Fix resizes back to initial remote session size

Since the expected client size wasn't updated when the browser window
resized, noVNC didn't resize the canvas properly when going back to
the exact same dimensions.

Fixes issue #1903

core/rfb.js

@@ -730,6 +730,7 @@ export default class RFB extends EventTargetMixin {
         window.requestAnimationFrame(() => {
             this._updateClip();
             this._updateScale();
+            this._saveExpectedClientSize();
         });
 
         if (this._resizeSession) {

tests/test.rfb.js

@@ -730,6 +730,28 @@ describe('Remote Frame Buffer protocol client', function () {
             container.style.width = '70px';
             container.style.height = '80px';
             client.scaleViewport = true;
+
+            const incoming = [ 0x00,        // msg-type=FBU
+                               0x00,        // padding
+                               0x00, 0x01,  // number of rects = 1
+                               0x00, 0x00,  // reason = server initialized
+                               0x00, 0x00,  // status = no error
+                               0x00, 0x04,  // new width = 4
+                               0x00, 0x04,  // new height = 4
+                               0xff, 0xff,
+                               0xfe, 0xcc,  // enc = (-308) ExtendedDesktopSize
+                               0x01,        // number of screens = 1
+                               0x00, 0x00,
+                               0x00,        // padding
+                               0x78, 0x90,
+                               0xab, 0xcd,  // screen id = 0
+                               0x00, 0x00,  // screen x = 0
+                               0x00, 0x00,  // screen y = 0
+                               0x00, 0x04,  // screen width = 4
+                               0x00, 0x04,  // screen height = 4
+                               0x12, 0x34,
+                               0x56, 0x78]; // screen flags
+            client._sock._websocket._receiveData(new Uint8Array(incoming));
         });
 
         it('should update display scale factor when changing the property', function () {
@@ -774,6 +796,28 @@ describe('Remote Frame Buffer protocol client', function () {
             expect(client._display.autoscale).to.have.been.calledWith(40, 50);
         });
 
+        it('should update the scaling resized back to initial size', function () {
+            sinon.spy(client._display, "autoscale");
+
+            container.style.width = '40px';
+            container.style.height = '50px';
+            fakeResizeObserver.fire();
+            clock.tick(1000);
+
+            expect(client._display.autoscale).to.have.been.calledOnce;
+            expect(client._display.autoscale).to.have.been.calledWith(40, 50);
+            client._display.autoscale.resetHistory();
+
+            container.style.width = '70px';
+            container.style.height = '80px';
+            fakeResizeObserver.fire();
+            clock.tick(1000);
+
+            expect(client._display.autoscale).to.have.been.calledOnce;
+            expect(client._display.autoscale).to.have.been.calledWith(70, 80);
+            client._display.autoscale.resetHistory();
+        });
+
         it('should update the scaling when the remote session resizes', function () {
             // Simple ExtendedDesktopSize FBU message
             const incoming = [ 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
@@ -941,6 +985,27 @@ describe('Remote Frame Buffer protocol client', function () {
             expect(RFB.messages.setDesktopSize).to.not.have.been.called;
         });
 
+        it('should request a resize when resized back to initial size', function () {
+            container.style.width = '40px';
+            container.style.height = '50px';
+            fakeResizeObserver.fire();
+            clock.tick(1000);
+
+            expect(RFB.messages.setDesktopSize).to.have.been.calledOnce;
+            expect(RFB.messages.setDesktopSize).to.have.been.calledWith(
+                sinon.match.object, 40, 50, 0x7890abcd, 0x12345678);
+            RFB.messages.setDesktopSize.resetHistory();
+
+            container.style.width = '70px';
+            container.style.height = '80px';
+            fakeResizeObserver.fire();
+            clock.tick(1000);
+
+            expect(RFB.messages.setDesktopSize).to.have.been.calledOnce;
+            expect(RFB.messages.setDesktopSize).to.have.been.calledWith(
+                sinon.match.object, 70, 80, 0x7890abcd, 0x12345678);
+        });
+
         it('should not resize until the container size is stable', function () {
             container.style.width = '20px';
             container.style.height = '30px';