,
     translationY: number,
     moving: boolean,
@@ -75,8 +77,10 @@ export default class ImageView extends React.Component<IProps, IState> {
     constructor(props) {
         super(props);
         this.state = {
+            zoom: 0,
+            minZoom: MAX_SCALE,
+            maxZoom: MAX_SCALE,
             rotation: 0,
-            zoom: MIN_ZOOM,
             translationX: 0,
             translationY: 0,
             moving: false,
@@ -99,43 +103,82 @@ export default class ImageView extends React.Component<IProps, IState> {
         // We have to use addEventListener() because the listener
         // needs to be passive in order to work with Chromium
         this.focusLock.current.addEventListener('wheel', this.onWheel, { passive: false });
+        window.addEventListener("resize", this.calculateZoom);
+        this.calculateZoom();
     }
 
     componentWillUnmount() {
         this.focusLock.current.removeEventListener('wheel', this.onWheel);
     }
 
-    private onKeyDown = (ev: KeyboardEvent) => {
-        if (ev.key === Key.ESCAPE) {
-            ev.stopPropagation();
-            ev.preventDefault();
-            this.props.onFinished();
-        }
-    };
-
-    private onWheel = (ev: WheelEvent) => {
-        ev.stopPropagation();
-        ev.preventDefault();
+    private calculateZoom = () => {
+        // TODO: What if we don't have width and height props?
+
+        const imageWrapper = document.getElementsByClassName(IMAGE_WRAPPER_CLASS)[0];
+
+        const zoomX = imageWrapper.clientWidth / this.props.width;
+        const zoomY = imageWrapper.clientHeight / this.props.height;
+        // We set minZoom to the min of the zoomX and zoomY to avoid overflow in
+        // any direction. We also multiply by MAX_SCALE to get a gap around the
+        // image by default
+        const minZoom = Math.min(zoomX, zoomY) * MAX_SCALE;
+        // If minZoom is bigger or equal to 1, it means we scaling the image up
+        // to fit the viewport and therefore we want to disable zooming, so we
+        // set the maxZoom to be the same as the minZoom. Otherwise, we are
+        // scaling the image down - we want the user to be allowed to zoom to
+        // 100%
+        const maxZoom = minZoom >= 1 ? minZoom : 1;
+
+        if (this.state.zoom <= this.state.minZoom) this.setState({zoom: minZoom});
+        this.setState({
+            minZoom: minZoom,
+            maxZoom: maxZoom,
+        });
+    }
 
-        const {deltaY} = normalizeWheelEvent(ev);
-        const newZoom = this.state.zoom - (deltaY * ZOOM_COEFFICIENT);
+    private zoom(delta: number) {
+        const newZoom = this.state.zoom + delta;
 
-        if (newZoom <= MIN_ZOOM) {
+        if (newZoom <= this.state.minZoom) {
             this.setState({
-                zoom: MIN_ZOOM,
+                zoom: this.state.minZoom,
                 translationX: 0,
                 translationY: 0,
             });
             return;
         }
-        if (newZoom >= MAX_ZOOM) {
-            this.setState({zoom: MAX_ZOOM});
+        if (newZoom >= this.state.maxZoom) {
+            this.setState({zoom: this.state.maxZoom});
             return;
         }
 
         this.setState({
             zoom: newZoom,
         });
+    }
+
+    private onWheel = (ev: WheelEvent) => {
+        ev.stopPropagation();
+        ev.preventDefault();
+
+        const {deltaY} = normalizeWheelEvent(ev);
+        this.zoom(-(deltaY * ZOOM_COEFFICIENT));
+    };
+
+    private onZoomInClick = () => {
+        this.zoom(ZOOM_STEP);
+    };
+
+    private onZoomOutClick = () => {
+        this.zoom(-ZOOM_STEP);
+    };
+
+    private onKeyDown = (ev: KeyboardEvent) => {
+        if (ev.key === Key.ESCAPE) {
+            ev.stopPropagation();
+            ev.preventDefault();
+            this.props.onFinished();
+        }
     };
 
     private onRotateCounterClockwiseClick = () => {
@@ -150,31 +193,6 @@ export default class ImageView extends React.Component<IProps, IState> {
         this.setState({ rotation: rotationDegrees });
     };
 
-    private onZoomInClick = () => {
-        if (this.state.zoom >= MAX_ZOOM) {
-            this.setState({zoom: MAX_ZOOM});
-            return;
-        }
-
-        this.setState({
-            zoom: this.state.zoom + ZOOM_STEP,
-        });
-    };
-
-    private onZoomOutClick = () => {
-        if (this.state.zoom <= MIN_ZOOM) {
-            this.setState({
-                zoom: MIN_ZOOM,
-                translationX: 0,
-                translationY: 0,
-            });
-            return;
-        }
-        this.setState({
-            zoom: this.state.zoom - ZOOM_STEP,
-        });
-    };
-
     private onDownloadClick = () => {
         const a = document.createElement("a");
         a.href = this.props.src;
@@ -217,8 +235,8 @@ export default class ImageView extends React.Component<IProps, IState> {
         if (ev.button !== 0) return;
 
         // Zoom in if we are completely zoomed out
-        if (this.state.zoom === MIN_ZOOM) {
-            this.setState({zoom: MAX_ZOOM});
+        if (this.state.zoom === this.state.minZoom) {
+            this.setState({zoom: this.state.maxZoom});
             return;
         }
 
@@ -251,7 +269,7 @@ export default class ImageView extends React.Component<IProps, IState> {
             Math.abs(this.state.translationY - this.previousY) < ZOOM_DISTANCE
         ) {
             this.setState({
-                zoom: MIN_ZOOM,
+                zoom: this.state.minZoom,
                 translationX: 0,
                 translationY: 0,
             });
@@ -290,13 +308,15 @@ export default class ImageView extends React.Component<IProps, IState> {
         let cursor;
         if (this.state.moving) {
             cursor= "grabbing";
-        } else if (this.state.zoom === MIN_ZOOM) {
+        } else if (this.state.maxZoom === this.state.minZoom) {
+            cursor = "pointer";
+        } else if (this.state.zoom === this.state.minZoom) {
             cursor = "zoom-in";
         } else {
             cursor = "zoom-out";
         }
         const rotationDegrees = this.state.rotation + "deg";
-        const zoomPercentage = this.state.zoom/100;
+        const zoom = this.state.zoom;
         const translatePixelsX = this.state.translationX + "px";
         const translatePixelsY = this.state.translationY + "px";
         // The order of the values is important!
@@ -308,7 +328,7 @@ export default class ImageView extends React.Component<IProps, IState> {
             transition: this.state.moving ? null : "transform 200ms ease 0s",
             transform: `translateX(${translatePixelsX})
                         translateY(${translatePixelsY})
-                        scale(${zoomPercentage})
+                        scale(${zoom})
                         rotate(${rotationDegrees})`,
         };
 
@@ -427,7 +447,7 @@ export default class ImageView extends React.Component<IProps, IState> {
                         {this.renderContextMenu()}
                     </div>
                 </div>
-                <div className="mx_ImageView_image_wrapper">
+                <div className={IMAGE_WRAPPER_CLASS}>
                     <img
                         src={this.props.src}
                         title={this.props.name}